This paper studies the collapse of a void in an elastomer caused by osmosis. The void is filled with liquid water, while the elastomer is surrounded by unsaturated air.  The difference in humidity motivates water molecules to permeate through the elastomer, from inside the void to outside the elastomer, leaving the liquid water inside the void in tension.  When the tension is low, the void reduces size but retains the shape, a mode of deformation which we call breathing.  When the tension is high, the void changes shape, possibly by two types of instability:  buckling and creasing.  The critical conditions for both types of instability are calculated.  A tubular elastomer collapses by buckling if the wall is thin, but by creasing if the wall is thick.  As the tension increases, a thin-walled tube undergoes a buckle-to-crease transition.

This paper can be found at http://www.seas.harvard.edu/suo/papers/233.pdf

We are looking for suitable candidates for a PhD research work in Computational Mechanics and numerical simulation, to be carried out at the Department of Mechanical Engineering, University of Aveiro, Portugal, in one of the following areas:

- development of new finite elements for metal forming applications;

- numerical simulation of metal forming (sheet and bulk forming);

- tubular hydroforming numerical simulation;

- structural stability and buckling analysis of reinforced aircraft panels;

- integrated design, modelling and reliability assessment (iDMR) by computational tools.

 Candidates are free to contact me using the email: robertt AT ua DOT pt

In this paper, we report the size effects on elastic modulus and fracture strength of ZnO nanowires from the tension, and that the measured (nominal) elastic moduli under tension and bending (from the buckling experiment) are different as a manifestation of the size effects. 

F. Xu, Q. Qin, A. Mishra, Y. Gu, and Y. Zhu, Nano Research, DOI: 10.1007/s12274-010-1030-4, 2010

Abstract:

Buckling of thin layers or aligned arrays of stiff materials on elastomeric substrates has many important applications, such as stretchable electronics, precision metrology and flexible optoelectronics.  These systems show one common phenomenon, the stiff thin layers buckle normal to the substrate surface (out-of-surface buckling).  By contrast, we recently reported for the first time that silicon nanowires (SiNWs) on elastomeric substrates buckle only within the substrate surface, i.e. in-surface buckling.  Experimental process to obtain buckled SiNWs is described.

hi all,

 I am doing buckling analysis of pressure vessel. I want to check the buckling load for individual components.

This pressure vessel is subject to hydrostatic pressure.

So if i want to check this, how to do that. I am not perticular about the softwares.

thanks

Q. Lu and R. Huang, Excess energy and deformation along free edges of graphene nanoribbons. Posted online at arXiv:0910.0912, October 2009.

Hi all,

I'm trying to run a nonlinear (elastic for now) buckling analysis in ANSYS. Basically I have a thin cylindrical shell (made up of SHELL181). fixed at one end (rigid) and applied force and/or displacement specified on the other end to make it buckle.

I have pretty much tried all options. These were:

i) Linear buckling (Eigenbuckling)

ii) Displacement controlled buckling with a lateral point force to provide eccentricity/imperfection.

iii)Force controlled buckling with, again, a lateral point force (arc-length method)

Salam and Hi!

Can anyone share here, your understanding on POST BUCKLING and PROGRESSIVE DAMAGE ANALYSIS.

Hi everyone,

Does anyone have the work experience on stepped column kind of structure?

I would like to know, how to determine the crippling load for stepped column kind of structures? If anyone have the materials pertaining to the subject, please do share (if interested).

Thanks and Regards

M Gopalakrishnan.

Thanks to Marino, I have found the reason for the difference in our bending stiffness calculation. The original discussion is here:
http://imechanica.org/node/4029

The reason why we have a higher bending stiffness is due to the dihedral term. This dihedral term does have a significant contribution to the bending stiffness. However, in Ref. [26], apparently, this dihedral term was ignored.
I have written a short document showing the contribution of the dihedral term to the bending stiffness. Please take a look at the attachment.
I received great help from Dr. Huang and Marino. Thank you very much.

We have studied the scaling of controlled nonlinear buckling processes in materials with dimensions in the molecular range (i.e., ～1 nm) through experimental and theoretical studies of buckling in individual single-wall carbon nanotubes on substrates of poly(dimethylsiloxane). The results show not only the ability to create and manipulate patterns of buckling at these molecular scales, but also, that analytical continuum mechanics theory can explain, quantitatively, all measurable aspects of this system. Inverse calculation applied to measurements of diameterdependent buckling wavelengths yields accurate values of the Young’s moduli of individual SWNTs.

Qiang Lu and Rui Huang

Department of Aerospace Engineering and Engineering mechanics, University of Texas, Austin,
TX 78712, USA

In MEMS fields, a need arises in engineering practice to predict accurately the nonlinear response of slender post-buckling beams, especially the nonlinear transverse stiffness. The bistability of the post-buckling beams is excellent in reducing power consumption of micro-devices or micro-systems. However, the major difficulty in analyzing the post-buckling and snap-through response is the intractability of the geometric nonlinear control equations of large deflection beams.

I. Arias and M. Arroyo, Size-Dependent Nonlinear Elastic Scaling of Multiwalled Carbon Nanotubes, Phys. Rev. Lett. 100, 085503 (2008).

Size matters for the mechanics of multiwalled carbon nanotubes (MWCNTs). It has been known for some time that MWCNTs often wrinkle under deformation exhibiting the so-called rippling deformation pattern, which makes MWCNTs much softer. Through large-scale multiscale simulations we have characterized with a power law the softer wrinkled response, and showed that the transition strain between the super-stiff behavior attributed to MWCNTs and this softer regime scales as the inverse of the tube diameter. Thus, the tera Pascal Young’s modulus can be fully exploited in devices and materials only for moderately sized tubes. Similarly, in interpreting experiments or designing devices, the classical Euler-Bernouilli beam theory can only be applied to such tubes. The elasticity of thicker tubes is nonlinear, typically display mixtures of wrinkled and unwrinkled sections, and often exhibit hysteretic mechanical behavior.

See http://imechanica.org/node/2395 for a related post.

Many studies on the thin film/substrate structure and its failure mechanism were reported in recent years. The direct experimental results of thin film/substrate structure by scanning electron microscopy (SEM) presents an intriguing problem:there exists a buckling failure mechanism at the lateral edge of metal film under pure bending. The qualitative theoretical analysis has been done on such buckling failure of thin film/substrate structure. The experimental results and theoretical analysis are helpful to understand the extrinsic stresses or deformations that are induced by external physical effects. Accepted by Appl. Phys. Lett.