Power Flow Analysis of Complex Structures Using Characteristic Constraint Modes

Abstract

Component mode synthesis (CMS) is used as a basis for predicting power flow in complex structures. The power flow formulation is cast in a general framework of multilevel CMS, in which a hierarchy of substructures can be recursively partitioned from a very large finite element model. Additional computational efficiency is achieved by finding characteristic constraint (CC) modes. The CC modes are computed by performing an eigenanalysis on the partitions of the CMS mass and stiffness matrices that correspond to the constraint-mode degrees of freedom. The CC modes describe the vibration, and the exchange of vibration energy, at the interface between connected substructures. Therefore, a relatively small number of CC modes that capture the primary interface motion can be selected to yield a reduced-order model for computing the power flow. The performance and accuracy of the method are illustrated by examples of a two-span beam, a cantilever plate, and the body structure of a military vehicle. For the vehicle structure, multiple levels of substructures are used to map the power flow in the system. It is seen that this multilevel, characteristic-mode-based approach provides a general framework for the efficient calculation of power How in the low- to midfrequency range.