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instability

saberelarem's picture

On a systematic approach for cracked rotating shaft study: breathing mechanism, dynamics and instability

We present a systematic approach to deal with the modelling and analysis of the cracked rotating shafts behaviour. We begin by revisiting the problem of modelling the breathing mechanism of the crack. Here we consider an original approach based on the form we give to the energy of the system and then identify the mechanism parameters using 3D computations with unilateral contact conditions on the crack lips. A dimensionless flexibility is identified which makes the application of the approach to similar problems straightforward.

saberelarem's picture

Nonlinear dynamics of rotating shaft with a breathing crack - CHINA SCHOLARSHIP COUNCIL PhD for 2017

Because of the increasing need of energy, the plants installed by electricity supply utilities throughout the world are becoming larger and more highly stressed. Thus, the risk of turbogenerator shaft cracking is increasing also. The development and propagation of a crack represents the most common and trivial beginning of integrity losses in engineering structures.

WaiChing Sun's picture

Call for Abstracts: 7th ICCM Berkeley - MS-054 Failure and instabilities in soft materials and geomaterials

Dear colleagues, 

I am writing to invite your contirbution to the mini-symposium on failure and instability in soft materials and geomaterials co-organized by myself, Joshua White, Pencheng Fu, Nikolaos Bouklas, Wei Wang and Christian Linder for the upcoming ICCM conference at Berkeley. More information can be found in the URL listed below. 

http://www.sci-en-tech.com/ICCM/index.php/iccm2016/2016/schedConf/trackP...

saberelarem's picture

Nonlinear dynamics of rotating shaft with a breathing crack - CHINA SCHOLARSHIP COUNCIL PhD for 2017

Because of the increasing need of energy, the plants installed by electricity supply utilities throughout the world are becoming larger and more highly stressed. Thus, the risk of turbogenerator shaft cracking is increasing also. The development and propagation of a crack represents the most common and trivial beginning of integrity losses in engineering structures.

ashutosh.agrawal's picture

Instability-driven vesicle growth in biological cells

Journal: PNAS, published ahead of print, March 9 2015, doi:10.1073/pnas.1418491112

Title: Endocytic proteins drive vesicle growth via instability in high membrane tension environment

Authors: Nikhil Walani, Jennifer Torres, and Ashutosh Agrawal 

Mike Ciavarella's picture

rate-state dependent friction in ANSYS

Dear collegues

a quick question:- I am playing with continuum models of Contact (Hertz, Westergaard and so on) and friction laws. However, I prefer for my students to use ANSYS FEM code. In Ansys there is standard Coulomb, rate-dependence but not rate-state (unless one codes some user subroutines). See

https://www.sharcnet.ca/Software/Fluent14/help/ans_ctec/Hlp_ctec_realkey...

Cai Shengqiang's picture

Drying-induced cavitation in a constrained hydrogel

Cavitation can be often observed in soft materials. Most previous studies were focused on cavitation in an elastomer, which is under different mechanical loadings. In this paper, we investigate cavitation in a constrained hydrogel induced by drying. With taking account of surface tension and chemo-mechanics of gels, we calculate the free energy of the system as a function of cavity size. The free energy landscape shows double-well structure, analogous to first-order phase transition.  Above the critical humidity, a cavity inside the gel is tiny.

Justification for use of Riks method to investigate gross plastic deformation

Hi, my question is on the use of Riks and other Arc length methods when analysing  a system for gross plastic deformation. ASME B&PV code , in its investigation for Gross plastic deformation as a Load at which convergence does not take place. Now, as far as I understand, Newton Raphson method fails at locations of singularity in the stiffness matrix and also at Bifurcation points, it can trace the unstable primary paths. Both these issues can be overcome ( provided the limit point is not too sharp) by Riks and other Arc length methods.

Stabilization method in local instability problems

Dear all,

 in commercial FE codes, such as ABAQUS, ANSYS, there is option to get convergence in quasi-static analysis by using artificial damping factor. I tried to dig their documentation about this method, but it is somewhat sparse. Could some body recommend me some literature about this topic so that I can gain a better understanding about it.

 

I thank you in advance.

 

Sincerely yours,

Ken 

Oleg Kirillov's picture

Nonconservative Stability Problems of Modern Physics

This monograph gives a complete overview on the subject of nonconservative stability from the modern point of view. Relevant mathematical concepts are presented, as well as rigorous stability results and numerous classical and contemporary examples from mechanics and physics.

Stephan Rudykh's picture

Wrinkling of Interfacial Layers in Stratified Composites

by Y. Li, N. Kaynia, S. Rudykh and M. C. Boyce

 Massachusetts Institute of Technology 

 Abstract:

 

zichen's picture

Postdoctoral research associate position in mechanics of materials, morphogenesis and biosinspired structures

One postdoctoral research associate position is available (dates negotiable). The successful candidate will work on one or multiples of the following topics: mechanics of morphogenesis in plants and embryos, fast motion of plants (e.g., the Venus flytrap's rapid closure), mechanical self-assembly and instability of thin structures (e.g., DNA, plant tendrils, self-assembly of nanostructures, etc.), and bioinspired structures. The candidate should have received (or expect to receive very soon) a Ph.D.

Bo Li's picture

Modeling of the muscle-like actuation in soft dielectrics: deformation mode and electromechanical stability

Soft dielectric elastomer is able to generate an
electromechanical response in terms of reversible shape
changing, which is a muscle-like behavior. The deformation
and electromechanical stability of dielectric elastomers,
classified by their deformation modes, uniaxial extension,
equal biaxial expansion and pure shear, are investigated.
Pull-in instability occurs in equal biaxial and uniaxial modes
at a small stretch ratio, while the pure shear mode features
wrinkling instability after a large stable deformation. The

Davide Bigoni's picture

Effects of the constraint’s curvature on structural instability: tensile buckling and multiple bifurcations

Choose a channel featured in the header of iMechanica: 

Can a single-degree-of-freedom elastic structure have two buckling loads?

We provide a positive answer to this question, see http://www.ing.unitn.it/~bigoni/multiple_bifurcations.html

 

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