I'm still working, with Ansys APDL here in the context:

Nonlinear geometry, linear viscoelastic material behavior via prony parameters from master curves, 3D model using SOLID 185, creep test.

Everything works quite well, but I can't find the right 'switch' for a problem and I'm left a bit like a "ox before the mountain".

We are looking for, among other things, the total energy of the model at a certain point in time, divided into storage energy and loss energy, ditto for certain regions of the structure or individual elements.

It seems clear that one has to evaluate the solution in the complex number range, however the simulations do not have any frequency-dependent boundary conditions, the structure is only exposed to a force or displacement that is applied in a ramp shape for the first 10 seconds.

I would be grateful for any tips, including those relating to possible 'switches' in the Ansys Workbench.

With constructive greetings

Lutz Müller ]]>

I have the following experimental data from the DMA measurment of temperature sweap.In the MCalibration software, I tried to fit the ABAQUS LE-PRONY01-WLF model to this data.

But I can't adjust anything except a horizontal line. I tried to keep the first part of the data from 20°C to 50°C to see if the software could adapt something to it, but the adapted data was a horizontal line!

I would be appreciated if you have some ideas about this problem.

Many thanks in advance

]]>I want to define a viscoelastic model in Ansys that behaves according to Maxwell's viscoelastisity model. My goal is to find the viscoelastic parameter η, in order to gain the same curve with the one I got from the tensile experiment.

My data include: stress-strain curve, Young modulus and poisson's ratio.

1) I've been thinking about assuming a value for η, selecting the 'prony shear relaxation' option and defining the 'Relaxation time' as: t=η/E. Is it correct?

And of course repeating this procedure until the graphs are the same.

2) Do you have any other idea about how to calculate the viscosity parameter from the data?

Thank you in advance!

]]>I have the DMTA data for storage and loss modulus curves with frequency on x-axis.

I want to ask how do we know the frequency range for which we have to fit the equations of loss and storage modulus to the data to get the right prony terms for my simulation.

My simulation is a simple impact of a rigid body on the elastomer.

Does the frequency range for the fitting correspond to my loading curve frequency of simulation, or the timestep of my simulation or anything else?

Best Regards!]]>

I am using Abaqus to simulate the damping response of a constrained layer damper made of rubber, which is a hyperelastic and viscoelastic material. The structure is a hollow cylindrical cantilever, and I am measuring damping by applying a static load to the free end of the structure and then deactivating the load for the implicit step. The Ogden model with instantaneous hyperelasticity was used to define the hyperelastic properties, and shear-relaxation test data was used to define the time-domain viscoelasticity. However, every time I run the simulation I get a non-damped response.

Is there another way to measure the damping of the material using Abaqus, or is it hard to achieve damping on such a structure? I would appreciate any input regarding this.

I am currently writing my Masterthesis and I need help in modelling a viscoelastic material in ANSYS Mechanical. I don't know how exactly I should add my material properties in the Engineering Data field.

I experimentally measured the shear modulus G(t), and calculated the Bulk Modulus K(t) with the following formula: K(t) = 1/(3*(1-2nu)) * E(t), with E(t) = stress(t)/strain. - Attached, you can find an example with my data for G(t)-.

When I run my model with only this two Viscoelastic Test Data series, I get this error:

Elasticity is required, but is currently undefined.

I tried to add the required Isotropic Elasticity Property Data (Youngs Modulus and Poisson's Ratio) but when I run my model again, I get the same results as if I had only a Linear Elastic Material, it returns the same value. Ansys is not considering my viscoelastic property data I gave him.

Thank you and I hope You can help me!

Best regards,

Ioana

1. Polymer samples have been tested in tension with a constant elongation and a 10mins dwell time. This is regarded as one step and stress relaxation repeated many times in the test. Now curves of strain-stress and time-stress are gained, but I have no idea how to get the viscoelastic parameters.

2. Relaxation test data is considered in the beginning since I have done some relaxation tests. I then found there are shear test data and volumetric test data which obviously are not suitable. Maybe Prony should be used and, I should do curve fitting according to the equations of g_i and k_i? In my case the tau_i should be a constant of 10 mins.

I am new to this topic and really confused with it. Thank you all!

243Thank you all!

]]>I am working on simulating quasi-static contact between a metal and a polymer gear in Abaqus. I wanted to use the viscoelastic model. So I performed DMA in frequency sweep mode to determine the prony series. I compared the results of the linear elastic model and viscoelastic model. They return the same value. The values are the same for both low loads and high loads. So, I am not sure whether this is a proper result or some error in the model.

]]>I am trying to develop a model for soft tissue using fractional viscoelasticity in abaqus. I am using a springpot model defined using a VUMAT subroutine.

I am testing with a single solid element (C3D8) in a displacement controlled simulation. I am currently running a tension test with displacement control along x varying linearly from 0 to 0.1 at the end of the dynamic step. With VUMAT, the strain at the end of the time increment is already known and the corresponding stress has to be evaluated and updated.

However, when I run the model, within a few increments my simulation errors out with excessive element distortion. Upon printing the strains, I notice that the strains in the y and z directions (lateral strains) quickly blow up causing excessive distortion.

Has anyone encountered similar issues? if so, can you please suggest how to debug the problem.

Paramesh

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1. Get load, displacement, time values from nanoindentation test

2. I found an equation to get the creep compliance Js(t) = contact_area /

3. For my berkovich indenter, contact_area = 24.5*h^2, theta is 71 degrees

4. Next I have to normalize Js(t) to obtain js(t) which is required by ABAQUS, so I divide all values of Js(t) by the value at t=0 i.e.: Js(0)

Some of the values I have input in ABAQUS are as follows;

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