FE model updating with the measured data obtained from the CSLDV technique

Abstract

One major problem facing finite element model updating is the spatial incompatibility between the measurement of mode shapes through a limited set of physical sensors and the corresponding analytical predictions at a large number of finite element DOFs. Expansion of the measured mode shape data or reduction of the size of the initial FE model to the measured degrees of freedom is normally used to match the requirement. However, both techniques bring some erroneous information into the process. With the Continuous Scanning Laser Doppler Vibrometry (CSLDV) technique, a large number of degrees of freedom (DOFs) can be measured and accurate mode shapes can be achieved in a relatively short testing time. Such features provide great potential for dealing with the problem of the spatial incompatibility in FE model updating. In this paper, an application of finite element model updating using the continuous scanning laser Doppler vibrometry measurement is discussed. A real test piece of a square steel plate and its FE model were built. The first 20 natural frequencies and the corresponding mode shapes expressed by a large number of DOFs were measured using the CSLDV technique and further used for FE model updating. The initial FE model was assumed that random errors up to 20% of the theoretical values of Young's modulus were distributed among 25 areas of the plate due to uncertainties on the physical parameters. Model updating was undertaken to minimise the discrepancy between the FE model predicted and the experiment measured modal parameters and satisfactory results were obtained.