Contactless modal analysis of elastic structures with acousto-elastic transmission matrix

Abstract

Modal analysis is a major issue in the industry to identify resonances in mechanical parts. Indeed, resonances can induce high vibration levels that are potentially destructive. Active modal analysis methods require on the one hand to excite the controlled part and on the other hand to record the induced displacements/acceleration/stresses. Conventional methods, called SIMO, involve a mechanical excitation source associated with several receivers. More rarely, the analysis is performed with several sources and one receiver (MISO). Finally, for several years, MIMO techniques with several sources and several receivers are commonly implemented. However, for some parts, it may be difficult to implement an array of mechanical sources. That is why, here, we propose to carry out the modal analysis with a set of 8 loudspeakers as sources, and the measurements are performed at a large number of measurement points using a LASER vibrometer. The analysis of the singular value decomposition of the contactless transmission matrix allows to identify superposed modes. We will discuss the advantages and disadvantages of such a configuration. This method based on acousto-elastic coupling is successfully applied to the modal analysis of two axi-symmetric parts: a pinion and a rotating wheel. Finally, we will see that the same device can be used to control vibration fields.