Component Mode Synthesis in ANSYS Workbench Simulation

At ANSYS Workbench 11.0, the ANSYS Rigid Dynamics add-on module enables users to define joint connections in complex kinematic assemblies. This ability to model rigid and flexible parts in ANSYS Workbench Simulation via joints is beneficial since the rigid parts are modeled with mass and rigid links (that is, rigid contact elements), thus providing load transfer capabilities and allowing users to evaluate system-level performance with less computational cost. However, the solution time is dictated by the size of the flexible mesh, and in some cases the rigid assumption may not be accurate enough for specific applications. A better approach in these cases is the use of Component Mode Synthesis (CMS) superelements, in which the flexibility of the model is retained yet the number of degrees of freedom (DOF) is reduced, thereby providing efficient solutions. A superelement has a reduced number of DOF compared with the “full” model, yet it still can accurately model the flexibility of structures. Superelements can be created by regular substructuring or by component mode synthesis, in which DOF at interface nodes are retained while all other DOF are eliminated by condensation of the matrices. CMS appends a regular substructure with generalized coordinates, thereby improving the accuracy of the superelement response in dynamic applications. Since CMS superelements can be used in large-deflection nonlinear analyses, they are especially attractive for nonlinear transient problems. This is because of the low number of DOF (that is, interface nodes and generalized coordinates) and the accurate dynamic representation. CMS superelements, however, also can be used in static, modal, harmonic and response spectrum analyses. If contact is used with superelements (regular substructure or CMS), the number of interface nodes Figure 1. Flexible Dynamic analysis setup with all nine original assembly parts as rigid components Figure 2. System-level analysis with joints defined Figure 3. Reference Coordinate System location and orientation