Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations SDETERS on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

understanding/implementing free effective mass

ghylander

Marine/Ocean
Jun 5, 2023
14
This topic could belong either here or in the aerospace section I believe

I am performing free-free modal analysis on a floating structure, and I'm looking for a way to determine significant vibration modes (without forced response simulations).

In my investigation, I came across the following papers (open access):

And this other more recent paper implementing it (also open access):

I am trying to implement this EMf but I'm struggling to grasp the concept.

As far as I understand, there's no need for DMAP (I'm using NX/SC Nastran), this should be achievable by post-processing the results.
I am requesting the eigenvector data and outputting it to the f06 file, and I have already setup a routine to extract the eigenvector matrix and compute the trace of the product.

However, I'm getting lost in the notation:
1743663663265.png
EMf.png

1743663597049.png


The last paper also confuses me further:
1743663845428.png

Any help would be appreciated
 

Part and Inventory Search

Sponsor