Hi,

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 

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.

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.

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.

Thanks,

Muhammad Farhan

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

 A.B. Tran, J. Yvonnet, Q.-C. He, C. Toulemonde, J. Sanahuja, A simple computational homogenization method for structures made of linear heterogeneous viscoelastic material. Comput. Methods Appl. Mech. Eng. 200 (45-46):2956-2970 (2011).

hi,

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

ANSYS.

Thanks

BIPIn

Hi

I am working on the modeling of curing process of polymer

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

Hossain, M. ; Possart, G. ; Steinmann, P.A Finite Strain Framework for the Simulation of Polymer Curing. Part II. Viscoelasticity and shrinkage .Computational Mechanics, published online

Hi
all,

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.

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

Hi,

 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!

-André

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???

Hi

hi

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

thanks 

NONEQUILIBRIUM THERMODYNAMICS OF DIELECTRIC ELASTOMERS
Xuanhe Zhao, Soo Jin Adrian Koh, Zhigang Suo

Abstract
This paper describes an approach to construct models of dielectric elastomers undergoing dissipative processes, such as viscoelastic, dielectric and conductive relaxation. The approach is guided by nonequilibrium thermodynamics, characterizing the state of a dielectric elastomer with kinematic variables through which external loads do work, as well as internal variables that describe the dissipative processes.

Constitutive relations, 2-D vs. 3-D. The starting point for modeling cellular membranes is the constitutive relations in 2-D space. It is important to set up the corresponding equations directly in two dimensions rather than to consider them as an asymptotic limit of three-dimensional relationships, like it is done in the shell theory. The main reason for the direct 2-D relations is that 3-D continuum approaches are not applicable to membranes whose thickness in on the order of magnitude of the dimension of a single molecule.

SUSHIL SINGH
Address: 417 Reed street
Tuscaloosa, AL 35401
Tel :   (205) 239 1696 E-mail : singh.sushil@live.com

Hi,

 I am trying to model a sheet of Poly Vinyl Butryl (PVB), which is a viscoelastic material in ANSYS. I have all the regular properties like elastic, shear and bulk modulus, poisson ratio, denstiy and damping factor. I also have a stress- strain curve of PVB. With all this data, is it possible for me to find the various constants in the viscoelastic models using ANSYS?

 Thanks

Saurabh 

Dielectric elastomer, as an important category of electroactive polymers, is known to have viscoelastic properties that strongly affect its dynamic performance and limit its application. Very few models accounting for the effects of both electrostatics and viscoelasticity exist in the literature, and even fewer are capable of making reliable predictions under general loads and constraints. Based on the principals of nonequilibrium thermodynamics, this paper develops a field theory that fully couples the large inelastic deformations and electric fields in deformable dielectrics. Our theory recovers existing models of elastic dielectrics in the equilibrium limit.

We present a new wrinkling-based measurement technique for quantifying the viscoelastic properties of confined polymer thin films. This approach utilizes real-time laser-light scattering to observe the kinetics of thermally-induced surface wrinkling, which evolves isothermally as a function of annealing time. Specifically, wrinkling is induced by applying a thermal stress to a polystyrene film that is sandwiched between a silicon substrate and an aluminium thin film superstrate. By following the time evolution of the wrinkle wavelength and amplitude, we can infer the rubbery modulus and shear viscosity of the polystyrene film with the aid of a theoretical model.

Hi,

Does anyone have a small strain FE viscoelasticity routine or code that I can use, prefreably in Fortran? Thanks.

Shriram

HI!

I applied constant load on the viscoelastic body.

Now i want to see the displacement of one of the node with respect to time.

Can any body help me in this regard?

thank you.

Hi Guys,

I have the shear relaxation modulus given as: G(t)=Go*EXP(-t/tau). In ABAQUS, the normalized shear modulus for one term in Prony series is given as: g(t)=Go(1-g1(1-EXP(-t/tau)). The parameters that must be entered in ABAQUS are g1 and tau. For Maxwell (in our case) G(t=infinity)=0.

Consequently, g1=1-G(t=infinity)/Go=1. ABAQUS requires that g1 must be less than 1. Has anyone encountered this problem?

thanks

Ah