SENSITIVITY ANALYSIS OF MULTIPLE-EIGENVALUES

This paper is devoted to sensitivity analysis of eigenvalues of nonsym metric operators that depend on parameters. Special attention is given to the case of multiple eigenvalues. Due to the nondifferentiability (in the common sense) of multiple roots, directional derivatives of ei genvalues and eigenvectors in parametric space are obtained. Sensitivi ty analysis is based on the perturbation method of eigenvalues and eig envectors. The generalized eigenvalue problem and vibrational systems are also investigated. Strong and weak interaction of eigenvalues are distinguished and interactions in two- and three-dimensional space are treated geometrically. It is shown that the strong interaction of eig envalues is a typical catastrophe. Simple examples that illustrate the main ideas are presented. The results obtained are important for qual itative and quantitative study of mechanical systems subjected to stat ic and dynamic instability phenomena.