Learning Forum

[seventanapply]

Hi, 

I am trying to verify the tan delta of viscoelastic material in Workbench. The model is simply a 10x10x10 mm cube.  Transient structural is chosen. 

For the part of Shear modulus and bulk modulus, I obtained the experimental data from DMA and import those data points into Engineering data. And I have already verified that if there is a constant stress, then a creep compliance curve is obtained which is matched with my experimental data of creep compliance.

For tan delta,

I measured the storage modulus vs freq curve from DMA and import those data into WB by APDL commands.

Then I set my pressure as a kind of sinusoidal pressure upon the top surface. The function of pressure is as follow.

Pressure=-0.4*sin(6.28*time) if pressure<0

otherwise pressure=0.

Those data are imported by XML file. I am pretty sure the pressure is correct. Here is the screenshot.

Other boundary condition is a fixed support at the bottom.

According to the definition of tan delta, delta is a lag phase angle between stress and strain if the input is a sinusoidal stress.

But I cannot see any phase lag in my results. 

Can you give any suggestions? or maybe I made some conceptional mistakes? Should I do it under Harmonic analysis?

Thanks in advance.

 

 

[caogang7758]

I recently also find out that transient structural analysis does not shown any phase lag and energy dissipation when you use prony series viscoelastic.I feel puzzled.