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viscoelasticity

Question reg ABAQUS-VUMAT and Updated Lagrangian formulation.

Hello all,

I am working on implementing a viscoelastic constitutive model from a hyperelastic stored energy potential (for finite-elasticity) and a dissipation potential (for the viscouls evolution). The elastic constitutive relation, hence derived from the stored energy potential is rate-independent and it is expressed as T(Cauchy's Stress) = f(B), where B is the Left-cauchy green deformation tensor.

The evolution equation is derived out in an objective rate form, which I am integrating over time using a 2nd order accurate explicit method.

My question:

Viscoelastic damping behavior of structural bamboo material and its microstructural origins

In this study, the intrinsic viscoelastic mechanical behavior of a hierarchical bio-composite, structural bamboo material, was experimentally investigated and correlated with its microstructural constituents and molecular building blocks. The macroscopic viscoelastic responses of bulk bamboo at ambient temperature and dehydrated condition were evaluated through dynamic compression experiments with various loading frequencies, whereas the localized viscoelasticity of bamboo's microstructural phases, viz.

shreeram111's picture

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.

Thanks in advance for your time and consideration

Regards

Shree

El Kouri mohamed's picture

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

 

Zhigang Suo's picture

FRAME INDIFFERENCE

The attached notes are written for a course on plasticity.  When I update the notes, I will post a link on my twitter account:  https://twitter.com/zhigangsuo.

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. 

Oden Warren's picture

UPDATED: Nanobrücken 2014 Nanomechanical Testing Workshop

Dear Colleague: You are cordially invited to participate in the Nanobrücken 2014 Nanomechanical Testing Workshop, which 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 annual Nanobrücken workshop series. This year's Keynote Speaker will be Andrew Minor (University of California, Berkeley).

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?  

Oden Warren's picture

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).

Controllable viscoelastic behavior of vertically aligned carbon nanotube arrays

Controllable viscoelastic behavior of vertically aligned carbon nanotube arrays

 

Kilho Eom, Kihwan Nam, Huihun Jung, Pilhan Kim, Michael S. Strano, Jae-Hee Han, Taeyun Kwon

 

Abstract

UMAT Multi-element Error

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 

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) .

 

Matt Pharr's picture

Rupture of a highly stretchable acrylic dielectric elastomer (VHB)

Dielectric elastomer transducers are often subject to large tensile stretches and are susceptible to rupture. Here we carry out an experimental study of the rupture behavior of membranes of an acrylic dielectric elastomer (VHB 4905). Pure-shear test specimens are used to measure force-displacement curves, using samples with and without pre-cracks. We find that introducing a pre-crack into a membrane drastically reduces the stretch at rupture. Furthermore, we measure the stretch at rupture and fracture energy using samples of different heights at various stretch-rates. The stretch at rupture is found to decrease with sample height, and the fracture energy is found to increase with stretch-rate.
This paper has appeared in the Journal of Applied Physics and can be downloaded from:

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