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Thanks for your positive

Fri, 2019-01-11 08:06

In reply to Dear Zhaohe and Nanshu, 

Thanks for your positive comments!

Ph. D positions in Solid Mechanics

Thu, 2019-01-10 16:31

In reply to Ph. D positions open at UNH

Ph.D positions now open (for Fall 2019) in Mechanics, Biomimetics, and 3D Printing Lab at the University of New Hampshire/Mechanical Engineering Department.

More information about the lab can be found at

Please directly send CV to Prof. Yaning Li at:  

Online Applications:


University of New Hampshire (UNH) is located in Durham, NH, which is about 1.5 hours northeast to Boston.



Wed, 2019-01-09 11:04

In reply to great



Sat, 2019-01-05 06:03

Just published: New Book "Precursors on IsoGeometric Analysis"

Sat, 2019-01-05 02:34

In reply to NEW BOOK: "Precursors of IsoGeometric Analysis: Finite elements, Boundary elements, and Collocation methods", Author: C. Provatidis

Following to emails I receive,

I am very pleased to inform you that my book has been published and it is available on

Customer can order it via 


Dear Zhaohe and Nanshu, 

Fri, 2019-01-04 23:20

In reply to Interface-Governed Deformation of Nanobubbles and Nanotents Formed by Two-Dimensional Materials

Dear Zhaohe and Nanshu, 

Beautiful work! Congratualtions!


Nice work!!

Wed, 2019-01-02 22:58

In reply to A review on modeling of electro-chemo-mechanics in lithium-ion batteries

Peter,  Congratulations to you, Ying, and Baixiang on the very nice review! 

Hi Tongqing,

Tue, 2019-01-01 23:58

In reply to Hi Qihan,

Hi Tongqing,

Very good question. The bending you mentioned should come from the residual stress in the bulk material. The interfacial layer is probably too thin to cause anything noticable for the size of a common device. I guess the bending should be gone if you can control the drying of the gel during the bonding process?

Macroscopic stress-strain computation in ParaDis

Fri, 2018-12-28 23:19

In reply to ParaDis : Discrete Dislocation Dynamics Simulation

How the macro stress strain are evaluated in ParaDis?


Fri, 2018-12-28 19:07

Thank you, Yonggang !

Fri, 2018-12-28 13:22

In reply to 2018 Timoshenko Medal Acceptance Lecture: Academy Family, by Prof. Ares Rosakis

Ares is always nice and thoughtful to our graduate students.


Hi Qihan,

Thu, 2018-12-27 21:41

In reply to Journal Club for December 2018: Bonding hydrophilic and hydrophobic soft materials for functional soft devices

Hi Qihan,

I have learned a lot form your interesting and inspiring work. My question is would any residual stress exist after the adhension. Some students here found that after adhension of two layers, the bilayer bent a lot. Is the stress good or bad for the adhension?


Congratulations Guoying!

Thu, 2018-12-27 08:37

In reply to Soft wall-climbing robots

Congratulations Guoying!

Hi Ruobing, thanks for

Thu, 2018-12-27 08:35

In reply to Review: fatigue of hydrogels

Hi Ruobing, thanks for sharing this wonderful review, which will shed light on a new exciting field.

Crystallization in NR

Mon, 2018-12-17 13:35

In reply to Nice work

Hi Jingda,

Regarding natural rubber, I recall the crystallization melting temperature is below the room temperature. As a result, crystallization forms when the natural rubber undergoes large stretch (e.g., at the crack tip), but melts when the stretch is released. For comparison, the crystallization of PVA is (largely) thermodynamically stable at room temperature.

People have indeed studied crack deflection in fatigue crack growth of natural rubber. See:

[1] 2010 Le Cam The mechanism of fatigue crack growth in rubbers under severe loading: the effect of stress-induced crystallization

[2] 2011 Saintier Cyclic loadings and crystallization of natural rubber: An explanation of fatigue crack propagation reinforcement under a positive loading ratio

If you cut a rubber band with a notch, and cyclically stretch it, you can observe the rough crack surface growing by eye. I'm fascinated to wonder why the threshold of NR is only 50 J/m2. Perhaps it's because the crystallization domain around the crack front is too small, as Shaoting mentioned. However, this "self-activated" composite effect deserves further development in soft materials.



notice incidentally that if you define a problem

Mon, 2018-12-17 09:39

In reply to Thanks!

classically in terms of a remote stress and a crack size, the problem is indifferent on E, and hence the DKth formulation is more interesting.  If you reach a value close to a metal in these respects it is even more fascinating.


Mon, 2018-12-17 00:07

In reply to Nice work


Hi Jingda,

Thanks for your insightful discussion. We thought about the difference between nature rubber with strain induced crystallization and PVA hydrogels. The main difference may come from the different types of crystalline domains. The strain-crystallization in natural rubbers is reversible. The crystalline domains mostly dissapear when releasing the natural rubbers to undeformed state, but the cyrstalline domains form and preserve in undeformed as-prepared PVA samples.

If I refer correctly, Lake [1] measured the fatigue threshold of nature rubber in this paper which is 50 J/m2. They particularly focused on the case with cut growth at small deformations. At small deformations, strain-crystallization is only activated in the region at crack tip. The crack may still propagate by cutting amorphus chains instead of fracturing the crystalline domains at crack tip. The paper also mentioned the other effect coming from ozone attacking, which is not the case in swollen PVA in water either.

It would be very interesting to investigate fatigue behaviors in varous semi-crystalline soft materials in future works.  

For the dc/dN ~G curve at high G zone, it is truly nolinear with m larger than 2 if we fit the curve into Paris Law as I discussed with Mike.

BTW, your papers on fatigue fracure of hydrogels motivate the study in fatigue fracture in hydrogels. Look forward to more interesting results.


[1] G. Lake, P. J. J. o. A. P. S. Lindley, The mechanical fatigue limit for rubber. 9, 1233-1251 (1965).




Sun, 2018-12-16 21:43

In reply to you are just 1 order of magnitude below a metal!



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