iMechanica - micromechanics
https://imechanica.org/taxonomy/term/18
enPhD (4 years) on micromechanical testing and interface characterization of composites
https://imechanica.org/node/26924
<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/5899">Micromechanical testing</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/185">experimental mechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/580">DIC</a></div><div class="field-item even"><a href="/taxonomy/term/581">digital image correlation</a></div><div class="field-item odd"><a href="/taxonomy/term/13192">fiber analysis</a></div><div class="field-item even"><a href="/taxonomy/term/8467">fiber debonding</a></div><div class="field-item odd"><a href="/taxonomy/term/684">interface 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">We are looking for a PhD student for a research project on microscale mechanical characterization of fiber reinforced polymer composites using in-situ microscopic techniques. Much more fundamental insights and measurements at the micro-scale are necessary to enable fully predictive multi-scale modelling and faster adaptation of composites. Therefore, we have developed advanced micromechanical test methods for fibre reinforced polymer composites based on in-situ optical and electron microscopy during loading. This includes micro-scale Digital Image Correlation (DIC) which gives full-field strain information at the sub-micron scale, force measurement and correlation of the damage mechanisms at micro- and macro-scale. This also generates accurate input data for multi-scale models for composites. This PhD will further develop and enhance these micromechanical tests and optimize the microscopic measurement techniques for different types of composites.</p>
<p align="justify">Further micromechanical tests will be done to characterize the fibre/matrix interface in composites. Fibre debonding will be monitored in real-time and different loading conditions to the interface will be applied.</p>
<p align="justify"><strong>This PhD requires an experimentalist to do the micromechanical characterization of the composites. Experience with experimental testing of materials and microscopy is required. Knowledge of composites and/or instrumentation techniques such as Digital Image Correlation (DIC) is an advantage.</strong></p>
<p class="MsoNormal"><span>More information can be found on <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>.</span></p>
</div></div></div>Fri, 20 Oct 2023 12:55:35 +0000wvpaepeg26924 at https://imechanica.orghttps://imechanica.org/node/26924#commentshttps://imechanica.org/crss/node/26924PhD (4 years) on micromechanical testing and interface characterization of composites
https://imechanica.org/node/26754
<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/185">experimental mechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/934">Composites</a></div><div class="field-item even"><a href="/taxonomy/term/2088">micro-mechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/79">testing</a></div><div class="field-item even"><a href="/taxonomy/term/10363">microscopy</a></div><div class="field-item odd"><a href="/taxonomy/term/2777">SEM</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 align="justify">We are looking for a PhD student for a research project on microscale mechanical characterization of fiber reinforced polymer composites using in-situ microscopic techniques. Much more fundamental insights and measurements at the micro-scale are necessary to enable fully predictive multi-scale modelling and faster adaptation of composites. Therefore, we have developed advanced micromechanical test methods for fibre reinforced polymer composites based on in-situ optical and electron microscopy during loading. This includes micro-scale Digital Image Correlation (DIC) which gives full-field strain information at the sub-micron scale, force measurement and correlation of the damage mechanisms at micro- and macro-scale. This also generates accurate input data for multi-scale models for composites. This PhD will further develop and enhance these micromechanical tests and optimize the microscopic measurement techniques for different types of composites.</p>
<p align="justify">Further micromechanical tests will be done to characterize the fibre/matrix interface in composites. Fibre debonding will be monitored in real-time and different loading conditions to the interface will be applied.</p>
<p align="justify"><strong>This PhD requires an experimentalist to do the micromechanical characterization of the composites. Experience with experimental testing of materials and microscopy is required. Knowledge of composites and/or instrumentation techniques such as Digital Image Correlation (DIC) is an advantage.</strong></p>
<p align="justify"><strong>More information can be found on:</strong></p>
<p align="justify"><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></p>
</div></div></div>Sun, 09 Jul 2023 06:25:55 +0000wvpaepeg26754 at https://imechanica.orghttps://imechanica.org/node/26754#commentshttps://imechanica.org/crss/node/26754Journal Club for February 2023: Understanding Engineering Alloy Behavior by Combining 3D X-ray Characterization and Finite Element Modeling
https://imechanica.org/node/26506
<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/1088">3D</a></div><div class="field-item odd"><a href="/taxonomy/term/753">X-ray diffraction</a></div><div class="field-item even"><a href="/taxonomy/term/169">Plasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/499">dislocations</a></div><div class="field-item odd"><a href="/taxonomy/term/641">finite element</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>Darren C. Pagan a, Romain Quey b, Matthew P. Kasemer c</strong></p>
<p><strong>a </strong>Materials Science and Engineering, The Pennsylvania State University, University Park PA 16802, US</p>
<p><strong>b </strong>Mines Saint-Etienne, Univ. Lyon, CNRS, UMR 5307 LGF, F–42023 Saint-Etienne, France</p>
<p><strong>c </strong>Mechanical Engineering, The University of Alabama, Tuscaloosa AL 35487, US</p>
<p> </p>
<p><strong>1. Introduction</strong></p>
<p>Modeling the deformation response of polycrystalline metallic alloys has developed rapidly in the past three decades from traditional mean-field and adjacent methods (e.g., Taylor, Sachs, and self-consistent modeling) to full-field crystal plasticity methods which consider explicit representations of microstructures (e.g., crystal plasticity finite element method [CPFEM] and crystal plasticity fast fourier transform [CPFFT]). While modeling methods have enjoyed rapid development, the advent of full-field models was not immediately met with commensurate gains in experimental microstructural and micromechanical characterization methods. Largely, comparison of micromechanical simulations to experimental me- chanical data has been limited to the macroscopic response or (more rarely) orientation averages within aggregates [1]. Consequently, model calibration (and thus model predictions) has suffered from a degree of ambiguity, owing to the fact that non-unique parameter sets may lead to similar macroscopic responses, yet very different micromechanical responses [2]. As such, the relative lack of robust experimental micromechanical data has held back the 15 verification, validation, and proper progress of crystal plasticity modeling.</p>
<p>Within the past decade, however, the field has been witness to an extremely rapid development of experimental techniques to track the micromechanical response of materials. While 2D techniques (e.g., electron backscatter diffraction and high-resolution digital image correlation [3, 4]) have demonstrated the ability to track the development of elasticity and plasticity on the surfaces of alloy samples, the rise of non-destructive 3D measurement modalities have been particularly attractive. Chief among these methods are synchrotron 3D X-ray diffraction microscopy (3DXRD) [5], high energy X-ray diffraction microscopy (HEDM) [6, 7], diffraction contrast tomography (DCT) [8], and more recently laboratory X-ray [9] and neutron diffraction [10], which utilize large panel area detectors and rapid diffraction simulations to reconstruct microstructures and micromechanical response in 3D. With these methods, the micromechanical response of all individual grains in appreciable volumes of material (order mm3) are tracked in situ during deformation, allowing for an unmatched ability to track the spatiotemporal evolution of elasticity and plasticity. In addition, these techniques provide the ability to non-destructively characterize the three- dimensional geometric morphology of microstructures including the spatial distribution of orientations at intrangranular length scales. In conjunction, these methods may be used to offer a cohesive material state characterization and mechanical behavior measurement and modeling workflow [11].</p>
<p>Owing to the development of fast, wide dynamic-range X-ray detectors, precision load frames, synchrotron control software, and data reduction software, the once-arduous task of collecting these 3D data has begun transitioning from “experiment” to “measurement”. As these methods have matured and become more standard and accessible, along with expected continued progress in this regard, the ability to (more rapidly and more easily) gather mechanical data at relevant length scales presents a path forward to develop better deformation modeling frameworks. Model instantiation and calibration can now take place with grain-scale mechanical data, leading to the optimization of more-deterministic modeling parameter sets [12, 13], and consequently better micromechanical predictions. Beyond traditional uses, these can be integrated even more closely with modeling (i.e., data assimilation) and surrogate model training to provide novel predictive capabilities and insights 45 into alloy deformation.</p>
<p>Here, we give examples of how these new data and finite-element micromechanical modeling of metallic alloys can be brought together with increasing amounts of integration: instantiation, calibration, assimilation, and hybrid surrogate model development (transfer machine learning).</p>
<p><strong>2. Instantiating Crystal-Plasticity Simulations with 3D Experimental Data</strong></p>
<p>The availability of 3D data of the microstructure of polycrystalline materials, and quantitative comparison to simulations, have motivated the development and use of novel methods for the generation of accurate representations of polycrystalline microstructures. For simulations, 3D measurement techniques provide quantitative information on the microstructures that generally cannot be reproduced by the models historically used in numerical simulations of polycrystal deformation, which were often based on purely mathematical models such as regular-shaped grains or Voronoi tessellations. The microstructural information provided by the new experimental techniques can be of different types. Far-field techniques provide accurate information of the average orientation, centroid location, and size of the grains within a polycrystal, while near-field techniques provide accurate information of the polycrystal morphology. Quey and Renversade [14] presented a general and fully-automated method to generate a polycrystal morphology from the various types of information that these experimental characterization techniques may provide, which is implemented in the Neper code [15]. The method is based on a (constraint-free) optimization of Laguerre tessellations (or “weighted Voronoi tessellations”), which can virtually represent any polycrystal morphology, in the framework of convex cells. Using the minimization function of the optimization approach, different types of microstructural information can be provided as input (statistical distributions of grain sizes, positions and volumes of the grains, images of the grains), and a geometrical tessellation conforming to said input is generated. This applies for the standard (single-phase or multi-phase) polycrystal, while an extension of the method allows for the representation of the multiscale microstructures found in many industrial alloys [4]. The 3D tessellations can then be meshed for CPFEM simulations, at the desired resolution (in terms of number of elements per grain), or “rasterized” for CPFFT simulations. A schematic of the various steps of moving from raw 3D microstructural data to a computable mesh is given in Fig. 1.</p>
<p><img title="Mesh" src="https://imechanica.org/files/Mesh.png" alt="" width="656" height="347" /></p>
<p><strong>Figure 1:</strong> Schematic of the various levels of processing from raw 3D microstructural data to cleaned microstructural data to a tesselation to a mesh upon which finite element simulations can be performed (left to right) [14].</p>
<p>While instantiation and meshing precede the actual simulation and post-processing, this typical workflow also benefits from close dialogue with the associated numerical tools. With this in mind, the Neper code [15] for polycrystal generation and meshing and the FEPX code [16] for parallel crystal-plasticity finite-element simulation have recently come together to form an extensive and homogeneous ensemble for polycrystal plasticity studies [17]. Beyond the direct benefits resulting from the convergence of the two codes, the project has also led to the standardization of the typical workflow of polycrystal plasticity studies. The post-processing capabilities include operations such as the computation of grain (or mesh) average values or other statistical treatments. The same post-processing operations can be applied to the experimental data, which makes direct comparisons between experiments and simulations straightforward.</p>
<p><strong>3. Calibrating Micromechanical Models</strong></p>
<p>While maybe obvious, it is worth stating that the accuracy of a micromechanical simulation is influenced by the accuracy of the material properties used in the simulation. Even with a perfectly accurate constitutive model, micro and macroscopic mechanical predictions will be inaccurate if the wrong material parameters are used. An on-going challenge for the crystal plasticity (and broader micromechanics) community is the determination of accurate microscale material parameters. Typically, micromechanical material parameters (e.g., elastic moduli, slip system strengths, rate sensitivities) are determined by fitting macroscopic data. However, it is well established that non-unique sets of microscale parameters can be used to fit a macroscopic response [2], so while the macroscopic response may be correct, confidence in conclusions drawn regarding micromechanical response is diminished. A benefit of these 3D micromechanical data is that model parameters in simulations can be fit at the length scales at which they influence the mechanical response. In a recent study by Boyce et al., a novel methodology was presented that combined HEDM data with elasticity FEM modeling to optimize single crystal moduli for Inconel 625 [18]. While often overlooked, accurate single crystal elastic moduli, particularly for standard engineering alloys, are often difficult to find in the literature. Historically, to measure single crystal elastic moduli, large single crystals of various orientations needed to be grown (often a major undertaking, and for some alloys an impossible task), and then single crystal elastic moduli were determined from either mechanical testing or acoustic measurements. In the work of Boyce et al., the hundreds of grain elastic strain responses measured during in situ uniaxial tension were used to avoid arduous single crystal testing. Through a minimization process, single crystal moduli that best predicted the elastic strain response of all grains (spanning a wide range of orientations) with respect to the measured elastic strain tensors were found. The applicability of this approach is wide, as many (most) engineering alloys in literature are missing rigorous and appropriate experimental measurement to provide accurate moduli for micromechanical modeling.</p>
<p>A similar approach was adopted by Pagan et al. to determine the strengths of the various families of slip systems in Ti-7Al [19]. Like single crystal moduli, the traditional approach for determining slip system strengths relies on measuring the critical resolved shear stresses for slip system activation by loading single crystals along different crystallographic orientations. Measuring slip system strengths, however, is even more difficult than elastic moduli because, ideally, only a single slip system should be activated at yield, which isn’t always possible. For example, hexagonal-symmetry crystals, which exhibit a propensity to slip on different families of slip systems (prismatic, basal, and pyramidal), often have large differences in CRSS, making activation of high-strength families alone not possible. Instead, Pagan et al. used the evolving grain scale stresses of over five hundred grains to estimate the bounds of a single crystal yield surface and in turn determine evolving slip system strengths of prismatic, basal, and pyramidal slip systems (see Fig. 2A). This work highlights the need for micromechanical data, because while the macroscopic response showed relatively little work hardening, significant amounts of softening and hardening (depending on the family of slip systems) were observed at the microscale. If only fitting simulation parameters to the macroscopic response, this microscale slip behavior would not have necessarily been captured by the model’s predictions. The ultimate consequence ultimate need for these data is showcased by the fact that the inclusion of this microscale softening behavior (only observable with new 3D techniques) in a CPFEM framework was found to increase plastic deformation localization, which is linked to fatigue and fracture failure (illustrated in Fig. 2B).</p>
<p><img src="https://imechanica.org/files/Properties_0.png" alt="" width="802" height="347" /></p>
<p><strong>Figure 2:</strong> A) Measured evolving slip system strengths (τ*) in various families of slip systems in Ti-7Al measured from far-field HEDM data. B) Effect of increased plastic deformation localization (shading) with inclusion of slip system softening into crystal plasticity model. [19]</p>
<p><strong>4. Data Assimilation Approaches</strong></p>
<p>In a traditional micromechanical modeling approach, the evolution of a stress field is determined using either an implicit or explicit formulation based solely on initial and boundary conditions. Accuracy is then a function of the material parameters, constitutive model, and solution scheme. However, with 3D micromechanical data, interesting opportunities to gain new insights into mechanical response are possible by directly combining micromechanical modeling with measured data. This approach, dubbed “data assimilation”, is common in the geosciences [20] and meteorology [21] fields, where data is plentiful, but predictive models are known to lack perfect accuracy. By including data continuously into the model predictions, accuracy can be greatly enhanced without new constitutive models, which can be of great value to engineering applications of micromechanics.</p>
<p>As a micromechanics example, formulations have long existed for determining the stress fields that arise due to incompatible plastic deformation [22]. However, the utility of such a formulation is limited because, historically, there were no means of determining what this plastic deformation field is. This has changed with the 3D characterization techniques now available. For example, Pagan and Beaudoin combined high-resolution 3D far-field diffraction data with continuum dislocation mechanics to solve for the stress field around a pair of shear bands [23]. High-resolution diffraction data was utilized to reconstruct the plastic deformation fields around the shear bands, and importantly, the incompatible portion of this plastic deformation field was used as input for a continuum dislocation formulation, which allowed for the stress fields around these slip bands to be solved for. Figure 3A shows both the reconstructed 3D deformation and stress fields. In this case, measurement and modeling were used together in a fully integrated fashion to address a long standing challenge associated with the use of continuum dislocation mechanics.</p>
<p><img src="https://imechanica.org/files/Reconstructions.png" alt="" width="759" height="494" /></p>
<p><strong>Figure 3:</strong> A) Combining plastic deformation fields from 3D X-ray data (γ) and continuum dislocation mechanics enables reconstruction of stress fields (σVM) around shear bands in a Cu single crystal [23]. B) Combining continuum dislocation mechanics with measured 3D grain-average elastic strain data (ϵ) enables full intragranular stress fields (σ) to be reconstructed in deforming polycrystals [24]. C) Combining measured 3D orientation fields with crystal plasticity enables reconstruction of crystallographic slip fields (Γ).</p>
<p>This combination of combining 3D X-ray data with continuum dislocation mechanics was extended by Naragani et al. to reconstruct intergranular stress fields in deforming polycrystals without evolving plasticity descriptions [24]. The full 3D orientation field of an Inconel 625 polycrystal was measured using near-field HEDM [25] along with the grain average elastic strain tensors in situ during monotonic plastic deformation. Typically, far-field HEDM is only capable of probing the average elastic strain and stress states of individual grains; however, combining these data with a micromechanics formulation derived to maintain compatibility and equilibrium, more information can be extracted from the data than can be measured directly (as seen in Fig. 3B, which shows the raw 3D and reconstructed intragranular stress fields). Of particular value is the ability to now probe the stress concentrations that develop around grain boundaries which may ultimately influence macroscopic 170 fatigue and fracture properties.</p>
<p>In a similar fashion, Pagan et al. combined near-field HEDM and far-field HEDM along with constitutive modeling to extract more from the data than would be available directly [26]. In this case, crystal plasticity was used to reconstruct the slip field in a deforming Ti-7Al polycrystal. Direct characterization of crystallographic slip through diffraction methods has traditionally not been possible, as dislocations moving through a crystal lattice leave the lattice unchanged [27]. As the lattice is what is interrogated with diffraction, complete crystallographic slip is generally “invisible”. However, by looking at heterogeneities of orientation that remain after heterogeneous plastic flow through the lens of crystal plasticity kinematics, determining the slip that must have occurred for the deformation to happen can be possible. Figure 3C shows the total crystallographic slip and slip resolved on to different slip system families in the Ti-7Al polycrystal after 2% strain. With these extended slip fields, it was found that slip through the polycrystal was dictated not just by local grain orientation and immediate grain neighborhoods (following prevailing understanding), but by extended networks of grains favorably oriented for slip.</p>
<p><strong>5. Reduced-Order Surrogate Modeling</strong></p>
<p>While CPFEM and CPFFT simulations present the state-of-the-art with respect to prediction of the complex heterogeneous deformation fields in polycrystalline materials, they come at a relatively high computational cost. Indeed, high-fidelity simulations often require (at the least) high-powered computational workstations and (more often) multi-nodal computational clusters. While the level of fidelity afforded by these simulation methods allow for inspection at intragranular scales, this is not always necessary for specific applications and likewise may be too computationally expensive to embed in component-scale simulations. Consequently, the development of reduced-order—or surrogate—models offers a path forward in including the user-desired essence of full-field models at reduced computational cost.</p>
<p>Machine learning methods have been increasingly attractive to help distill these complex trends into relatively efficient computational models. One such approach is to utilize a graph neural network (GNN) framework. GNNs model the response (generally) of networks of “nodes” and “edges” connecting those nodes, which both may be described by “features”, and together define a graph. This adheres naturally to the microstructural topology of a polycrystal, where grains or crystals correspond to nodes, and the granular connectivity or boundaries to edges). In [28], a GNN framework was employed to model the grainaveraged elastic response of grains in polycrystalline materials of varying degrees of elastic anisotropy. A transfer learning approach was demonstrated, where the GNN is trained with CPFEM data and used to predict the micromechanical response of an experimental specimen’s micromechanical response measured via far-field HEDM (an overview of the process is presented in Fig. 4). Results of this study yielded predictions which correspond well to both CPFEM and experimental data, and surpass the predictions from mean-field approaches, though at significantly reduced computational cost compared to CPFEM simulations. In the future, both CPFEM and 3D data can be used in tandem for surrogate model training with enhanced accuracy for engineering applications.</p>
<p><img src="https://imechanica.org/files/Graphs.png" alt="" width="792" height="534" /></p>
<p><strong>Figure 4:</strong> Overview of a transfer learning approach to move GNN surrogate models between simulated and measured 3D deformation data in polycrystalline metallic alloys [28].</p>
<p><strong>6. Summary and Outlook</strong></p>
<p>In summary, the existing and nascent 3D X-ray characterization and micromechanical measurement capabilities offer an exciting path forward to more directly interface with predictive modeling frameworks. The progress of 3D predictive models has been historically limited by the lack of robust experimental data to properly characterize, verify, and validate against, instead comparing to bulk material response. This has limited both the predictive capabilities of models, which inherently had high error due to ambiguity in optimized parameter sets, as well as a physically and experimentally guided progress of crystal plasticity models. As the above-described 3D X-ray methods become increasingly commonplace and accessible, we expect the synergy between these data and crystal plasticity simulation methods to increase further. In the coming decade, we expect that reduced-order models— especially those derived from machine learning techniques—which capture the essence of computationally complex full-field models will become more commonplace. As models are only as good as the physics they contain, the training of said reduced-order models will lean even more heavily on data derived from 3D experimental methods to better capture complex polycrystalline behaviors that may not be explicitly considered in full-field models.</p>
<p><strong>References</strong></p>
<p>[1] J. Bernier, M. Miller, A direct method for the determination of the mean orientation-dependent elastic strains and stresses in polycrystalline materials from strain pole figures, Journal of applied crystallography 39 (2006) 358–368.</p>
<p>[2] J. Hochhalter, G. Bomarito, S. Yeratapally, P. Leser, T. Ruggles, J. Warner, W. Leser, Non-deterministic calibration of crystal plasticity model parameters, in: Integrated Computational Materials Engineering (ICME), Springer International Publishing, 2020, 235 pp. 165–198.</p>
<p>[3] M. P. Echlin, J. C. Stinville, V. M. Miller, W. C. Lenthe, T. M. Pollock, Incipient slip and long range plastic strain localization in microtextured ti-6al-4v titanium, Acta Materialia 114 (2016) 164–175.</p>
<p>[4] M. Kasemer, M. P. Echlin, J. C. Stinville, T. M. Pollock, P. Dawson, On slip initiation in equiaxed α/β ti-6al-4v, Acta Materialia 136 (2017) 288–302.</p>
<p>[5] H. F. Poulsen, Three-dimensional X-ray diffraction microscopy: mapping polycrystals and their dynamics, Vol. 205, Springer Science & Business Media, 2004.</p>
<p>[6] R. Suter, D. Hennessy, C. Xiao, U. Lienert, Forward modeling method for microstructure reconstruction using x-ray diffraction microscopy: Single-crystal verification, Review of scientific instruments 77 (12) (2006) 123905.</p>
<p>[7] J. V. Bernier, N. R. Barton, U. Lienert, M. P. Miller, Far-field high-energy diffraction microscopy: a tool for intergranular orientation and strain analysis, The Journal of Strain Analysis for Engineering Design 46 (7) (2011) 527–547.</p>
<p>[8] W. Ludwig, S. Schmidt, E. M. Lauridsen, H. F. Poulsen, X-ray diffraction contrast tomography: a novel technique for three-dimensional grain mapping of polycrystals. i. direct beam case, Journal of Applied Crystallography 41 (2) (2008) 302–309.</p>
<p>[9] F. Bachmann, H. Bale, N. Gueninchault, C. Holzner, E. M. Lauridsen, 3d grain reconstruction from laboratory diffraction contrast tomography, Journal of Applied Crystallography 52 (3) (2019) 643–651.</p>
<p>[10] A. Cereser, M. Strobl, S. A. Hall, A. Steuwer, R. Kiyanagi, A. S. Tremsin, E. B. Knudsen, T. Shinohara, P. K. Willendrup, A. B. da Silva Fanta, et al., Time-of-flight three dimensional neutron diffraction in transmission mode for mapping crystal grain structures, Scientific reports 7 (1) (2017) 1–11.</p>
<p>[11] H. Proudhon, J. Li, P. Reischig, N. Gu´eninchault, S. Forest, W. Ludwig, Coupling diffraction contrast tomography with the finite element method, Advanced Engineering Materials 18 (6) (2016) 903–912.</p>
<p>[12] E. Wielewski, D. E. Boyce, J.-S. Park, M. P. Miller, P. R. Dawson, A methodology to determine the elastic moduli of crystals by matching experimental and simulated lattice strain pole figures using discrete harmonics, Acta Materialia 126 (2017) 469–480.</p>
<p>[13] P. R. Dawson, D. E. Boyce, J.-S. Park, E. Wielewski, M. P. Miller, Determining the strengths of HCP slip systems using harmonic analyses of lattice strain distributions, Acta Materialia 144 (2018) 92–106.</p>
<p>[14] R. Quey, L. Renversade, Optimal polyhedral description of 3d polycrystals: Method and application to statistical and synchrotron x-ray diffraction data, Computer Methods in Applied Mechanics and Engineering 330 (2018) 308–333.</p>
<p>[15] Neper: Polycrystal Generation and Meshing. URL <a href="https://neper.info/">https://neper.info/</a></p>
<p>[16] FEPX: Finite Element Polycrystal Plasticity. URL <a href="https://fepx.info/">https://fepx.info/</a></p>
<p>[17] R. Quey, M. Kasemer, The Neper/FEPX project: Free / open-source polycrystal generation, deformation simulation, and post-processing, IOP Conference Series: Materials Science and Engineering 1249 (1) (2022) 012021.</p>
<p>[18] D. Boyce, P. Shade, W. Musinski, M. Obstalecki, D. Pagan, J. Bernier, T. Turner, Estimation of anisotropic elastic moduli from high energy x-ray data and finite element simulations, Materialia 12 (2020) 100795.</p>
<p>[19] D. C. Pagan, P. A. Shade, N. R. Barton, J.-S. Park, P. Kenesei, D. B. Menasche, J. V. Bernier, Modeling slip system strength evolution in ti-7al informed by in-situ grain stress measurements, Acta Materialia 128 (2017) 406–417.</p>
<p>[20] A. Carrassi, M. Bocquet, L. Bertino, G. Evensen, Data assimilation in the geosciences: An overview of methods, issues, and perspectives, Wiley Interdisciplinary Reviews: Climate Change 9 (5) (2018) e535.</p>
<p>[21] M. Ghil, P. Malanotte-Rizzoli, Data assimilation in meteorology and oceanography, in: Advances in geophysics, Vol. 33, Elsevier, 1991, pp. 141–266.</p>
<p>[22] E. Kr¨oner, et al., Continuum theory of defects, Physics of defects 35 (1981) 217–315.</p>
<p>[23] D. C. Pagan, A. J. Beaudoin, Utilizing a novel lattice orientation based stress characterization method to study stress fields of shear bands, Journal of the Mechanics and Physics of Solids 128 (2019) 105–116.</p>
<p>[24] D. Naragani, P. Shade, W. Musinski, D. Boyce, M. Obstalecki, D. Pagan, J. Bernier, A. Beaudoin, Interpretation of intragranular strain fields in high-energy synchrotron xray experiments via finite element simulations and analysis of incompatible deformation, Materials & Design 210 (2021) 110053.</p>
<p>[25] K. E. Nygren, D. C. Pagan, J. V. Bernier, M. P. Miller, An algorithm for resolving intragranular orientation fields using coupled far-field and near-field high energy x-ray diffraction microscopy, Materials Characterization 165 (2020) 110366.</p>
<p>[26] D. C. Pagan, K. E. Nygren, M. P. Miller, Analysis of a three-dimensional slip field in a hexagonal ti alloy from in-situ high-energy x-ray diffraction microscopy data, Acta Materialia 221 (2021) 117372.</p>
<p>[27] E. Kr¨oner, Dislocations in crystals and in continua: a confrontation, International journal of engineering science 33 (15) (1995) 2127–2135.</p>
<p>[28] D. C. Pagan, C. R. Pash, A. R. Benson, M. P. Kasemer, Graph neural network modeling of grain-scale anisotropic elastic behavior using simulated and measured microscale data, npj Computational Materials 8 (1) (2022) 259.</p>
<p> </p>
</div></div></div>Fri, 27 Jan 2023 22:00:03 +0000dcp530326506 at https://imechanica.orghttps://imechanica.org/node/26506#commentshttps://imechanica.org/crss/node/26506Postdoctoral and PhD positions in synthesis and in situ micromechanics of nanocrystalline alloys
https://imechanica.org/node/26316
<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/13632">nanocrystalline alloys</a></div><div class="field-item odd"><a href="/taxonomy/term/13633">in-situ SEM</a></div><div class="field-item even"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/13634">magnetron sputter deposition</a></div><div class="field-item even"><a href="/taxonomy/term/581">digital image correlation</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>Applications are invited for postdoctoral and doctoral (PhD) research positions in the Department of Mechanical Engineering at the University of Vermont (USA) and are available immediately. The successful researchers will work in the Sansoz Laboratory for Nanostructured Materials Science and Engineering on funded projects to study grain boundary segregation and strain localization mechanisms in a range of nanocrystalline metallic alloys. These positions are focused on experimental nanocrystalline film synthesis and in-situ tensile SEM characterization. Desired fields of expertise are magnetron sputtering film deposition, film photolithography, in-situ SEM, EBSD, high-resolution digital image correlation, experimental mechanics and microplasticity, Matlab programming.</p>
<p>To apply or for more information, please follow this link: </p>
<p><a href="https://www.uvm.edu/~fsansoz/Openings/UVM_SansozGroup_Postdoctoral_and_PhD_Positions_2022.pdf" target="_blank" rel="noopener noreferrer">https://www.uvm.edu/~fsansoz/Openings/UVM_SansozGroup_Postdoctoral_and_PhD_Positions_2022.pdf</a></p>
</div></div></div>Wed, 26 Oct 2022 04:03:42 +0000Fred Sansoz26316 at https://imechanica.orghttps://imechanica.org/node/26316#commentshttps://imechanica.org/crss/node/26316Journal Club for September 2022: Mechanics of soft network materials
https://imechanica.org/node/26194
<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/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/9428">mechanical metamaterials</a></div><div class="field-item even"><a href="/taxonomy/term/6667">tissue engineering</a></div><div class="field-item odd"><a href="/taxonomy/term/13579">soft network materials</a></div><div class="field-item even"><a href="/taxonomy/term/13580">biomedical devices</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">Renheng Bo, Shunze Cao, and Yihui Zhang</p>
<p class="MsoNormal">Department of Engineering Mechanics, Tsinghua University</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>1. Introduction</strong></p>
<p class="MsoNormal">Soft network materials are a family of artificial materials consisting of strategically engineered microstructures, through which a tunable “softness” could always be achieved, regardless of the nature of constituent materials. For example, soft networks made of rigid materials can still offer a high level of stretchability and a low effective modulus. The conceptual design of network roots in nature – the ubiquitous fractal networks touching nearly every corner of living biosystems. Similar to the abundant biological diversity created by natural networks, the unparalleled design flexibility[1-6] of man-made soft networks enables the precision engineering of a huge family of structured materials with outstanding mechanical/physical properties[1, 2, 7-9], such as high stretchability, tunable porosity, high air permeability, defect-insensitive behavior, among others. </p>
<p class="MsoNormal">According to the geometry of the network microstructure, the existing soft network materials could be basically classified into two categories, including network materials with periodic microstructures and those with randomly distributed microstructures. Given the large variety of network designs and their prominent mechanical/physical properties, soft network materials are intensively explored for numerous applications (<strong>Figure 1a-d</strong>), including the cellular encapsulation of stretchable electronics (<strong>Figure 1a</strong>)[5, 10, 11], self-cooling emitter[12], mechanical metamaterials (<strong>Figure 1b</strong>)[1], regenerative medicine (<strong>Figure 1c</strong>)[13], and artificial tissues with biomimetic mechanical properties (<strong>Figure 1d</strong>)[13-15]. In this journal club, we discuss structural designs and mechanics modeling of soft network materials, and provide our perspectives on future research opportunities in this exciting area. </p>
<p><img title="Figure 1" src="https://imechanica.org/files/Figure%201_4.jpg" alt="" width="1141" height="501" /></p>
<p><strong>Figure 1 Applications of soft network materials.</strong> <strong>a)</strong> Encapsulation of stacked flexible electronics[10]. <strong>b)</strong> Mechanical metamaterials with tunable Poisson’s ratios[1]. <strong>c)</strong> Soft LCE networks for wound healing, scale bars = 1 cm[13]. <strong>d)</strong> 3D soft networks mimicking the J-shaped stress-strain curve of natural biological tissues, scale bars = 5 mm[16]. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>2. Design principles of soft network materials</strong></p>
<p class="MsoNormal"><strong>2D Soft Network Materials</strong></p>
<p class="MsoNormal"><strong>Figure 2a</strong> shows a representative random soft network prepared by electrospinning. This sort of network design originates mainly from simply replicating disorder natural structures. By taking advantage of the specific mechanical/biocompatible properties of synthetic/natural elastic polymer fibers, such designs can offer an excellent stretchability, and tunable effective modulus. This type of network materials usually consists of randomly oriented fibers with diameters varying from few nanometers (e.g., 2 nm) to micrometer scale (e.g., 10 mm), and micropores of dimensions ranging from 50 to 250 mm. Such relatively dense microstructures with additional growth factor would mimic extracellular matrix (ECM) in nature, providing a comfortable environment for spreading, proliferation, and differentiation of cells, thereby holding promising applications as tissue scaffolds. To be noted, the microstructure dimensions and physical properties of such networks (e.g., pore size, fiber diameters, stretchability, modulus, conductivity, and etc.) could be tuned by varying the precursor concentration, extruding velocity, applied voltage and other parameters.</p>
<p class="MsoNormal">Inspired by wavy microstructures found in many collagen tissues, 2D network design with periodic topologies consisting of curved filaments were derived from straight-beamed networks (<strong>Figure 2b i</strong>) to offer biomimetic J-shaped stress-strain response and strain-limiting behavior[17]. In particular, the curved building-block structures enable a bending-dominated deformation mode at small strains, with a transition into a stretching-dominated mode at high strains, which is close to that of biological tissues in nature. <strong>Figure</strong> <strong>2b</strong> <strong>ii</strong> shows a typical periodic 2D soft network design with horseshoe microstructures formed by two identical circular arcs. For a prescribed constituent material, tunable nonlinear mechanical responses could be achieved via adjusting its geometric parameters including the arc angle, and normalized width. Therefore, such network materials can be used in flexible electronics to allow its integration with skins in a mechanically-invisible manner[18]. </p>
<p class="MsoNormal">To further increase the stretchability, artificial fractals were introduced to the design of 2D networks (<strong>Figure 2c i</strong>)[19]. The fractal-inspired design harnesses the unique deformation mechanism of ordered unraveling (of the fractal microstructure) to offer a significantly enhanced elastic stretchability than the transitional pattern (without the fractal design). <strong>Figure 2c ii</strong> presents an example of network materials with fractal horseshoe microstructures and the deformation under uniaxial stretching. Introducing rotatable structural nodes (e.g., in the forms of ring or disk, as shown in <strong>Figure 2d i</strong>)[20] represents another design strategy to achieve an increased stretchability in the soft network material. Specifically, assuming an unvaried area of the topological unit, the use of rotatable nodes would reduce the bending strain of curved filaments by increasing their curvature radius and allowing the rotation to occur (<strong>Figure 2d ii</strong>). For a unit cell with structural node (i.e., composed of six identical circular arcs), its key geometric parameters include the arc angle, radius, normalized ligament width and node radius. The normalized ligament width plays a crucial role on the utmost strength of network, while the arc angle and normalized nodal radius mainly affect the stretchability. </p>
<p> </p>
<p class="MsoNormal"><strong>3D Soft Network Materials</strong></p>
<p class="MsoNormal">The burgeoning of additive manufacturing (AM) spurs rapid developments of 3D soft network materials in recent years. Amongst them, cylindrical networks stand as a typical 3D derivative of 2D soft networks with tunable mechanical properties[21]. Such cylindrical designs could take advantage of the relatively mature 2D designs to expand them into steric configurations. For instance, <strong>Figure 2e</strong> presents a 3D tube-like network consisting of three types of zigzag microstructures at different locations, enabling an unusual Poisson effect, as manifested by the various cross-sectional deformations. </p>
<p>To better replicate the real 3D configuration of natural collagenous fibers and their nonlinear mechanical responses, 3D soft network materials with engineered helical microstructures were developed, as shown in <strong>Figure 2f i </strong>(with an octahedral topology in this example). To avoid the geometric overlap of differently aligned microstructures at the connective nodes, an unconventional helical microstructure consisting of three segments is designed, including a central part that corresponds to an ideal helical structure and two joint parts that are modified to ensure a tangential attachment to the nodal regions of the network (<strong>Figure 2f ii</strong>). The central line of this helical microstructure can be characterized by parametric equations in analytical forms. The key geometrical parameters of helical microstructures include the fiber diameter, helix radius, the number of coils, pitch as well as joint length. </p>
<p><img title="Figure 2" src="https://imechanica.org/files/Figure%202_6.jpg" alt="" width="1140" height="644" /></p>
<p class="MsoNormal"><strong>Figure 2 Structural designs of soft network materials.</strong> <strong>a)</strong> SEM images of the soft network material with randomly distributed fibers: left side, non-oriented; right side, oriented, scale bar = 2μm. <strong>b)</strong> Representative configurations of rationally designed network materials containing straight (<strong>i</strong>) and curved horseshoe microstructures (<strong>ii</strong>)[17]. <strong>c)</strong> Schematical illustrations of 2D soft network with fractal horseshoe microstructures (<strong>i</strong>), and unravelling sequences of a second-order horseshoe microstructure with an arc angle of 240o under uniaxial stretching, scale bars = 5mm (<strong>ii</strong>)[19]. <strong>d) </strong>Schematical illustrations of 2D soft network with rotatable structural nodes (<strong>i</strong>), and the deformation sequence of a building-block structure under uniaxial stretching (<strong>ii</strong>)[20]. <strong>e)</strong> 3D printed cylindrical shells with engineered Poisson effects, where the left segment, middle segment, and right segment possess negative, zero (middle), and positive Poisson’s ratios, respectively, scale bars = 20μm.[21]. <strong>f) </strong>Schematical illustrations of 3D network materials with octahedral topology (<strong>i</strong>) and the geometric configurations of a representative helical microstructure (<strong>ii</strong>)[16].</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>3. Mechanics modeling of soft network materials</strong></p>
<p class="MsoNormal"><strong>Mechanical responses of soft network materials</strong></p>
<p class="MsoNormal">For random 2D network materials, the alignment of its composing fibers would gradually occur under uniaxial stretching. For instance, <strong>Figure 3a </strong>shows the true stress-strain curve of an electrospun amorphous PI network material with randomly distributed fibers, and the SEM images of its microstructures at initial state (0% strain) and deformed state (41% strain)[22]. Due to a lack of control over the microstructure topology, the nonlinear mechanical response can be adjusted only in a limited range.</p>
<p class="MsoNormal">For conventional lattice material with straight microstructures, the typical elastic-plastic responses under tension and compression before failure are presented in<strong> Figure 3b</strong>[23]. Obviously, it is quite difficult for such designs to replicate the nonlinear J-shaped stress-strain curves of biological tissues. </p>
<p class="MsoNormal">In terms of well-organized 2D soft networks (<strong>Figure 3c i</strong>)[18], its typical uniaxial stress-strain curve (<strong>Figure 3c ii</strong>) presents three phases, which is in line with that of soft biological tissues. The first phase (i.e., ‘toe’ region) is attributed to bending-dominated deformations of the curved filaments, yielding a low effective modulus. During the second phase (i.e., ‘heel’ region), the continuous stretching causes the curved filaments to rotate, bend and align to the loading direction, leading to a gradually increased modulus. When entering the third phase (i.e., ‘linear’ region), the stretching of constituent materials dominates the structural response. As a result, the soft network material shows a J-shaped stress-strain curve, which combines high levels of stretchability with a natural ‘strain-limiting’ mechanism that protects tissues from excessive strains. It is also notable that the effective modulus of the network material in the third phase could be 1-2 orders of magnitude higher than that seen in the first phase. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>Mechanics modeling of 2D soft network materials</strong></p>
<p class="MsoNormal">Given rapid developments of various 2D soft network materials, mechanics modeling has been attracting more and more attentions, aiming to provide theoretical basis of rapid network designs. Both micromechanics and phenomenological models have been established.</p>
<p class="MsoNormal">A micromechanics model of soft networks with horseshoe microstructures was developed through combining a <a title="Learn more about finite deformation from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/finite-deformation">finite deformation</a> constitutive relation of the building-block structure (i.e., horseshoe microstructure), with the analysis of equilibrium and deformation compatibility[17]. The mechanics analysis of the horseshoe microstructure is schematically illustrated in<strong> Figure 3d i</strong>, where the nonlinear load-displacement relationship can be obtained by the finite-deformation theory of curved beams. Considering the structural periodicity, a unit cell composed of three differently oriented horseshoe microstructures is further analyzed to establish the equilibrium equations and deformation compatibility of the entire network, as schematically shown in <strong>Figure</strong> <strong>3d</strong> <strong>ii</strong>. The equilibrium equations can be derived by considering the equilibrium of the unite cell and the connective node. The deformation compatibility requires that the side lengths and interior angles of the deformed triangle should satisfy a set of geometric equations. Besides, the angle between the tangent lines of different horseshoe microstructures keeps unchanged during the deformation. By solving these sets of equations, the nonlinear stress-strain curves and deformed patterns can be predicted, which agree well with both finite element analyses (FEA) results and experiments, for a wide range of geometric parameters, as shown in <strong>Figure 3e i </strong>and<strong> ii</strong>.</p>
<p class="MsoNormal">Later on, this micromechanics model was extended to study nonlinear mechanical behaviors of soft networks with fractal-inspired horseshoe microstructures (<strong>Figure 2c</strong>)[19], <a title="Learn more about anisotropic from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/anisotropic">anisotropic</a> mechanical responses of soft networks with horseshoe microstructures[24], and stretchability enhancement in soft networks with rotatable nodes and horseshoe microstructures[20]. Recently, the model was further extended to consider soft networks with a wide range of microstructures (with varying curvatures) whose central lines can be depicted by parametric functions in polygonal forms[25].</p>
<p class="MsoNormal">Despite the progress, the above micromechanics models are applicable only to soft network materials with a certain type of geometric constructions. A more general micromechanics model allowing the prediction of arbitrarily architected soft networks remain challenging. The phenomenological model can overcome this limitation to some extent, however, by sacrificing a certain degree of prediction accuracy. Based on this concept, a single-parameter phenomenological framework, incorporating a two-segment model that exploits simple, explicit expressions to capture the J-shaped stress-strain relationship, was proposed. Additionally, the machine learning (ML) approach was introduced to enable the determination of the single phenomenological parameter (<strong>Figure 3f i</strong>)[26]. The mechanical responses of several randomly generated 2D soft networks were well predicted via the phenomenological framework, and the results were validated through FEA and experimental measurements (<strong>Figure 3f ii</strong>). </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>Mechanics modeling of 3D soft network materials</strong></p>
<p class="MsoNormal">Recently, a micromechanics model was established to investigate the nonlinear anisotropic mechanical properties of the soft 3D network materials consisting of helical microstructures[27]. The model starts with the mechanics analyses of an ideal helix under uniaxial stretching, where the deformed structure was assumed to maintain an ideal helical configuration, as schematically shown in<strong> Figure 3g i</strong>. The constitutive relation of the loading force (<em>F</em>) and the elongation (<em>p</em>/<em>p_</em>0) of the helix along the helical axis could be obtained based on this assumption. Then, every unit segment (d<em>S</em>) of the helical microstructure (including two joint parts) undergoes a similar deformation to that of an ideal helical structure, as schematically shown in<strong> Figure 3g ii</strong>. This allowed us to exploit the theory of the ideal helical structure to analyze the deformation of every unit segment in the helical microstructure, and resort to the concept of calculus to determine the elongation of the entire structure. As the force components of load-bearing microstructures along the loading direction mainly contribute to the effective stress (<em>σ</em>) of soft 3D network materials, the contributions from the other helical microstructures are neglected for simplicity. Based on the connection of mechanical responses of building-block structures (i.e., helical microstructures) and that of 3D soft network materials, a theoretical model can be developed to predict effective stress-strain (<em>σ</em>–<em>ɛ</em>applied) curves of 3D soft network materials. For instance, for 3D soft cubic network materials consist of helical microstructures under the uniaxial stretching along a principal direction, only the group of helical microstructures parallel with the loading direction is straightened, and thereby contributes to the stress of the entire 3D network. The other two groups of helical microstructures perpendicular to the loading direction mainly undergo rigid body translation to ensure the connectivity, and experience negligible stretching/compression deformations. Due to the lattice periodicity, a representative unit cell can be used to establish the equilibrium equations and deformation compatibility of the entire 3D soft cubic network materials, as schematically shown in <strong>Figure 3g iii</strong>. The stress-strain curves obtained from theoretical model show good agreements with FEA and experimental results, as shown in <strong>Figure 3g iv</strong>.</p>
<p><img title="Figure 3" src="https://imechanica.org/files/Figure%203_6.jpg" alt="" width="1141" height="645" /></p>
<p><strong>Figure 3 Mechanical properties of soft network materials.</strong> <strong>a)</strong> Representative uniaxial tensile characterization of electrospun PI membrane, and the SEM images showing the microstructural network at the initial and deformed states[22]. <strong>b)</strong> Tensile and compressive stress-strain curves of 3D network materials with straight beams[23]. <strong>c)</strong> optical images of soft network materials with horseshoe microstructures at different tensile strain (<strong>i</strong>), a representative J-shaped stress-strain curve of soft network material with horseshoe microstructures with three distinct phases (<strong>ii</strong>). <strong>d)</strong> Schematic illustration of a mechanics model for the horseshoe microstructure (<strong>i</strong>), schematic illustration of the theoretical model of the hierarchical triangular lattice subject to a uniform tensile stress along horizontal stretching (<strong>ii</strong>)[17]. <strong>e) </strong>Theoretical, FEA, and experimental results of stress–strain curves for the triangular network materials with horseshoe microstructure: (i) theoretical and experimental results of stress-strain curves for a wide range of arc angle, and fixed normalized width, (ii) theoretical and FEA results of stress-strain curves for a wide range of normalized width, and fixed arc angle (<strong>iii</strong>)[17]. <strong>f)</strong> Flow chart for acquiring nonlinear stress-strain curves of soft network materials with randomly curved microstructures based on the phenomenological framework (<strong>i</strong>), uniaxial tensile responses of two types of random soft networks predicted by the phenomenological framework, and their corresponding validation via FEA and experiments (<strong>ii</strong>)[26]. <strong>g)</strong> Schematic illustration of mechanics model for helical microstructure under uniaxial stretching, initial and deformed configurations of an ideal helical structure (<strong>i</strong>), deformation of a unit element for a helical microstructure with nonuniform curvature (<strong>ii</strong>), deformation analyses of soft cubic network materials with helical microstructure under horizontal stretching (<strong>iii</strong>), the representative stress-strain curves of 3D cubic network material obtained from theoretical model, FEA, and experiments (<strong>iv</strong>)[27].</p>
<p class="MsoNormal"><strong> </strong></p>
<p class="MsoNormal"><strong>4. Summaries and perspectives </strong></p>
<p class="MsoNormal">Overall, we have briefly discussed the structural designs and mechanics modeling of soft network materials, covering network materials with both randomly and periodically distributed microstructures, either in 2D or 3D constructions. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>Perspectives on mechanics</strong></p>
<p class="MsoNormal">In practical applications, soft network materials would often undergo biaxial tension or coupled tension/shear loadings, instead of the uniaxial tension. Therefore, to understand the intricate deformation and failure behaviors of soft network materials under these complex loading conditions, developing a new micromechanics model in a general stress space is highly desirable. </p>
<p class="MsoNormal">In addition, functionalities and performances of soft network materials rely on both their structural design and the nature of constituent materials. Therefore, strategic integration of soft active materials (under external thermal, electric, magnetic or optical stimuli) with the network design could allow access to active mechanical metamaterials that offer exotic mechanical behavior or mechanical properties that surpass those of conventional materials in nature, such as negative Poisson’s ratios, unusual swelling and thermal expansion responses, programmable multistability, and abnormal acoustic properties[1,2,8,13,28]. This would offer great opportunities for future device designs and applications. For instances, the use of LCEs[29] in soft network materials might give reversible biaxial deformation capability inaccessible previously. Soft network materials composed of supramolecular polymers[30] might present extreme stretchability exceeding 4000% strain under uniaxial stretching[31]. Soft network materials affording rapid reversible transformation of topologies could be prepared thanks to the uncover of a liquid-induced mechanism[32]. Developing coupled multifield mechanics model for active network materials is more challenging, yet of pivotal importance in the network designs.</p>
<p class="MsoNormal">Last but not least, as mentioned previously, we have preliminarily used machine learning (i.e., to obtain phenomenological parameters) to assist the phenomenological framework to predict the J-shaped stress-strain curves of arbitrary network materials. Considering its strong capability, machine learning could be further used to resolve the inverse design problems of soft network materials for any targeted nonlinear mechanical responses. Future opportunities might lie in establishment of the mapping relation from one desired stress-strain curve to several potential network configurations, by providing additional key factors such as the microstructure geometry, and topological information (e.g., number of microstructures connecting to each structural node). </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>Perspective on synthesis and fabrication</strong></p>
<p class="MsoNormal">Well-organized 2D and 3D networks show an extraordinary level of design flexibility, and thus, their properties (i.e., not only mechanical properties but also others, such as electrical and optical properties) could be customized on demands. This makes them promising candidates for emerging biomedical applications such microtissues scaffolds and organoid culture, which often require densely distributed nanostructures. However, due to current fabrication limits, preparation approaches for macroscopic network materials with well-defined nanostructures have not yet been developed. Meanwhile, random 2D network materials, usually in the form of films or membranes, feature densely distributed self-assembled nanostructures, which are similar to naturally developed ECMs. This makes them ideal for both <em>in vitro</em> and <em>in vivo</em> biomedical applications. However, the lack of structural control hinders their practical applications. Therefore, hybrid architectures consisting of active surfaces (i.e., random network materials with nanostructures) supported by well-designed network materials could be of great interest for future explorations.</p>
<p class="MsoNormal">The blossoms of flexible electronics and materials sciences have enabled the integration of functional devices with advanced artificial structures. The highly designable soft network materials with tunable physical/chemical properties stand as very suitable candidates for such purpose, which would offer unprecedented opportunities for applications spanning real-time monitoring of growing tissues, <em>in</em> <em>situ</em> study of organisms regeneration, smart patch for regenerative medicine, and continuously shaping of organoids among others.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><strong>References</strong></p>
<p class="EndNoteBibliography">1. H. Zhang, X. Guo, J. Wu, D. Fang, Y. Zhang, Soft mechanical metamaterials with unusual swelling behavior and tunable stress-strain curves. <em>Science Advances</em> <strong>4</strong>, eaar8535 (2018).</p>
<p class="EndNoteBibliography">2. J. Liu, D. Yan, W. Pang, Y. Zhang, Design, fabrication and applications of soft network materials. <em>Materials Today</em> <strong>49</strong>, 324-350 (2021).</p>
<p class="EndNoteBibliography">3. Y. Yin, M. Li, Z. Yang, Y. Li, Stretch-induced shear deformation in periodic soft networks. <em>Extreme Mechanics Letters</em> <strong>47</strong>, 101370 (2021).</p>
<p class="EndNoteBibliography">4. W. Yang, Q. Liu, Z. Gao, Z. Yue, B. Xu, Theoretical search for heterogeneously architected 2D structures. <em>Proceedings of the National Academy of Sciences</em> <strong>115</strong>, E7245-E7254 (2018).</p>
<p class="EndNoteBibliography">5. Z. Yang<em> et al.</em>, Conductive and elastic 3D helical fibers for use in washable and wearable electronics. <em>Advanced Materials</em> <strong>32</strong>, 1907495 (2020).</p>
<p class="EndNoteBibliography">6. Z.-P. Wang, Y. Wang, L. H. Poh, Z. Liu, Integrated shape and size optimization of curved tetra-chiral and anti-tetra-chiral auxetics using isogeometric analysis. <em>Composite Structures</em>, 116094 (2022).</p>
<p class="EndNoteBibliography">7. A. Rafsanjani, A. Akbarzadeh, D. Pasini, Snapping mechanical metamaterials under tension. <em>Advanced Materials</em> <strong>27</strong>, 5931-5935 (2015).</p>
<p class="EndNoteBibliography">8. Y. Chen, T. Li, F. Scarpa, L. Wang, Lattice metamaterials with mechanically tunable Poisson’s ratio for vibration control. <em>Physical Review Applied</em> <strong>7</strong>, 024012 (2017).</p>
<p class="EndNoteBibliography">9. Q. Wang<em> et al.</em>, Lightweight mechanical metamaterials with tunable negative thermal expansion. <em>Physical review letters</em> <strong>117</strong>, 175901 (2016).</p>
<p class="EndNoteBibliography">10. H. Song<em> et al.</em>, Highly-integrated, miniaturized, stretchable electronic systems based on stacked multilayer network materials. <em>Science Advances</em> <strong>8</strong>, eabm3785 (2022).</p>
<p class="EndNoteBibliography">11. Z. Ma<em> et al.</em>, Permeable superelastic liquid-metal fibre mat enables biocompatible and monolithic stretchable electronics. <em>Nature Materials</em> <strong>20</strong>, 859-868 (2021).</p>
<p class="EndNoteBibliography">12. D. Li<em> et al.</em>, Scalable and hierarchically designed polymer film as a selective thermal emitter for high-performance all-day radiative cooling. <em>Nature Nanotechnology</em> <strong>16</strong>, 153-158 (2021).</p>
<p class="EndNoteBibliography">13. J. Wu<em> et al.</em>, Liquid crystal elastomer metamaterials with giant biaxial thermal shrinkage for enhancing skin regeneration. <em>Advanced Materials</em> <strong>33</strong>, 2106175 (2021).</p>
<p class="EndNoteBibliography">14. X. Xin, L. Liu, Y. Liu, J. Leng, 4D pixel mechanical metamaterials with programmable and reconfigurable properties. <em>Advanced Functional Materials</em> <strong>32</strong>, 2107795 (2022).</p>
<p class="EndNoteBibliography">15. Y. Gao, B. Li, J. Wang, X.-Q. Feng, Fracture toughness analysis of helical fiber-reinforced biocomposites. <em>Journal of the Mechanics and Physics of Solids</em> <strong>146</strong>, 104206 (2021).</p>
<p class="EndNoteBibliography">16. D. J. Yan<em> et al.</em>, Soft three-dimensional network materials with rational bio-mimetic designs. <em>Nature Communications</em> <strong>11</strong>, (2020).</p>
<p class="EndNoteBibliography">17. Q. Ma<em> et al.</em>, A nonlinear mechanics model of bio-inspired hierarchical lattice materials consisting of horseshoe microstructures. <em>Journal of the Mechanics and Physics of Solids</em> <strong>90</strong>, 179-202 (2016).</p>
<p class="EndNoteBibliography">18. K. I. Jang<em> et al.</em>, Soft network composite materials with deterministic and bio-inspired designs. <em>Nature Communications</em> <strong>6</strong>, (2015).</p>
<p class="EndNoteBibliography">19. Q. Ma, Y. H. Zhang, Mechanics of Fractal-Inspired Horseshoe Microstructures for Applications in Stretchable Electronics. <em>Journal of Applied Mechanics, Transactions ASME</em> <strong>83</strong>, (2016).</p>
<p class="EndNoteBibliography">20. J. X. Liu, D. J. Yan, Y. H. Zhang, Mechanics of unusual soft network materials with rotatable structural nodes. <em>Journal of the Mechanics and Physics of Solids</em> <strong>146</strong>, (2021).</p>
<p class="EndNoteBibliography">21. J. X. Liu, Y. H. Zhang, Soft network materials with isotropic negative Poisson's ratios over large strains. <em>Soft Matter</em> <strong>14</strong>, 693-703 (2018).</p>
<p class="EndNoteBibliography">22. M. N. Silberstein, C.-L. Pai, G. C. Rutledge, M. C. Boyce, Elastic–plastic behavior of non-woven fibrous mats. <em>Journal of the Mechanics and Physics of Solids</em> <strong>60</strong>, 295-318 (2012).</p>
<p class="EndNoteBibliography">23. B. B. Babamiri, H. Askari, K. Hazeli, Deformation mechanisms and post-yielding behavior of additively manufactured lattice structures. <em>Materials & Design</em> <strong>188</strong>, 108443 (2020).</p>
<p class="EndNoteBibliography">24. Y. F. Yin, Z. Zhao, Y. H. Li, Theoretical and experimental research on anisotropic and nonlinear mechanics of periodic network materials. <em>Journal of the Mechanics and Physics of Solids</em> <strong>152</strong>, (2021).</p>
<p class="EndNoteBibliography">25. L. Dong<em> et al.</em>, Modeling and Design of Periodic Polygonal Lattices Constructed from Microstructures with Varying Curvatures. <em>Physical Review Applied</em> <strong>17</strong>, 044032 (2022).</p>
<p class="EndNoteBibliography">26. S. Cao<em> et al.</em>, A phenomenological framework for modeling of nonlinear mechanical responses in soft network materials with arbitrarily curved microstructures. <em>Extreme Mechanics Letters</em>, 101795 (2022).</p>
<p class="EndNoteBibliography">27. J. H. Chang, D. J. Yan, J. X. Liu, F. Zhang, Y. H. Zhang, Mechanics of Three-Dimensional Soft Network Materials With a Class of Bio-Inspired Designs. <em>Journal of Applied Mechanics, Transactions ASME</em> <strong>89</strong>, (2022).</p>
<p class="EndNoteBibliography">28. Y. Kim, H. Yuk, R. Zhao, S. A. Chester, X. Zhao, Printing ferromagnetic domains for untethered fast-transforming soft materials. <em>Nature</em> <strong>558</strong>, 274-279 (2018).</p>
<p class="EndNoteBibliography">29. K. M. Herbert<em> et al.</em>, Synthesis and alignment of liquid crystalline elastomers. <em>Nature Reviews Materials</em> <strong>7</strong>, 23-38 (2022).</p>
<p class="EndNoteBibliography">30. Z. Huang<em> et al.</em>, Highly compressible glass-like supramolecular polymer networks. <em>Nature materials</em> <strong>21</strong>, 103-109 (2022).</p>
<p class="EndNoteBibliography">31. J. Liu<em> et al.</em>, Tough supramolecular polymer networks with extreme stretchability and fast room<span lang="ZH-CN" xml:lang="ZH-CN">‐</span>temperature self-healing. <em>Advanced Materials</em> <strong>29</strong>, 1605325 (2017).</p>
<p class="EndNoteBibliography">32. S. Li<em> et al.</em>, Liquid-induced topological transformations of cellular microstructures. <em>Nature</em> <strong>592</strong>, 386-391 (2021).</p>
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</div></div></div>Tue, 30 Aug 2022 15:54:35 +0000Yihui Zhang26194 at https://imechanica.orghttps://imechanica.org/node/26194#commentshttps://imechanica.org/crss/node/26194Two postdoctoral positions in computational mechanics in Ben Gurion university and Ariel university, Israel, are available immediately
https://imechanica.org/node/25479
<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/4201">Python</a></div><div class="field-item odd"><a href="/taxonomy/term/9601">FE modeling</a></div><div class="field-item even"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/13273">Structural impact analysis</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="MsoBodyText">Two postdoctoral positions are available in Israel for one year, with the possibility</p>
<p class="MsoBodyText">of renewal for up to three years. The projects will be conducted in AU and BGU, under close collaboration, and will be jointly mentored by Dr. Pavel Trapper (BGU) and Dr.</p>
<p class="MsoBodyText">Avshalom Ganz (AU).</p>
<p class="MsoBodyText"><span> </span></p>
<p>Research:<br /></p><p class="MsoBodyText"><strong><span> </span></strong></p>
<p class="MsoBodyText">Research topics include:</p>
<p class="MsoBodyText"><span> </span></p>
<p class="MsoListParagraph"><span>1.<span> </span></span>Improving stability and durability of submarine transport pipeline free spans:</p>
<p class="MsoBodyText"><span> </span></p>
<p class="MsoBodyText">In this research we plan to investigate the effect of buoyancy modules on static and dynamic pipeline free span performance. In addition, the efficiency of adding additional masses and tuned-mass dampers (TMD) on free span to move its natural frequencies from the resonant ones.</p>
<p class="MsoBodyText"><span> </span></p>
<p class="MsoBodyText">The proposed study will be mostly based on detailed comprehensive parametric study, performed within FE program Abaqus. The result data base obtained within the above parameter analysis will be adopted to develop simplified methodology regarding the way free spans enhanced with those devices.</p>
<p class="MsoBodyText"> </p>
<p class="MsoBodyText"><span> </span></p>
<p class="MsoListParagraph"><span>2.<span> </span></span>Assimilating the effects of aggregates on concrete under impact to LDPM model: In this research we plan to enhance the LDPM model, developed at Northwestern</p>
<p class="MsoBodyText">University, at the dynamic domain. Specifically, we will consider the micro inertia effects and the dynamic crack propagation affected by the aggregates. We will characterize those effects in the mesoscopic level, develop computational algorithms to represent those effects, indirectly, and assimilate the algorithm in the LDPM model</p>
<p class="MsoBodyText"><span> </span></p>
<p class="MsoNormal"><strong>Start date: Available immediately</strong>, open until filled.</p>
<p class="MsoBodyText"><span> </span></p>
<p class="MsoBodyText"><strong>Qualifications: </strong>Ph.D. in civil engineering, mechanical engineering, or related field.</p>
<p class="MsoBodyText"> </p>
<p class="MsoBodyText">Candidates are expected to have strong background in one or more of the following:</p>
<p class="MsoBodyText"><span> </span></p>
<p class="MsoListParagraph"><span><span>·<span> </span></span></span>Structural dynamics modelling and simulation, preferably Abaqus</p>
<p class="MsoListParagraph"><span><span>·<span> </span></span></span>Experience in programming and scientific algorithms, <strong>Python</strong></p>
<p class="MsoListParagraph"><span><span>·<span> </span></span></span>Micromechanics</p>
<p class="MsoListParagraph"><span><span>·<span> </span></span></span>Structural impact analysis</p>
</div></div></div>Wed, 06 Oct 2021 13:30:14 +0000Mirit Sharabi25479 at https://imechanica.orghttps://imechanica.org/node/25479#commentshttps://imechanica.org/crss/node/25479A micromechanics-based deep learning model for short fiber composites
https://imechanica.org/node/25080
<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/12101">deep learning</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/13106">short fiber composites</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 curious about application of machine learning techniques in mechanics problems, our latest paper is probably interesting for you. In this paper, we are proposing a micromechanics-based artificial neural networks model for short fiber composites. You can find the paper here: </span><span><span><a href="https://www.sciencedirect.com/science/article/pii/S1359836821001281 ">https://www.sciencedirect.com/science/article/pii/S1359836821001281 </a></span></span></p>
</div></div></div>Tue, 30 Mar 2021 13:19:55 +0000Mirkhalaf25080 at https://imechanica.orghttps://imechanica.org/node/25080#commentshttps://imechanica.org/crss/node/25080Postdoc in micromechanical characterization of lithium ion batteries
https://imechanica.org/node/24998
<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/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/293">nanoindentation</a></div><div class="field-item even"><a href="/taxonomy/term/7849">lithium-ion batteries</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>A one-plus-one year post-doctoral position is available at KTH Royal Institute of Technology in Stockholm, Sweden. The project aim is to develop reliable methods for material characterization of the mechanical properties on the micrometer scale.</span></p>
<p>The application deadline is 2021-04-15.</p>
<p>Apply on the KTH website: <a href="https://www.kth.se/en/om/work-at-kth/lediga-jobb/what:job/jobID:386387/where:4/">https://www.kth.se/en/om/work-at-kth/lediga-jobb/what:job/jobID:386387/where:4/</a></p>
<p> </p>
<p> </p>
</div></div></div>Fri, 05 Mar 2021 14:47:26 +0000August Brandberg24998 at https://imechanica.orghttps://imechanica.org/node/24998#commentshttps://imechanica.org/crss/node/24998Integrated Computational Materials Engineering (ICME) conference
https://imechanica.org/node/24604
<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/934">Composites</a></div><div class="field-item odd"><a href="/taxonomy/term/12265">Printed materials</a></div><div class="field-item even"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item odd"><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>The <strong>ICME Conference 2020</strong>, a HxGN LIVE event is a 3-days intensive <a href="https://icmeconference.com/agenda/">online conference</a> on <strong>October 6-8, 2020</strong> for executives, R&D, manufacturing professionals, engineers, and designers to learn, explore and share about Integrated Computational Materials Engineering (ICME) to enable companies to blur the boundaries between manufacturing, materials and part performance for the optimal design of innovative quality products. As a bonus, we offer you free <strong><a href="https://icmeconference.com/workshops/">workshops</a></strong> and <a href="https://icmeconference.com/material-experts/">introductory trainings</a> as well on the following week – on <strong>October 13-16, 2020</strong>.</p>
<p>Join hundreds of participants across the globe at this <strong><a href="https://icmeconference.com/agenda/">technical conference</a></strong> to listen to inspiring keynotes, thought leaders of the industries, best-in-class presenters from Material Suppliers, Tiers and OEMs from around the world. If you are using ICME or looking into using it to accelerate the rate of production from concept to reality, this event is for you. During the event, our material experts and <a href="https://icmeconference.com/sponsors/">sponsors</a> will be at your disposal. You can visit the dedicated event room and request for a live & online one-to-one meeting.</p>
<p><a href="https://www.icmeconference.com/the-event/">https://www.icmeconference.com/the-event/</a></p>
</div></div></div>Fri, 18 Sep 2020 15:00:14 +0000Marieme Imene EL GHEZAL24604 at https://imechanica.orghttps://imechanica.org/node/24604#commentshttps://imechanica.org/crss/node/24604PhD scholarship application in Geomechanics at University of Lyon - Micromechanical and multi-scale behaviour of damaged heterogeneous rocks around underground excavations
https://imechanica.org/node/24083
<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/7267">numerical modelling</a></div><div class="field-item odd"><a href="/taxonomy/term/7457">rock mechanics</a></div><div class="field-item even"><a href="/taxonomy/term/12754">FEM in porous media</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/545">damage</a></div><div class="field-item odd"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item even"><a href="/taxonomy/term/12755">double-scale behaviour</a></div><div class="field-item odd"><a href="/taxonomy/term/12756">underground drilling</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><strong>Description:</strong></p>
<p>The goal of this project is to investigate the multi-scale behaviour of clay rocks, going from microscopic to macroscopic scale, with application to underground drilling. The research will be based on multi-scale approach and numerical method allowing to model microstructure media in a double-scale framework (FEMxFEM). Please, see the full description in the attached file here below.</p>
<p>Applications are welcome from students graduated in the areas of civil, mechanical, physical, and materials engineering, or geosciences. Basic knowledge in mechanics of porous media, constitutive modelling of geomaterials and interest for numerical methods is required. Applications should be submitted by May 2020 by emailing a CV, a PhD summary, publications references, scientific/academic references, and recommendation letter.</p>
<p> </p>
<p><strong>Details:</strong></p>
<p>Full description: See attached file</p>
<p>Laboratory: Laboratoire de Tribologie et Dynamique des Systèmes (LTDS), Ecole Nationale des Travaux Publics de l'Etat (ENTPE), Géo-matériaux et Constructions Durables (GCD).</p>
<p>Location: Lyon, France</p>
<p>Period: 3-year scholarship application</p>
<p>Contact: Benoît Pardoen, <a href="mailto:benoit.pardoen@entpe.fr">benoit.pardoen@entpe.fr</a></p>
<p> </p>
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</div></div></div>Fri, 03 Apr 2020 08:12:31 +0000benoit.pardoen24083 at https://imechanica.orghttps://imechanica.org/node/24083#commentshttps://imechanica.org/crss/node/24083Nonlocal Micromechanics of Composites of both Random and Periodic Structures (Background, Opportunities and Prospects)
https://imechanica.org/node/23841
<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/5914">nonlocal</a></div><div class="field-item odd"><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>An extended abstract dedicated to nonlocal (in the sense of either Eringen or Silling) micromechanics is attached. It can’t be considered as a review in any sense. It is just a personal vision on a new area of micromechanics, in particularly based on the author’s publications (references on hundreds related papers can be found in the referred publications). The style of the abstract is plausible rather than rigorous that willfully used by the author just for initiation of discussions in the new prospective area of micromechanics.</span></p>
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</div></div></div>Mon, 16 Dec 2019 03:13:02 +0000Valeriy Buryachenko23841 at https://imechanica.orghttps://imechanica.org/node/23841#commentshttps://imechanica.org/crss/node/23841Micromechanical 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/23105PhD position at Technical University of Denmark (DTU) in Damage Tolerant Composite Materials
https://imechanica.org/node/22315
<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/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/8386">Microscale testing</a></div><div class="field-item even"><a href="/taxonomy/term/1464">finite element modeling</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 new PhD position is vacant at the Section of Composites and Materials Mechanics of the Department of Wind Energy at the Technical University of Denmark (DTU). The PhD project will concern damage tolerance of composite materials subjected to static and cyclic loading. The objective is to creacte enhanced fracture resistance by facilitating the formation of multiple cracks with large-scale fiber bridging along the interfaces in a layered composite by controlled mechanical properties by surface treatments.</p>
<p>Read more about the position at the DTU hime page:<span lang="EN-US" xml:lang="EN-US"> </span><span lang="EN" xml:lang="EN"><a href="http://www.dtu.dk/english/About/JOB-and-CAREER/vacant-positions/job?id=b79a817d-32d9-4c4f-bdf4-7d7265c8e2ca">PhD scholarship in Damage Tolerant Composite Materials for Wind Turbine Blades</a></span></p>
<p> </p>
</div></div></div>Mon, 16 Apr 2018 07:03:04 +0000Bent F. Sørensen22315 at https://imechanica.orghttps://imechanica.org/node/22315#commentshttps://imechanica.org/crss/node/22315PhD position at University of Lorraine, France
https://imechanica.org/node/22267
<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/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/7035">Constitutive modeling Damage</a></div><div class="field-item even"><a href="/taxonomy/term/10784">phase field approach</a></div><div class="field-item odd"><a href="/taxonomy/term/309">evolution of microstructure</a></div><div class="field-item even"><a href="/taxonomy/term/6784">homogenisation methods</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>Project title: Micromechanical modeling of geomaterials by considering the microstructural anisotropy </p>
<p>Location: Nancy (France), Georessources Laboratory, University of Lorraine</p>
<p>Starting date and duration: September/October, 2018, 3 years</p>
<p>Candidates: First-class undergraduate and master degrees in mechanics, applied mathematics, civil engineering or other related disciplines. The candidates should be motivated by research in theoretical and numerical modeling and have a good background in mathematics, mechanics of materials, finite element method, etc. </p>
<p>Application: the applicant could firstly contact Prof. Albert Giraud (<a href="mailto:albert.giraud@univ-lorraine.fr">albert.giraud@univ-lorraine.fr</a>) and Dr. Long Cheng (<a href="mailto:long.cheng@univ-lorraine.fr">long.cheng@univ-lorraine.fr</a>) by Email enclosing a CV, the grades obtained for the Master (or equivalent) degree and a copy of the diploma if it is available, two letters of recommendation with the contact of referees.</p>
<p>The official application should be realized on the website of the Doctoral school RP2E (Science and Engineering for "Resources, Processes, Products and Environment"): <a href="http://rp2e.univ-lorraine.fr/index.php?id=5">http://rp2e.univ-lorraine.fr/index.php?id=5</a></p>
<p>An interview will be summoned to the appropriate candidates after a first examination of applications.</p>
<p>Deadline for application: 30 April, 2018</p>
<p> </p>
<p> </p>
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</div></div></div>Thu, 29 Mar 2018 14:01:48 +0000Long.Cheng22267 at https://imechanica.orghttps://imechanica.org/node/22267#commentshttps://imechanica.org/crss/node/222672 PhD Positions: Solid mechanics, fibre networks
https://imechanica.org/node/22075
<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/179">solid mechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/935">FEA</a></div><div class="field-item odd"><a href="/taxonomy/term/11921">Fibre-based Materials</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 lang="EN-US" xml:lang="EN-US">Would you like to be a part of the Ph.D. research training program linked to the industry and leading European research organizations? Are you interested in mastering advanced experimental and modelling tools? Please, apply!</span></p>
<p class="MsoNormal"><span lang="EN-US" xml:lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="SV" xml:lang="SV"><a href="https://www.kth.se/en/om/work-at-kth/lediga-jobb/what:job/jobID:189601/where:4/"><span lang="EN-US" xml:lang="EN-US">https://www.kth.se/en/om/work-at-kth/lediga-jobb/what:job/jobID:189601/where:4/</span></a></span></p>
<p class="MsoNormal"><span lang="SV" xml:lang="SV"> </span></p>
<p class="MsoNormal"><span lang="SV" xml:lang="SV"><a href="https://www.kth.se/en/om/work-at-kth/lediga-jobb/what:job/jobID:189846/where:4/">https://www.kth.se/en/om/work-at-kth/lediga-jobb/what:job/jobID:189846/where:4/</a></span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span lang="SV" xml:lang="SV">More about the FibreNet consortium:</span></p>
<p class="MsoNormal"><span lang="EN-US" xml:lang="EN-US"><a href="http://fibrenet.eu/positions/">http://fibrenet.eu/positions/</a></span></p>
</div></div></div>Wed, 24 Jan 2018 20:34:10 +0000August Brandberg22075 at https://imechanica.orghttps://imechanica.org/node/22075#commentshttps://imechanica.org/crss/node/22075Call for papers: Special issue of IJMCE journal on Multiscale multiphysics modellig of materials
https://imechanica.org/node/21970
<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/519">call for papers</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/11524">Atomistic Computer Modeling of Materials; Atomistic continuum coupling; Multiscale modelling; Composites; Computational micromechanics; Computational materials science; Strength;</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>Call for papers: </strong><span><strong>Special issue of IJMCE journal on Multiscale multiphysics modellig of materials</strong></span></p>
<p>International Symposium on Multiscale Computational Analysis of Complex Materials (MCACM) took place in Copenhagen, Denmark, 29-31.August 2017 (<a href="http://www.conferencemanager.dk/mcacm">http://www.conferencemanager.dk/mcacm</a>). The programm of the symposium is given <a href="https://drive.google.com/open?id=0ByqVBuYpuldFbm83bjdTMzU2dnM">here</a>, and the short photo report is given on<a href="https://drive.google.com/file/d/1qeeNZjGmsHAAikuOiT7epNZ7HNxz96aq/view?usp=sharing"> this page</a>. </p>
<p class="MsoNormal"><span lang="EN-US" xml:lang="EN-US">A special issue of the </span>International Journal for Multiscale Computational Engineering/ IJMCE, devoted to the presentations at the MCACM Symposium, will be published in 2018. The best paper selected by the symposium participants, will receive a special plaque and monetary award, which will be handed over officially at at the WCCM 2018/World Congress in Computational Mechanics in 2018 in New York. The journal webpage is: <a href="http://www.begellhouse.com/journals/multiscale-computational-engineering.html">http://www.begellhouse.com/journals/multiscale-computational-engineering...</a>, Chief-in-Editor: Professor Jacob Fish/Columbia. As for now, 8 papers have been registered for this journal issue (4 from Europe, 4 from USA).</p>
<p class="MsoNormal">In order to ensure even more broad coverage of the subject, we would like to invite additional papers for this journal issue from specialists working in this area, who did not participate at the symposium. If you are interested to submit your paper to this journal issue, please send us a short message (lemi’at’dtu.dk) with the provisional title of your paper/short abstract, before January 20, 2018. The full papers are expected in early March. </p>
<p class="MsoNormal">Best Regards</p>
<p class="MsoNormal">Leon Mishnaevsky Jr.</p>
</div></div></div>Sun, 24 Dec 2017 08:24:53 +0000Leon Mishnaevsky21970 at https://imechanica.orghttps://imechanica.org/node/21970#commentshttps://imechanica.org/crss/node/21970Effect of Loading on Slipping of Crystal Planes
https://imechanica.org/node/21353
<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 know when a metal is subjected to proper loading, there exists plastic strain. A great part of plastic strain is developed from the slipping of the crystal planes of that metal in microstructure level. Now, when the load is uniaxial, it is simple to calculate the amount of shear strain acts on that plane. But, when the load is not uniaxial, the life is harder. It is very hard to calculate which slip plane feels how much shear strain. It is reuired to know about this shear stress as it plays an important role in the activation of the slipping system and thus determines the plastic strain occurs due to slipping. I will be very glad if someone can help me with the procedure to calculate those shear strain acting on the different slip plane in case of a non-uniaxial stress.</p>
<p> </p>
</div></div></div><div class="field field-name-taxonomy-forums field-type-taxonomy-term-reference field-label-above"><div class="field-label">Forums: </div><div class="field-items"><div class="field-item even"><a href="/forum/109">Ask iMechanica</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-above"><div class="field-label">Free Tags: </div><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/1040">Crystal plasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/557">slip</a></div></div></div>Mon, 26 Jun 2017 21:10:16 +0000AfzalRony1221353 at https://imechanica.orghttps://imechanica.org/node/21353#commentshttps://imechanica.org/crss/node/21353A theoretical study on the piezoresistive response of carbon nanotubes embedded in polymer nanocomposites in an elastic region
https://imechanica.org/node/21258
<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/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/8194">piezoresistivity</a></div><div class="field-item even"><a href="/taxonomy/term/11647">Experimental analysis</a></div><div class="field-item odd"><a href="/taxonomy/term/7567">Strain sensor</a></div><div class="field-item even"><a href="/taxonomy/term/4512">characterization</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>Herein, we report a theoretical study of polymeric nanocomposites to provide physical insight into complex material systems in elastic regions. A self-consistent scheme is adopted to predict piezoresistive characteristics, and the effects of the interface and of tunneling on the effective piezoresistive and electrical properties of the nanocomposites are simulated. The overall piezoresistive sensitivity is predicted to be reduced when the lower interfacial resistivity of multi-walled carbon nanotubes (MWCNTs) and the higher effective stiffness of nanocomposites are considered. In addition, thin film nanocomposites with various MWCNT weight percentages are manufactured and their electrical performance capabilities are measured to verify the predictive capability of the present simulation. From experimental tests, the nanocomposites show clear piezoresistive behaviors, exhibiting a percolation threshold at less than 0.5 wt% of the MWCNTs. Three sets of comparisons between the experimental data and the present predictions are conducted within an elastic range, and the resulting good correlations between them demonstrate the predictive capability of the present model.</span></p>
<p>Published in Carbon: <a href="http://www.sciencedirect.com/science/article/pii/S0008622317305079">http://www.sciencedirect.com/science/article/pii/S0008622317305079</a></p>
</div></div></div>Wed, 24 May 2017 12:56:06 +0000Hamid Souri21258 at https://imechanica.orghttps://imechanica.org/node/21258#commentshttps://imechanica.org/crss/node/21258Post-doctoral position in Failure of Brittle Materials at National University of Singapore
https://imechanica.org/node/20926
<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/5205">Post-Doctoral Position</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/7468">Brittle failure</a></div><div class="field-item odd"><a href="/taxonomy/term/11533">mechanims</a></div><div class="field-item even"><a href="/taxonomy/term/5597">statistics</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 anticipate an opening for a post-doctoral fellow position in micromechanics based failure modeling of heterogeneous brittle materials. The focus will be on characterizing the roles of flaw distributions on rate-dependent failure in materials such as concrete. The objective is to develop an understanding of failure processes with the aim of designing high performance brittle materials. </p>
<p>An ideal candidate must have a strong background in computational materials mechanics and in writing computational codes, with a good knowledge of failure and fracture processes. Experience with developing or implementing discrete element modeling is desirable. Knowledge of high performance computing will be a definite plus. Candidates must possess a PhD in Mechanical/ Civil/ Materials Science or allied fields with strong written skills (demonstrated in the form of publications in reputed journals) and oral communication. </p>
<p>Salary and benefits will be commensurate with educational qualifications and work experience. The initial appointment will be for one year with a possible one year extension depending on the performance and availability of funds. For more information on benefits and living in Singapore, please refer to <a href="http://www.nus.edu.sg/careers/whatyougettoenjoy.html. ">http://www.nus.edu.sg/careers/whatyougettoenjoy.html. </a> If you are interested, please contact me (<a href="mailto:shailendra@nus.edu.sg">shailendra@nus.edu.sg</a>). The application package should include your detailed CV and the names of at least two references.</p>
</div></div></div>Sat, 18 Feb 2017 02:09:49 +0000Shailendra20926 at https://imechanica.orghttps://imechanica.org/node/20926#commentshttps://imechanica.org/crss/node/20926Post-doctoral position in Failure of Brittle Materials at National University of Singapore
https://imechanica.org/node/20925
<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/5205">Post-Doctoral Position</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/7468">Brittle failure</a></div><div class="field-item odd"><a href="/taxonomy/term/11533">mechanims</a></div><div class="field-item even"><a href="/taxonomy/term/5597">statistics</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 anticipate an opening for a post-doctoral fellow position in micromechanics based failure modeling of heterogeneous brittle materials. The focus will be on characterizing the roles of flaw distributions on rate-dependent failure in materials such as concrete. The objective is to develop an understanding of failure processes with the aim of designing high performance brittle materials. </p>
<p>An ideal candidate must have a strong background in computational materials mechanics and in writing computational codes, with a good knowledge of failure and fracture processes. Experience with developing or implementing discrete element modeling is desirable. Knowledge of high performance computing will be a definite plus. Candidates must possess a PhD in Mechanical/ Civil/ Materials Science or allied fields with strong written skills (demonstrated in the form of publications in reputed journals) and oral communication. </p>
<p>Salary and benefits will be commensurate with educational qualifications and work experience. The initial appointment will be for one year with a possible one year extension depending on the performance and availability of funds. For more information on benefits and living in Singapore, please refer to <a href="http://www.nus.edu.sg/careers/whatyougettoenjoy.html. ">http://www.nus.edu.sg/careers/whatyougettoenjoy.html. </a> If you are interested, please contact me (<a href="mailto:shailendra@nus.edu.sg">shailendra@nus.edu.sg</a>). The application package should include your detailed CV and the names of at least two references.</p>
</div></div></div>Sat, 18 Feb 2017 02:09:24 +0000Shailendra20925 at https://imechanica.orghttps://imechanica.org/node/20925#commentshttps://imechanica.org/crss/node/20925Textile Composite Property Calculator in the Cloud
https://imechanica.org/node/20639
<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/8069">textile composites</a></div><div class="field-item odd"><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>I hope this information will be helpful for some researchers. We recently integrated TexGen with SwiftComp, called <a href="https://cdmhub.org/resources/texgen4sc">TexGen4SC</a>, to provide a very easy app to compute thermoelastic properties for textile composites for all the types of woven microstructures which can be generated by TexGen. This tool can achieve RVE analysis accuracy with a very small fraction of its computing time. This tool can respect the finite thickness of a woven fabric. It can be freely launched on any device (smart phones, ipads, etc) connected to Internet. I thought this might be useful for some of Imechanica members. Feel free to make use of it. To get a quick start, please watch our tutorial video at <a href="https://www.youtube.com/watch?v=VSjZ-boG4Bg&list=PLGwp8OYDfmxFhtnDNJVRUJ8J-HP8FsnIU">Multiscale Structural Mechanics</a>. </p>
</div></div></div>Fri, 02 Dec 2016 03:03:29 +0000Wenbin Yu20639 at https://imechanica.orghttps://imechanica.org/node/20639#commentshttps://imechanica.org/crss/node/20639A Better Alternative to RVE Analysis
https://imechanica.org/node/20517
<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/11200">Mechanics of Structure Genome</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/11391">composites.</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>RVE analysis is popular for computational homogenization. It can be used independently for virtual testing or as a module for multiscale modeling. Its popularity is mainly due to the maturity and acceptance of commercial finite element software. RVE analysis usually requires a 3D domain to obtain 3D properties and local fields. If a 2D RVE is used, only 2D properties and local fields are obtained. To obtain the complete set of properties, multiple analysis is needed. For example, to obtain the complete stiffness matrix, six 3D RVE analyses are needed. The main drawbacks are the computational cost, and difficulty in applying the right boundary conditions. </span></p>
<p>The recently discovered mechanics of structure genome (MSG) and its companion code SwiftComp, when specialized to 3D structures, can provide a general-purpose micromechanics theory. Many examples, including the <a href="https://cdmhub.org/projects/mmsimulationchalleng">micromechanics simulation challenge</a> have been used to demonstrate that MSG/SwiftComp is more versatile, efficient, and simpler than RVE analysis with out lossing any accuracy and geometric modeling flexibility. More detailed comparison between MSG and RVE analysis can be found <a href="https://cdmhub.org/blog/2016/10/rve-analysis-vs-mechanics-of-structure-genome">here</a>. <span>SwiftComp can be freely launched in the cloud at </span><a href="https://cdmhub.org/resources/scstandard">https://cdmhub.org/resources/scstandard</a><span>. In other words, one can run a super-efficient "RVE analysis" on any devices including smart phones and tablets connected to Internet via a browser. Various GUIs are available for users to choose from including Gmsh, TexGen, ANSYS, and ABAQUS4, all of which are free available on </span><a href="http://cdmhub.org/">cdmHUB</a><span>. </span><span> </span></p>
</div></div></div>Thu, 27 Oct 2016 02:37:07 +0000Wenbin Yu20517 at https://imechanica.orghttps://imechanica.org/node/20517#commentshttps://imechanica.org/crss/node/20517Post-doctoral position in failure micromechanics
https://imechanica.org/node/20266
<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/427">failure</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/6998">crystal plasticity models</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>There is an opening for a post-doc in Prof. Shailendra Joshi’s research group at NUS, starting November 2016, in the area of micromechanics of advanced structural steels. An ideal candidate for this position must possess a PhD in mechanical engineering or related field with a strong background in computational materials mechanics. Experience of developing mesoscale methods such as dislocation dynamics or crystal plasticity and mesoscale fracture mechanics will be a definite plus. Large-scale computational modeling and simulation using finite element software is highly desirable. </span></p>
<p><span>You will be interacting regularly with our industry collaborators from DNV GL (Singapore) as a part of this research project. If you are interested, please email me (<a href="mailto:shailendra@nus.edu.sg"><span><strong>ravi.ayyagari@nus.edu.sg</strong></span></a>) your CV and the names of at least two references. </span></p>
<p><span>~Ravi</span></p>
</div></div></div>Wed, 07 Sep 2016 01:42:08 +0000Ravi Sastri Ayyagari20266 at https://imechanica.orghttps://imechanica.org/node/20266#commentshttps://imechanica.org/crss/node/20266Fully – funded PhD opportunity in Metal-Forming and Materials Modelling Group, Imperial College London, Deadline 31st of Aug. 2016
https://imechanica.org/node/20137
<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/5349">metal forming</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/616">materials</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>The Metal Forming and Materials Modelling group <a name="OLE_LINK8" id="OLE_LINK8"></a><a name="OLE_LINK7" id="OLE_LINK7"></a>wishes to provide a FULLY funded studentship to <strong>EXCEPTIONAL</strong> candidates to conduct PhD research work in the Mechanical Engineering department, at Imperial College London. The research work will be focused on the development of <strong>novel metal forming technologies</strong>, e.g. lightweight metal forming technologies, such as forging of lightweight gears; materials and process experiments and modelling to address fundamental problems including the evolution of defects, damage and microstructure, and their effects on macroscopic crystalline material deformation behaviour for a wide range of applications, particularly in automotive and aerospace.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>The Department was the top-ranked Mechanical Engineering Department in the 2014 UK REF exercise. The Metal Forming and Materials Modelling group is recognised as being at the leading-edge of research in hot and warm forming technologies for lightweight components and structures, which covers a wide range of activities, in theory, innovative testing, materials and process modelling. The Group has made a significant contribution to the development of new forming technologies and novel materials modelling methods. Led by 4 academic staff, the Metal-forming and Materials Modelling Research Group has expanded very quickly during the last five years with <strong>3</strong> industry funded research centres and <strong>1</strong> joint laboratory. It has secured PI funding of over £15 million from EPSRC, Innovate UK, EC and international companies, and has been involved in projects with total funding of over £50 million. </span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>Potential Candidates must have a distinction honour and ranked at the top 10% of an MSc or MEng course in Mechanical/Materials/Aerospace/Automotive Engineering. Background in metal forming is beneficial but not essential. </span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>For further details of the post contact Dr Jun Jiang, at </span><a href="mailto:jun.jiang@imperial.ac.uk"><span>jun.jiang@imperial.ac.uk</span></a><span>. </span></p>
<p class="MsoNormal"><span>Interested applicants should complete an electronic application form at Imperial College London in order for their qualifications to be addressed by College Registry. </span></p>
<p class="MsoNormal"><span> </span></p>
<p> </p>
<p class="MsoNormal"><span>Closing date: until <strong>31st of August</strong> <strong>2016</strong> </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">
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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/Fully%20funded_PhD_Imperial%20College.pdf" type="application/pdf; length=66058">Fully funded_PhD_Imperial College.pdf</a></span></td><td>64.51 KB</td> </tr>
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</div></div></div>Thu, 28 Jul 2016 11:31:12 +0000Jiang_Jun_Metal_Forming20137 at https://imechanica.orghttps://imechanica.org/node/20137#commentshttps://imechanica.org/crss/node/20137RVE analysis without BCs and periodic mesh requirements
https://imechanica.org/node/20013
<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/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/934">Composites</a></div><div class="field-item even"><a href="/taxonomy/term/1092">constitutive modeling</a></div><div class="field-item odd"><a href="/taxonomy/term/11200">Mechanics of Structure Genome</a></div><div class="field-item even"><a href="/taxonomy/term/11201">SwiftComp</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>RVE analysis becomes a routine exercise in material modeling. Usually it is carried out using finite element codes such as ABAQUS or ANSYS. The main thing one should pay attention is to applying the right boundary conditions. It is settled that periodic boundary conditions are the preferred boundary conditions to be applied. The BCs are that u_i-\epsilon_{ij}x_j should be equal on the corresponding edges. This type of boundary conditions can be applied using coupled equations constraints. This requires that one creates a mesh with corresponding nodes on periodic edges. For real, complex microstructures, this could be a challenge. Another issue that with a 2D RVE analysis, one can only obtain in-plane properties and local fields, for 3D properties and local fields, 3D RVE analysis are always needed. Six 3D analyses are needed to compute the complete set of 3D elastic properties. Another analysis is needed to compute the local fields for each global state. </p>
<p>A recently developed general-purpose multiscale constitutive modeling code called SwiftComp based on <a href="http://imechanica.org/node/18928">Mechanics of Structure Genome</a>, can be used for micromechanics which is essentially a RVE analysis for dummies. The user does not have to specify the boundary conditions and periodic mesh is not required. All the user has to do is to provide the finite element mesh as input. Another unique feature of SwiftComp is that it can compute complete set of 3D properties from a 2D RVE if the material features 2D periodicity such as unidirectional fiber reinforced composites. All the properties are computed within one analysis and thus it is at least six times more efficient than traditional 3D RVE analysis. The code can be launched freely in the cloud at <a class="js-link post-link" href="http://www.linkedin.com/redir/redirect?url=https%3A%2F%2Fcdmhub%2Eorg%2Fresources%2Fscstandard&urlhash=O970&_t=tracking_anet" target="_blank">https://cdmhub.org/resources/scstandard</a> or used as a plugin for ABAQUS or ANSYS. You are welcome to try it to see the difference from the RVE analysis you are familiar with. </p>
<p> </p>
</div></div></div>Sun, 19 Jun 2016 21:56:48 +0000Wenbin Yu20013 at https://imechanica.orghttps://imechanica.org/node/20013#commentshttps://imechanica.org/crss/node/20013Abstract deadline approaching - 37th Risø International Symposium on Materials Science: "Understanding performance of composite materials – mechanisms controlling properties"
https://imechanica.org/node/19579
<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/934">Composites</a></div><div class="field-item odd"><a href="/taxonomy/term/11020">models</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>The deadline of Abstract submission for the 37th Risø International Symposium is the <strong>15th March 2016</strong>. The theme of the symposium is the scientific basis for understanding the performance of composite materials.</p>
<p><span>The symposium will cover studies on the underlying mechanisms that control the properties of composites leading to better and more reliable model predictions. Such studies will be carried out on the range of currently studied fibre composite systems, e.g. polymer matrix composites, metal matrix composites, biocomposites, nanocomposites, hybrid composites, and involving the typical elements of materials development: processing, characterization, testing and modelling.</span></p>
<p><span>Among the specific topics to be addressed are:</span></p>
<ul><li><span>Fibres and matrices</span></li>
<li><span>Interfaces and interphases </span></li>
<li><span>Composite microstructure</span></li>
<li><span>Composite micromechanics </span></li>
<li><span>Composite properties and performance</span></li>
</ul><p>The 37th Risø International Symposium will be held 5 - 8 September 2016 at The Risø Campus of the Technical University of Denmark.</p>
<p>Important dates:</p>
<p><strong>Deadline for submission of abstracts: 15 March 2016 </strong></p>
<p><strong>Deadline for paper submission: 1 May 2016</strong></p>
<p><strong>Deadline for registration: 1 July 2016</strong></p>
<p><strong> </strong> Read more:<strong><a href="http://www.vindenergi.dtu.dk/english/Research/Conferences/Symp37/Contributions"> http://www.vindenergi.dtu.dk/english/Research/Conferences/Symp37/Contributions</a></strong></p>
</div></div></div>Mon, 07 Mar 2016 20:19:18 +0000Bent F. Sørensen19579 at https://imechanica.orghttps://imechanica.org/node/19579#commentshttps://imechanica.org/crss/node/19579Micromechanics Simulation Challenge
https://imechanica.org/node/19379
<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/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/350">simulation</a></div><div class="field-item even"><a href="/taxonomy/term/3823">challenge</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><a href="https://cdmhub.org/">cdmHUB</a> has completed the level I micromechanics simulation challenge. Several micromechanics methods/tools including both commercially available tools such as </span><span>Altair MDS, ESI VPS, Digimat, SwiftComp and research codes such as MAC/GMC/HFGMC and FVDAM, </span><span>are used to analyze six typical 2D/3D microstructures. All the results and model files, inputs and outputs, and the report are hosted on cdmHUB as a live project at </span><a href="https://cdmhub.org/projects/mmsimulationchalleng/">https://cdmhub.org/projects/mmsimulationchalleng/</a><span>. Some tools can also be directly launched from cdmHUB. If you have a micromechanics code/tool, you are welcome to contribute your own results. These problems are also a good learning tool for students who want to study micromechanics. </span></p>
<p><span>Level I problems focus on linear thermoelastic properties and corresponding local fields. We are starting to draft level II problems which will focus on nonlinear problems. If you want to contribute, please feel free to let me know.</span></p>
<p> </p>
</div></div></div>Mon, 25 Jan 2016 23:00:52 +0000Wenbin Yu19379 at https://imechanica.orghttps://imechanica.org/node/19379#commentshttps://imechanica.org/crss/node/1937937th Risø International Symposium on Materials Science: "Understanding performance of composite materials – mechanisms controlling properties"
https://imechanica.org/node/19334
<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/10939">fibre composites</a></div><div class="field-item odd"><a href="/taxonomy/term/1029">interfaces</a></div><div class="field-item even"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/5361">properties</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 theme of the coming 37th Risø International symposium is the scientific basis for understanding the performance of composite materials.</span></p>
<p><span>The symposium will cover studies on the underlying mechanisms that control the properties of composites leading to better and more reliable model predictions. Such studies will be carried out on the range of currently studied fibre composite systems, e.g. polymer matrix composites, metal matrix composites, biocomposites, nanocomposites, hybrid composites, and involving the typical elements of materials development: processing, characterization, testing and modelling.</span></p>
<p><span>Among the specific topics to be addressed are:</span></p>
<ul><li><span>Fibres and matrices</span></li>
<li><span>Interfaces and interphases </span></li>
<li><span>Composite microstructure</span></li>
<li><span>Composite micromechanics </span></li>
<li><span>Composite properties and performance</span></li>
</ul><p><span>The 37th Risø International Symposium will be held 5 - 8 September 2016 at The Risø Campus of the Technical University of Denmark.</span></p>
<p><span>Important dates:</span></p>
<ul><li><span>Deadline for submission of abstracts: 1 March 2016 </span></li>
<li><span>Deadline for paper submission: 1 May 2016</span></li>
<li><span>Deadline for registration: 1 July 2016</span></li>
</ul><p> <span> R</span><span><span>ead more: </span><strong><span><a href="http://www.vindenergi.dtu.dk/english/Research/Conferences/Symp37">http://www.vindenergi.dtu.dk/english/Research/Conferences/Symp37</a></span></strong></span></p>
</div></div></div>Wed, 13 Jan 2016 19:47:41 +0000Bent F. Sørensen19334 at https://imechanica.orghttps://imechanica.org/node/19334#commentshttps://imechanica.org/crss/node/19334A paper on: Mathematical modeling of the overall time-dependent behavior of non-ageing viscoelastic reinforced composites.
https://imechanica.org/node/19326
<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>abstract:<span class="apple-converted-space"> </span><br /> New mathematical and numerical formulations are developed for effective time-dependent non<span class="apple-converted-space"> </span><span>ageing</span><span class="apple-converted-space"> </span><span>viscoelastic</span><span class="apple-converted-space"> </span>behavior of linear<span class="apple-converted-space"> </span><span>viscoelastic</span><span class="apple-converted-space"> </span>composites. The modeling is based on the dynamic Green's functions, integral equations, and<span class="apple-converted-space"> </span><span>Volterra</span><span class="apple-converted-space"> </span>product. The time concentration tensor is derived through numerical solution of the integral equation and the<span class="apple-converted-space"> </span><span>Mori</span>-<span>Tanaka</span><span class="apple-converted-space"> </span><span>micromechanical</span></span></p>
<p><span>model. The developed modeling gives explicit expressions of effective properties through convolution products in the<span class="apple-converted-space"> </span><span>Stieltjes</span><span class="apple-converted-space"> </span>space. A numerical procedure is developed allowing the calculation of the<span class="apple-converted-space"> </span><span>tensoriel</span><span class="apple-converted-space"> </span>convolution product and its inverse. Based on Carson-Laplace transform, the frequency dependent effective properties are also obtained and converted to the time domain. For<span class="apple-converted-space"> </span><span>viscoelastic</span><span class="apple-converted-space"> </span><span>Prony</span><span class="apple-converted-space"> </span>laws and inclusions with various shapes, numerical results are presented and </span><span>compared with the approach based on the Laplace transform and the correspondence principle.</span></p>
<p><span><br /><a href="http://www.sciencedirect.com/science/article/pii/S0307904X15007465">http://www.sciencedirect.com/science/article/pii/S0307904X15007465</a></span></p>
<p><span><span>below our email addresses, feel free to contact us for any questions discussions about this paper.</span></span></p>
<p><span lang="FR" xml:lang="FR">M. <span>El</span> <span>Kouri :</span></span><span lang="FR" xml:lang="FR"> <a href="mailto:mohamed.lstm@gmail.com">mohamed.lstm@gmail.com</a></span></p>
<p>A. <span>Bakkali : </span><span><a href="mailto:bakkali.abdel@gmail.com">bakkali.abdel@gmail.com</a> </span></p>
<p>L. <span>Azrar : <a href="mailto:azrar@fstt">azrar@fstt</a></span>.ac.ma</p>
<p><span>I hope you enjoy reading the paper!</span></p>
<p><span>Best regards,</span></p>
<p> </p>
<p><span>EL Kouri Mohamed</span></p>
</div></div></div><div class="field field-name-taxonomy-forums field-type-taxonomy-term-reference field-label-above"><div class="field-label">Forums: </div><div class="field-items"><div class="field-item even"><a href="/forum/390">Materials Forum</a></div></div></div><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-above"><div class="field-label">Free Tags: </div><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/10933">Viscoelastic composites</a></div><div class="field-item odd"><a href="/taxonomy/term/10934">non ageing behavior</a></div><div class="field-item even"><a href="/taxonomy/term/10935">Volterra product</a></div><div class="field-item odd"><a href="/taxonomy/term/10936">Mori-Tanaka</a></div><div class="field-item even"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item odd"><a href="/taxonomy/term/10937">time dependent</a></div><div class="field-item even"><a href="/taxonomy/term/10938">convolution integrals</a></div></div></div>Tue, 12 Jan 2016 17:35:32 +0000El Kouri mohamed19326 at https://imechanica.orghttps://imechanica.org/node/19326#commentshttps://imechanica.org/crss/node/19326Postdoctoral position in Multiscale Modeling and Experimental Characterization of Polymer Composites under High Strain Rate Deformations
https://imechanica.org/node/18903
<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/3043">multiscale modelling</a></div><div class="field-item odd"><a href="/taxonomy/term/18">micromechanics</a></div><div class="field-item even"><a href="/taxonomy/term/934">Composites</a></div><div class="field-item odd"><a href="/taxonomy/term/1565">failure model</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 lang="EN-US" xml:lang="EN-US">Applications are invited for an immediate Postdoctoral position within the Cognitive Performance Optimization Laboratory (COPOL) in the Department of Mechanical Engineering at the University of New Brunswick. </span><span>The candidate will perform research in the area of multiscale modeling and failure analysis of high-performance light materials such as Long Fiber Thermoplastic Composites under high strain rate deformations. The candidate will also use several experimental techniques to characterize the advanced materials such as Quasi static, elevated, and high strain rate uniaxial tension and compression tests, EBSD measurements, fractography, and SEM and TEM studies. </span></p>
<p class="MsoNormal"><span>The candidate will be expected to contribute to a vibrant multidisciplinary research group and be able to work in close collaboration with industrial and governmental partners. The project will be externally funded and strong oral and communication skills will be required. Knowledge of solid mechanics, high performance computing and programing, materials science, and finite element modeling (LS-DYNA, ABAQUS) will be crucial. Please send CV and sample publications to <a href="mailto:Mohsen.Mohammadi@unb.ca">Mohsen.Mohammadi@unb.ca</a></span></p>
</div></div></div>Mon, 28 Sep 2015 03:01:31 +0000moh2200018903 at https://imechanica.orghttps://imechanica.org/node/18903#commentshttps://imechanica.org/crss/node/18903Error | iMechanica