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MAT9ORT is changing to MAT9 in optimization

Hello,

I am doing Optimization on MAT9ORT and getting a MAT9 after the optimization. Why is Optistruct changing the material designation, I need to have it in the MAT9ORT.

1. How can I force it to keep MAT9ORT?

2. The output file spits some material properties for the last iteration, but that material properties don't give the same Eigenvalues if you run the model with MAT9ORT from the output file.

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OptiStruct

v2020.0

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PaulAltair

MAT9OR (or MAT9ORT in older versions) is always internally converted to MAT9 for the actual analysis run, MAT9ORT doesn't really 'exist' from the solver point of view, it is just a more convenient way for the user to input MAT9 data.

The results should be the same with either the MAT9ORT or the echo'd MAT9 data (since the MAT9 input is what is being used in the first place)

How are you trying to 'compare eigenvalues'?

If you run your baseline with MAT9ORT as input, or substitute the echo'd MAT9 for that MAT9ORT, the results should be the same.

Numair

Thank you Paul for responding. You are right, I just verified the results for MAT9 vs. MAT9ORT.

I am using the NVH MAC to correlate the result. It seems that the Modal Correlation calculations of the MAC in the NVH Module are different when you pick the OP2 file form the optimization last iteration vs when you plug the material in the original file and run Normal Modes analysis again then compare the results. This might need some investigation.

It would be really helpful if the optimization could spit the MAT9ORT with the MAT9 in the Property file of the optimization. It is far easier to interpret the results this way, especially if the design variable is based on the MAT9ORT.

Thank you!