DERIVATION OF STRUCTURAL DESIGN SENSITIVITIES FROM VIBRATION TEST DATA

Structural sensitivities are often required in dynamic analyses of eng ineering structures, such as system identification and control, struct ural modification and optimization; Many different methods have been d eveloped in the last three decades for the efficient computation of su ch sensitivities. Though these existing methods have proven to be very useful tools to structural analysts, they, are restricted to those ca ses where accurate analytical or finite element models are available. In many practical applications where sensitivities are needed in the s olution of troubleshooting problems only limited measured data are ava ilable; existing methods being inapplicable. In this paper, a new and effective method has been developed to derive structural design sensit ivities, both frequency response function sensitivities and eigenvalue and eigenvector sensitivities, from limited vibration test data. Desi gn sensitivities calculated directly from measured data are more accur ate than those calculated from analytical or finite element models sin ce structural modelling errors are inevitable due to the complexity of almost all engineering structures. The relationship between frequency response function sensitivities and eigenvalue and eigenvector sensit ivities has been established. This relationship provides the theoretic al basis for the experimental determination of eigenvalue and eigenvec tor sensitivities. The effect of residue (contribution of out-of-range modes) upon analysis accuracy has been examined. Detailed numerical a ssessment based on a turbine bladed disk model as well as experimental investigation of a beam structure have been conducted and the results have demonstrated the practicality of the proposed method. (C) 1997 A cademic Press Limited.