lumpm#

AnalysisOptions.lumpm(key='', keyelt='', **kwargs)#

Specifies a lumped mass matrix formulation.

Mechanical APDL Command: LUMPM

Parameters:
keystr

Formulation key:

  • OFF - Use the element-dependent default mass matrix formulation (default).

  • ON - Use a lumped mass approximation.

keyeltint or str

Formulation key for elements with rotational degrees of freedom; applicable only when the lumped mass formulation key is turned on ( Key = ON):

  • 0 (blank) - Use direct diagonalization of the element mass matrix (default).

  • 1 - Use translational mass only.

  • 2 - Use the frame invariant formulation.

Notes

In a modal analysis, the lumped mass matrix option ( lumpm,ON) is not allowed when using the Supernode mode-extraction method ( modopt,SNODE). The eigensolver will automatically be switched to Block Lanczos (LANB) in this case.

In the use pass of a substructuring analysis, the lumped mass matrix formulation ( lumpm,ON) modifies the superelement mass matrix and may give unexpected results.

The translational mass only option ( lumpm,ON,,1) applies to the following elements: SHELL181, BEAM188, BEAM189, SHELL208, SHELL209, SHELL281, PIPE288, PIPE289, and ELBOW290. The frame invariant formulation ( lumpm,ON,,2) applies only to BEAM188, BEAM189, PIPE288, and PIPE289 elements.

For more information, see Lumped Matrices

This command is also valid in PREP7. If used in SOLUTION, this command is valid only within the first load step.