Eigenvetor as response in Hyperstudy

Altair Forum User

Hello,

 

I created a finite element model of a wing in HyperMesh. An experimental modal analysis has been performed on the real model of that wing, so I know what the eigenfrequencies and the eigenvectors are. Now I want to do a system identification in HyperStudy. As a response in this study I want to retrieve the eigenvectors at some nodes from output files of the optistruct solver.

 

Under Define Responses - Expression - File sources I can actually see for the .res output file the option to select the eigenvector at a certain node, however, I can't select for which Mode/Eigenfrequency this eigenvector is.

 

Is there a way to select a Eigenvector as a response at a certain node AND for a certain mode?

 

Thanks!

Altair Forum User

First, I think you would be better off using the h3d rather than the res file from OptiStruct.  I am not an OptiStruct expert, but it is my understanding that the h3d is the preferred modern format and the res is an older legacy format.

 

The steps you are using are correct.  When you are reading from the file source, you are getting a vector of the diplacement at that node over the modes.  So if you have ten modes, then the vector will have a length of 10: the first entry (for example v_1[0]) is for the first mode, the second entry v_1[1] is for mode 2.

 

If you want the list of frequencies for the modes that would require another vector source to read that information. 

 

You can then compare or cross reference the two as you see fit.

 

You may benefit from using a HyperMath function to perform more logic related operations.