Learning Forum

[Mateus Fiorini]

I'm trying to simulate the harmonic response of viscoelastic material, and I noticed some points that I think are important to share. If anyone can explain to me why this happens, I would be very grateful.

To do this simulation, I used a tutorial produced by Ansys itself (High-Frequency Damper Using Viscoelastic Materials) which explains how to enter the storage modulus and loss modulus for each frequency of the viscoelastic material via commands. For this to be done, it is taught that it is necessary to create a viscoelastic material in Engineering Data just to allocate the material, but its properties would be defined by the commands. Consequently, one would expect that by changing the value of Young's modulus to any value, the response would be the same as it should be reading the command.

The image below shows the result obtained in the tutorial, which uses 23000Mpa for Young's modulus:

However, when analyzing whether this result would remain using different Young's Modulus values, an extremely high divergence was noticed when changing this property in the Engineering Data. Starting from zero and varying the order of magnitude of the value entered for Young's modulus, I obtained the following results:

Note that from a certain value of Young's modulus the response stabilizes, I would like to know why this occurs, since this behavior does not make sense, since it should be considering the command from the beginning.

 

[peteroznewman]

Read up on viscoelasticity on the Wiki Page. https://en.wikipedia.org/wiki/Viscoelasticity

 Note the section on Prony series.

In other words, Ansys is using the Young's Modulus in conjuction with the Prony series data.

[Mateus Fiorini]

i did the same simulation in ansys APDL, i defined the viscoelastic material and the results were the same to diferents values of Young Modulus, because ansys was reading the commands that i used with the prony series data. So, why doesn't it happen with ansys workbench if i created a material in engineering data just to alocate the viscoelastic material?