Effects of Errors in Finite Element Models on Component Modal Tests

Abstract

It has become increasingly difficult to perform modal tests for large structures because they are not strong enough to withstand the force of gravity. This study aimed to predict the dynamic characteristics of large structures with component modal tests. In this method, to simulate the dynamic behavior of structures, the effect of untested components is considered as additional mass and stiffness attached to a tested component. Additional mass and stiffness are calculated with mass and stiffness matrices of both structure and tested component. Because additional mass and stiffness vary with modeling errors in finite element models, it is difficult to obtain structure frequencies and modes by component modal tests. In this paper, the method is extended in order to deal with modeling errors. A formulation is given to show that modal tests for different tested components give an identical predicted frequency when there are no modeling errors. Variation in predicted frequency obtained for different tested components is the basis of frequency error estimation. Numerical examples are given to show that the proposed method has the potential to predict the dynamic characteristics of large structures.