iMechanica - Fatigue
https://imechanica.org/taxonomy/term/256
enPh.D. and Postdoc positions on mechanics of compostie materials and structures
https://imechanica.org/node/26931
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/13914">mechanic</a></div><div class="field-item odd"><a href="/taxonomy/term/1517">erosion</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/190">impact</a></div><div class="field-item even"><a href="/taxonomy/term/13401">wind turbine blade</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal" align="left"><span lang="EN-US" xml:lang="EN-US">Ph.D. and Postdoc positions are available in the School of Traffic and Transportation Engineering (First Class Academic Discipline) at Central South University in Dr. Li's research group. Lists of topics of interest are:</span></p>
<p class="MsoNormal" align="left"> </p>
<p class="MsoNormal" align="left"><span lang="EN-US" xml:lang="EN-US">1. Rain/sand erosion;</span></p>
<p class="MsoNormal" align="left"><span lang="EN-US" xml:lang="EN-US">2. Fatigue of fiberglass composite for wind turbine blade;</span></p>
<p class="MsoNormal" align="left"><span lang="EN-US" xml:lang="EN-US">3. Impact mechanics;</span></p>
<p class="MsoNormal" align="left"> </p>
<p class="MsoNormal" align="left"><span lang="EN-US" xml:lang="EN-US">Interested applicants are welcome to send a detailed CV to Dr. Li at </span><span lang="EN-US" xml:lang="EN-US"><a href="mailto:jianli1@csu.edu.cn">jianli1@csu.edu.cn</a></span><span lang="EN-US" xml:lang="EN-US">. More details about the PI can be found at</span></p>
<p class="MsoNormal" align="left"><span lang="EN-US" xml:lang="EN-US">Google cholar: </span><span lang="EN-US" xml:lang="EN-US"><a href="https://scholar.google.com/citations?user=4Kfu5p8AAAAJ&hl=en">https://scholar.google.com/citations?user=4Kfu5p8AAAAJ&hl=en</a></span></p>
<p class="MsoNormal" align="left"><span lang="EN-US" xml:lang="EN-US">Doi: </span><span lang="EN-US" xml:lang="EN-US"><a href="https://orcid.org/0000-0002-0492-7263">https://orcid.org/0000-0002-0492-7263</a></span></p>
<p> </p>
<p class="MsoNormal" align="left"><span lang="EN-US" xml:lang="EN-US">Faculty page: </span><span lang="EN-US" xml:lang="EN-US"><a href="https://faculty.csu.edu.cn/lijian123456/zh_CN">https://faculty.csu.edu.cn/lijian123456/zh_CN</a></span></p>
</div></div></div>Mon, 23 Oct 2023 08:37:42 +0000Jian_Li26931 at https://imechanica.orghttps://imechanica.org/node/26931#commentshttps://imechanica.org/crss/node/26931Workshop on Computational Fatigue Analysis 2023 – FKM-Guideline Non-Linear
https://imechanica.org/node/26855
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/74">conference</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/12152">FKM-Guideline</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/13873">low-cycle fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/13874">high-cycle fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/249">durability</a></div><div class="field-item odd"><a href="/taxonomy/term/949">Workshop</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>From October 30 to November 1, 2023, we hold 11th Workshop on Computational Fatigue Analysis in Prague, Czechia. This time, we chose the attractive topic of the latest extension of the FKM-Guideline for Analytical Strength Assessment. This guideline developed for years by FKM Association in Germany provides clear description how to deal with static and fatigue analysis of industrial components. While all preceding versions were focused only on the high-cycle fatigue regime above 10,000 cycles, the new non-linear extension is deemed to be usable for both low-cycle and high-cycle fatigue problems. It was published for the first time in 2019, and it does not have other than German version until these days. Luckily, Klemens Rother from Hochschule München is capable of lecturing this interesting topic to English speaking participants and he promised to prepare the presentation for newcomers completely enough to allow them to run the analysis without missing any important points.</p>
<p>There are different modes of access to the workshop available – on-site, on-line and also from recordings. Note however that the on-site and on-line versions of attendance have the special <strong>Early Bird Fee option</strong> available only for registration and payments made <strong>till September 18, 2023</strong>.</p>
<p>More details about the workshop can be found on its website <a href="https://www.pragtic.com/FKMNL.php">https://www.pragtic.com/FKMNL.php</a>.</p>
</div></div></div>Wed, 13 Sep 2023 10:46:10 +0000pragtic26855 at https://imechanica.orghttps://imechanica.org/node/26855#commentshttps://imechanica.org/crss/node/26855Lecture by P. Yadegari on “Fatigue strength of ultra-high strength steels and surface-hardened components”
https://imechanica.org/node/26837
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/128">education</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/13861">UHS steel</a></div><div class="field-item even"><a href="/taxonomy/term/13862">surface-hardened components</a></div><div class="field-item odd"><a href="/taxonomy/term/12152">FKM-Guideline</a></div><div class="field-item even"><a href="/taxonomy/term/3522">non-linear</a></div><div class="field-item odd"><a href="/taxonomy/term/13863">on-line</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Lecture by Patrick Yadegari on “Fatigue strength of ultra-high strength steels and surface-hardened components” will be held on-line on <strong>Tuesday September 5 at 3PM CET</strong>. Its approximate duration is expected 1 hour, but it will depend on the scope of the discussion and the questions of participants. If you wish to take part, please write me to <a href="mailto:papuga@pragtic.com">papuga@pragtic.com</a>, so that I could send you the access link to the Zoom platform. Here is the abstract to the lecture:</p>
<p><em>This presentation will discuss how the methods of the German “FKM-Guideline Nonlinear”, which provides a fatigue strength assessment based on the local strain approach, are extended to be applicable for ultra-high strength steels as well as for surface-hardened components. Various experimental investigations were used to adapt the methods of the guideline to estimate the cyclic material behaviour of higher strength steels, thus allowing the estimation of the cyclic stress-strain curve, mean-stress sensitivity and damage parameter life curves based on ultimate tensile strength. Furthermore, an approach was developed to allow an assessment of structural durability for surface hardened components with regards to the existing procedures of the guideline. Since the failure of these components can originate from both the notch root and the transition area between the low-strength core material and the high-strength surface layer due to the inhomogeneous material properties and the residual stresses present, the proof of structural durability was extended to include a so-called two-point assessment and the consideration of residual stresses.</em></p>
<p>Similarly to the previous lecture by C. Liang (see the link here: <a href="https://www.pragtic.com/lectures.php">https://www.pragtic.com/lectures.php</a>), the lecture will also be recorded for those who cannot attend at this specific moment.</p>
<p> </p>
</div></div></div>Sun, 03 Sep 2023 21:16:12 +0000pragtic26837 at https://imechanica.orghttps://imechanica.org/node/26837#commentshttps://imechanica.org/crss/node/268371st Workshop on Thermodynamics of Fatigue Process
https://imechanica.org/node/26702
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/180">thermodynamics</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/13808">self-heating</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>The workshop takes place on-line only on June 14 from 2 PM CET. It is intended to serve as a networking event, where interested researchers present their focused domain. The subsequent brainstorming will help us to evaluate whether there is a will for a broader cooperation among the participants, and if to transform this workshop into something more regular.</p>
<p>If you do not feel strong enough to present, you are still invited to join us - simply let me know to my e-mail address to get the access to the workshop. No fee requested.</p>
<p>More to be found on: <a href="https://www.pragtic.com/W1TFP.php">https://www.pragtic.com/W1TFP.php</a>.</p>
<p>Thanks for sharing this information with anyone who might be interested.</p>
<p> </p>
</div></div></div>Mon, 05 Jun 2023 18:06:41 +0000pragtic26702 at https://imechanica.orghttps://imechanica.org/node/26702#commentshttps://imechanica.org/crss/node/26702Modeling fatigue life and hydrogen embrittlement of bcc steel with unified mechanics theory
https://imechanica.org/node/26574
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/314">corrosion</a></div><div class="field-item even"><a href="/taxonomy/term/8387">hydrogen embrittlement</a></div><div class="field-item odd"><a href="/taxonomy/term/13695">unified mechanics theory</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><strong>50 days' of free access</strong> to the article. Anyone clicking on this link before <strong>May 12, 2023,</strong> will be taken directly to the latest version of the article on ScienceDirect, which you are welcome to read or download. No sign-up, registration, or fees are required.</p>
<p><a title="//authors.elsevier.com/a/1go6t1HxM513av. Click or tap if you trust this link." href="https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fauthors.elsevier.com%2Fa%2F1go6t1HxM513av&data=05%7C01%7Ccjb%40buffalo.edu%7Cc2c43e1c6ba2407e12f708db2b620668%7C96464a8af8ed40b199e25f6b50a20250%7C0%7C0%7C638151473681118925%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=L8Uzmz67eaDkCRoLUX2fSLdrYUpCsqSwjFBXYKNu3hk%3D&reserved=0" target="_blank" rel="noopener noreferrer" data-auth="Verified" data-safelink="true" data-linkindex="2">https://authors.elsevier.com/a/1go6t1HxM513av</a></p>
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<tr class="odd"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/Paper%20167-%20Hsiao%20Wei.pdf" type="application/pdf; length=4539416" title="Paper 167- Hsiao Wei.pdf">Modeling hydrogen embrittlement + fatigue without curve fitting.</a></span></td><td>4.33 MB</td> </tr>
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</div></div></div>Thu, 23 Mar 2023 18:13:12 +0000Cemal Basaran26574 at https://imechanica.orghttps://imechanica.org/node/26574#commentshttps://imechanica.org/crss/node/26574PhD position in france : modelling of fatigue crack propagation in metallic materials weakened by hydrogen
https://imechanica.org/node/26513
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/5784">hydrogen</a></div><div class="field-item odd"><a href="/taxonomy/term/6692">phase field</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/641">finite element</a></div><div class="field-item even"><a href="/taxonomy/term/539">phd</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Dear all</p>
<p>Please fin attached a PhD proposal for the beginning of the 2023 academic year, proposed by the <a href="https://pprime.fr/en/research/physics-and-mechanics-of-materials/damaging-and-durability-endo/">Institut P'</a> (Poitiers, France) in collaboration with the <a href="https://www.lspm.cnrs.fr/en/research/mecameta/interactions-materiaux-environnement-mecanique/">LSPM</a> lab (University Sorbonne Paris Nord), aiming at modelling fatigue crack propagations in metallic materials under gazeous hydrogen environnement.</p>
<p> This PhD proposition is part of the collaborative french governement research programme "<a href="https://www.celluleenergie.cnrs.fr/pepr/hyperstock/">HyperStock</a>" dedicated to the hyperbaric storage of hydrogen.</p>
<p>Please send, if interested, a resume and a motivation letter to</p>
<ul><li>Damien HALM: damien.halm(at)ensma.fr</li>
<li>Azdine NAIT-ALI: <a href="mailto:azdine.nait-ali@ensma.fr">azdine.nait-ali@ensma.fr</a></li>
<li>Yann CHARLES: <a href="mailto:yann.charles@univ-paris13.fr">yann.charles@univ-paris13.fr</a></li>
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<tr class="odd"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/fatigue%20FPH_EN.pdf" type="application/pdf; length=77739" title="fatigue FPH_EN.pdf">PhD position</a></span></td><td>75.92 KB</td> </tr>
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</div></div></div>Sun, 05 Feb 2023 16:22:59 +0000yann.charles26513 at https://imechanica.orghttps://imechanica.org/node/26513#commentshttps://imechanica.org/crss/node/26513Predicting high cycle and ultrasonic vibration fatigue with unified mechanics theory
https://imechanica.org/node/26423
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/1055">entropy</a></div><div class="field-item odd"><a href="/taxonomy/term/13695">unified mechanics theory</a></div><div class="field-item even"><a href="/taxonomy/term/13700">microplasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/180">thermodynamics</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item even"><a href="/taxonomy/term/13701">ultrasonic vibration testing</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>The unified mechanics theory (UMT) is ab-initio unification of the second law of thermodynamics and Newton's universal laws of motion, in which Boltzmann's second law of entropy formulation governs dissipation & degradation. Hence, the unified mechanics theory does not require any empirical dissipation & degradation potential function or an empirical void evolution function. Material degradation is quantified on the Thermodynamic state index (TSI) axis based on the specific entropy production, which starts at zero and asymptotically approaches one at failure. However, to calculate the TSI coordinate, the thermodynamic fundamental equation of the material must be derived analytically. </p>
<p>The unified mechanics theory (UMT) was used to predic the high cycle fatigue and ultrasonic vibration fatigue life of low-carbon steel in these two studies, respectively. Thermal conduction due to thermo-mechanical coupling, microplastic energy dissipation at defect sites, and internal friction scattering due to rate-dependent dislocation motion, during the elastic fatigue loading are discussed in detail.</p>
<p><a class="doi" title="Persistent link using digital object identifier" href="https://doi.org/10.1016/j.mechmat.2021.104116" target="_blank" rel="noopener noreferrer">https://doi.org/10.1016/j.mechmat.2021.104116</a></p>
<p><a class="doi" title="Persistent link using digital object identifier" href="https://doi.org/10.1016/j.ijsolstr.2021.111313" target="_blank" rel="noopener noreferrer">https://doi.org/10.1016/j.ijsolstr.2021.111313</a></p>
<p> </p>
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<tr class="odd"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/UMT-HCF.pdf" type="application/pdf; length=6678380" title="UMT-HCF.pdf">Predicting high cycle fatigue life with unified mechanics theory</a></span></td><td>6.37 MB</td> </tr>
<tr class="even"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/UMT-Ultrasonic%20Vibration%20Fatigue.pdf" type="application/pdf; length=13918530" title="UMT-Ultrasonic Vibration Fatigue.pdf">Modeling ultrasonic vibration fatigue with unified mechanics theory</a></span></td><td>13.27 MB</td> </tr>
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</div></div></div>Mon, 12 Dec 2022 19:48:11 +0000Hsiao-Wei Lee26423 at https://imechanica.orghttps://imechanica.org/node/26423#commentshttps://imechanica.org/crss/node/26423Modeling fatigue of pre-corroded metals with unified mechanics theory
https://imechanica.org/node/26414
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/1055">entropy</a></div><div class="field-item odd"><a href="/taxonomy/term/13695">unified mechanics theory</a></div><div class="field-item even"><a href="/taxonomy/term/180">thermodynamics</a></div><div class="field-item odd"><a href="/taxonomy/term/314">corrosion</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/354">vibration</a></div><div class="field-item even"><a href="/taxonomy/term/10396">electrochemistry</a></div><div class="field-item odd"><a href="/taxonomy/term/13696">structural steel</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>The unified mechanics theory (UMT) was used to develop a model to predict the fatigue life of pre-corroded steel samples with BCC structure. Details of the experimental validation are also provided.</p>
<p><a class="doi" title="Persistent link using digital object identifier" href="https://doi.org/10.1016/j.matdes.2022.111383" target="_blank" rel="noopener noreferrer">https://doi.org/10.1016/j.matdes.2022.111383</a></p>
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<tr class="odd"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/1-s2.0-S026412752201005X-main.pdf" type="application/pdf; length=7671123" title="1-s2.0-S026412752201005X-main.pdf">Unified mechanics theory-corrosion </a></span></td><td>7.32 MB</td> </tr>
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</div></div></div>Thu, 08 Dec 2022 16:43:25 +0000Hsiao-Wei Lee26414 at https://imechanica.orghttps://imechanica.org/node/26414#commentshttps://imechanica.org/crss/node/26414Defect-based Physics-Informed Machine Learning Framework for Fatigue Prediction
https://imechanica.org/node/26216
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/10902">machine learning</a></div><div class="field-item even"><a href="/taxonomy/term/12835">physics-informed</a></div><div class="field-item odd"><a href="/taxonomy/term/13593">additive</a></div><div class="field-item even"><a href="/taxonomy/term/1834">LEFM</a></div><div class="field-item odd"><a href="/taxonomy/term/3280">defects</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span>I would like to draw your attention to our recently proposed predictive method based on a semi-empirical model (LEFM) and Neural Network, exploiting the Physics-informed Machine Learning concept. W</span><span>e show how the accuracy of state-of-the-art fatigue predictive models, based on defects present in materials, can be significantly boosted by accounting for additional morphological features via Physics-Informed Machine Learning. Although defect-based methodologies are widely employed in additively manufactured materials in these days, the methods can be effectively employed to other problems dealing with metallic materials presenting defects. I believe this is the way to go for the identification and quantification of “hidden” fatigue influencing factors while ensuring the soundness of the prediction. </span></p>
<p><span>The paper published in Journal of Materials & Design (JMAD - IF 9.4) can be found here:</span></p>
<p><span>ResearchGate: <a href="https://www.researchgate.net/publication/362851602_A_defect-based_Physics-Informed_Machine_Learning_Framework_for_Fatigue_Finite_Life_Prediction_in_Additive_Manufacturing">https://www.researchgate.net/publication/362851602_A_defect-based_Physic...</a></span></p>
<p><span>Science Direct (Open Access): <a href="https://www.sciencedirect.com/science/article/pii/S0264127522007110?via%3Dihub">https://www.sciencedirect.com/science/article/pii/S0264127522007110?via%...</a></span></p>
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</div></div></div>Mon, 12 Sep 2022 22:15:33 +0000enrico.salvati126216 at https://imechanica.orghttps://imechanica.org/node/26216#commentshttps://imechanica.org/crss/node/26216PhD fully-funded position in Computational Solid Mechanics - emphasis on Fracture Mechanics (call deadline: end of July 2022) – University of Udine (Italy)
https://imechanica.org/node/26005
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/539">phd</a></div><div class="field-item odd"><a href="/taxonomy/term/1747">computational</a></div><div class="field-item even"><a href="/taxonomy/term/584">mechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/9383">phase-field</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal"> </p>
<p class="MsoNormal"><a href="https://simed.uniud.it/"><span lang="EN-GB" xml:lang="EN-GB">Structural Integrity and MEchanical Design (SIMED)</span></a><span lang="EN-GB" xml:lang="EN-GB"> group is seeking a PhD candidate to conduct research in computational solid mechanics, mainly applied to structural problems. The successful applicant will work at the Polytechnic Engineering and Architecture Department (DPIA) of the University of Udine, under Dr Enrico Salvati’s supervision.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">The project focuses, but not limited to, on the development of computational models for structural problems. In particular, the candidate will develop new algorithms and codes to predict crack nucleation and propagation in homogeneous and </span><span lang="EN-US" xml:lang="EN-US">heterogeneous materials in the context of quasi-static and fatigue loading conditions, using several numerical approaches such as Phase-Field, XFEM, CZM. Fatigue modelling and the effects of residual stress will be also covered. Machine learning approaches may also be pursued.</span></p>
<p class="MsoNormal"><span lang="EN-US" xml:lang="EN-US">Aimed at verifying the developed numerical models,</span><span> </span><span lang="EN-US" xml:lang="EN-US">the holder of the PhD studentship will have the</span><span> opportunity </span><span lang="EN-US" xml:lang="EN-US">to be</span><span> involved </span><span lang="EN-US" xml:lang="EN-US">in the design and execution of experimental tests at the laboratories of DPIA or at partner universities across Italy and Europe. </span><span>The appointee will be able to work closely with </span><span lang="EN-US" xml:lang="EN-US">undergraduate students</span><span>.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">The candidates should possess a master’s degree in a relevant field with knowledge in fracture mechanics, FEM modelling, computational tools, and – most importantly - willingness to learn! Strong interpersonal skills are required alongside the ability to work on a collaborative project.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">The call will be published shortly, and the <strong>deadline</strong> will be at the <strong>end of July 2022</strong>, presumably. The PhD journey <strong>starts</strong> in early <strong>November 2022</strong>. As a part of the PhD programme, the successful candidate will spend at least 6 months in a university or research institute abroad to conduct his/her research to establish new collaborations; extra costs will be covered.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">If you are interested, strongly motivated and you believe you are a good candidate, please get in touch:</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Enrico Salvati (<a href="mailto:enrico.salvati@uniud.it">enrico.salvati@uniud.it</a>)</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Web: <a href="https://simed.uniud.it/">https://simed.uniud.it/</a></span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB"> </span></p>
<p class="MsoNormal"><strong><span lang="EN-GB" xml:lang="EN-GB">PI’s additional information</span></strong><span lang="EN-GB" xml:lang="EN-GB">:</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Enrico Salvati is currently an Assistant Professor in Mechanical Engineering at the University of Udine, since March 2020. He obtained his doctorate from the University of Oxford (2017) and his master’s degree in Mechanical Engineering from the University of Ferrara (2011). Enrico’s research mainly focuses on the evaluation and modelling of fatigue and fracture problems across the scales, as well as problems related to material inhomogeneities, such as residual stress and defects. He is also interested in biomaterials with hierarchical structures and biomedical problems. He is often involved as Principal Investigator in industry-oriented projects for the performance evaluation of components and structures in aerospace, manufacturing, energy and biomedical applications.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Throughout the years, Enrico has established strong collaborations with leading scientists and universities, some examples: University of Oxford (UK), NTNU (Norway), TU Delft (The Netherlands), National Aeronautics and Space Administration - NASA (US), Università Roma Trè (Italy)</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Enrico is Editor of Materials Today Communications (Elsevier, IF: 3.383) and member of the editorial board of: Forces in Mechanics (Elsevier), Engineering Reports (Wiley) and Materials Design & Processing Communications (Wiley).</span></p>
</div></div></div>Tue, 31 May 2022 11:09:00 +0000enrico.salvati126005 at https://imechanica.orghttps://imechanica.org/node/26005#commentshttps://imechanica.org/crss/node/26005Postdoctoral Researcher in Machine Learning for Fatigue Fracture prediction with commitment for the submission of a proposal in the framework of the MSCA Global Postdoctoral Fellowship 2022
https://imechanica.org/node/25788
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/871">postdoc</a></div><div class="field-item odd"><a href="/taxonomy/term/541">job</a></div><div class="field-item even"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/10902">machine learning</a></div><div class="field-item odd"><a href="/taxonomy/term/6344">Marie Curie</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal"><a href="https://simed.uniud.it/"><span lang="EN-GB" xml:lang="EN-GB">Structural Integrity and MEchanical Design (SIMED)</span></a><span lang="EN-GB" xml:lang="EN-GB"> group is seeking a 1-year full-time Postdoctoral Researcher in Machine Learning applied to fracture mechanics. The successful applicant will work at the Polytechnic Engineering and Architecture Department (DPIA) of the University of Udine, under Dr Enrico Salvati’s supervision.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">The project focuses, but not limited to, on feasibility study and application of Machine Learning methods to applied and numerical fatigue fracture mechanics problems.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">The applicants will submit a project proposal on this topic or related ones. Project proposals relevant to the fields of fatigue are also welcome, e.g. residual stress, biomaterials, additive manufacturing, welding, multi-physics problems, etc.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">The candidates should possess a doctorate in a relevant field with experience in fracture mechanics, FEM modelling, computational tools, probabilistic approaches and demonstrate willingness to learn new techniques. Strong interpersonal skills are required alongside the ability to work on a collaborative project. Maximum of 7 years of experience since completion of a PhD or an equivalent doctoral degree is required.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">The call is dedicated to applicants committed to applying for a </span><a href="https://ec.europa.eu/research/mariecurieactions/actions/postdoctoral-fellowships"><span lang="EN-GB" xml:lang="EN-GB">Marie Skłodowska-Curie (MSCA)</span></a><span lang="EN-GB" xml:lang="EN-GB"> <strong>Postdoctoral Global Fellowship</strong> 2022 (deadline 14th September 2022). This MSCA fellowship offers a great opportunity for a national or international early-stage researcher to work for up to 24 months in a non-EU state member and 12 months in the host institute (University of Udine).</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">A competitive salary will be offered, and a +20% salary add-on applies if the successful candidate holds the </span><a href="https://ec.europa.eu/info/research-and-innovation/funding/funding-opportunities/seal-excellence_en"><span lang="EN-GB" xml:lang="EN-GB">Seal of Excellence</span></a><span lang="EN-GB" xml:lang="EN-GB"> certificate. Additional funds (up to 8 k€) will be available to support the MSCA application. Annual leave and medical benefits will be offered</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Appointment start date: no later than <strong>15th May 2022</strong>.</span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">The call deadline is <strong>22nd March 2022 2 pm (CET).</strong></span></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Further details and how to apply: </span><a href="https://titulus-uniud.cineca.it/albo/viewer?view=files/002017041-UNUD001-9cf3ba9e-69d5-4732-ae28-3d24aa570a76-002.pdf"><span lang="EN-GB" xml:lang="EN-GB">English</span></a><span lang="EN-GB" xml:lang="EN-GB">; </span><a href="https://titulus-uniud.cineca.it/albo/viewer?view=files/002017041-UNUD001-9cf3ba9e-69d5-4732-ae28-3d24aa570a76-001.pdf"><span lang="EN-GB" xml:lang="EN-GB">Italian</span></a></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Annexes (for application): </span><a href="https://titulus-uniud.cineca.it/albo/viewer?view=files/002017041-UNUD001-9cf3ba9e-69d5-4732-ae28-3d24aa570a76-003.pdf"><span lang="EN-GB" xml:lang="EN-GB">Annexe A</span></a><span lang="EN-GB" xml:lang="EN-GB">; </span><a href="https://titulus-uniud.cineca.it/albo/viewer?view=files/002017041-UNUD001-9cf3ba9e-69d5-4732-ae28-3d24aa570a76-004.pdf"><span lang="EN-GB" xml:lang="EN-GB">Annexe B</span></a></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Applicants must apply online and upload an up-to-date CV alongside a project proposal and letter of commitment at the following link:</span> <a title="https://pica.cineca.it/" href="https://pica.cineca.it/" target="_blank" rel="noopener noreferrer"><span lang="EN-GB" xml:lang="EN-GB">https://pica.cineca.it/</span></a></p>
<p class="MsoNormal"><span lang="EN-GB" xml:lang="EN-GB">Informal enquiries may be addressed to Enrico Salvati (<a href="mailto:enrico.salvati@uniud.it">enrico.salvati@uniud.it</a>)</span></p>
</div></div></div>Fri, 18 Feb 2022 16:03:24 +0000enrico.salvati125788 at https://imechanica.orghttps://imechanica.org/node/25788#commentshttps://imechanica.org/crss/node/25788Journal Club for May 2021: Strong and tough hydrogels with hierarchical architectures
https://imechanica.org/node/25145
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/1099">hydrogel</a></div><div class="field-item odd"><a href="/taxonomy/term/13133">tough</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/8785">hierarchical structures</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal"> </p>
<p class="MsoNormal"><em>Mutian Hua, Shuwang Wu, Ximin He</em></p>
<p class="MsoNormal"><a href="http://www.seas.ucla.edu/xhe-lab/index.html">Bioinspired Soft Materials Group</a></p>
<p class="MsoNormal"><em>University of California, Los Angeles</em></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><strong>Introduction</strong></span></p>
<p class="MsoNormal">A hydrogel can be viewed as a unique combination of liquid and solid, the liquid side properties endow it with generally good biocompatibility and high porosity for fast diffusion, yet they are shape fixable as a solid material, by applying knowledge of molecular and structural engineering, they can also be made to bear moderate external loads. These unique combinations of physical and chemical properties make them promising materials for a number of applications.</p>
<p class="MsoNormal">However, fragileness and low durability are major examples of the obstacles that hindered broad application of hydrogels in real life scenarios. It is a long dealt and studied topic over the past decade, and a number of methods have been developed to tackle this issue, such as double-networking, mechanical stretching, etc. Ximin He’s group recently developed a class of strong and tough hydrogels by tailoring hydrogel structure across several hierarchical length-scales via modulation of polymer aggregation. The series of hydrogels were prepared by combining freeze-casting and salting out in sequential steps, which could realize simultaneously high strength, toughness, stretchability and fatigue resistance (Nature), and also tunability of those properties over broad ranges (Advanced Materials).</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><strong>Standing on the shoulder of Giants</strong></span></p>
<ul><li class="MsoNormal"><strong>Double-network tough hydrogel</strong></li>
</ul><p class="MsoListParagraphCxSpMiddle">Two chemically crosslinked interpenetrating networks1 or one chemically crosslinked and another physically crosslinked interpenetrating networks2.</p>
<ul><li class="MsoListParagraphCxSpMiddle"><strong>Ice templating hydrogel</strong></li>
</ul><p class="MsoListParagraphCxSpMiddle">Hydrogels with micro-aligned channels created by growth of columnar ice crystals3.</p>
<ul><li class="MsoListParagraphCxSpMiddle"><strong>Mechanical Stretching / Training tough hydrogel</strong></li>
</ul><p class="MsoListParagraphCxSpMiddle">Anisotropic hydrogels with polymer alignments created by stretching, accompanied by chain crystallization induced by mechanical training or drying4-6.</p>
<ul><li class="MsoListParagraphCxSpMiddle"><strong>Low hysteresis hydrogel</strong></li>
</ul><p class="MsoListParagraphCxSpMiddle">Composite hydrogels showing both high toughness, fatigue resistance and low hysteresis7,8.</p>
<p class="MsoListParagraphCxSpLast"><strong> </strong></p>
<p class="MsoNormal"><span><strong>Motivation and Design</strong></span></p>
<p class="MsoNormal">Natural materials offer unique combination of attractive properties that many synthetic materials could not achieve. For example, Wood is light and strong; nacres are hard and resilient; muscles and tendons are soft and tough. These combination of normally contradicting mechanical properties, are often attributed to their hierarchical structures across multiple length scales, in which the basic building blocks are tightly joint together by physical or chemical bonds, and those bundles or clusters are joint together in a more macroscopic architecture. Current bottom-up (e.g. self-assembly) and top-down (e.g. freeze-casting) fabrication methods often have difficulty in effectively tuning material structure across broad length-scales, therefore, it becomes inevitable to combine those methods together to fabricate hierarchically structured hydrogels.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><strong>1. Introducing tough hydrogels via freezing-assisted salting out (<a href="https://imechanica.org/files/2021_Nature_Tough%20hydrogel.pdf">2021 Nature</a>)</strong></span></p>
<p class="MsoNormal"><span><a href="https://youtu.be/jH7NcQK0B_Y">Video: <span>Tendon-like Tough Hydrogel</span></a></span></p>
<p> </p>
<p class="MsoNormal"><span><img title="Fig. 1 Tough hydrogels via freezing-assisted salting out" src="https://imechanica.org/files/Fig.%201_0.png" alt="" width="809" height="942" /></span></p>
<p class="MsoNormal"><strong>Fig. 1 Tough Hydrogels via Freezing-assisted Salting Out</strong></p>
<p class="MsoNormal"> <span> </span></p>
<ul><li class="MsoNormal">A freezing assisted salting out method was introduced to fabricate hydrogel with hierarchical structures, involving both bottom-up and top-down processes (Fig. 1a).</li>
<li class="MsoNormal">Directional freezing created the micrometer and up length scale structures (Fig. 1b, c). Directional freezing concentrated PVA to form the aligned pore walls and increased the local concentration of PVA to higher values than the nominal concentration. Freezing served as an indispensable step as the concentration and closer packing of polymer during freezing prepared the polymer chains for subsequent strong aggregation and crystallization induced by salting out.</li>
<li class="MsoNormal">Salting out strongly induced the aggregation and crystallization of PVA by phase separation to form the nanofibrils (Fig. 1f). Under the influence of kosmotropic ions, the pre-concentrated PVA chains strongly self-coalesced and phase-separated from the original homogeneous phase, which in turn formed the mesh-like nanofibril network on the surface of the micrometer-scale aligned pore walls (Fig. 1d, e).</li>
<li class="MsoNormal">The produced hydrogel with nominal 5% PVA concentration showed an ultra-high ultimate stress of 11.5 MPa and ultimate strain of 2900% (Fig. 1g).</li>
<li class="MsoNormal">The HA-5PVA hydrogel showed a remarkable gradual failure mode featuring stepwise fracture and pull-out of fibers typical for highly anisotropic materials like tendons (Fig. 1g).</li>
<li class="MsoNormal">Even with pre-existing cracks, the hydrogel showed a remarkable crack-blunting ability, and the initial crack did not advance into the material at high strains, indicating flaw-insensitivity.</li>
<li class="MsoNormal">The HA-PVA hydrogels showed high ultimate stress and strain that well surpassed the values seen in many reported tough hydrogels. The HA-PVA hydrogels demonstrated excellent toughness of 175 ± 9 MJ m−3 to 210 ± 13 MJ m−3 in the absence of flaws, as the direct result of their combination of high strength and high ductility (Fig. 1i-k). At a water content of over 70% in these hydrogels, these toughness values are well above those of water-free polymers such as polydimethylsiloxane (PDMS), Kevlar and synthetic rubber, even surpassing the toughness of natural tendon1 and spider silk.</li>
</ul><p class="MsoNormal"> </p>
<p class="MsoNormal"><strong> </strong></p>
<p class="MsoNormal"><span><strong>2. Highly Tunable Mechanical Properties and Microstructure (<a href="https://onlinelibrary.wiley.com/action/showCampaignLink?uri=uri%3A50f8e3f7-5693-4d95-9530-166f0b035a67&url=https%3A%2F%2Fsecure.wiley.com%2FGlassEbook&viewOrigin=offlinePdf">2021 Adv. Mater.</a>)</strong></span></p>
<p> </p>
<p class="MsoNormal"><span><img title="Fig. 2 Tunable Mechanical Properties" src="https://imechanica.org/files/Fig.%202.png" alt="" width="688" height="645" /></span></p>
<p class="MsoNormal"><strong>Fig. 2 Broad tunability of mechanical properties.</strong></p>
<p class="MsoNormal"> </p>
<ul><li class="MsoNormal">Depending on the ion species, there are three kinds of possible interactions between the ions, the polymer chains, and the hydration water of polymer. First, some anions can polarize the hydration water molecules, which destabilizes the hydrogen bonds between the polymer and its hydration water molecules. Second, some ions can interfere with the hydrophobic hydration of the macromolecules by increasing the surface tension of the cavity surrounding the backbone. Third, other anions can bind directly and thus add extra charges to the PVA chains, which increase the solubility of the polymer (Fig. 2a, b).</li>
<li class="MsoNormal">Ions such as SO42− and CO32− exhibit the first and second effects and could lead to the salting-out of polymers, thereby resulting in the collapse of polymer chains and forming small pores (Fig. 2c). Hydrogen bonds formed between the hydroxyl groups, which resulted in aggregation/ crystallization of the polymer chains.</li>
<li class="MsoNormal">Other ions like NO3− and I− exhibit the third interaction and lead to the salting-in of polymers, thereby resulting in the dissolution of polymer chains and forming large pores. The hydrogen bonds were dissociated, and the solubility increased when the frozen samples were melted in solutions of these other ions (Fig. 2d).</li>
<li class="MsoNormal">By comparing the mechanical properties of 5 wt% PVA in different anions, a typical Hofmeister series emerged following the sequence SO4<span>2-</span> > CO32- > Ac- > Cl- > NO3- > I-, with Na+ as the constant counterion. The cation sequence based on critical PVA gelation concentration followed K+ > Na+ ≈ Cs+ > Li<span>+</span> ≈ Ca2+ ≈ Mg2+.</li>
<li class="MsoNormal">The specific ion effect is usually concentration sensitive. Here, Na2SO4 was used as an example to study the influence of concentrations. As concentration of Na2SO4 increased from 0.5 M to saturated (~1.8 M at room temperature), the ultimate stress and maximum strain of the resulted hydrogel increased significantly from 1.0 MPa to 15.0 MPa and from 1500% to 2100%, respectively (Fig. 2e).</li>
<li class="MsoNormal">Via changing the ions or concentrations, the modulus of PVA hydrogels can be easily tuned within a broad range, from near 24 kPa to 2500 kPa, which covered all the moduli of soft tissues in the human body (Fig. 2f).</li>
</ul><p class="MsoNormal"> </p>
<p class="MsoListParagraphCxSpLast"> </p>
<p class="MsoNormal"><strong> </strong></p>
<p class="MsoNormal"><span><strong>3. Versatile application in 3D Printing (<a href="https://imechanica.org/files/2020_ACS%20AMI_4D%20Printable%20Tough%20Gel.pdf">2020 ACS Appl. Mater. Interfaces</a>)</strong></span></p>
<p class="MsoNormal"><img title="Fig. 3 3D printed tough hydrogel architectures and forceful actuators" src="https://imechanica.org/files/Fig.%203_0.png" alt="" width="712" height="381" /></p>
<p class="MsoNormal"><strong>Fig. 3</strong><span><strong> 3D printed tough hydrogel architectures and forceful actuators</strong></span></p>
<p class="MsoNormal"> </p>
<ul><li class="MsoNormal">By chemical modification of PVA, the polymer is enabled the UV polymerization capability. By blending the modified PVA with functional monomers such as NIPAM, stimuli responsive tough hydrogels could be fabricated.</li>
<li class="MsoNormal">Fig. 3a showed three types of printed lattice, respectively with Kelvin cell, Simple Cubic and Octet truss unit cells. . When using the lattice design with octet truss cells, the lattice could tolerate high external loading and deformation and still recover (Fig. 3b).</li>
<li class="MsoNormal">A thermally activated bilayer tough hydrogel gripper was 3D printed (Figure 3c). Upon heating, the gripper arm bent toward the object and locked onto the object, which enabled the subsequent lifting of the object out of the water bath. The tough gel showed 20X higher actuation force than conventional pNIPAM hydrogel grippers of the same size.</li>
<li class="MsoNormal">Remote actuation could be realized by coating the hydrogel with poly(pyrrole) and gained remote actuatability using an IR laser (50 mW). The illuminated part on the hydrogel actuators were locally heated quickly to induce bending, while the unilluminated parts remained cool and static. By controlling the illumination, good spatial control of actuation could be realized in the hydrogel actuator.</li>
</ul><p class="MsoListParagraphCxSpLast"> </p>
<p class="MsoNormal"><strong> </strong></p>
<p class="MsoNormal"><span><strong>Future and beyond</strong></span></p>
<p class="MsoListParagraphCxSpFirst"><span>·<span> </span></span><strong>Tough hydrogel coating</strong></p>
<p class="MsoListParagraphCxSpMiddle">The PVA solution could easily infiltrate into or coat upon various structures, after freezing and salting out in appropriate salt solution, the structure would gain a tough hydrogel coating for reinforcement or protection.</p>
<p class="MsoListParagraphCxSpMiddle"><span>·<span> </span></span><strong>Application in Soft Robotics</strong></p>
<p class="MsoListParagraphCxSpMiddle">Blending PVA and stimuli responsive polymers yield hydrogels with increased strength and toughness, which leads to improved actuation force compared to conventional hydrogels.</p>
<p class="MsoListParagraphCxSpMiddle"><span>·<span> </span></span><strong>Application in Tissue / Organ Replacement</strong></p>
<p class="MsoListParagraphCxSpLast">With 3D printing, the hydrogel could be fabricated into biomimetic geometries, the printed structure could then be toughened to desired level by choosing appropriate salt and concentration to achieve the compatible mechanical strength. PVA is bio-compatible and serves as good scaffold for cell seeding.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><strong>Open Questions </strong></span></p>
<p class="MsoNormal">1. More understanding on the hierarchical structure- property relationship is needed. For example, how many levels are need in the structure to have a prominent effect?</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">2. More understanding on role of feature at specific length scale is needed. For example, is smaller structures more effective at toughening than larger structures?</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">3. More understanding of polymer-ion interaction mechanism is needed to explain Hofmeister effect. Currently, all trends are empirical and we do notice differences in effectiveness for different polymers.</p>
<p class="MsoNormal"><strong> </strong></p>
<p class="MsoNormal"><span><strong>References</strong></span></p>
<p class="MsoNormal">1. Gong, J. P., Katsuyama, Y., Kurokawa, T. & Osada, Y. Double-network hydrogels with extremely high mechanical strength. <em>Adv. Mater.</em> <strong>15</strong>, 1155–1158 (2003).</p>
<p class="MsoNormal">2. Sun, J.-Y. <em>et al.</em> Highly stretchable and tough hydrogels. <em>Nature</em> <strong>489</strong>, 133–136 (2012).</p>
<p class="MsoNormal">3. Zhang, H. <em>et al.</em> Aligned two- and three-dimensional structures by directional freezing of polymers and nanoparticles. <em>Nat. Mater.</em> <strong>4</strong>, 787–793 (2005).</p>
<p class="MsoNormal">4. Mredha, M. T. I. <em>et al.</em> A Facile Method to Fabricate Anisotropic Hydrogels with Perfectly Aligned Hierarchical Fibrous Structures. <em>Adv. Mater.</em> <strong>30</strong>, 1–8 (2018).</p>
<p class="MsoNormal">5. Mredha, M. T. I. <em>et al.</em> Anisotropic tough multilayer hydrogels with programmable orientation. <em>Mater. Horizons</em> <strong>6</strong>, 1504–1511 (2019).</p>
<p class="MsoNormal">6. Lin, S., Liu, J., Liu, X. & Zhao, X. Muscle-like fatigue-resistant hydrogels by mechanical training. <em>Proc. Natl. Acad. Sci. U. S. A.</em> <strong>116</strong>, 10244–10249 (2019).</p>
<p class="MsoNormal">7. Xiang, C. <em>et al.</em> Stretchable and fatigue-resistant materials. <em>Mater. Today</em> <strong>34</strong>, 7–16 (2020).</p>
<p class="MsoNormal"><span><span></span></span></p>
<p class="MsoNormal"><span>8. Wang, Z. <em>et al.</em> Stretchable materials of high toughness and low hysteresis. <em>Proc. Natl. Acad. Sci. U. S. A.</em> <strong>116</strong>, 5967–5972 (2019).</span></p>
</div></div></div><div class="field field-name-upload field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><table class="sticky-enabled">
<thead><tr><th>Attachment</th><th>Size</th> </tr></thead>
<tbody>
<tr class="odd"><td><span class="file"><img class="file-icon" alt="Image icon" title="image/png" src="/modules/file/icons/image-x-generic.png" /> <a href="https://imechanica.org/files/Fig.%201_0.png" type="image/png; length=1424935" title="Fig. 1.png">Fig. 1</a></span></td><td>1.36 MB</td> </tr>
<tr class="even"><td><span class="file"><img class="file-icon" alt="Image icon" title="image/png" src="/modules/file/icons/image-x-generic.png" /> <a href="https://imechanica.org/files/Fig.%202.png" type="image/png; length=790957" title="Fig. 2.png">Fig. 2</a></span></td><td>772.42 KB</td> </tr>
<tr class="odd"><td><span class="file"><img class="file-icon" alt="Image icon" title="image/png" src="/modules/file/icons/image-x-generic.png" /> <a href="https://imechanica.org/files/Fig.%203_0.png" type="image/png; length=1465280" title="Fig. 3.png">Fig. 3</a></span></td><td>1.4 MB</td> </tr>
<tr class="even"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/2021_Nature_Tough%20hydrogel.pdf" type="application/pdf; length=8211586" title="2021_Nature_Tough hydrogel.pdf">2021_Nature_Tough hydrogel</a></span></td><td>7.83 MB</td> </tr>
<tr class="odd"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/2021_AM_Tunable%20tough%20hydrogel.pdf" type="application/pdf; length=2073260" title="2021_AM_Tunable tough hydrogel.pdf">2021_Adv. Mater._Tunable tough hydrogel</a></span></td><td>1.98 MB</td> </tr>
<tr class="even"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/2020_ACS%20AMI_4D%20Printable%20Tough%20Gel.pdf" type="application/pdf; length=9294829" title="2020_ACS AMI_4D Printable Tough Gel.pdf">2020_ACS AMI_4D Printable Tough Gel</a></span></td><td>8.86 MB</td> </tr>
</tbody>
</table>
</div></div></div>Sun, 02 May 2021 18:55:25 +0000XiminHeGroup25145 at https://imechanica.orghttps://imechanica.org/node/25145#commentshttps://imechanica.org/crss/node/25145PhD Candidate required in Computational fracture mechanics
https://imechanica.org/node/24954
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/539">phd</a></div><div class="field-item odd"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/1859">creep</a></div><div class="field-item even"><a href="/taxonomy/term/13067">institute sponsored</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>I am looking for a PhD candidate who will be sponsered by my Institute to work in the area of fracture mechanics. </p>
<p>ABAQUS experience would be an advantage and concepts in fracture mechanics and finite elements will be desirable.</p>
<p>If you are interested to work in this area at Indian Institute of Technology Ropar in Metallurgical and Materials Engg. department, please dont hesitate to contact me at <a href="mailto:abhishek.tiwari@iitrpr.ac.in">abhishek.tiwari@iitrpr.ac.in</a></p>
<p>The APPLICATION IS OPEN FOR INTERNATIONAL CANDIDATES until 30Th APRIL 2021. APPLY NOW at: <a href="https://www.iitrpr.ac.in/phd-admissions">https://www.iitrpr.ac.in/phd-admissions</a></p>
<p>You may have a look at the CFM lab here: <a href="https://sites.google.com/view/cfmlab">https://sites.google.com/view/cfmlab</a></p>
<p>Have a look at department website at: <a href="https://mme.iitrpr.ac.in/people/faculty">https://mme.iitrpr.ac.in/people/faculty</a></p>
<p> </p>
<p>With best regards,</p>
<p><span><span>Dr. Abhishek Tiwari</span></span><span>Asst. Prof. Department of Metallurgical and Materials Engg.<br /></span><span>Room 113, Satish Dhawan Block</span><span>Indian Institute of Technology Ropar</span><span>Nangal Marg, Rupnagar, Punjab, India-140001<br /></span><span>Phone: 01881-23-2410</span><span><span>ORCID: </span><span>0000-0003-1038-4987</span></span><span><a href="mailto:abhishektiwari@daad-alumni.de" target="_blank" rel="noopener noreferrer"><span>http://www.iitrpr.ac.in/mme/abhishek</span></a><br /></span>
</p><p><a href="https://sites.google.com/view/cfmlab" target="_blank" rel="noopener noreferrer">https://sites.google.com/view/cfmlab</a> </p>
</div></div></div>Tue, 16 Feb 2021 06:05:21 +0000hermatician24954 at https://imechanica.orghttps://imechanica.org/node/24954#commentshttps://imechanica.org/crss/node/24954Postdoc vacancy (2.5 years) on multi-scale modelling of fatigue in 3D printed metals
https://imechanica.org/node/24919
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/3568">additive manufacturing</a></div><div class="field-item even"><a href="/taxonomy/term/9171">3D printing</a></div><div class="field-item odd"><a href="/taxonomy/term/3282">metals</a></div><div class="field-item even"><a href="/taxonomy/term/1040">Crystal plasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/846">FEM</a></div><div class="field-item even"><a href="/taxonomy/term/13056">fatigue indicators</a></div><div class="field-item odd"><a href="/taxonomy/term/447">Finite Element Method</a></div><div class="field-item even"><a href="/taxonomy/term/162">computational mechanics</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p align="justify">The use of 3D printed metal structures is taking a very fast ramp-up in industry. General Electric has demonstrated the possibility of printing titanium fuel injectors for their LEAP engine, EADS has printed a nacelle hinge bracket for the Airbus A320, Boeing is printing plastic inlet ducts for high-altitude aircrafts, hip implants and other prosthetics are exploiting the design freedom of additive manufacturing (AM),...</p>
<p align="justify">Additive manufacturing of titanium and inconel superalloys yields great potential for the aerospace industry (and others) as it allows the generation of geometrically complex structures with high specific strength, low density and high corrosion and creep resistance at high temperatures. However the fatigue life prediction of such components cannot be done with traditional fatigue models for traditionally manufactured metals, because the fatigue life is influenced by various factors that are specific for 3D printing: process parameters, induced voids and defects, microstructure, surface roughness, etc.</p>
<p align="justify">In this Postdoctoral position, it is the purpose to further develop multi-scale models for fatigue of AM metals, taking into account the microstructure of the material. Those models will be implemented in an already developed software environment. The final objective is to develop an industrial software solution that can be applied to complex AM components and predict their fatigue life. The position is a fully numerical position, requiring advanced knowledge in numerical simulations (finite element method, Representative Volume Element-based multi-scale modelling), fatigue mechanics, computational crystal plasticity and also on extreme value statistics.</p>
<p align="justify">The project will be carried out in close collaboration with a large number of industrial companies in the field of additive manufacturing (Siemens, Materialise, Sabca, ESMA,…).</p>
<p align="justify"><strong>Only candidates with a PhD degree in Computational Mechanics, Mechanical Engineering, Materials Science, Civil Engineering, (Applied) Physics or similar should apply. You have a strong background in computational mechanics and have strong programming skills (preferably in C++ and/or Python), you are interested to perform numerical research and to interact and collaborate with industry.</strong></p>
<p align="justify"><strong>More information can be found on:</strong></p>
<p align="justify"><span><strong><a href="https://composites.ugent.be/PhD_job_vacancies_PhD_job_positions_composites.html">https://composites.ugent.be/PhD_job_vacancies_PhD_job_positions_composit...</a></strong></span></p>
</div></div></div>Mon, 01 Feb 2021 15:13:10 +0000wvpaepeg24919 at https://imechanica.orghttps://imechanica.org/node/24919#commentshttps://imechanica.org/crss/node/24919Entropy Based Fatigue, Fracture, Failure Prediction and Structural Health Monitoring
https://imechanica.org/node/24881
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/1055">entropy</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item odd"><a href="/taxonomy/term/1810">structural health monitoring</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span>If you are interested in the most recent advances in physics-based </span><span>Fatigue, Fracture, Failure Prediction, and Structural Health Monitoring</span><br /><span>You may find this publication helpful.</span></p>
<p><span>free download site <a href="https://www.mdpi.com/books/pdfview/book/3299">https://www.mdpi.com/books/pdfview/book/3299</a></span></p>
</div></div></div>Thu, 21 Jan 2021 18:31:20 +0000Cemal Basaran24881 at https://imechanica.orghttps://imechanica.org/node/24881#commentshttps://imechanica.org/crss/node/24881Four Fully Funded PhD Positions
https://imechanica.org/node/24484
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/539">phd</a></div><div class="field-item odd"><a href="/taxonomy/term/5003">Functional Materials</a></div><div class="field-item even"><a href="/taxonomy/term/1152">Shape Memory Alloys</a></div><div class="field-item odd"><a href="/taxonomy/term/9341">steels</a></div><div class="field-item even"><a href="/taxonomy/term/934">Composites</a></div><div class="field-item odd"><a href="/taxonomy/term/169">Plasticity</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span class="ql-hashtag">#IPPTPAN</span> in collaboration with Department of Engineering at <span class="ql-hashtag">#NTU</span> is offering four fully supported <span class="ql-hashtag">#PhD</span> positions in the following fields:</p>
<p> </p>
<p>1) Non-linear thermo-mechanical behaviour of polycrystalline shape memory alloys undergoing complex loadings < <a href="https://www.ippt.pan.pl/_download/tem_prac_dok/2020_z_kowalewski_en_1.pdf">https://www.ippt.pan.pl/_download/tem_prac_dok/2020_z_kowalewski_en_1.pdf</a> ></p>
<p> </p>
<p>2) Thermo-mechanical fatigue characterization of metallic tubular structures fabricated by selective laser melting < <a href="https://www.ippt.pan.pl/_download/tem_prac_dok/2020_z_kowalewski_en_2.pdf">https://www.ippt.pan.pl/_download/tem_prac_dok/2020_z_kowalewski_en_2.pdf</a> ></p>
<p> </p>
<p>3) Thermo-mechanical response of 9Cr-1Mo-V-Nb (P91) steel under multi-axial loading: Experiments and numerical modelling < <a href="https://www.ippt.pan.pl/_download/tem_prac_dok/2020_z_kowalewski_en_3.pdf">https://www.ippt.pan.pl/_download/tem_prac_dok/2020_z_kowalewski_en_3.pdf</a> ></p>
<p> </p>
<p>4) Thermo-mechanical responses of fibre-reinforced composites subjected to multi-axial loading conditions: Experimental characterization and numerical life-time prediction < <a href="https://www.ippt.pan.pl/_download/tem_prac_dok/2020_z_kowalewski_en_4.pdf">https://www.ippt.pan.pl/_download/tem_prac_dok/2020_z_kowalewski_en_4.pdf</a> ></p>
<p> </p>
<p>Please get in touch if you are interested and send your CV to Prof. Kowalewski (<a href="mailto:zkowalew@ippt.pan.pl">zkowalew@ippt.pan.pl</a>), Dr Serjouei (<a href="mailto:ahmad.serjouei@ntu.ac.uk">ahmad.serjouei@ntu.ac.uk</a>), and Dr Bodaghi (<a href="mailto:mahdi.bodaghi@ntu.ac.uk">mahdi.bodaghi@ntu.ac.uk</a>).</p>
<p> </p>
<p><span class="ql-hashtag">#poland</span> <span class="ql-hashtag">#uk</span> <span class="ql-hashtag">#functionalmaterials</span> <span class="ql-hashtag">#shapememoryalloys</span> <span class="ql-hashtag">#steel</span> <span class="ql-hashtag">#composites</span> <span class="ql-hashtag">#plasticity</span> <span class="ql-hashtag">#complexloadings</span> <span class="ql-hashtag">#fatigue</span> </p>
</div></div></div>Sat, 01 Aug 2020 09:09:16 +0000Mahdi-Bodaghi24484 at https://imechanica.orghttps://imechanica.org/node/24484#commentshttps://imechanica.org/crss/node/24484Postdoctoral Research Fellowship at the University of Udine in Phase-Field modelling of fracture
https://imechanica.org/node/24410
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/871">postdoc</a></div><div class="field-item odd"><a href="/taxonomy/term/9383">phase-field</a></div><div class="field-item even"><a href="/taxonomy/term/32">fracture mechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal"><span><span lang="EN-US" xml:lang="EN-US">I am</span> seeking a full-time Postdoctoral Research <span lang="EN-US" xml:lang="EN-US">Fellow</span> in <span lang="EN-US" xml:lang="EN-US">Phase-Field modelling of fracture to join the Design of Machines group at the Polytechnic Engineering and Architecture Department (DPIA) of the University of Udine. The position is fixed-term for 1 year with funding provided by the European Social Fund (ESF).</span></span> </p>
<p class="MsoNormal"><span>The project will include, but not limited to, the<span lang="EN-US" xml:lang="EN-US"> development and verification of the Phase-Field method for the prediction of cracks nucleation and propagation using a commercial FEM code (e.g. Comsol). More in particular, the problems of interest will be the analysis of strongly heterogeneous materials in the contest of quasi-static and fatigue loading modes. Aimed at verifying the developed numerical models,</span> <span lang="EN-US" xml:lang="EN-US">the holder of the fellowship will have the</span> opportunity <span lang="EN-US" xml:lang="EN-US">to be</span> involved <span lang="EN-US" xml:lang="EN-US">in the design and execution of experimental tests at the laboratory of Advanced Materials of the DPIA. </span>The appointee will be able to work closely with <span lang="EN-US" xml:lang="EN-US">undergraduate and graduate </span>research students.</span></p>
<p class="MsoNormal"><span><span lang="EN-US" xml:lang="EN-US">The applicant</span> should possess a doctorate in a relevant field with experience in <span lang="EN-US" xml:lang="EN-US">FEM modelling & fracture mechanics and demonstrate willing to learn and put into practice experimental techniques. S</span>trong interpersonal skills<span lang="EN-US" xml:lang="EN-US"> are required alongside</span> the ability to work on a collaborative project.</span></p>
<p class="MsoNormal"><span>Informal enquiries may be addressed to <span lang="EN-US" xml:lang="EN-US">Enrico Salvati, DPhil</span> (<span lang="EN-US" xml:lang="EN-US">enrico.salvati</span>@<span lang="EN-US" xml:lang="EN-US">uniud.it</span></span><span><span>)</span></span></p>
<p class="MsoNormal"><span> </span></p>
</div></div></div>Tue, 21 Jul 2020 13:30:49 +0000enrico.salvati124410 at https://imechanica.orghttps://imechanica.org/node/24410#commentshttps://imechanica.org/crss/node/244104th INT. CONFERENCE ON DAMAGE MECHANICS
https://imechanica.org/node/23978
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/74">conference</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/866">damage mechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/11609">#Plasticity</a></div><div class="field-item even"><a href="/taxonomy/term/3948">computatinal solid mechanics</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span id="ember39639" class="ember-view"><span><span>Deadline for short abstract submission - February 15, 2020</span></span></span></p>
<p><span><a id="ember39643" class="feed-shared-text-view__hyperlink ember-view" tabindex="0" href="https://lnkd.in/dQUgfhv" target="_blank" rel="noopener noreferrer">https://lnkd.in/dQUgfhv</a></span></p>
</div></div></div>Mon, 10 Feb 2020 15:16:34 +0000Cemal Basaran23978 at https://imechanica.orghttps://imechanica.org/node/23978#commentshttps://imechanica.org/crss/node/23978Fatigue of Graphene
https://imechanica.org/node/23962
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/671">graphene</a></div><div class="field-item odd"><a href="/taxonomy/term/10717">graphene oxide</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span>Materials can suffer mechanical fatigue when subjected to cyclic loading at stress levels much lower than the ultimate tensile strength, and understanding this behaviour is critical to evaluating long-term dynamic reliability. The fatigue life and damage mechanisms of two-dimensional (2D) materials, of interest for mechanical and electronic applications, are currently unknown. Here, we present a fatigue study of freestanding 2D materials, specifically graphene and graphene oxide (GO). Using atomic force microscopy, monolayer and few-layer graphene were found to exhibit a fatigue life of more than 10^</span><span><span>9</span></span><span> cycles at a mean stress of 71 GPa and a stress range of 5.6 GPa, higher than any material reported so far. Fatigue failure in monolayer graphene is global and catastrophic without progressive damage, while molecular dynamics simulations reveal this is preceded by stress-mediated bond reconfigurations near defective sites. Conversely, functional groups in GO impart a local and progressive fatigue damage mechanism. This study not only provides fundamental insights into the fatigue enhancement behaviour of graphene-embedded nanocomposites, but also serves as a starting point for the dynamic reliability evaluation of other 2D materials.</span></p>
<p><span><span>Cui, T. </span><em>et al.</em><span> Fatigue of graphene.<strong> </strong></span><span><strong><em>Nat. Mater.</em></strong></span><span><strong> </strong>(2020). <a href="https://doi.org/10.1038/s41563-019-0586-y">https://doi.org/10.1038/s41563-019-0586-y</a></span></span></p>
<p><span><span>This work has been featured in <a href="https://phys.org/news/2020-01-stress-reveals-graphene-wont-pressure.html">PHYS.ORG</a>.</span></span></p>
</div></div></div>Sun, 02 Feb 2020 23:08:23 +0000Teng Cui23962 at https://imechanica.orghttps://imechanica.org/node/23962#commentshttps://imechanica.org/crss/node/23962Entropy Special Issue
https://imechanica.org/node/23768
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/11609">#Plasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/866">damage mechanics</a></div><div class="field-item even"><a href="/taxonomy/term/6659">contact mechanics; rolling contact; wheel-rail contact; friction; tribology</a></div><div class="field-item odd"><a href="/taxonomy/term/32">fracture mechanics</a></div><div class="field-item even"><a href="/taxonomy/term/427">failure</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/7907">Entropy generation</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p> </p>
<p><span class="si-deadline">Deadline for manuscript submissions: <span>30 November 2019</span></span><span>. </span></p>
<p> </p>
<p><span><span>Special Issue "Entropy Based Fatigue, Fracture, Failure Prediction and Structural Health Monitoring"</span></span></p>
<p><span><a href="https://www.mdpi.com/journal/entropy/special_issues/fatigue">https://www.mdpi.com/journal/entropy/special_issues/fatigue</a></span></p>
<p> </p>
</div></div></div>Fri, 22 Nov 2019 16:25:45 +0000Cemal Basaran23768 at https://imechanica.orghttps://imechanica.org/node/23768#commentshttps://imechanica.org/crss/node/23768Analytical Models for Fatigue Life Prediction of Metals in the Stress-Life Approach -- phd thesis by Pietro D’Antuono
https://imechanica.org/node/23693
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/11616">sn curves</a></div><div class="field-item even"><a href="/taxonomy/term/834">crack growth</a></div><div class="field-item odd"><a href="/taxonomy/term/12659">variable amplitudes</a></div><div class="field-item even"><a href="/taxonomy/term/5180">notches</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>dear collegues</p>
<p> I'd be very grateful if you could have a look, if not a deep reading, at the phd thesis of my last student, playing on classical results on uniaxial fatigue, but with a view of simple, unified perspective on constant and varying amplitude fatigue. We made large use of e-fatigue.com web site and the data in there.<br clear="all" /> Thanks in advance for any remark. The final thesis will be submitted in few weeks time.</p>
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</div></div></div>Sat, 19 Oct 2019 18:49:58 +0000Mike Ciavarella23693 at https://imechanica.orghttps://imechanica.org/node/23693#commentshttps://imechanica.org/crss/node/23693SEM Fracture and Fatigue Call for Papers
https://imechanica.org/node/23600
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/74">conference</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/48">conferences</a></div><div class="field-item odd"><a href="/taxonomy/term/185">experimental mechanics</a></div><div class="field-item even"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal"><span>Dear Colleagues,</span></p>
<p class="MsoNormal"><span>We invite you to submit a paper to the <strong>2020 Society for Experimental Mechanics (SEM) Annual Meeting </strong>in one of the many sessions in the <strong>Fatigue and Fracture Track</strong>. See below for further information on these sessions, and please forward this to others who may be interested.</span></p>
<p class="MsoNormal"><span>The conference will be held in <strong>Orlando, Florida </strong>from June 8-11, 2020.</span><span> <strong>Abstracts are due October 21, 2019</strong> via the SEM website. General submissions are always welcome. <strong>When submitting your abstract for a specific session please enter the name of the session on the abstract submission form.</strong> Also please email a copy of your abstract to the session organizer(s) directly.</span></p>
<p class="MsoNormal"><span>Conference Website: </span><span class="MsoHyperlink"><span><a href="https://sem.org/annual">https://sem.org/annual</a></span></span></p>
<p class="MsoNormal"><span>The abstract submission link is: </span><span class="MsoHyperlink"><span><a href="https://sem.org/annualauthor">https://sem.org/annualauthor</a></span></span><span> (click “Upload/Edit Submission” button)</span></p>
<p class="MsoNormal"><span>Although SEM encourages the submission of full conference papers or extended abstracts, <strong>oral-only presentations are welcome in the following sessions</strong>.</span></p>
<p class="MsoNormal"><span>We are looking forward to seeing you at SEM in 2020!</span></p>
<p class="MsoNormal"><strong><span>SEM Fracture and Fatigue Session Organizers:</span></strong></p>
<p class="MsoNormal"><span>Shuman Xia Allison Beese Ryan Berke<span> </span>Garrett Pataky <br /></span><span>Jay Carroll<span> </span>Kavan Hazeli Siva Nadimpalli </span><span>Scott Grutzik<br /></span><span>Onome Scott-Emaukpor<span> </span> <span> </span>Shelby Hutchens <span> </span>Bala Sundaram<br /></span><span>Phillip Noell<span> </span>Will LePage Bikramjit Mukherjee</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>1.</span></strong><span> </span><strong><span>In Situ Techniques</span></strong><strong><span> and Microscale Effects </span></strong><strong><span>on Mechanical Behaviors<br /></span></strong><span>Organizer(s): Jay Carroll<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:jcarrol@sandia.gov"><span>jcarrol@sandia.gov</span></a></span></span></p>
<p class="MsoNormal"><strong><span>2. Fatigue and Fracture under Extreme Environments (</span></strong><em><span>In collaboration with Thermomechanical TD and Time Dependent Materials TD)<br /></span></em><span>Organizer(s): Ryan Berke, Kavan Hazeli<br /></span><span>Email: </span><span><a href="mailto:ryan.berke@usu.edu" target="_blank" rel="noopener noreferrer"><span>ryan.berke@usu.edu</span></a></span><span>, </span><span><a href="mailto:kavan.hazeli@uah.edu" target="_blank" rel="noopener noreferrer"><span>kavan.hazeli@uah.edu</span></a></span></p>
<p class="MsoNormal"><strong><span>3. Mechanics of Energy Materials<br /></span></strong><span>Organizer(s): Shuman Xia, Siva Nadimpalli, Will LePage<br /></span><span>Email: </span><span><a href="mailto:shuman.xia@me.gatech.edu" target="_blank" rel="noopener noreferrer"><span>shuman.xia@me.gatech.edu</span></a></span><span>, </span><span><a href="mailto:nadimpal@njit.edu" target="_blank" rel="noopener noreferrer"><span>nadimpal@njit.edu</span></a></span><span>, </span><span class="MsoHyperlink"><span><a href="mailto:wlepage@umich.edu">wlepage@umich.edu</a></span></span></p>
<p class="MsoNormal"><strong><span>4. Vibration Effects and High Cycle Fatigue in Fracture and Fatigue<br /></span></strong><span>Organizer(s): Ryan Berke, Onome Scott-Emuakpor<br /></span><span>Email: </span><span><a href="mailto:ryan.berke@usu.edu" target="_blank" rel="noopener noreferrer"><span>ryan.berke@usu.edu</span></a></span><span>, </span><span><a href="mailto:onome.scott-emuakpor.1@us.af.mil" target="_blank" rel="noopener noreferrer"><span>onome.scott-emuakpor.1@us.af.mil</span></a></span></p>
<p class="MsoNormal"><strong><span>5. Fracture and Fatigue in </span></strong><strong><span>Additive Manufacturing</span></strong><em><span> (In collaborations with Additive Manufacturing Track)<br /></span></em><span>Organizer(s): Garrett Pataky, Allison Beese <br /></span><span>Email:</span><span> <a href="mailto:gpataky@clemson.edu" target="_blank" rel="noopener noreferrer"><span>gpataky@clemson.edu</span></a></span><span>, </span><span><a href="mailto:amb961@psu.edu" target="_blank" rel="noopener noreferrer"><span>amb961@psu.edu</span></a></span><span> </span></p>
<p class="MsoNormal"><strong><span>6. Interfacial and Mixed-Mode Fracture<br /></span></strong><span>Organizer(s): Scott Grutzik, Bala Sundaram<br /></span><span>Email: </span><span><a href="mailto:sjgrutz@sandia.gov" target="_blank" rel="noopener noreferrer"><span>sjgrutz@sandia.gov</span></a></span><span>, </span><span class="MsoHyperlink"><span><a href="mailto:meenakshb@corning.com">meenakshb@corning.com</a></span></span></p>
<p class="MsoNormal"><strong><span>7. Integration of Models and Experiments<br /></span></strong><span>Organizer(s): Scott Grutzik<br /></span><span>Email: </span><span><a href="mailto:sjgrutz@sandia.gov" target="_blank" rel="noopener noreferrer"><span>sjgrutz@sandia.gov</span></a></span></p>
<p class="MsoNormal"><strong><span>8. Fracture and Fatigue in Brittle Materials<br /></span></strong><span>Organizer(s): Bala Sundaram, Scott Grutzik<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:meenakshb@corning.com">meenakshb@corning.com</a></span></span><span>, </span><span><a href="mailto:sjgrutz@sandia.gov" target="_blank" rel="noopener noreferrer"><span>sjgrutz@sandia.gov</span></a></span></p>
<p class="MsoNormal"><strong><span>9. Fracture and Fatigue in Elastomers and Gels (</span></strong><em><span>In collaboration with Time Dependent Materials TD)<br /></span></em><span>Organizer(s): Shelby Hutchens, Bikramjit Mukherjee<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:hutchs@illinois.edu">hutchs@illinois.edu</a>, </span></span><a href="mailto:bmukherjee1@dow.com">bmukherjee1@dow.com</a></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong><span>10. Damage Initiation Mechanisms and the Influence of Incipient Damage<br /></span></strong><span>Organizer(s): Kavan Hazeli, Phillip Noell<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:kavan.hazeli@uah.edu">kavan.hazeli@uah.edu</a></span></span><span>, </span><span class="MsoHyperlink"><span><a href="mailto:pnoell@sandia.gov">pnoell@sandia.gov</a></span></span></p>
<p class="MsoNormal"><strong><span>11. Advances in Mechanics of Deformation, Plasticity and Failure<br /></span></strong><span>Organizer(s): Will LePage, Jay Carroll<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:wlepage@umich.edu">wlepage@umich.edu</a></span></span><span>, </span><span class="MsoHyperlink"><span><a href="mailto:jcarrol@sandia.gov"><span>jcarrol@sandia.gov</span></a></span></span></p>
<p class="MsoNormal"><strong><span> </span></strong></p>
<p class="MsoNormal"><strong><span>1.</span></strong><span> </span><strong><span>In Situ Techniques</span></strong><strong><span> and Microscale Effects </span></strong><strong><span>on Mechanical Behaviors<br /></span></strong><span>Organizer(s): Jay Carroll<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:jcarrol@sandia.gov">jcarrol@sandia.gov</a></span></span></p>
<p class="MsoNormal"><span>In situ techniques provide a wealth of information for the understanding of fatigue and fracture mechanisms and behavior. Techniques including in situ digital image correlation (DIC) with optical or scanning electron microscope imaging, in situ neutron diffraction, in situ synchrotron imaging, and tomography can allow for the observation and identification of failure mechanisms across a wide range of length and time scales. The usefulness of in situ experimental data has been recognized and is becoming the standard for validation of models and qualification of components.</span></p>
<p class="MsoNormal"><span>Deformation and fracture involve processes at the atomic and molecular length scales. However, deformation and fracture have been approached historically on length scales that tend to homogenize the material, due to a lack of small-scale interrogation tools</span><span>. Over the past decade, the application of modern tools for the fabrication and interrogation of materials and structures at the micron size scale and below is revolutionizing mechanics. It is now possible to measure the mechanical behavior of structures with dimensions well below one micron, where surface effects and microstructure become critical. In larger scale structures, deformations can be captured at nanometer size scales, allowing for the measurement of strains in separate grains, or in separate phases of a material, as a crack progresses or damage accumulates.</span></p>
<p class="MsoNormal"><span>This symposium will bring together researchers using in situ and/or small scale experimental techniques to address common mechanics issues. In addition to fatigue and fracture, experiments on other topics, such as plasticity, creep, dynamic effects, and engineering development, are welcome.</span> <span>Novel experimental methods, studies linking </span><span>size scales, and studies linking experiments to theory or simulation are particularly sought.</span></p>
<p class="MsoNormal"><strong><span> </span></strong></p>
<p class="MsoNormal"><strong><span>2. Fatigue and Fracture under Extreme Environments (</span></strong><em><span>In collaboration with Thermomechanical TD and Time Dependent Materials TD)<br /></span></em><span>Organizer(s): Ryan Berke, Kavan Hazeli<br /></span><span>Email: </span><span><a href="mailto:ryan.berke@usu.edu" target="_blank" rel="noopener noreferrer"><span>ryan.berke@usu.edu</span></a></span><span>, </span><span><a href="mailto:hazeli@jhu.edu" target="_blank" rel="noopener noreferrer"><span>hazeli@jhu.edu</span></a></span></p>
<p class="MsoNormal"><span>This session is intended to provide a forum for researchers from the academic, industrial and government sectors to share, discuss, and debate the latest improvements on the science, technology, and application fronts in fatigue and fracture under extreme environments. Of particular interest is to develop an understanding of material behavior under extreme conditions that include but not limited to cyclic loading, photonic and phononic interactions, elevated temperatures, highly corrosive environments, high radiation fluxes or a multitude of above factors. The goal is to investigate the constitutive response and roles of evolving intrinsic field variables to provide kinematic, kinetic and dynamic descriptions of the way cracks nucleate and propagate through solids.</span></p>
<p class="MsoNormal"><span>Abstracts are solicited in (but not limited to) the following topics:</span></p>
<p class="MsoListParagraphCxSpFirst"><span><span>·<span> </span></span></span><span>Fatigue strength and resistance under extreme environments</span></p>
<p class="MsoListParagraphCxSpMiddle"><span><span>·<span> </span></span></span><span>Quantitative and/or qualitative relationships between micro-macro environments and fatigue properties along with life prediction under extreme environments</span></p>
<p class="MsoListParagraphCxSpMiddle"><span><span>·<span> </span></span></span><span>Thermal and thermomechanical fatigue</span></p>
<p class="MsoListParagraphCxSpMiddle"><span><span>·<span> </span></span></span><span>Photonic and phononic material response</span></p>
<p class="MsoListParagraphCxSpMiddle"><span><span>·<span> </span></span></span><span>Dynamic fatigue</span></p>
<p class="MsoListParagraphCxSpMiddle"><span><span>·<span> </span></span></span><span>High cycle fatigue</span></p>
<p class="MsoListParagraphCxSpMiddle"><span><span>·<span> </span></span></span><span>Creep fatigue and/or creep rupture</span></p>
<p class="MsoListParagraphCxSpLast"><span><span>·<span> </span></span></span><span>Microstructure evolution and stability</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>3. Mechanics of Energy Materials<br /></span></strong><span>Organizer(s): Shuman Xia, Siva Nadimpalli, Will LePage<br /></span><span>Email: </span><span><a href="mailto:shuman.xia@me.gatech.edu" target="_blank" rel="noopener noreferrer"><span>shuman.xia@me.gatech.edu</span></a></span><span>, </span><span><a href="mailto:nadimpal@njit.edu" target="_blank" rel="noopener noreferrer"><span>nadimpal@njit.edu</span></a></span><span>, </span><span class="MsoHyperlink"><span><a href="mailto:wlepage@umich.edu">wlepage@umich.edu</a></span></span></p>
<p class="MsoNormal"><span>Energy materials hold one of the keys to fundamental advances in generation, storage, conversion, absorption, and harvesting of energy for a broad range of automotive, industrial and defense applications. The successful development and deployment of these materials relies critically on a fundamental understanding of strongly coupled multiphysical phenomena, including mechanical deformation, heat and mass transfer, phase transformation, electromagnetism, and chemistry. The objective of this symposium is to provide a forum for the presentation and discussion of experimental and integrated computational/experimental investigations in this highly interdisciplinary field. The symposium will cover the latest research advances from the mechanics and materials prospective and will seek to identify new research challenges by exploring interfaces with other disciplines. Suggested topics include but are not limited to: in-situ and ex-situ experimental characterization of coupled phenomena between mechanical and other physical processes, microstructure/property relationships, phase transformation in energy materials, multiscale characterizations, and integrative experimental and modeling approaches.</span></p>
<p class="MsoNormal"><strong><span> </span></strong></p>
<p class="MsoNormal"><strong><span>4. Vibration Effects and High Cycle Fatigue in Fracture and Fatigue<br /></span></strong><span>Organizer(s): Ryan Berke, Onome Scott-Emuakpor<br /></span><span>Email: </span><span><a href="mailto:ryan.berke@usu.edu" target="_blank" rel="noopener noreferrer"><span>ryan.berke@usu.edu</span></a></span><span>, </span><span><a href="mailto:onome.scott-emuakpor.1@us.af.mil" target="_blank" rel="noopener noreferrer"><span>onome.scott-emuakpor.1@us.af.mil</span></a></span></p>
<p class="MsoNormal"><span>High Cycle Fatigue (HCF) is important for many engineering applications, such as gas turbine engines and other rotating machinery. In order to ensure the performance, safety, and reliability of such assemblies, materials must be characterized to withstand HCF under relevant operating conditions. However, HCF experiments can be costly and time-consuming -- a single axial fatigue test operating at 40 Hz requires almost 70 hours to accumulate enough cycles (on the order of 10^7) to generate a single point on an S-N Curve. Compared to axial test methods, vibration-based methods can not only better reproduce the operating environments of high cycle machinery, but can be conducted at much higher frequencies and thus accumulate HCF data more quickly. In this symposium, abstracts are sought which explore the use of vibration-based methods in experimental mechanics, and/or new advances in HCF characterization. Topics may include, but are not limited to, use of computational approaches, statistical models, experimental methods, and/or error quantification.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>5. Fracture and Fatigue in </span></strong><strong><span>Additive Manufacturing</span></strong><em><span> (In collaborations with Additive Manufacturing Track)<br /></span></em><span>Organizer(s): Garrett Pataky, Allison Beese <br /></span><span>Email: </span><span> <a href="mailto:gpataky@clemson.edu" target="_blank" rel="noopener noreferrer"><span>gpataky@clemson.edu</span></a></span><span>, </span><span><a href="mailto:amb961@psu.edu" target="_blank" rel="noopener noreferrer"><span>amb961@psu.edu</span></a></span></p>
<p class="MsoNormal"><span>Additive manufacturing (AM) of metals, polymers, and ceramics enables the layer-by-layer fabrication of complex geometries that cannot be fabricated through traditional techniques, as well as the fabrication of custom components, and the repair of existing parts. However, the processing of components by AM varies drastically from traditional processing techniques. For example, AM typically involves thermal cycles not seen in conventional processing, resulting in microstructures and properties that widely vary from traditionally-manufactured counterparts. Therefore, in order to open the application space for, and wider adoption of AM, an understanding of the processing, structure, and mechanical property relationships is required. In this symposium, we seek experimental and computational studies that link processing to structure, and/or structure to mechanical properties in materials made by AM, including, but not limited to, metals, polymers, and ceramics.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>6. Interfacial and Mixed-Mode Fracture<br /></span></strong><span>Organizer(s): Scott Grutzik, Bala Sundaram<br /></span><span>Email: </span><span><a href="mailto:sjgrutz@sandia.gov" target="_blank" rel="noopener noreferrer"><span>sjgrutz@sandia.gov</span></a></span><span>, </span><span class="MsoHyperlink"><span><a href="mailto:meenakshb@corning.com">meenakshb@corning.com</a></span></span></p>
<p class="MsoNormal"><span>Many engineering designs involve interfaces between different materials. These interfaces can act as flaws resulting in failure that initiates at or propagates along them. Analysis of such interfacial failures are extremely complex. Depending on the relative toughness between the bonded materials, interfacial toughness and its orientation, the crack may be restricted to or can kink out of the interface. Under certain conditions, the crack may even branch into multiple cracks at the interface. Measurement of interfacial toughness for wide range of mode-mixities is essential as a constrained crack often propagates along an interface under varying mode-mixity. This makes the characterization and analysis of interfaces significantly more challenging than bulk materials, which are often characterized by their mode-I (opening mode) toughness. This session will focus on interfacial fracture phenomena such as mode-mixity, cohesive/adhesive failure, traction separation laws, crack kinking, unique specimen geometries, mixed-mode fracture, crack branching at an interface, interfacial toughness along with interfacial fatigue for both quasi-static and dynamic loading conditions.</span></p>
<p class="MsoNormal"><span><span> </span></span></p>
<p class="MsoNormal"><strong><span>7. Integration of Models and Experiments<br /></span></strong><span>Organizer(s): Scott Grutzik<br /></span><span>Email: </span><span><a href="mailto:sjgrutz@sandia.gov" target="_blank" rel="noopener noreferrer"><span>sjgrutz@sandia.gov</span></a></span></p>
<p class="MsoNormal"><span>Models and experiments have much to learn from one another. The integration of these two disciplines at all scales, promises to accelerate our understanding of fracture and fatigue, and related phenomena. This will be important for designing future materials with enhanced fracture resistance and for designing structures that fully exploit these properties. To foster further interaction of experiments and modeling, this session will provide a venue for work emphasizing the integrating and validating models with experiments. The phenomena discussed will include mechanical behavior of materials such as fatigue, fracture, plasticity, creep, etc. Expected topics will include novel combined modeling/experimental techniques, different approaches to model validation, and work in which models and experiments inform one another. This session will bring together researchers from a number of fields in including crystal plasticity; fatigue crack growth; fracture and ductile failure; and effects of combined mechanical loading and extreme environments such as corrosion, elevated temperatures, hydrogen embrittlement, and radiation effects. Presentations with a wide range of backgrounds from basic research to engineering development are welcome.</span></p>
<p class="MsoNormal"><strong><span> </span></strong></p>
<p class="MsoNormal"><strong><span>8. Fracture and Fatigue in Brittle Materials<br /></span></strong><span>Organizer(s): Bala Sundaram, Scott Grutzik<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:meenakshb@corning.com">meenakshb@corning.com</a></span></span><span>, </span><span><a href="mailto:sjgrutz@sandia.gov" target="_blank" rel="noopener noreferrer"><span>sjgrutz@sandia.gov</span></a></span></p>
<p class="MsoNormal"><span>Brittle materials such as glass and ceramics with their high stiffness, high hardness and low failure strains pose significant challenges for their fracture study. Although these attributes have led to them being used widely for various engineering applications, unlike other materials, their strength is not an intrinsic property but rather dependent on the flaw distribution. Glass is very much susceptible to static fatigue - the duration of the application of the loading influences the strength of glass - especially in high humidity environment. Ceramics on other hand exhibit cyclic fatigue. Then there exists glass-ceramics, which is a material system with both amorphous and crystalline phase. With rapid advancement in computational capabilities, some of these complex behaviors can be simulated numerically. Other brittle glassy materials, apart from inorganic glasses and ceramics, that show similar characteristics are also welcome in this session.<span> </span>This session aims to connect several interesting topics such as stress corrosion, static fatigue, slow crack growth, indentation and scratch, fast fracture, crack branching, characterization techniques and specialized test methods, cyclic fatigue, transformation toughening, R-curves etc. - be it computational or experiment based.</span></p>
<p class="MsoNormal"><strong><span> </span></strong></p>
<p class="MsoNormal"><strong><span>9. Fracture and Fatigue in Elastomers and Gels (</span></strong><em><span>In collaboration with Time Dependent Materials TD)<br /></span></em><span>Organizer(s): Shelby Hutchens, Bikramjit Mukherjee<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:hutchs@illinois.edu">hutchs@illinois.edu</a>, </span></span><a href="mailto:bmukherjee1@dow.com">bmukherjee1@dow.com</a></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>In contrast to high-load structural applications, soft materials find use when engineering designs require large deformations and high compliance. Though these properties enable protective, conformable, or biocompatible designs, they pose challenges in failure characterization. Material fragility may prevent the use of standard fracture geometries and testing procedures. Measurement of the large deformations requires advanced strain field characterization techniques (e.g., particle tracking, large deformation DIC, light scattering). Difficulties arise when attempting to apply linear elastic fracture mechanics framework to characterize fracture of soft materials and structures. Besides, instabilities associated with interfacial (e.g. viscous/elastic finger formation) and bulk fracture (e.g., cavitation or fracture) of soft materials have become a rich area of experimental and theoretical research providing unique avenues to engineer bio-mimetic properties. In addition, many soft materials, including elastomers, gels, foams, and biological tissues, possess properties that are highly sensitive to environmental conditions (e.g., temperature, humidity). Somewhat uniquely, the solution-like nature of many soft materials enable the use of molecular sensors (e.g., mechano-chemistry) to probe the nature of micro structural contributions to failure processes. Abstracts are solicited on the above or related topics relevant to the characterization of soft fracture.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>10. Damage Initiation Mechanisms and the Influence of Incipient Damage<br /></span></strong><span>Organizer(s): Kavan Hazeli, Phillip Noell<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:kavan.hazeli@uah.edu">kavan.hazeli@uah.edu</a></span></span><span>, </span><span class="MsoHyperlink"><span><a href="mailto:pnoell@sandia.gov">pnoell@sandia.gov</a></span></span></p>
<p class="MsoNormal"><span>This session is intended to provide a forum for researchers from the academic, industrial and government sectors to discuss the latest understanding about damage initiation mechanisms under a wide range of environments including plasticity, fatigue, creep, thermomechanical loading, impact, corrosive environments, and radiation. The particular emphasis is on understanding how damage initiates at the micro and nano scales and the effects of this incipient damage on the mechanical properties of the material leading to fracture.</span></p>
<p class="MsoNormal"><strong><span> </span></strong></p>
<p class="MsoNormal"><strong><span>11. Advances in Mechanics of Deformation, Plasticity and Failure<br /></span></strong><span>Organizer(s): Will LePage, Jay Carroll<br /></span><span>Email: </span><span class="MsoHyperlink"><span><a href="mailto:wlepage@umich.edu">wlepage@umich.edu</a></span></span><span>, </span><span class="MsoHyperlink"><span><a href="mailto:jcarrol@sandia.gov"><span>jcarrol@sandia.gov</span></a></span></span></p>
<p class="MsoNormal"><span>This session welcomes submissions from a broad field encompassing many phenomena beyond the scopes of the above sessions, such as plasticity, non-linear elasticity, time dependent deformation, novel evaluation techniques, etc. The goal is to allow attendees to gain exposure to a wide range of different phenomena in mechanics of deformation, plasticity and failure.</span></p>
</div></div></div>Mon, 23 Sep 2019 20:20:00 +0000Shuman_Xia23600 at https://imechanica.orghttps://imechanica.org/node/23600#commentshttps://imechanica.org/crss/node/23600PhD Positions Available (up to 2) on Fatigue Resistance of Bone
https://imechanica.org/node/23349
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/315">bone</a></div><div class="field-item odd"><a href="/taxonomy/term/584">mechanics</a></div><div class="field-item even"><a href="/taxonomy/term/1268">deformation</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/427">failure</a></div><div class="field-item odd"><a href="/taxonomy/term/12114">bone disease</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal"><strong><span lang="EN-AU" xml:lang="EN-AU">Bones not only support and protect the various organs of our body but provide structure and enable mobility making them the most important structural materials in the human body. While aging, diet and health are known to significantly affect the structural integrity and fracture resistance of bone, fatigue, a significantly more important loading condition, is rarely studied. The aim of this project is to develop an understanding of the deformation mechanisms that occur during cyclic loading of young and aged bone and investigate the influence of diseases like osteoporosis or diabetes in combination with administered drugs on its fatigue resistance.</span></strong></p>
<p class="MsoNormal"><span lang="EN-AU" xml:lang="EN-AU">This opportunity is for a PhD scholarship for up to two students commencing in 2020 which includes an annual stipend of AUD$ 41,209k (2019 rate, indexed) tax free, fully covered UNSW tuition fees, and up to AUD$ 10k p.a. for career development and conference travel. The project duration is four years.</span></p>
<p class="MsoNormal"><span lang="EN-AU" xml:lang="EN-AU">This scholarship is given only to the most competitive applicants. Candidates ideally hold a Bachelor or Master’s degree in Biomechanics/Biomedical Engineering, Materials Science & Engineering or Mechanical Engineering from a top university. Applicants should have strong interest in biological research and/or fracture and fatigue as well as a strong desire to perform experimental research and publish in highly ranked, peer-reviewed field-specific and interdisciplinary journals. Experimental skills such as structural and mechanical characterisation, as well as synchrotron and tomography experience are anticipated. Furthermore, they should be ambitious and resilient team-players with high leadership potential. The successful candidates will be supervised by a team of academics from both Biomedical Engineering (A/Prof. Penny Martens) and Mechanical Engineering (Dr. Bernd Gludovatz and Prof. Jay Kruzic).</span></p>
<p class="MsoNormal"><span lang="EN-AU" xml:lang="EN-AU">Application information about UNSW Sydney and the Scientia PhD program can be found in the Biomedical Sciences strategy area of the Faculty of Engineering at: <span class="MsoHyperlink"><a href="http://www.2025.unsw.edu.au/apply/">http://www.2025.unsw.edu.au/apply/</a></span> </span></p>
<p class="MsoNormal"><span lang="EN-AU" xml:lang="EN-AU">The deadline to submit an expression of interest is 14 July 2019.</span></p>
<p class="MsoNormal"><span lang="EN-AU" xml:lang="EN-AU">Further questions can be directed at the supervisor team:<br /><a href="mailto:b.gludovatz@unsw.edu.au">b.gludovatz@unsw.edu.au</a> – <a href="mailto:p.martens@unsw.edu.au">p.martens@unsw.edu.au</a> – <a href="mailto:j.kruzic@unsw.edu.au">j.kruzic@unsw.edu.au</a></span></p>
</div></div></div>Mon, 03 Jun 2019 22:45:58 +0000b.gludovatz23349 at https://imechanica.orghttps://imechanica.org/node/23349#commentshttps://imechanica.org/crss/node/23349Open PhD position in multi-resolution fatigue modeling at the University of Tennessee
https://imechanica.org/node/23332
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/6900">polycrystal plasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>We have an open PhD position starting in the Spring or Fall semester 2020 at the Computational Laboratory for the Mechanics of Interfaces at the University of Tennessee – Knoxville. A high quality PhD student is sought to study failure of structural materials under fatigue by developing a novel computational approach that explicitly targets traction equilibrium and displacement compatibility along the grain boundaries. Potential aspects of the research topic include: Discontinuous Galerkin methods for interfacial mechanics, multi-resolution computational solid mechanics, high performance and adaptive computing, and data analytics with machine learning. See more information at <a href="http://clmi.utk.edu/research/">http://clmi.utk.edu/research/</a>.</p>
<p>Candidates should possess a master’s degree in civil, mechanical, or other related engineering field at the time of enrollment at UTK. A strong background in computational mechanics, materials science of metals, and/or computer programming in MATLAB and FORTRAN is desired. US citizenship or residency is also desired, though not required.</p>
<p>If interested, contact Dr. Truster directly at <a href="mailto:ttruster@utk.edu">ttruster@utk.edu</a>. Please include your CV along with a brief description of prior research experiences and how your interests align with the research conducted at CLMI. In your CV, include: GPA, GRE test scores, and publication list. Minimum GRE scores for admission are Q = 155 and Q+V = 310. Only shortlisted candidates will be contacted after May 31.</p>
</div></div></div>Mon, 27 May 2019 21:16:53 +0000Timothy Truster23332 at https://imechanica.orghttps://imechanica.org/node/23332#commentshttps://imechanica.org/crss/node/23332Call for papers: International Workshop on Plasticity, Damage and Fracture
https://imechanica.org/node/23217
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/74">conference</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/11609">#Plasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/12420">#fracture</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/10122">Materials with Microstructure</a></div><div class="field-item even"><a href="/taxonomy/term/7389">Computational Fracture Mechancis</a></div><div class="field-item odd"><a href="/taxonomy/term/866">damage mechanics</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p> </p>
<p class="MsoBodyText3"><span lang="en-US" xml:lang="en-US">Dear colleagues,</span></p>
<p class="MsoBodyText3"><span lang="en-US" xml:lang="en-US">We would like to draw your attention to the </span><a href="http://iwpdf.ae.metu.edu.tr/"><span lang="en-US" xml:lang="en-US">International Workshop on Plasticity, Damage and Fracture of Engineering Materials</span></a><span lang="en-US" xml:lang="en-US">, which will take place in </span><span lang="en-US" xml:lang="en-US">Ankara, Turkey on 22-23 August 2019</span><span lang="en-US" xml:lang="en-US">. The deadlines for abstract and full paper submissions are </span><span lang="en-US" xml:lang="en-US">April 19 </span><span lang="en-US" xml:lang="en-US">and </span><span lang="en-US" xml:lang="en-US">June 17 2019</span><span lang="en-US" xml:lang="en-US">,</span><span lang="en-US" xml:lang="en-US">respectively. </span></p>
<p class="MsoBodyText3"><span lang="en-US" xml:lang="en-US">The workshop will include invited lectures by both early career and experienced researchers in the field of plasticity, damage and fracture, and presentations by the participants (oral or poster). The meeting and the publication of full papers in </span><a href="https://www.journals.elsevier.com/procedia-structural-integrity"><span lang="en-US" xml:lang="en-US">Procedia Structural Integrity</span></a><span lang="en-US" xml:lang="en-US"> is supported by the </span><a href="https://www.structuralintegrity.eu/"><span lang="en-US" xml:lang="en-US">European Structural Integrity Society</span></a><span lang="en-US" xml:lang="en-US">. Please note that s</span><span><span>ubmission of full papers is not mandatory. Abstract submission for IWPDF 2019 is handled via this <a href="https://easychair.org/conferences/?conf=iwpdf2019">EasyChair link</a>. The abstract template could be downloaded <a href="http://iwpdf.ae.metu.edu.tr/IWPDF_Abstract_Template.docx">here</a>. The registration is open at the <a href="https://www.eventbrite.co.uk/e/1st-international-workshop-on-plasticity-damage-and-fracture-of-engineering-materials-registration-59271737362?utm_term=eventurl_text">eventbrite link</a>. </span></span></p>
<p class="MsoBodyText3"><span lang="en-US" xml:lang="en-US">The confirmed invited lecturer list is as follows:</span><span lang="en-US" xml:lang="en-US"><br /></span><span lang="en-US" xml:lang="en-US">Majid Reza Ayatollahi</span><span lang="en-US" xml:lang="en-US">, Iran University of Science & Technology, Iran<br /></span><span lang="en-US" xml:lang="en-US">Laurence Brassart</span><span lang="en-US" xml:lang="en-US">, Monash University, Australia <br /></span><span lang="en-US" xml:lang="en-US">Johan Hoefnagels</span><span lang="en-US" xml:lang="en-US">, Eindhoven University of Technology, The Netherlands<br /></span><span lang="en-US" xml:lang="en-US">Kaan Inal</span><span lang="en-US" xml:lang="en-US">, University of Waterloo, Canada<br /></span><span lang="en-US" xml:lang="en-US">David Morin</span><span lang="en-US" xml:lang="en-US">, Norwegian University of Science and Technology, Norway<br /></span><span lang="en-US" xml:lang="en-US">Kamran Nikbin</span><span lang="en-US" xml:lang="en-US">, Imperial College London, UK. <br /></span><span lang="en-US" xml:lang="en-US">Thomas Pardoen</span><span lang="en-US" xml:lang="en-US">, Université catholique de Louvain (UCL), Belgium<br /></span><span lang="en-US" xml:lang="en-US">Cem Tasan</span><span lang="en-US" xml:lang="en-US">, Massachusetts Institute of Technology, US</span></p>
<p class="MsoBodyText3"><span lang="en-US" xml:lang="en-US">Please visit the workshop website for detailed information: </span><span lang="en-US" xml:lang="en-US"><a href="http://iwpdf.ae.metu.edu.tr/">http://iwpdf.ae.metu.edu.tr/</a></span></p>
<p class="MsoBodyText3"><span lang="en-US" xml:lang="en-US">We are looking forward to receiving your contribution for a fruitful discussion in Ankara.</span></p>
<p class="MsoBodyText3"><span lang="en-US" xml:lang="en-US">Best regards,</span></p>
<p class="MsoBodyText3"><span lang="en-US" xml:lang="en-US">Tuncay Yalcinkaya (On behalf of the organizing committee)</span></p>
<p> </p>
<p class="MsoNormal"><span lang="en-US" xml:lang="en-US"> </span></p>
<p> </p>
<p> </p>
</div></div></div>Tue, 02 Apr 2019 22:35:17 +0000Tuncay Yalcinkaya23217 at https://imechanica.orghttps://imechanica.org/node/23217#commentshttps://imechanica.org/crss/node/23217Critical porosity in the fatigue of additively manufactured IN718 via crystal plasticity modeling
https://imechanica.org/node/23187
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/12451">Critical Porostiy</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/1040">Crystal plasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/3568">additive manufacturing</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><a class="doi" title="Persistent link using digital object identifier" href="https://doi.org/10.1016/j.matdes.2018.04.022" rel="noreferrer noopener" target="_blank">https://doi.org/10.1016/j.matdes.2018.04.022</a></p>
<p>Highlights<br /></p><p id="sp0140">1. Critical porosity is estimated in additively manufactured IN718 via crystal plasticity.</p>
<p>2. Porosity is characterized using high resolution tomography.</p>
<p>3. Non-local damage indicator parameters identify the location of fatigue crack initiation.</p>
<p>4. The critical pore size is 20 μm in IN718 with average grain size of 48 μm.</p>
<p>5. From the tomography characterization, 1% of the pores may result in failure.</p>
</div></div></div>Mon, 25 Mar 2019 19:33:49 +0000rajan_prithivi23187 at https://imechanica.orghttps://imechanica.org/node/23187#commentshttps://imechanica.org/crss/node/23187Journal Club for March 2019: Fatigue of hydrogels
https://imechanica.org/node/23127
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/1596">jClub</a></div><div class="field-item odd"><a href="/taxonomy/term/1099">hydrogel</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal"><strong><span>Fatigue of hydrogels</span></strong></p>
<p class="MsoNormal"><span>Ruobing Bai (1,2), Zhigang Suo (1)<br /></span></p>
<p class="MsoNormal"><span>(1) John A. Paulson School of Engineering and Applied Sciences, </span><span>Kavli Institute for Bionano Science and Technology,</span><span> Harvard University</span></p>
<p class="MsoNormal"><span>(2) Department of Mechanical and Civil Engineering, California Institute of Technology</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>We have recently published a review article titled “Fatigue of Hydrogels” in <em>European Journal of Mechanics / A Solids</em>. This article is the first review on the fatigue of hydrogels. Hydrogels have been developed since the 1960s <span>[1]</span> for applications in personal care, medicine, and engineering. Evidence has accumulated that hydrogels under prolonged loads suffer fatigue. Symptoms include change in properties, as well as nucleation and growth of cracks. In this Journal Club, I would like to share with you this exciting field at the interface of physics, chemistry and mechanics. <strong>Fatigue of hydrogels is an interplay of chemistries of bonds, topologies of connection, and mechanics of dissipation.</strong> Discussions here will be focused on an outlined understanding we have recently gained on the topic. For more details, see the full version of the <a href="https://imechanica.org/node/22954">review</a>.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>Motivation</span></strong></p>
<p class="MsoNormal"><span>The motivation to study the fatigue of hydrogels is two-fold.</span></p>
<p class="MsoNormal"><span>From the perspective of application, a</span><span>s the property space spans and applications proliferate, hydrogels—like all materials—will be used under conditions that push their limits. Many applications require hydrogels to sustain prolonged static and cyclic loads. F</span><span>atigue of hydrogels is recent and scanty. </span><span>The first report on crack growth in a hydrogel under prolonged static load was reported by Tanaka et al. in 2000 <span>[2]</span>. </span><span>The first report on crack growth in a hydrogel under prolonged cyclic loads has only appeared recently by Tang et al. in 2017 <span>[3]</span>.</span></p>
<p class="MsoNormal"><span>From the perspective of fundamental study, all symptoms of fatigue originate from one fundamental cause: molecular units of a hydrogel change neighbors under prolonged loads. Fatigue is a molecular disease, and correlates with rheology. As a result, <strong>fatigue is </strong></span><strong><span>a lens to view molecular processes</span></strong><span>.</span><span> Because of the molecular diversity in hydrogels, the chemistry of fatigue holds the key to the discovery of hydrogels of properties previously unimagined.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>Symptoms of fatigue (Fig. 1)</span></strong></p>
<p class="MsoNormal"><span>Historically, the word <em>fatigue</em> has been used to describe many symptoms observed in materials under prolonged loads (in mechanics fatigue mostly refers to failure under cyclic loads). </span><span>Two idealized profiles of loads are commonly used to characterize fatigue: static loads and cyclic loads. We call </span><span>f</span><span>atigue under prolonged static loads <em>static fatigue</em>, and fatigue under prolonged cyclic loads <em>cyclic fatigue</em>. In a real experiment, a load is either prescribed by stretch or stress.</span></p>
<p class="MsoNormal"><span>Fatigue may refer to the degradation of properties (e.g., modulus, toughness, conductivity, and swelling ratio). We call distributed damage under prolonged loads <em>fatigue damage</em>.</span></p>
<p class="MsoNormal"><span>Fatigue may also refer to the nucleation and growth of cracks in hydrogels. The nucleation of cracks is commonly studied using samples with no precut cracks, whereas the growth of cracks is commonly studied using samples with precut cracks. We call fracture under prolonged loads <em>fatigue fracture</em>. We call crack growth under prolonged loads <em>fatigue crack growth</em>. The speed of the crack under static loads (or crack growth per cycle under cyclic loads) is a function of the energy release rate. A hydrogel under fatigue crack growth (either static or cyclic) exhibits a threshold and a toughness (fracture energy). The crack does not grow when the energy release rate is below the threshold, and grows rapidly when the energy release approaches the toughness.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%201_2.png" alt="" width="500" height="256.3" /></span></p>
<p class="MsoNormal"><strong><span>Fig. 1.</span></strong><span> Symptoms of fatigue. (a) Fatigue studied using </span><span>samples with no precut crack. (b) </span><span>Fatigue studied using </span><span>samples with precut crack. The load is prescribed by stretch here.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>Chemistries of bonds and topologies of connection</span></strong></p>
<p class="MsoNormal"><span>Symptoms of fatigue vary with chemistries of bonds and topologies of connection. </span><span>Representative bonds and complexes in hydrogels include covalent bonds (static or dynamic), ionic bonds, hydrogen bonds, hydrophobic interaction, dipole-dipole interaction, pai-pai </span><span>stacking, and host-guest interaction. </span></p>
<p class="MsoNormal"><span>Irreversible bonds can be relatively strong, but do not reform after breaking despite extreme conditions (e.g., C-C bonds). Reversible bonds are typically weak, and may reform after breaking (e.g., some ionic bonds). By a topology of connection we mean an arrangement of bonds of various types to link monomer units into polymer chains, and crosslink the polymer chains into polymer networks. The difference in the topologies of connection causes difference in the symptoms of fatigue.</span><span>Under a monotonic load, a double-network hydrogel resists the growth of a crack by dissipating energy through two mechanisms: scission of primary polymer networks on the plane of the crack, and breaking of sacrificial bonds in the bulk of the hydrogel. The sacrificial bonds act as a <em>toughener</em>. Representative topologies of connection are presented in Fig. 2.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%202_0.png" alt="" width="500" height="364.9" /></span></p>
<p class="MsoNormal"><strong><span>Fig. 2.</span></strong><span> Representative topologies of connection in hydrogels.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>Energy release rate for large-scale inelasticity and complex rheology</span></strong></p>
<p class="MsoNormal"><span>In a hydrogel or an elastomer, a crack typically grows when large deformation prevails in the main part of the body, where nonlinear elasticity applies. For elastomers, the use of samples with precut cracks was initiated by Rivlin and Thomas <span>[4]</span> to study crack growth under monotonic loads, by Thomas <span>[5]</span> to study crack growth under prolonged cyclic loads, and by Greensmith and Thomas* <span>[6]</span> to study crack growth under prolonged static loads. The latter two papers, which initiated the study of cyclic and static fatigue crack growth in elastomers, predate the corresponding literature on metals. Also see recent reviews on fracture and adhesion of soft materials <span>[7]</span>, measurement and interpretation of toughness of hydrogels <span>[8]</span>, and crack-front fields in materials modeled with specific Helmholtz functions <span>[9]</span>. </span></p>
<p class="MsoNormal"><span>Large-scale inelasticity and complex rheology prevail when the major portion of a sample undergoes inelastic deformation, such as a tough hydrogel. While the energy release rate may be rigorously defined in theoretical calculation, it is usually not well defined or related to the external measuring parameters in experiments. Here we highlight three experimental setups, where energy release rate can be readily obtained </span><span>for materials of any type of rheology: pure shear, tear, and peel.</span></p>
<p class="MsoNormal"><span>In a pure shear test (Fig. 3), the energy release rate in a precut sample is <em>G</em> = <em>HW</em>(lambda</span><span>), where <em>H</em> is the height of the sample in the undeformed state. For an elastic hydrogel, <em>W</em>(</span><span>lambda) is the elastic energy density of the uncut sample. </span></p>
<p class="MsoNormal"><span>For a hydrogel of complex rheology subject to static fatigue crack growth, the sample needs to be held at a fixed stretch for a long enough time. The extension of the crack reaches a steady state of constant speed. <em>W</em>(</span><span>lambda) is the area under the stress-stretch curve of a sample without precut crack, measured at a low enough loading rate to allow stress relaxation. The <em>v</em>-<em>G</em> curve is measured by conducting experiments at different applied stretch </span><span>lambda. </span></p>
<p class="MsoNormal"><span>For a hydrogel of complex rheology subject to cyclic fatigue crack growth, <em>W</em>(</span><span>lambda)</span><span> is the area of the stress-stretch curve of an uncut sample in the steady state </span><span>after many loading cycles</span><span> <span>[10]</span>.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%203_0.png" alt="" width="500" height="102" /></span></p>
<p class="MsoNormal"><strong><span>Fig. 3.</span></strong><span> Pure shear. <strong>(a)</strong> A sample without a precut crack is used to measure the stress-stretch curve and the energy density as a function of stretch, <em>W</em>(</span><span>lambda). <strong>(b)</strong> A sample with a precut crack is used to measure the critical stretch for fracture, </span><span>lambda_cr</span><span>.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>In peel (Fig. 4a) or tear (Fig. 4b), the sample is often attached with two inextensible backing layers, which suppress the deformation far away from the crack front. Upon loading, the crack may grow into a steady state, and the force may reach a plateau (Fig. 4c). In the steady state, the energy release rate is <em>G</em> </span><span>= 2<em>F</em>/<em>w</em> for peel, and <em><span>G</span></em> = 2<em>F</em>/<em>h</em> for tear, where <em>w</em> is the width and <em>h</em> is the thickness of the sample<span>.</span></span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><span><img src="https://imechanica.org/files/Fig%204.png" alt="" width="500" height="258.7" /></span></span></p>
<p class="MsoNormal"><strong><span>Fig. 4.</span></strong><span> <strong>(a)</strong> Peel. <strong>(b)</strong> Tear. <strong>(c)</strong> Force-displacement curve.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>Because the thickness of the sample can be readily adjusted over a large range in peel and tear, peel and tear can be used to probe the scale of inelasticity <span>[11]</span>. The measured toughness is a function of the thickness of the sample (Fig. 5), determined by small-scale or large-scale inelasticity (Fig. 5).</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%205.png" alt="" width="500" height="390.4" /></span></p>
<p class="MsoNormal"><strong><span>Fig. 5. </span></strong><span>The measured toughness is thickness-dependent under the condition of large-scale inelasticity, but is thickness-independent under the condition of small-scale inelasticity </span><span>[11]</span><span>.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>Peel and tear have some advantages in studying static fatigue crack growth in hydrogels of complex rheology. Because the backing layers limit the active deformation around the crack front, the expression of energy release rate holds at any crack speed, and is independent of the rheology. Cyclic fatigue crack growth has been characterized by tear <span>[5]</span> and peel <span>[12]</span> in elastomers, but has not been characterized by tear or peel in any hydrogel.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>Lake-Thomas threshold, cyclic-fatigue threshold, and static-fatigue threshold</span></strong></p>
<p class="MsoNormal"><span>Lake and Thomas noted that the experimentally determined cyclic-fatigue threshold of several elastomers is </span><span>G</span><span>0</span><span> = 50 J/m^2 <span>[13]</span>. They hypothesized that this threshold is entirely due to the scission of the polymer chains lying across the crack plane (Fig. 6). They further hypothesized that just before scission every covalent bond along a polymer chain is stretched close to the covalent energy of the bond, and the scission causes the chain to dissipate the energy of the entire chain.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%206.png" alt="" width="500" height="216.3" /></span></p>
<p class="MsoNormal"><span><span></span></span></p>
<p class="MsoNormal"><strong><span>Fig. 6</span></strong><span>. The Lake-Thomas model.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>The thresholds for static and cyclic fatigue crack growth are often called the <em>intrinsic toughness</em>. The notion of intrinsic toughness is used in studying tough hydrogels <span>[7, 8, 14-16]</span>. </span><span>In the literature, it has been unclear whether the two thresholds measured under static and cyclic loads are identical and corresponding to a single material constant. As described next, our own experimental data indicate the two thresholds can differ greatly.</span></p>
<p class="MsoNormal"><span>The Lake-Thomas threshold qualitatively predicts the cyclic-fatigue threshold of hydrogels. For example, </span><span>for polyacrylamide hydrogels, t</span><span>he experimental data and theoretical prediction of the cyclic-fatigue threshold agree well for hydrogels with higher water content, but deviate for hydrogels with low water content <span>[17]</span> (Fig. 7). </span><span>Cyclic-fatigue thresholds have also been measured for a few other hydrogels <span>[3, 10, 18-20]</span>. The measured cyclic-fatigue thresholds in all these hydrogels are close to the estimated values using the Lake-Thomas threshold. In all cases, the cyclic-fatigue threshold is much smaller than the toughness of the hydrogel, by one or two orders of magnitude.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%207.png" alt="" width="500" height="351.3" /></span></p>
<p class="MsoNormal"><strong><span>Fig. 7. </span></strong><span>The cyclic-fatigue threshold of polyacrylamide hydrogels with different water content (represented by the polymer volume fraction) <span>[17]</span>.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>A hypothesis has emerged recently that tougheners increase the toughness of a hydrogel greatly, but contribute little to the cyclic-fatigue threshold <span>[18]</span>. Cyclic fatigue crack growth has been studied in hydrogels of two kinds, identical in all aspects except for tougheners. By doing so, we have ascertained this hypothesis in the polyacrylamide-polyvinyl alcohol hydrogel (Fig. 8a <span>[18]</span>) and the polyacrylamide-Ca-alginate hydrogel (Fig. 8b <span>[20]</span>).</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%208.png" alt="" width="500" height="211.1" /></span></p>
<p class="MsoNormal"><strong><span>Fig. 8.</span></strong><span> The cyclic-fatigue threshold negligibly depends on tougheners. (a) polyacrylamide-polyvinyl alcohol <span>[18]</span>. (b) polyacrylamide-Ca-alginate <span>[20]</span>.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>While tougheners contribute little to the cyclic-fatigue threshold, experiments show that they can contribute greatly to the static-fatigue threshold <span>[11]</span>. To explain this observation, we find a useful way to classify tougheners. Under a constant stretch for a long time, a toughener that relaxes to zero stress is called liquid-like, whereas a toughener that relaxes to a nonzero stress is called solid-like. We hypothesize that a liquid-like toughener does not contribute to the static-fatigue threshold, while a solid-like toughener contributes to the static-fatigue threshold through the rate-independent dissipation around the crack front. To test this hypothesis, we measured static-fatigue thresholds in polyacrylamide-Ca-alginate hydrogels identical in all aspects except for the concentration of calcium (Fig. 9a). The measured thresholds for different compositions differ by orders of magnitude. Furthermore, even for samples of the same composition, when the size of the inelastic zone is comparable or larger than the sample size at the threshold, large-scale inelasticity takes place, and the measured static-fatigue threshold depends on the sample size (Fig. 9b).</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%209.png" alt="" width="500" height="191.2" /></span></p>
<p class="MsoNormal"><strong><span>Fig. 9. </span></strong><span>(a) <em>v</em>-<em>G</em> curves of polyacrylamide-Ca-alginate hydrogels with same thickness <em>h</em> = 1.5 mm but different concentrations of calcium. (b) <em>v</em>-<em>G</em> curves of polyacrylamide-Ca-alginate hydrogels with fixed concentrations of calcium but different thicknesses. </span><span>[11]</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>The difference between the cyclic-fatigue threshold and static-fatigue threshold of a hydrogel with solid-like tougheners is reminiscent of the fatigue of rate-independent ductile metals, where the cyclic-fatigue threshold is much smaller than the toughness – in this case the static-fatigue threshold – of a ductile metal. </span><span>Such difference, however, is not distinguished in the study of elastomers.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>Poroelastic, viscoelastic, and elastic-plastic fatigue</span></strong></p>
<p class="MsoNormal"><span>Fatigue correlates with rheology, according to which we distinguish poroelastic fatigue, viscoelastic fatigue, and elastic-plastic fatigue.</span></p>
<p class="MsoNormal"><span>By poroelastic fatigue we mean the fatigue in a hydrogel due to the time-dependent migration of water. Wang and Hong (2012) initiated the poroelastic theory of cracks in hydrogels <span>[21]</span>. We propose a material-specific <em>poroelastic</em> <em>relaxation speed</em> for crack growth in poroelastic gels, <em>D</em>/(</span><span>G</span><span>0</span><span>/<em>W</em>f), where <em>D</em> is the effective diffusivity of solvent, </span><span>G</span><span>0</span><span> is the static-fatigue threshold, and <em>W</em>f is the work of fracture tested at low loading rate (i.e., the area under the stress-stretch curve measured from a sample with no precut crack, under a loading rate low enough to allow equilibrium). The ratio </span><span>G</span><span>0</span><span>/<em>W</em>f defines a flaw-sensitivity length for samples tested at a low loading rate <span>[22]</span>. When the crack speed is small compared to this relaxation speed, the energy release rate approaches the static-fatigue threshold. When the crack speed is large compared to the relaxation speed, the energy release rate significantly exceeds the threshold.</span></p>
<p class="MsoNormal"><span>Viscoelastic relaxation may also accompany the static-fatigue crack growth. We define a <em>viscoelastic relaxation speed</em> as (</span><span>G</span><span>0</span><span>/<em>W</em>f)/tau</span><span>, where tau</span><span> is the viscoelastic relaxation time. When the crack speed is small compared to this speed, the viscoelasticity of the toughener is completely relaxed.</span></p>
<p class="MsoNormal"><span>Under the condition of small-scale inelasticity, a comparison of (</span><span>G</span><span>0</span><span>/<em>W</em>f)/tau</span><span> and <em>D</em>/(</span><span>G</span><span>0</span><span>/<em>W</em>f) defines a dimensionless parameter: (</span><span>G</span><span>0</span><span>/<em>W</em>f)^2/(<em>D*</em>tau</span><span>). When this parameter is small, viscoelasticity sets the relaxation speed to approach the static-fatigue threshold. When this parameter is large, poroelasticity sets the relaxation speed. Under the condition of large-scale inelasticity, the flaw-sensitivity length </span><span>G</span><span>0</span><span>/<em>W</em>f will be replaced by the relevant length of the sample.</span></p>
<p class="MsoNormal"><span>All hydrogels have time-dependent rheology. Yet, the long-time, slow-crack behavior of hydrogels approaches that of a material of time-independent plasticity. Elastic-plastic fatigue serves as a good starting point to study the complex behaviors. As an example, Qi et al. have analyzed toughness of soft materials of time-independent hysteresis <span>[23]</span>.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>Strategy for hydrogels of high endurance</span></strong></p>
<p class="MsoNormal"><span>Designing a fatigue-resistant (i.e., endurant) hydrogel should address all symptoms of fatigue: change in properties, as well as nucleation and growth of cracks, in samples with and without precut cracks, under prolonged static and cyclic loads. </span></p>
<p class="MsoNormal"><span>One design principle has been recently demonstrated for endurant elastomers <span>[24]</span> and hydrogels <span>[25]</span>. A composite can be made from a matrix of compliant (long-chain) network and fibers of a stiff (short-chain) network (Fig. 10a), both elastic, having high modulus contrast, and strongly adhering. The stress-stretch curve has low hysteresis cycle by cycle. When the composite with a precut crack is subject to a stretch along the direction of fibers, the soft matrix shears greatly at the crack front, and spreads large stress over a long segment of each fiber. When a fiber ruptures, all the elastic energy stored in the highly stretched segment is released. The fibers can be further replaced by aligned bundles of polymer chains at the molecular level in a double-network hydrogel (Fig. 10b).</span></p>
<p class="MsoNormal"><span>Also highlighted is the principle for anti-fatigue-fracture hydrogels recently demonstrated by Lin and Zhao et al. <span>[26]</span>. They use crystalline domains to replace the single layer of polymer chains that dissipates energy at the crack front and determines the cyclic-fatigue threshold (Fig. 10c). The cyclic-fatigue threshold is enhanced to around 1000 J/m^2. For comparison, the highest cyclic-fatigue threshold achieved using a long-chain polymer network in a double-network hydrogel is about 500 J/m^2 <span>[19]</span>.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span><img src="https://imechanica.org/files/Fig%2010.png" alt="" width="500" height="163.3" /></span></p>
<p class="MsoNormal"><strong><span>Fig. 10.</span></strong><span> Strategy for hydrogels of high endurance. (a) A composite with a matrix of compliant network and fibers of a stiff network, both elastic, having high modulus contrast and strongly adhering <span>[24]</span>. (b) Bundles of polymer chains are aligned at the molecular level to deflect a crack <span>[25]</span>. (c) Crystalline domains replace the single layer of polymer chains to dissipate more energy at the crack front <span>[26]</span>.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><strong><span>Opportunities</span></strong></p>
<p class="MsoNormal"><span><strong>Experiment.</strong> Numerous opportunities exist in the experiment of fatigue of hydrogels. Hydrogels can be synthesized with various bonding chemistries, molecular topologies, physical conditions (e.g., temperature, water content, ambient solution, etc.), and geometries. An adequate theoretical thinking together with carefully designed experiments can readily lead to proof of valuable hypotheses, or new discoveries previously unnoticed. The large variety of hydrogels makes many of their behaviors analogous to behaviors of metals, ceramics, porous media, and other well-studied material systems. Yet, these hydrogels are readily synthesized in university laboratories of modest means. <strong>Hydrogels provide a platform for us to study interesting mechanics, through making new discoveries as well as realizing old thoughts.</strong></span></p>
<p class="MsoNormal"><span><strong>Theory and computation.</strong> The various compositions and complex rheologies of hydrogels further motivate the development of theoretical models and computational methods, but also challenge the good agreement between theoretical predictions and experimental observations. After all, a quantitative agreement between theory and experiments is not common in fatigue. Valuable theoretical analysis and computation will inspire novel experiments and new discoveries, of which we have witnessed many examples in this field.</span></p>
<p class="MsoNormal"><strong><span> </span></strong></p>
<p class="MsoNormal"><strong><span>Relevant previous discussions on iMechanica and your feedback</span></strong></p>
<p class="MsoNormal"><span>The fields of fracture mechanics and polymer science are broad and deep. We have been inspired a lot from the previous discussions on iMechanica. Here are a few links of some previous Journal Clubs:</span></p>
<p class="MsoNormal"><a href="https://imechanica.org/node/22900"><span class="MsoHyperlink"><span>Bonding hydrophilic and hydrophobic soft materials for functional soft devices</span></span><span class="MsoHyperlink"><span><span><br /></span></span></span></a></p>
<p class="MsoNormal"><a href="//imechanica.org/node/21461"><span class="MsoHyperlink"><span>Fracture Mechanics of Soft Materials<br /></span></span></a></p>
<p class="MsoNormal"><a href="https://imechanica.org/node/15218"><span class="MsoHyperlink"><span>Stretchable Ionics</span></span></a></p>
<p class="MsoNormal"><a href="https://imechanica.org/node/13088"><span class="MsoHyperlink"><span>Fracture of polymeric gels</span></span></a></p>
<p class="MsoNormal"><span class="MsoHyperlink"><span><a href="https://imechanica.org/node/1641">Mechanics of Hydrogels</a></span></span></p>
<p class="MsoNormal"><span><strong>We love to see your feedback.</strong> New opportunities, challenges, your own work in related fields, or your comments on anything related to this topic. Please leave your comment below.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>* </span><span>In our review article, we wrote that the </span><span>crack growth in elastomers under prolonged static loads was initiated by Mullins. While these two papers belong to the same series of articles, the paper by Greensmith and Thomas dated earlier.</span></p>
<p class="MsoNormal"> </p>
<p class="EndNoteBibliography"><strong><span>Reference</span></strong></p>
<p class="EndNoteBibliography"> </p>
<p class="EndNoteBibliography">[1] Wichterle O & Lim D (1960) Hydrophilic gels for biological use. <em>Nature</em> 185(4706):117.</p>
<p class="EndNoteBibliography">[2] Tanaka Y, Fukao K, & Miyamoto Y (2000) Fracture energy of gels. <em>The European Physical Journal E</em> 3(4):395-401.</p>
<p class="EndNoteBibliography">[3] Tang J, Li J, Vlassak JJ, & Suo Z (2017) Fatigue fracture of hydrogels. <em>Extreme Mech. Lett.</em> 10:24-31.</p>
<p class="EndNoteBibliography">[4] Rivlin R & Thomas AG (1953) Rupture of rubber. I. Characteristic energy for tearing. <em>J. Polym. Sci., Part A: Polym. Chem.</em> 10(3):291-318.</p>
<p class="EndNoteBibliography">[5] Thomas A (1958) Rupture of rubber. V. Cut growth in natural rubber vulcanizates. <em>J. Polym. Sci.</em> 31(123):467-480.</p>
<p class="EndNoteBibliography">[6] Greensmith HW & Thomas AG (1955) Rupture of rubber. III. Determination of tear properties. <em>J. Polym. Sci.</em> 18(88):189-200.</p>
<p class="EndNoteBibliography">[7] Creton C & Ciccotti M (2016) Fracture and adhesion of soft materials: a review. <em>Rep. Prog. Phys.</em> 79(4):046601.</p>
<p class="EndNoteBibliography">[8] Long R & Hui CY (2016) Fracture toughness of hydrogels: measurement and interpretation. <em>Soft Matter</em> 12(39):8069-8086.</p>
<p class="EndNoteBibliography">[9] Long R & Hui CY (2015) Crack tip fields in soft elastic solids subjected to large quasi-static deformation—A review. <em>Extreme Mech. Lett.</em> 4:131-155.</p>
<p class="EndNoteBibliography">[10] Bai R<em>, et al.</em> (2017) Fatigue fracture of tough hydrogels. <em>Extreme Mech. Lett.</em> 15:91-96.</p>
<p class="EndNoteBibliography">[11] Bai R, Chen B, Yang J, & Suo Z (2019) Tearing a hydrogel of complex rheology. <em>J. Mech. Phys. Solids</em> 125:749-761.</p>
<p class="EndNoteBibliography">[12] Baumard TLM, Thomas AG, & Busfield JJC (2012) Fatigue peeling at rubber interfaces. <em>Plastics, Rubber and Composites</em> 41(7):296-300.</p>
<p class="EndNoteBibliography">[13] Lake G & Thomas A (1967) The strength of highly elastic materials. <em>Proc. R. Soc. London, Ser. A</em> 300(1460):108-119.</p>
<p class="EndNoteBibliography">[14] Zhao X (2014) Multi-scale multi-mechanism design of tough hydrogels: building dissipation into stretchy networks. <em>Soft Matter</em> 10(5):672-687.</p>
<p class="EndNoteBibliography">[15] Zhang T, Lin S, Yuk H, & Zhao X (2015) Predicting fracture energies and crack-tip fields of soft tough materials. <em>Extreme Mech. Lett.</em> 4:1-8.</p>
<p class="EndNoteBibliography">[16] Creton C (2017) 50th Anniversary Perspective: Networks and Gels: Soft but Dynamic and Tough. <em>Macromolecules</em> 50(21):8297-8316.</p>
<p class="EndNoteBibliography">[17] Zhang E, Bai R, Morelle XP, & Suo Z (2018) Fatigue fracture of nearly elastic hydrogels. <em>Soft Matter</em> 14(18):3563-3571.</p>
<p class="EndNoteBibliography">[18] Bai R, Yang J, Morelle XP, Yang C, & Suo Z (2018) Fatigue Fracture of Self-Recovery Hydrogels. <em>ACS Macro Lett.</em>:312-317.</p>
<p class="EndNoteBibliography">[19] Zhang W<em>, et al.</em> (2018) Fatigue of double-network hydrogels. <em>Eng. Fract. Mech.</em> 187:74-93.</p>
<p class="EndNoteBibliography">[20] Zhang W<em>, et al.</em> (2019) Fracture toughness and fatigue threshold of tough hydrogels. <em>ACS Macro Lett.</em> 8:17-23.</p>
<p class="EndNoteBibliography">[21] Wang X & Hong W (2012) Delayed fracture in gels. <em>Soft Matter</em> 8(31):8171-8178.</p>
<p class="EndNoteBibliography">[22] Chen C, Wang Z, & Suo Z (2017) Flaw sensitivity of highly stretchable materials. <em>Extreme Mech. Lett.</em> 10:50-57.</p>
<p class="EndNoteBibliography">[23] Qi Y, Caillard J, & Long R (2018) Fracture toughness of soft materials with rate-independent hysteresis. <em>J. Mech. Phys. Solids</em> 118:341-364.</p>
<p class="EndNoteBibliography">[24] Wang Z<em>, et al.</em> (2018) Stretchable materials of high toughness and low hysteresis. <em>Proc. Natl. Acad. Sci. </em>In press.</p>
<p class="EndNoteBibliography">[25] Bai R, Yang J, Morelle XP, & Suo Z (2019) Flaw-Insensitive Hydrogels under Static and Cyclic Loads. <em>Macromol. Rapid Commun.</em> 0(0):1800883.</p>
<p class="EndNoteBibliography">[26] Lin S<em>, et al.</em> (2019) Anti-fatigue-fracture hydrogels. <em>Sci. Adv.</em> 5(1):eaau8528.</p>
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</div></div></div>Fri, 01 Mar 2019 01:29:30 +0000Ruobing Bai23127 at https://imechanica.orghttps://imechanica.org/node/23127#commentshttps://imechanica.org/crss/node/23127Micromechanical model for prediction of fatigue limit of fibre composites
https://imechanica.org/node/23105
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/5989">fiber composites</a></div><div class="field-item odd"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item even"><a href="/taxonomy/term/18">micromechanics</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span>We have published a paper called "</span>Micromechanical model for prediction of the fatigue limit for unidirectional fibre composites" in Mechanics of Materials. See the link <a href="https://www.sciencedirect.com/science/article/pii/S0167663618306690?dgcid=author" target="_blank">here</a>.</p>
<p>The model shows that the change in the debond crack tip stress intensity factor is zero if there is a sticking friction zone at the debond crack tip. This has very important consequences, implying that cyclic crack growth of the Paris–Erdogan type cannot occur. With sticking friction at the tip of the debond no cyclic crack growth is expected under cyclic loading. This explains experimental observations.</p>
<p>An equation is given for the prediction of a fatigue limit expressed in terms of maximum strain as a function of basic composite and interface parameters.</p>
<p>Model predictions, based on independent micromechanical experiments, show that the fatigue limit will increase for higher R-ratio. This prediction is consistent with the experimental findings. Also, t<span>he model predicts that the fatigue limit will decrease with increasing fibre volume fraction. This prediction is also consistent with the experimental findings.</span></p>
</div></div></div>Wed, 20 Feb 2019 19:07:03 +0000Bent F. Sørensen23105 at https://imechanica.orghttps://imechanica.org/node/23105#commentshttps://imechanica.org/crss/node/23105Tearing a hydrogel of complex rheology
https://imechanica.org/node/23067
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/1099">hydrogel</a></div><div class="field-item odd"><a href="/taxonomy/term/12380">slow crack</a></div><div class="field-item even"><a href="/taxonomy/term/4716">rheology</a></div><div class="field-item odd"><a href="/taxonomy/term/12381">tear</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal">Dear colleagues,</p>
<p class="MsoNormal">I would like to share with you our latest paper focusing on the fracture of hydrogels of complex rheology.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>Title</strong>: Tearing a hydrogel of complex rheology</p>
<p class="MsoNormal"><strong>Authors</strong>: Ruobing Bai, Baohong Chen, Jiawei Yang, Zhigang Suo*</p>
<p class="MsoNormal"><strong>Abstract</strong>:</p>
<p class="MsoNormal">Tough hydrogels of many chemical compositions are being discovered, and are opening new applications in medicine and engineering. To aid this rapid and worldwide development, it is urgent to study these hydrogels at the interface between mechanics and chemistry. A tough hydrogel often deforms inelastically over a large volume of the sample used in a fracture experiment. The rheology of the hydrogel depends on chemistry, and is usually complex, which complicates the crack behavior. This paper studies a hydrogel that has two interpenetrating networks: a polyacrylamide network of covalent crosslinks, and an alginate network of ionic (calcium) crosslinks. When the hydrogel is stretched, the polyacrylamide network remains intact, but the alginate network partially unzips. We tear a thin layer of the hydrogel at speed v and measure the energy release rate G. The v-G curve depends on the thickness of the hydrogel for thin hydrogels, and is independent of the thickness of the hydrogel for thick hydrogels. The energy release rate approaches a threshold, below which the tear speed vanishes. The threshold depends on the concentration of calcium. The threshold may also depend on the thickness when the thickness is comparable to the size of inelastic zone. The threshold determined by slow tear differs from the threshold determined by cyclic fatigue. We discuss these experimental findings in terms of the mechanics of tear and the chemistry of the hydrogel.</p>
<p class="MsoNormal"><a href="https://www.sciencedirect.com/science/article/pii/S0022509618309785">https://www.sciencedirect.com/science/article/pii/S0022509618309785</a></p>
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<tr class="odd"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/Tearing%20a%20hydrogel%20of%20complex%20rheology.pdf" type="application/pdf; length=2940210">Tearing a hydrogel of complex rheology.pdf</a></span></td><td>2.8 MB</td> </tr>
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</div></div></div>Thu, 07 Feb 2019 05:30:03 +0000Ruobing Bai23067 at https://imechanica.orghttps://imechanica.org/node/23067#commentshttps://imechanica.org/crss/node/23067On unified crack propagation laws
https://imechanica.org/node/23006
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div><div class="field-item odd"><a href="/taxonomy/term/834">crack growth</a></div><div class="field-item even"><a href="/taxonomy/term/10019">Crack growth rate</a></div><div class="field-item odd"><a href="/taxonomy/term/12361">Short crack</a></div><div class="field-item even"><a href="/taxonomy/term/12362">Long crack</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span>The anomalous propagation of short cracks shows generally exponential fatigue crack growth but the dependence on stress range at high stress levels is not compatible with Paris’ law with exponent m=2. Indeed, some authors have shown that the standard uncracked SN curve is obtained mostly from short crack propagation, assuming that the crack size a increases with the number of cycles N as da/dN=H\Delta\sigma^h where h is close to the exponent of the Basquin’s power law SN curve. We therefore propose a general equation for crack growth which for short cracks has the latter form, and for long cracks returns to the Paris’ law. We show generalized SN curves, generalized Kitagawa–Takahashi diagrams, and discuss the application to some experimental data. The problem of short cracks remains however controversial, as we discuss with reference to some examples.</span></p>
<p><a class="doi" title="Persistent link using digital object identifier" href="https://doi.org/10.1016/j.engfracmech.2018.12.023" rel="noreferrer noopener" target="_blank">https://doi.org/10.1016/j.engfracmech.2018.12.023</a> </p>
<p><span><span><a href="https://www.researchgate.net/publication/330342133_On_unified_crack_propagation_laws">https://www.researchgate.net/publication/330342133_On_unified_crack_prop...</a></span></span></p>
<p><span><span><a href="https://www.researchgate.net/profile/Antonio_Papangelo">https://www.researchgate.net/profile/Antonio_Papangelo</a></span></span></p>
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<tr class="odd"><td><span class="file"><img class="file-icon" alt="PDF icon" title="application/pdf" src="/modules/file/icons/application-pdf.png" /> <a href="https://imechanica.org/files/guarino12.pdf" type="application/pdf; length=671756">guarino12.pdf</a></span></td><td>656.01 KB</td> </tr>
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</div></div></div>Mon, 14 Jan 2019 13:54:42 +0000Antonio Papangelo23006 at https://imechanica.orghttps://imechanica.org/node/23006#commentshttps://imechanica.org/crss/node/23006Error | iMechanica