I'm having issues understanding the constraint force output of a simple plane strain solution with hyperelastic material.
Benchmark: I'm using plane strain CPLSTN4 element with a PPLANE card and MAT1 property in a SOL101, I apply a displacement. The resulting stress is the reaction force divided by the segment length. Simple.
Case 1: I'm now using CQUAD4 in SOL106 with a PLPLANE card and MATHP property (hyperelastic). I apply a displacement. However, the output stress is no longer equal to the constraint force divided by the deformed segment length. Is this a bug?
Please see attached file for Case 1. Look at the YY Stress and T2 Constraint forces.
Deformed segment Length = 0.009436 m
YY stresses = 8326Pa
8326*0.009436 ~ 80N
The output constraint T2 forces is ~480N. (vs 80N) What am I missing?
Thanks for your help.
Does anyone have an idea? I ran additional cases:
Case 1: I use CQUAD4 elements with PLPLANE card and MATHP property. I run a simple model (see attached sol106) where I apply a displacement on one end. If I look at the SPCForces, and divide by the deformed area, I do NOT recover the output stresses.
Case 2: I Run the same analysis in SOL601,106. The obtained SPCForces divided by the deformed area match the output Cauchy stress, which is expected. (see attached sol601)
Case 3: Using an isotropic linear-elastic material in SOL106 also yields consistent results.
On a side note, the results are completely different. Can someone please comment?
Please see attached .dat file.