Learning Forum

[Matthew Mayo]

Greetings, 

I have a silicone-rubber type material that I have had a lab perform Dynamic Mechanical Analysis on. The data they have provided me is Shear Complex Modulus (storage and loss moduli) over a frequency range. 

I would like to model this material in ANSYS mechanical, but first I need to validate the lab data by running a displacement sweep and comparing the force response with the force response in the lab data.

I have used MATLAB to curve fit the data, pulling out the G_e, G_i and T_i terms, thus allowing me to plot the Prony Series, G(t), the shear relaxation as a function of time. 

I have entered the G(t) at 22degC data into a new ANSYS material and I have now tried to run the same DMA displacment vs freq test as a Harmonic Response analysis, AND a single sin freq vibration Transient Structural analysis. In both cases my force response is much (10x) lower than the force response from my lab data.

Any ideas? Are Harmonic Response and Transient Structural not appropriate for Viscoelastic materials?

A clue that something might be off is that in both analyses, i got an error saying the material model was missing Linear Elastic data. I had that data in both shear and compression so I added it, in both Harmonic and Transient the simulation then completed, but I beleive I should be able to do this DMA simulation with just shear relaxation data, not quasi static linear elastic data.

[Ashish Khemka]

Hi Matthew,

 

Please see if the following discussions help:

 

Modelling visco-elastic material for harmonic response analysis (ansys.com)

Harmonic analysis using viscoelastic material (ansys.com)

 

Regards,

Ashish Khemka