Modal Mass Participation

Published 2013-06-12
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Question

Do you know how to extract modal mass participation factors out of Nastran when running a normal modes analysis (SOL 103)? I see reference to it in the DDAM Solution, but I don’t really want to use that one.

I saw something about adding

METHOD=100
MEFFMASS(ALL)=YES

To the .bdf, but that gives me all sorts of fatal errors. (I used the Bulk Data input form in Patran, trying both on subcase and overall analysis level)

Answer

The METHOD card is already written by Patran and SimXpert for Normal Modes (Sol 103). This card is used to select the eigenvalue extraction card (EIGR or EIGRL) that determines how many modes are to be extracted.

To get the modal effective mass, you only need to add the MEFFMASS(ALL)=YES in a direct text input in the case-control section.

In Patran it can be done either on the main analysis form -> Direct text input or on the direct text input section for a subcase.

I think this is...