# [Workbench] Converging problem with hyper elastic material

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April 24, 2020, 16:31
Converging problem with hyper elastic material
#1
New Member

omid
Join Date: Jun 2019
Posts: 8
Rep Power: 3
I'm doing 2-way FSI simulation with hyper elastic materials, i'm trying to use Mooney Rivlin 5 parameter model for hyper elastic behavior. I borrowed all 5 parameters from an article with the same concept, but i'm having a serious converging problem. I have tried to run the simulation with different mesh size and different elements, also with different time step size (increasing and decreasing the step size) but each time Solution information gives me the same Error below:

[U]Distributed sparse solver minimum pivot in absolute value=
3.737065875E-02 at node 281725 UZ.
DISP CONVERGENCE VALUE = 0.7277 CRITERION= 0.3713E-01
EQUIL ITER 1 COMPLETED. NEW TRIANG MATRIX. MAX DOF INC= 0.7277
FORCE CONVERGENCE VALUE = 5.978 CRITERION= 0.7782E-03
DISP CONVERGENCE VALUE = 7.648 CRITERION= 0.3987
EQUIL ITER 2 COMPLETED. NEW TRIANG MATRIX. MAX DOF INC= 7.648

*** ERROR *** CP = 619.418 TIME= 221:22
Element 152312 (type = 6, SOLID186) (and maybe other elements) has
become highly distorted. Excessive distortion of elements is usually
a symptom indicating the need for corrective action elsewhere. Try
may need to improve your mesh to obtain elements with better aspect
ratios. Also consider the behavior of materials, contact pairs,
and/or constraint equations. Please rule out other root causes of
this failure before attempting rezoning or nonlinear adaptive
solutions. If this message appears in the first iteration of first
substep, be sure to run shape checking of elements
.

I have already run the same model with elastic materials and it converged with little changes in mesh size. But for the hyper elastic material, nothing seems to effect the converging process. I'm attaching a picture of what happens to the model after the element distortion.

Could anyone help me?
Attached Images
 Capture.PNG (49.7 KB, 3 views)

 Tags distorted elements, error, fsi, mechanical, structural