Simcenter 3D Solutions Dealing with dense Mass Matrix in sol103

Simcenter Nastran Simcenter 3D


Using RBE3 elements with many legs and a mass element on the intepolated node can bring to a dense mass matrix and slow calculation time. In this article we will see how to improve calculation time.


Using RBE3 elements with many legs and a mass element on the slave node can bring to a dense mass matrix. Since used numerical algorithms are optimized for sparse matrices, this can cause a slowdown of calculation time and even bring to calculation failure for the largest models.

In the attached example, which was developed in version 2206, we have a cube made of shell element at which center there is a conentrated mass; this mass is connected to all other nodes by means of an RBE3. A normal mode solution sol103 is taken. When the solution is launched, the following warning is thrown:   

     The mass matrix is relatively dense. This could lead to a significant reduction in the computational
     performance in the analysis. This could be caused by a scenario where a few dependent DOFs with defined
     mass elements are associated with too many independent DOFs in the model. For example, a dependent DOF

     with CONM2 is connected to lots of independent DOFs by a RBE3 element.

If we change the Rigid element Method, by setting RIGID=LAGRAN in deck case control or Rigid Element Method as Lagrange multiplier in solution case control tab in Simcenter 3D interface (as depicted in the following figure), the previous warnig disappear and calculation time significantly decreases (from more then 4 minutes to 8 seconds in the attached example). 

KB Article ID# KB000066148_EN_US



Associated Components

Other SOL101 SOL103 SOL105 SOL106 SOL107 SOL108 SOL109 SOL110 SOL111-SOL112 SOL144 SOL145 SOL146 SOL153 SOL159 SOL200 SOL401 SOL402 SOL414 SOL601-SOL701 Superelement