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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:

cbrinson's picture

Postdoc Position in Advanced Materials Lab, Northwestern University

A postdoctoral position is available immediately in Brinson’s Advanced Materials Lab involving collaborative work on finite element modeling of nanostructured polymer composites. The majority of the work will be split across two projects on the subject.  The first project involves 3D modeling of filled elastomers, with a focus on the viscoelastic properties. Non-linear viscoelastic modeling experience is a plus, but not required.

azadpoor's picture

Call for special issue papers: Mechanics of cells, tissues, and biomaterials

The paramount role of mechanics in life has recently been the center of attention of many researchers. This special issue will be focusing on the role of mechanics in the life of cells and tissues and their interactions with biomaterials. Original research and review papers are solicited for review and publication in the journal Mechanical Sciences . Mechanical Sciences is an academic open-access journal sponsored by the Library of Delft University of Technology and The Netherlands Organization for Scientific Research (NWO).

Meshing difficulty in viscoelastic constrained layer damping


I am simulating constrained layer damping with viscoelastic layer in Abaqus.

Used 3D continuum element - C3D20R for base an face sheet and and same with hybrid 

formulation C3D20RH for visco tape.

In FE mesh, I tied the nodes (through tie constraint) of base with that of visco tape and 

also the visco tape with that of face sheet. But in the deformed mode shape, I am finding 

the visco tape fully penetrated inside the casing (I guess as there is no contact, only tie 


wvmars's picture

Call for Papers - Rubber Division ACS mini-symposium on Mechanics and Modelling, Cincinatti, 9-11 Oct 2012

The Rubber Division, ACS is now accepting online
abstract submissions for the 182nd Technical Meeting being held during the
Rubber Expo at the Duke Energy Center, October 9-11, 2012, in Cincinnati, OH,
USA.  Papers will be judged and awards presented
for Best Paper and Best Paper - Honorable Mention.

Official Call for Papers:

Abstracts Due: Friday, May 18, 2012

Oden Warren's picture

EXTENDED ABSTRACT SUBMISSION: Nanobrücken II: A Nanomechanical Testing Workshop, March 22-23, 2012, INM Saarbrücken, Germany

Dear Colleague:

You are cordially invited to attend Nanobrücken II:  A Nanomechanical Testing Workshop, jointly presented by INM - Leibniz Institute for New Materials and Hysitron, Inc., with co-sponsorship from the JEOL company. This is the second workshop in the Nanobrücken series. The workshop's scope has been broadened, and the abstract submission deadline is now February 19, 2012.

farhan3d's picture

Viscoelastic properties of pre- and post-cure cellular rubbers using rheometer

Hi All,

I would like to know if anyone has had the opportunity to investigate cellular rubbers rheology. I am thinking of characterizing the viscoelastic properties of cellular rubber during cure and after cure in the rheometer, using ASTM D6601. What I am expecting is a distorted cellular structure due to very constrained foam expansion during the blowing agent's decomposition, so the results would obviously be different than the ones obtained from a DMTA machine.

Would like to hear from anyone with some rheology / viscoelastic characterization experience.

NANOVEA's picture

Viscoelastic Analysis With Nanoindentation DMA

Viscoelasticity can be studied using Dynamic Mechanical Analysis (DMA) during Nanoindentation. By applying controlled oscillatory stress the resulting strain can easily be measured. An elastic material will have stress and strain in phase while a viscous-elastic material will have strain lagging stress. In many applications during quality control and R&D, it is important to reliably test this behavior.

Julien Yvonnet's picture

Computational homogenization of linear viscoelastic materials: a simplified approach

Several methods have been proposed for numerical homogeniation of linear viscoelastic materials, mainly based on Laplace transform or on multilevel (FE^2) approaches. In this paper, we introduce a much simpler technique based on a discrete representation of the effective relaxation tensor related to the homogeneous medium, which can then be used to evaluate the constitutive law in the form of a convolution product. In practice, calculations on the RVE reduce to 3 transient simulations in 2D and 6  in 3D. More details in



I have to do stress relaxation of fabric under stress condition. For this I have assumed my fabric as orthotropic material.

I need to find a stress relaxation on fabric under stress condition. Can anyone suggest the procedure to solve this analysis in




mokarram76's picture

my recent publications in curing modeling


I am working on the modeling of curing process of polymer

we may like to take a look on my recent publications:

Viscoelastic RVE for CNT Composites


I am Mohammad Aramfard senior student of mechanical engineering and I joined this
great forum yesterday, so I am not very familiar with regulations and rules.Laughing

I am working on modeling CNT composites using cylindrical RVE and I found up to
now that there isn`t a viscoelastic RVE for representing behavior of these

mbrennan's picture

Position in Industry - Research Scientist Computational Modelling

Currently we, Huntsman (Europe) BVBA, are looking for a Research
Scientist Computational Modelling at our Everberg offices close to Brussels,

orthotropic nonlinear viscoelasticity/creep in Ansys


 I would like to know if there is any chance to simulate orthotropic nonlinear viscoelasticity/creep of CFRP in ANSYS (e.g. by means of user programmable features (UMAT subroutines) or using the software DIGIMAT or others)? For the nonlinear part I would like to use Schapery's method.

 Many thanks for yor help!


ANSYS 12 viscoelastic model

Choose a channel featured in the header of iMechanica: 

Does anyone know where can I find a manual and or tutorial for ANSYS 12.0 mechanical APDL , specifically where I can find something related to the use of viscoelastic material models???



viscoelasticity property material


please wgo can tell me what does mean the folowings:

   -", the modulus ratio in the first term in the Prony series expansion of the shear relaxation modulus."

   -", the modulus ratio in the first term in the Prony series expansion of the bulk relaxation modulus."

and how to calculate them in abaqus



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