Frequency-domain criteria for correlating and updating dynamic finite element models

This paper discusses the use of frequency-domain criteria for finite elemen t (FE) model correlation and updating. The criteria, which can be local or global, are either shape or amplitude based. The former are sensitive to mo de shape differences but not to relative scales, and the latter depend on t he actual response amplitudes. The updating objective function is formulate d in such a way that two global correlation criteria are satisfied simultan eously. A sensitivity-based updating problem is expressed as a set of linea r equations where the coefficient matrix contains the partial derivatives o f the correlation functions with respect to the chosen design variables. Th e formulation has the advantage of being able to deal with incomplete measu rements and there is no critical selection of updating frequency points. Th e correlation criteria were used successfully to quantify the initial close ness between 4 increasingly detailed FE models of an automotive oil pan. Th e updating of the second most detailed model, using simulated response func tions from the most detailed model, exhibited quick convergence properties and yielded a very good match between the target and updated frequency resp onse functions. However, the initial FE model was corrected in a curve-fitt ing/minimisation sense since actual modelling deficiencies were compensated by adjusting a small number of pre-selected design parameters. (C) 2001 Ac ademic Press.