MODAL EXPANSION METHOD FOR EIGENSENSITIVITY WITH REPEATED ROOTS

Extensions are made to the modal expansion eigensensitivity procedure for self-adjoint systems originally formulated by Fox and Kapoor. These allow the computation of sensitivity information for mode shapes associated with repeated roots and repeated root derivatives. The extensions follow a similar line to additions to Nelson's direct method proposed first by Ojalvo and later generalized independently by Mills-Curran and Dailey. The formulation based on modal expansion is simpler and more computationally efficient than the direct method. Although some accuracy is sacrificed by modal truncation, the method generally yields acceptable results for the primary application in optimization.