Techniques for Synthesizing FRFs from Analytical Models

Abstract

Modal correlation of test and analytical data is an important step in system identification and model updating. The Frequency Response Assurance Criterion (FRAC) is one of the metrics that can be used to quantify the strength of correlation between the test and analytical degrees of freedom (DOF). To calculate FRAC for test and analytical data, frequency response functions (FRF) are required. Techniques to synthesize FRFs from finite element models are discussed in this paper. Methods to represent damping in analytical models are also presented. These techniques were applied to synthesize FRFs from a finite element model of a rectangular steel plate structure. Comparing the synthesized FRFs with the measured FRFs for the rectangular plate structure aided in calibrating the rectangular plate FE model. The techniques presented in this paper can be used to visually check if the test and analytical data are well correlated and for calculating FRAC metric to quantify the strength of correlation.