ON A COMPONENT MODE SYNTHESIS METHOD AND ITS APPLICATION TO INCOMPATIBLE SUBSTRUCTURES

Component Mode Synthesis (CMS) methods are substructuring techniques frequently employed in structural dynamics. A given structure is subdivided into components or substructures which are analyzed independently for natural frequencies and for mode shapes. The substructure mode shapes are then assembled to give frequencies and mode shapes of the original structure. In this paper, we construct a substructure interface impedance operator and present a spectral analysis that demonstrates that the method of Craig and Bampton (CB) is the most 'natural' CMS method. Next, we consider the CB method for assembling heterogeneous substructures and recast it into a hybrid variational formulation. We develop finite element procedures for 'gluing' non-conforming and incompatible finite element substructure models, and discuss their computational aspects. The result is a Hybrid Craig-Bampton (HCB) method that is a finite element refinement of the 'intermediate structure' concept introduced by Hale and Meirovitch, and which can be used as an interface reduction method. It is illustrated with the eigen analysis of heterogeneous and homogeneous finite element models of a High Speed Civil Transport (HSCT) aircraft.