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Updated: 19 hours 11 min ago

Got it!

Wed, 2021-05-05 00:59

In reply to Update Response to Shaoting

Dear Mutian,

Sure. Thanks.

Best,

Shaoting

Thank you

Wed, 2021-05-05 00:55

In reply to Response to Shaoting

Dear Ximin and Mutian,

Got it. Thanks a lot. May I know if the paper "Tough-hydrogel reinforced low-tortuosity conductive networks for stretchable and high-performance supercapacitors" is online?

Best,

Shaoting

Update Response to Shaoting

Wed, 2021-05-05 00:51

In reply to Hearty Congratulations to Ximin

Shaoting, sorry I wasn't able to upload figures in the comments. The figure related to your first question can be found in Figure S9 of the paper "PVA hydrogel with broad-range tunable mechanical properties via Hofmeister effect".

---Mutian Hua

Response to Shaoting

Wed, 2021-05-05 00:45

In reply to Hearty Congratulations to Ximin

Hi Shaoting, thank you and also congrats to your recent paper "Strong fatigue-resistant nanofibrous hydrogels inspired by lobster underbelly"! Very inspiring result and numerical model!

For your first discussion, we believe the hydrogel does not have special retention of the salt ions. We have specifically studied the degeneration in the second paper in the post (although this paper does not have alignment for the hydrogels), after the hydrogel has been soaked in large volumes of water for fairly long time (which we believe should have removed all ions) the mechanical property decreased to about 40% for the the toughest hydrogel in that paper. The degeneration percentage is much smaller for the aligned hydrogels, but we do see a noticable decrease in the mechanical properties.

For your second discussion, to be honest we have not specifically studied the pH effect. Theoretically thinking, the mechanical properties should not be affected by dilute acid or base. However, H+ seems to be on the salting in side, which means that the hydrogel will have decreased mechanical property in high concentration acid solutions.

For your third discussion, which is a very interesting and open minded one, I have a few thoughts. Many of these additional properties may very well rely on the structural / mechanical stability of the hydrogel, for instance, the electrical performance should be more or less maintained if the conductive pathways are well preserved over cycles of loading, acoustic properties should also be maintained if the fine structures of the hydrogel is not damaged over cycles of loading. Viable methods may involve using those tough and fatigue resistant hydrogels as scaffolds or coatings to maintain the structural integrety for other functional properties. In our recently accepted paper "Tough-hydrogel reinforced low-tortuosity conductive networks for stretchable and high-performance supercapacitors", we kind of touched upon this idea. We applied the tough PVA hydrogel as coating layer to a low tortuous conductive foam, by using LiSO4 to toughen the hydrogel as well as to serve as electrolyte,  we were able to improve the mehcanical stability and electrical stability of the supercapacitor device.

 

Unified Mechanics Theory

Wed, 2021-05-05 00:11

In reply to A Review of Damage, Void Evolution, and Fatigue Life Prediction Models

Hello Dear Prof. Cemal Basaran,

Thanks for your input. Unified Mechanics Theory is interesting.  I am trying to find your new published book to understand more about it. Is damaging factor connected to thermodynamics or entropy?

Best Regards,

Lixiang

 

Response to Considerations for translational application

Wed, 2021-05-05 00:06

In reply to Considerations for translational application

Prof.Li, thank you for your valuable comment! Indeed, the PVA gels are highly biocompatible, we have been trying to seed cells on them and the result so far looks promising. We have not yet looked at biodegradability for these gels in body due to lack of in-vivo test, but we believe they will behave similar to conventional freeze-thawed hydrogels, maybe at a slower degradation rate. We have not looked at in-situ formation yet as the method requires high salt concentration, which would be more preferrably done outside the body.

---Mutian Hua

 

Hearty Congratulations to Ximin

Tue, 2021-05-04 13:55

In reply to Journal Club for May 2021: Strong and tough hydrogels with hierarchical architectures

Dear Ximin,

Hearty congratulation to the whole team for making this progress. The contribution of salt-induced aggregation and crystallization to strength and fatigue resistance is truly remarkable. Here, I would like to bring three discussions.

1, How much salt is retained in your resultant sample? Intuitively, salt ions are relatively mobile and dynamic. When you further immerse your sample in deionized water, did you see the degeneration of mechanical properties of your sample due to the leakage of salt? If not, that means the sample has some ability to retain salts, which should have many other interesting implications.

2, Related to the first question, how do the mechanical properties of the sample depend on pH value? 

3, Existing papers are mostly focused on long-term mechanical robustness. What could be the pathways in maintaining other properties such as electrical, optical, acoustic, thermal conductivities under long-term dynamic loadings?

Best,

Shaoting

 

Considerations for translational application

Tue, 2021-05-04 13:15

In reply to Journal Club for May 2021: Strong and tough hydrogels with hierarchical architectures

Congratulations to Ximin and your team on the nice papers and progress made in engineering PVA gels. The mechanical performance exhibited by your materials is truly remarkable. 

I like to comment on the translation aspects. The PVA gels have been studied and explored for orthopedic use such as cartilage replacements for years. Its biodegradability and in-situ forming ability are known concerns toward translation. I wonder whether the systems prepared with various conditions in your work could exhibit different degradation profiles, or they behave essentially the same with the conventional PVA gels like those after freeze-thawing. 

A few papers have shown different cross-linking strategies for PVA gels, which allow for in-situ formation. But the performance of the resulting gels is far from those made with methods like yours, noncompliance with in vivo conditions. 

Seems the link is not

Mon, 2021-05-03 16:13

In reply to Nice work, but I think an

Seems the link is not correctly reflected: 

Rao C, Sun H, Liu Y. Physics informed deep learning for computational elastodynamics without labeled data. arXiv preprint arXiv:2006.08472. 2020 Jun 10.

 

Nice work, but I think an

Mon, 2021-05-03 16:11

In reply to Exact imposition of boundary conditions in physics-informed neural networks

Nice work, but I think an important and very similar work is left out: https://arxiv.org/abs/2006.08472 

Spallation of polymers

Mon, 2021-05-03 13:04

In reply to Atomic-Scale Investigation on the Mechanical Behavior of Ultrathin Multilayers Under Shock Loading

A presentation (~11 mins) from our work on the spallation of polymers (ref. [5]) is available here: https://youtu.be/q8i2iAQ_w-g

Presentation

Mon, 2021-05-03 12:35

In reply to Energy absorption mechanisms of nanoscopic multilayer structures under ballistic impact loading

A presentation (~10 mins), based on this work, is available here: https://youtu.be/83OediwJM1U

Thanks for sharing.

Thu, 2021-04-29 12:34

In reply to Writing tips

Thanks for sharing.

Dear Prof. Xu,

Thu, 2021-04-29 06:00

In reply to Journal Club For April 2021: Variational phase-field modeling of brittle and cohesive fracture

Dear Prof. Xu,

I have sent you an email regarding your suggestion. 

Best regards,

Phu

Hi All there, if you have any

Thu, 2021-04-29 04:44

In reply to MoFEM: School on Advanced Topics in Computational Mechanics (UKACM 2021)

Hi All there, if you have any comments? You like to try, the easiest why try is to see examples on Google Colab,

 

2. Poisson's problem (Google Colab)

3. Linear Acoustics (Google Colab)

 

Experimental validation on crack nucleation and propagation

Wed, 2021-04-28 20:44

In reply to Journal Club For April 2021: Variational phase-field modeling of brittle and cohesive fracture

Dear Profs. Nguyen and Wu,

Interesting simulation approach. As an experimentalist on fracture and impact mechanics, I always try to learn some new simulation tools,  especially XFEM, CZ and PD cannot simulate my previous dynamic fracture experiments well.

For example, I have some unique crack nucleation (from zero length to a finite length), crack branching (branching angle is larger than the max. theoretical angle), sharply curved cracks which exceed the simulation capability of XFEM.  

I found you’re simulating old crack branching experiments in 1991. I suggest that we may have collaboration in the future. I attached three papers on dynamic fracture experiments co-authored with Prof. Rosakis at the California Institute of Technology.

1 L. R. Xu and A. J. Rosakis,  “An Experimental Study on Dynamic Failure Events in Homogeneous Layered Materials Using Dynamic Photoelasticity and High-speed Photography,” Optics and Laser in Engineering, Vol. 40, pp. 263-288,2003. ( PDF file)

2. L. R. Xu, Y. Y. Huang and A. J. Rosakis, “Dynamic Crack Deflection and Penetration at Interfaces in Homogeneous Materials: Experimental Studies and Model Predictions,” Journal of the Mechanics and Physics of Solids, Vol. 51, pp.425-460, 2003. ( PDF file)

3. L. R. Xu and A. J. Rosakis, “Real-time Experimental Investigation of Dynamic Crack Branching Using High-speed Optical Diagnostics,” SEM Experimental Techniques, Vol. 27,pp.23-26, 2003. (PDF file)

My email is l.roy.xu@alumni.caltech.edu Look forward to meeting you in the future.    

Roy Xu

Can Zerilli–Armstrong model or Johnson-Cook

Tue, 2021-04-27 16:22

In reply to Interesting review

Dear Prof. Yang;

Both of these models you mention are empirical curve fitting models. If you have a test data you can fit them to these functions and even if they don't work you can add new parameters to curve fit to your data. In my humble opinion, that is not science. I realize that, now it is called "Data Science".  :-)

Best Regards

Cemal Basaran

3D Hashin failure criteria with exponential damage evolution

Tue, 2021-04-20 03:41

In reply to Sharing ABAQUS UMAT and VUMAT subroutines

If you are looking to use the Hashin 3D criterion with exponential damage evolution, the following VUMAT subroutine is applicable in Abaqus software. You can get it for a small fee.

http://en.banumusagr.com/shop/3dhashin-vumat-abaqus/

There is a Ph.D. opening in

Mon, 2021-04-19 13:43

In reply to Ph.D. position at the Mechanical Engineering Department of University of Houston

There is a Ph.D. opening in my research group in the Mechanical Engineering department at the University of Houston to be filled as soon as possible.
The research topic is multiscale modeling of the deformation response of SMAs through Machine Learning and Bayesian Inference.

Interested applicants are requested to contact Theocharis Baxevanis (tbaxevanis@uh.edu) with a brief cover letter that includes a summary of skills and copy of CV.
A master's degree in the areas of computational/continuum/fracture mechanics is required.

Yes. Thank you again for your

Mon, 2021-04-12 05:53

In reply to I think that, the H history

Yes. Thank you again for your sharing! :)

 

Tianyu

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