# viscoelasticity

## UMAT Non linear Viscoelasticity - Algorithm verification?

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Hello everybody,

My task is to write a UMAT for Non-linear Viscoelasicity based on Schapery's model in ABAQUS. I have coded the routine, but I am still not able to predict correct response. I tried to debug it as much as I can. I understand that it would be difficult for anybody to understand my code. So, I have attached a flowchart (pdf) of the whole algorithm that I follow. It would be nice if you could check that and correct me if I am wrong.

Regards

Shree

## ageing viscoelastic

Hello everone

I am recently interested in viscoelastic composite materials with ageing effect. I will be very pleased if someone can advise me how to find a constitutive law with ageing effect.

sincerely

## Online finite element analysis of nanoindentation (indentation)

Dear All,

We (the NanoBIO Node at Illinois ) have a preliminary release of an online finite element analysis of nanoindentation (indentation) tool using FEAP

This preliminary release is limited to linear elastic material, axisymmetric geometry, spherical rigid indenter, and various boundary conditions.

## Residual stresses in elastic medium upon uniform cooling

Hi All,

I am a student working on a project involving the effect of residual stresses in elastic and viscoealstic materials. I have a related question: When an easltic body is heated to a certain temperature (say 400 deg C) and then cooled uniformly to room temperature (20 deg C) with a constant cooling rate "q", does this generate any "un-desirable" (residual) stresses within the elastic body? i.e at a steady state - room temperature, does the final stress state within the body would be non-zero? Else, it would eventually reach a state of zero stresses? How?

## Nanobrücken 2014 Nanomechanical Testing Workshop

The Nanobrücken 2014
Nanomechanical Testing Workshop
will take place March 26-28, 2014 at INM -
Leibniz Institute for New Materials in Saarbrücken, Germany. This will be the
4th edition of the now-annual Nanobrücken workshop series. This year's
Keynote Speaker will be Andrew Minor (University of California, Berkeley).

## UMAT Multi-element Error

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Hello All:

I have written a UMAT code to predict the viscoelastic behaviour within a
shape adaptive structure. I have followed similar steps used in Abaqus
subroutine manual, I have applied this UMAT to a single quad element and
it works as predicted. But when I apply it multiple elements model it
breaks down.

Is there any special command i need to put in UMAT subroutine to account
multi element analysis? I will appreciate all related comments,

## UMAT Multi-element Issues

Hello All:

I have written a UMAT code to predict the viscoelastic behaviour within a shape adaptive structure. I have followed similar steps used in Abaqus subroutine manual, I have applied this UMAT to a single quad element and it works as predicted. But when I apply it multiple elements model it breaks down.

Is there any special command i need to put in UMAT subroutine to account multi element analysis? I will appreciate all related comments,

Thanks

## Inaccurate UMAT result in SMP model

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Hello:

I have written a UMAT subroutine similar to the one shown in abaqus 6.11 subroutine manual 1.1.40 with a slight differences indicative of the material's rheological model.
my expanded isotropic model looks like:
sigma_x - sigmav_x/3 + vbar*sigma_dot_x + kappa*sigma_dot_x =
lambda*eplv + 2*mu*epl_x + lamdabar*eplv_dot_x +2*mubar*epl_x

## how to model the damping behavior of viscoelastic passive damper using ANSYS applied to a sandwich beam

dear all,

How can I model the changing
relationship of shear modulus with frequency for a passive constrained viscoelastic
damper used as part of a composite  sandwich beam which is subject to a walking
excitation using ANSYS ??

## modeling of a gel using visco elastic properties using ansys

sir,

i amhe currently doing project using ansys. i have to model the properties of a gel using viscoelastic properties. there are different viscoelastic models in ansys , i dont know which model should use and how we get the parameters for that model.hope a favourable reply

regards

## ECCMR 2013 - European Conference on Constitutive Models for Rubber - Abstract deadline: 1 Nov 2012

The 8th European Conference on Constitutive Models for Rubbers (ECCMR VIII) will be held at Tecnun/CEIT (San Sebastian, Spain) between June 25th and June 28th, 2013.

## UMAT in ABAQUS

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Hi,

I've been learning how to implement material models using UMAT in ABAQUS and I have

some simple questions:

I've been trying to implement the viscoelastic models in the paper:

Formulation and implementation of three-dimensional viscoelasticity at small and finite strains

Kaliske, M.; Rothert, H., Computational Mechanics, Volume 19, Issue 3, pp. 228-239 (1997) .