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