Usermat: Linear viscoelastic model with geometric nonlinearity - Finite Element Modeling
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https://polymerfem.com/community/finite-element-modeling-aa/usermat-linear-viscoelastic-model-with-geometric-nonlinearity/#post-11904
Sat, 14 May 2016 21:06:00 +0000Finite Element ModelingJorgenhttps://polymerfem.com/community/finite-element-modeling-aa/usermat-linear-viscoelastic-model-with-geometric-nonlinearity/#post-11904Usermat: Linear viscoelastic model with geometric nonlinearity
https://polymerfem.com/community/finite-element-modeling-aa/usermat-linear-viscoelastic-model-with-geometric-nonlinearity/#post-29457
Wed, 03 Feb 2016 14:14:49 +0000I have implemented a linear viscoelastic model using the user subroutine Usermat in Ansys.I have used the classical paper: Formulation and implementation of three-dimensional viscoelasticity at small and finite strains of Kaliske & Rothertand it works fine for small deformations.It is written in the documentation that in the case of a simulation with geometric nonlinearity (large deflection), one must rotate the state variables.Do I have to rotate these state variables if I use solid elements? I would like to simulate bending of layers (like a shell, but made of solid elements with only displacement as dof). Do I have to rotate the state variables because of the possible large bending even if the local deformation (strain) is small (I activate the option nonlinear geometric in Ansys) or can I leave the state variables as in the paper.If so, how should I do that. At the end of each time step, I just multiply the tensor of state variables with the rotation matrix and save then for the next time step? Do I have to rotate any other tensor or the old state variables at the beginning of the new time step?If I implement a viscoelastic model with a hyperelastic model, I dont have to rotate any tensor, if I define all the quantities in the reference configuration.many thanksXuxa]]>Finite Element Modelingdan1000https://polymerfem.com/community/finite-element-modeling-aa/usermat-linear-viscoelastic-model-with-geometric-nonlinearity/#post-29457