Boundary element formulation of shape sensitivity analysis for defect identification in free vibration problem

This paper deals with the application of variational-material derivative approach to sensitivity analysis of an objective function used for defect identification from knowledge of eigenfrequencies, in connection with the use of BEM for the relevant direct eigenvalue problem. The main motivation of this paper is to explore the possibility of the application of measured eigenfrequencies in detection of internal defects. In order to do this, the influence of position and geometry of a circular defect over the eigenfrequencies is examined. Analytical expressions for sensitivity of eigenfrequencies and an objective function that are suitable for DRBEM implementation in the presence of defects are obtained. Optimization procedure to identification of the defect based on a penalty function approach, a regularization scheme and a quasi-Newton method is presented. (C) 1997 Elsevier Science Ltd.