Characteristic constraint modes for component mode synthesis

A technique is presented for reducing the size of a model generated by the Craig-Bampton method (Craig, R. R., and Bampton, M. C, C., "Coupling of Sub structures for Dynamic Analyses," AIAA Journal, Vol. 6, No. 7, 1968, pp, 13 13-1319) of component mode synthesis (CMS). An eigenanalysis is performed o n the partitions of the CMS mass and stiffness matrices that correspond to the so-called constraint modes. The resultant eigenvectors are refer red to as characteristic constraint modes because they represent the characterist ic motion of the interface between the component structures. When the chara cteristic constraint modes are truncated, a CMS model with a highly reduced number of degrees of freedom maybe obtained. An example of a cantilever pl ate Is considered. It is shown that relatively few characteristic constrain t modes are needed to yield accurate approximations of the lower natural fr equencies, Furthermore, this method yields physical insight into the mechan isms of vibration transmission in complex structures; and it provides an ex cellent framework for the efficient calculation of power flow.