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Stiffness-generated rigid-body mode shapes for lanczos eigensolution with suport dof by way of a msc/nastran dmap alter
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Abdallah, Ayman A. Miller, Robert P. Barnett, Alan R. Manella, Richard T. Widrick, Timothy W. |
| Copyright Year | 1994 |
| Description | When using all MSC/NASTRAN eigensolution methods except Lanczos, the analyst can replace the coupled system rigid-body modes calculated within DMAP module READ with mass orthogonalized and normalized rigid-body modes generated from the system stiffness. This option is invoked by defining MSC/NASTRAN r-set degrees of freedom via the SUPORT bulk data card. The newly calculated modes are required if the rigid-body modes calculated by the eigensolver are not 'clean' due to numerical roundoffs in the solution. When performing transient structural dynamic load analysis, the numerical roundoffs can result in inaccurate rigid-body accelerations which affect steady-state responses. Unfortunately, when using the Lanczos method and defining r-set degrees of freedom, the rigid-body modes calculated within DMAP module REIGL are retained. To overcome this limitation and to allow MSC/NASTRAN to handle SUPORT degrees of freedom identically for all eigensolvers, a DMAP Alter has been written which replaces Lanczos-calculated rigid-body modes with stiffness-generated rigid-body modes. The newly generated rigid-body modes are normalized with respect to the system mass and orthogonalized using the Gram-Schmidt technique. This algorithm has been implemented as an enhancement to an existing coupled loads methodology. |
| File Size | 774421 |
| Page Count | 20 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19940024903 |
| Archival Resource Key | ark:/13960/t7pp4198n |
| Language | English |
| Publisher Date | 1994-03-01 |
| Access Restriction | Open |
| Subject Keyword | Structural Mechanics Dynamic Structural Analysis Stiffness Matrix Rigid Structures Degrees of Freedom Free Vibration Modal Response Steady State Finite Element Method Eigenvalues Coupled Modes Vibration Mode Transient Loads Nastran Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
