A Craig-Bampton test-analysis model

Several methods exist for reducing finite element mass and stiffness matrices to a smaller set of degrees of freedom. This paper describes an extension. of the Craig-Bampton component mode synthesis method that can be used for modal survey test-analysis correlation. In the original Craig-Bampton formulation, the model coordinates are a combination of physical coordinates and generalized coordinates. In the proposed test-analysis model (TAM), the accuracy of the original Craig-Bampton formulation is maintained, but the TAM is referred to the test physical coordinates only. A systematic procedure is presented to identify the fixed-interface normal modes that contribute most to the retained physical DOF's. This method is particularly useful when the target modes are not the lowest consecutive modes of the system. The performance of the proposed method is compared to the performance of two other popular model-reduction techniques.