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Technical Paper

Experimental and Hybrid Modeling of the Medium Frequency Behaviour of Car Panels

This paper discusses an approach to identify critical car panels and to derive detailed experimental models for these critical panels. The research was conducted in the framework of the Brite/Euram project SALOME and the EUREKA project HOLOMODAL. The panel identification method is based on a numerical or experimental contribution analysis, assessing the partial noise contributions of individual panels to the interior noise. The second step in the approach consists of the derivation of detailed modal analysis models for the critical panels. A novel Electronic Speckle Pattern Interferometry (ESPI) system was developed, and integrated in a classical CAE system. The components of this system are briefly reviewed, and their application to several industrial cases is shown.
Technical Paper

Structural Modelling of Car Panels Using Holographic Modal Analysis

In order to optimise the vibro-acoustic behaviour of panel-like structures in a more systematic way, accurate structural models are needed. However, at the frequencies of relevance to the vibro-acoustic problem, the mode shapes are very complex, requiring a high spatial resolution in the measurement procedure. The large number of required transducers and their mass loading effects limit the applicability of accelerometer testing. In recent years, optical measuring methods have been proposed. Direct electronic (ESPI) imaging, using strobed continuous laser illumination, or more recently, pulsed laser illumination, have lately created the possibility to bring the holographic testing approach to the level of industrial applicability for modal analysis procedures. The present paper discusses the various critical elements of a holographic ESPI modal testing system.