IMPROVED CALCULATIONS OF MODAL DESIGN SENSITIVITIES

An iterative method is presented for the improved calculation of modal design sensitivities. The procedure is simple and no complicated formulation is involved. The nonlinear perturbation equation is solved using successive approximation techniques. The first-order perturbation equation provides the starting point for the iterations. For the mode shape sensitivity of a structural system with multiple eigenvlaues, more accurate results are obtained by applying the nonlinear equation rather than using the second-order perturbation terms. An example problem shows that a single nonlinear iteration can give significant improvement for both eigenvalue and mode shape sensitivities of a system with multiple eigenvalues. The method can be applied to discrete eigenvalue problems as well as systems with multiple eigenvalues.