A MODIFIED SURFACE SPLINE FOR MODAL EXPANSION

Experimental modal data are widely used to validate and update Finite Element (FE) models. However, measured modes must be defined at all de grees of freedom (DOFs) in the FE model before such updating technique s can be applied effectively. At present Kidder Expansion is most comm only used to expand measured modes to the FE model DOFs. This method i s limited in several respects, such as its inability to accommodate sm oothing and its assumption that the measured DOFs are geometrically co incident with a subset of the FE model DOFs. These limitations can be overcome by adopting a spatial interpolation approach. A modified surf ace spline method is presented which makes use of the analytical modes in the interpolation of the experimental modes, This method is demons trated on an aircraft wing test structure and the results are shown to compare favorably with those generated by Kidder Expansion.