Description: Composite modal damping is available for eigenvalue extraction that uses the SIM-based Lanczos eigensolver. You specify composite modal damping in the frequency extraction step definition, which is in contrast to analyses using the traditional architecture, where you specify composite modal damping in the material definition.

In SIM-based analyses that use the Lanczos eigensolver, you can calculate mass proportional and stiffness proportional composite modal damping; for analyses that use the traditional architecture, only mass proportional composite modal damping is available.

You can calculate the fraction of critical damping per eigenmode and assign different damping values to different elements or elements sets. You can also assign mass proportional and stiffness proportional critical damping fractions to both mass and stiffness matrix input. The fraction of critical damping per eigenmode is output along with the eigenvalue table in the data (.dat) file. The calculated damping values per each eigenmode can be applied and scaled as diagonal damping in modal analyses in Abaqus/Standard.