Damping function estimation based on measured vibration frequency responses and finite-element displacement modes

An estimation strategy for extraction of isotropic material damping is presented. The method is based on a modal receptance model, material damping functions and experimentally measured frequency response functions (FRF). Least-squares estimation of modal parameters is done by projections of the measured vibration responses onto a set of finite-element calculated elastic displacement modes. From identified modal parameters, based on the modal receptance model, a fast straightforward incremental least-squares material damping parameter estimation method is proposed. The methodology is demonstrated on two Plexiglas (PMMA) plates. Estimated material damping parameters are then validated on a third Plexiglas plate, with considerably different geometry, in the frequency interval 40-500 Hz. Results from comparisons between measured and calculated frequency response functions, using direct finite element method calculations, show extremely good agreement with respect to resonance frequency 'location' and response amplitude values. Finally, sources of uncertainty between model simulation and measurements are briefly discussed. (C) 1999 Academic Press.