ON THE ACCURACY REQUIRED OF EXPERIMENTAL-DATA FOR FINITE-ELEMENT MODEL UPDATING

In this paper, the determination is considered of the required experim ental accuracy that must be attained when updating finite element mode ls with use of measured vibration test data. A theoretical basis is de veloped for FRF-based updating techniques, as these use measured data directly. It is shown that a well-defined relationship, that can be ex pressed as a characteristic function, exists between the system's prop erties, the correction matrices and the actual amount of experimental noise. The formulation is then applied to the standard response functi on updating formulation, where the element mass and stiffness matrices are corrected by using a single multiplier, the so-called p-value. In the presence of noise, the convergence of the updating algorithm is s hown to be dependent on a number of conditions which arise from two di stinct cases: one convergent and the other divergent. The findings are illustrated in the case of a 3-D space frame, and the efficacy of the proposed characteristic function is discussed in some detail. Finally , a way of selecting the optimum excitation frequency values is presen ted as a means of relaxing the minimum experimental accuracy. (C) 1996 Academic Press Limited