# hyperelasticity

## computational nonlinear elasticity references

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I will be developing constitutive material models into commercial FE codes for nonlinear elasticity and searching for good books to get started for computational aspects. There are many good books for computational plasticity but I did not find any for nonlinear elasticity. Suggestion for good books or references is welcome.

## Contact problem

Hello

Iam trying to model an orthodontic apparatus movement. Can anyone help me how to choose the type of interaction between the three parts. In attached the assembly. THE steps are : the ring will be opened then it will descend finally the ring will return to its initial position can anyone tell me how to choose interaction properties. Thanksa  lot

## Abaqus query on UMAT: NaN issues

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Hello, I have a written a UMAT for a hyperfoam type material in Abaqus. To validate it I am comparing my UMAT results with that from a *HYPERFOAM material definition. I am facing a particular problem:

## Compression buckling of polymeric beam/column

Hello,

I have a problem with a stacked colum of elastomeric membranes (natural rubber or silicone).

I am looking for a compression buckling criterion that applies for hyperelastic materials in presence of large deformations (up to 400%).

I've read about Haringx formula, that should apply for these materials, but I suspect that it is valid for small strains only.

My question is:

- is there a suitable buckling criterion for this case?

## How to get the update the local material coordinate in large deformation for hyperelasitc rubber-like materials?

Hello,

I want to ask things about the updation of local material coordinate in large deformation.

Does there exist two ways for this?

1. Polar decomposition of Gradient Deformation Tensor F to get the rotation tensor.

2. Update each basis vector of local material coordinate system using modified Gradient Deformation Tensor F_bar = F*J^(-1/3).

What I cared about is the second method, is the second method available?

Wish someone could help me, : ). Thanks!!

## Required - Verification test for Incompressible hyperelastic models

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Hi,

I am working with a finite element code implemented in C++ in my research group. Recentl I implemneted an incompressible finite strain element.

Currently I am making use of verification tests to check whether my element runs accurately for various hyperelastic strain-energy models. I have succesfully completed a verification test using the Mooney-rivlin strain-energy density function. However, I have been unable to find verification/benchmark tests which I may use to test other strain-energy density functions.

## Compatibility error: Type Volumetric

Hi all

i was performing 2D asymmetric analysis of rim mounting on tire.

i was using hybrid elements and the following error is appearing.

MAX. PENETRATION ERROR 265.670E-03   AT NODE 50327 OF CONTACT PAIR
(CARCASS-1_CONTACT,RIM-1_CONTACT)
MAX. CONTACT FORCE ERROR 7.46319E+03 AT NODE 10327 OF CONTACT PAIR
(CARCASS-1_CONTACT,RIM-1_CONTACT)
PENETRATION ERROR TOO LARGE COMPARED TO DISPLACEMENT INCREMENT.

## Anisotropic plasticity and hyperelasticity in Abaqus

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I am trying to model a polymer that has been processed in such a way that it has oriented (orthotropic) material properties and undergoes very high strains (>100%) before break.

## Constitutive models for rubber

Hi.

I found a very useful explanation about hyperelasticity here: http://en.wikipedia.org/wiki/Hyperelastic_material#cite_note-Ogden-1

In the proof3, there is a good explanation (I can't found anything better than this one) of how we can express the Cauchy stresses in terms of the principal streches.

I am interested to incompressible material, so this is the equation:

## Jacobian matrix of Mooney-Rivlin model

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Hi,

does anyone know where I can find the analytical expressions for the components

of the Jacobian matrix of the Mooney-Rivlin model.

I know the compact form of the matrix, with the tensor products, deviators etc,

but I'm looking for the explicit expressions of each component of the matrix.

many thanks!

## anisotropic hyperelastic ansys subroutine

Recently i work on finite element model of a human vertebral body, and focus on intervertebral disc.

Based on its structure which consist of collagen fibers i have to use anisotropic hyperelastic model with reinforced fiber, and i derived the coefficients of strain energy function.

but i have some troubles to modeling this material in ansys v.10 or v.12, because i have to use user material subroutine and i have not enough information about how to define material with macro in ansys

## hyperelastic or elastic skin model in Abaqus

Dears,  I am quite new in the area of Abaqus models and biomechanics. My background is related with textiles. However I am a post doc in Belgium at the moment and my new task is to model a fingertip skin section under the influence of contact with different objects.

## Postdoctoral position in mechanical and material engineering

My name is Georges Ayoub; I am looking for a postdoctoral research position in mechanical and material engineering in the field of the polymer science, polymer behaviour and fatigue.
I defended my PHD at the beginning of this academic year (2010/2011). I am very motivated to start a Postdoctoral position, at the end of my thesis, in an Anglo-Saxon country.

## Postdoctoral position in mechanical and material engineering

My name is Georges Ayoub; I am looking for a postdoctoral research position in mechanical and material engineering in the field of the polymer science, polymer behaviour and fatigue.
I am presently preparing my last year of PHD at Lille1 university (north France) and ill defence my thesis in September 2010. I am very motivated to start a Postdoctoral position, at the end of my thesis, in a Anglo-Saxon country.

## Quasi Linear Viscoelasticity vs. Linear Viscoelasticity

Can anyone explain what is main difference between Linear Viscoelasticity vs qlv (Quasi linear Viscoelasticity) proposed by Fung.  As far as I understand stress relaxation function and elastic response functions separated and given in convolution form which provides "strain rate independent" results in qlv application.

Is linear viscoelastic description is strain dependent?