Optimzation Stress Results Interpretation in a model made of Second order elements.

Rajendran

Instructions

1. The document explains how to interpret the stress results obtained in the *.out file compared to the stress values visualized in HyperView of an Optimization run. When stress is called as a Constraint or Objective.
2. Its a usual practice for customers to check if they can visualize in HyperView the same stress values obtained in the *.out file of the optimization run.

The results obtained in *.out file and the values shown in HyperView will differ if the user has used second order elements in his model with “CORNER” option ON in the stress DRESP1 card.

3. The reason behind this is, in the *.out file only the maximum nodal stress among all the nodes is written out. This has been verified by working on a sample model and the results comparison can be seen in the below image.

 

4. As you can see in the above snapshot from the *.out file the same element shows three different stress values whereas in HV we see only one maximum value in the Contour Plot this confuses the customer.
5. This behavior is due to the usage of second order elements, the solver basically outputs the maximum nodal stresses of that element in the *.out file. This can be verified through the query option in HyperView which is also attached here for reference.
6. This issue will not arise if user has not switched on the “CORNER” option when creating the DRESP1 stress response within a second order model.
7. Note: Make sure user has switched ON corner data at times user might miss switching ON this option which will lead to mismatch in *.out file values compared to HV values.