Stress vs Cauchy Stress MSC SOL600 or Marc

[flambter]

Hi,

I am currently performing an analysis using MSC SOL600 on shell elements. The results I am getting are stress and Cauchy stress. From what I understand, Cauchy stress theorem states that knowing the stress vectors on three mutually perpendicular planes, the stress vector on any other plane passing through that point can be found through coordinate transformation equations. So that leads me to think that CAuchy stress are just another way to present stresses.

Therefore, I thought that reading the stress results and the Cauchy stress results from SOL600 might be different values of the same stresses and by combining them into Von Mises stresses, I would get something pretty close one to the other. When I actually plot the Von Mises stresses, the stress results are more than 30% lower than the Cauchy stresses and the distribution changes.

I have looked in MSC documentation to find what is actually the difference between the stress and cauchy stress and how to interpret it in Patran, but haven't found anything.

Anyone one of you has an idea?

THe attached figures show the fringe plot of Von Mises stress (averaging: all entities, extrapolation centroid)for both stress and cauchy stress.

 

[flambter]

found the mistake. It was the non-layered results. If I plot for layer 1 or 5, then I get the same results whether it is Caucy or Stress. That is comforting. : )