STRATEGIES FOR IMPROVING AUTOMATED MULTI-LEVEL SUB-STRUCTURING

Frequency response analysis for complex dynamical systems requires the solution of huge eigenvalue problems. The Automated Multi-Level Sub-structuring (AMLS) method is a multi-level extension of the component mode synthesis method which has recently be shown to be efficient for performing vibration analysis for large scale models, in particular if a large number of eigenpairs is needed. On each level the stiffness matrix of substructures are decoupled from the remaining degrees of free-dom, and neglecting the coupling in the mass matrix the size of the substructure is reduced by modal truncation where eigen information corresponding to frequencies which exceed a given threshold is chopped off. In this paper we discuss two alterna-tive reduction methods based on moment matching and on Krylov subspaces which both incorporate the coupling of sub-structures and their boundaries, and we evaluate their approximation properties for a two-level version