Random Analysis

Betül Özer

Hello, I have to apply random vibration test to the part in Hypermesh. How should I go about it? Do I also need to do frequency response analysis? I could not find a detailed sample video and pdf on the Altair website. Thanks for be interested.

Best regards

Simon Križnik

Hi,

 

you need to have a power spectral density curve to perform Random vibration. Random analysis combines this curve with the results of frequency response to get random response results. 

 

Refer to:

https://altairuniversity.com/free-ebook-learn-dynamic-analysis-with-altair-optistruct/

https://www.youtube.com/watch?v=gRq4wYrr_6g

Betül Özer

Simon Križnik said:

Hi,

 

you need to have a power spectral density curve to perform Random vibration. Random analysis combines this curve with the results of frequency response to get random response results. 

 

Refer to:

https://altairuniversity.com/free-ebook-learn-dynamic-analysis-with-altair-optistruct/

https://www.youtube.com/watch?v=gRq4wYrr_6g

Tthank you. I watched this video and tried it. But I am getting an error message. 

I had downloaded the book before and examined its example. Unfortunately it is not enough

 

I applied static analysis and modal analysis to the part. I watched the video below for modal analysis. What could be the problem?

https://youtu.be/x6farkDiCp4 (Learn Modal Analysis with OptiStruct)

Simon Križnik

Betül Özer said:

Tthank you. I watched this video and tried it. But I am getting an error message. 

I had downloaded the book before and examined its example. Unfortunately it is not enough

 

I applied static analysis and modal analysis to the part. I watched the video below for modal analysis. What could be the problem?

https://youtu.be/x6farkDiCp4 (Learn Modal Analysis with OptiStruct)

These are not error messages (preventing the run), but warnings (will run, but the user should check).

These warnings are a result of Random response process (as shown in the video), wherein the METHOD and FREQUENCY cards are not assigned explicitly for each subcase (loadstep), but are assigned to all subcases through global case control. In case you need to have different METHOD and/or FREQUENCY cards in different subcases you should revise those loadcases and assign cards explicitly. 

I agree, the explanations for vibration and random analysis, in particular, are lacking from Altair resources. However, there are webinars on vibration for other solvers (Nastran has a similar syntax to Optistruct):

https://www.youtube.com/watch?v=_IkcDyG7cUw

https://www.youtube.com/watch?v=cgR5M8g_-Rk

https://www.youtube.com/watch?v=VKF5bMM-KpQ