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instability

Davide Bigoni's picture

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

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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

 

Bo Li's picture

Effect of temperature on the stability of dielectric elastomers

Dielectric elastomer (DE) is a kind of electroactive polymer material,
capable of large deformation up to 380%. However, under conservative
operating conditions, DE is susceptible to instability with a small
deformation due to various modes of failure, including electrical
breakdown, electromechanical instability (EMI), loss of tension and
rupture by stretch. This paper proposes a free energy model in the
thermodynamic system of DE involving thermoelastic strain energy,
electric energy and purely thermal contribution energy to obtain the
stability conditions of all failure modes. The numerical results
indicate that the increase in temperature can markedly contribute to
improving the entropy production, the actuation stress and the critical

Davide Bigoni's picture

Can an elastic structure buckle under tensile dead load?

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We all know Euler buckling of a beam under axial thrust, but can buckling occur in an elastic structure in which all elements are subject to tensile dead loading?

We provide a positive answer to this question, see http://www.youtube.com/user/RoyalSociety#p/u/0/EKngs1vvcJU

Davide Bigoni's picture

Can an elastic structure buckle under tensile dead load?

We all know Euler buckling of a beam under axial thrust, but can buckling occur in an elastic structure in which all elements are subject to tensile dead loading?

We provide a positive answer to this question, see http://www.youtube.com/user/RoyalSociety#p/u/0/EKngs1vvcJU

PhD positions in Computational Mechanics

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;

Rui Huang's picture

Effects of mismatch strain and substrate surface corrugation on morphology of supported monolayer graphene

In a previous work, substrate-modulated morphology of graphene was analyzed using a numerical Monte Carlo method. Here we present an analytical approach that explicitly relates the van der Waals interaction energy to the surface corrugation and the interfacial properties. Moreover, the effect of mismatch strain is considered, which predicts a strain-induced instability under a compressive strain and reduced corrugation under a tensile strain.

Teng Li's picture

Snap-through instability of graphene on substrates

T. Li, Z. Zhang, Snap-through instability of graphene on substrates, Nanoscale Research Letters,DOI: 10.1007/s11671-009-9460-1 (2009). (Open access)

Wei Hong's picture

Formation of creases on the surfaces of elastomers and gels

When a block of an elastomer is bent, the compressed surface may form a crease. This paper analyzes the critical condition for creasing by comparing the elastic energy in a creased body and that in a smooth body. This difference in energy is expressed by a scaling relation. Critical conditions for creasing are determined for elastomers subject to general loads and gels swelling under constraint. The theoretical results are compared with existing experimental observations.

Implementation of TRESCA yield certeria in ABAQUS plasticity material model using UMAT

hi everybody.

 I am interested to implement  tresca failure criteria in my plastic material model (ABAQUS/standard) using UMAT subrountine which is avaiable in ABAQUS code but it is primaryly made for Mises failure , so i made few attempt to modified it for tresca , but it did not work out, so if anyone have any idea , please guide me. 

thanks

prashant sharma 

Jinxiong Zhou's picture

Propagation of instability in dielectric elastomers

When an electric voltage is applied across the thickness of a thin layer of an dielectric elastomer, the layer reduces its thickness and expands its area. This electrically induced deformation can be rapid and large, and is potentially useful as soft actuators in diverse technologies. Recent experimental and theoretical studies have shown that, when the voltage exceeds some critical value, the homogenous deformation of the layer becomes unstable, and the layer deforms into a mixture of thin and thick regions.

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