turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Navigation
- Simcenter
- Forums
- Blogs
- Knowledge Bases

- Siemens PLM Community
- Simcenter
- 3D Simulation - NX Nastran Forum
- Residual Vectors and Effective Modal Mass Table

Options

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Highlight
- Email to a Friend
- Report Inappropriate Content

2 weeks ago

Morning

I was under the impression that the inclusion of residual vectors added the “missing modal” modal mass back to the model for frequency response run. In my model this is verified since the dynamic response at very low frequencies matches that which you would expect for a static analysis i.e. all the mass is present.

However I am confused.

In the modal effective mass table, the sum of the mass fractions does not sum to 100% the mass. The effective mass matrix is still less than the A-set rigid body mass matrix, but better than if residual vectors have not been accounted for. For example, the actual model mass is 9.8kg, in the X direction of the A-set rigid body mass matrix, the mass is 9.8kg, but the effective mass matrix is 6.908kg without resvec, and 8.52kg with resvec.

Why does the residual vectors not correct the effective modal mass table (via correcting the effective mass matrix), but corrects the transfer functions eg the SPC force at the base for the frequency response run?

Labels:

Follow Siemens PLM Software

© 2017 Siemens Product Lifecycle Management Software Inc