Viscoelastic Modeling in ANSYS

- February 11, 2020 at 11:04 pm
  
  Fuad87
  Subscriber
  
  Hello, I have a couple of questions. If you can, please answer separately with the question number.
  
  1. let's say I have prony series data for shear modulus. Do I also need to input "prony series for bulk modulus"? Or only initial bulk modulus, K0 (or other combination like young and poisson) will be enough?
  
  2. Since viscoelastic is time and rate-dependent property, do I need to use "transient analysis"? The reason behind my confusion is that I have done simple stress relaxation simulation in "static structural". I know in static structural time is not the actual time. But I intentionally define the viscoelastic property such that the first relaxation time lets say 5 seconds. Then in "static structural" I gave 20 time step (each 1 sec) and kept strain fixed to some value. What I saw that the stress relaxes in 5-6 sec. So I was really confused to see that in static structural, stress relaxation is happening. So I am asking if this is acceptable? Or I should do the transient analysis? Thanks.
- March 12, 2020 at 1:59 pm
  
  Sai Deogekar
  Ansys Employee
  
  Hello!
  
  1. You may input the prony series for both the shear and bulk modulus if you have the data. If either of these data are not inputted, they will be assumed to be constant (i.e. no relaxation for that particular term). You may refer to the part below eq. (4-263):
  
  https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v201/en/ans_thry/thy_mat6.html%23small
  
  2. In viscoelasticity modeling time (even in static structural) is real time, so you can use viscoelastic material in static structural analysis.