Dynamic Characterisation of Thin Metal Plates using Piezoelectric Film Sensor

Abstract

Complete understanding and appreciation of dynamic properties, comprising of natural frequencies and mode shapes helps in designing a structural system, to ensure safety and reliability. They could be determined via modal analysis. This study highlighted the utilisation of a piezoelectric film sensor in experimental modal analysis to extract the relevant modal parameter from light metal structures. Square-shape metal plates, comprised of copper, galvanized steel, zink, brass and aluminium were used and configured in a free-free boundary condition, to ensure good modal estimation. Simple modal testing was arranged using impact hammer as impulse exciter and piezo-film as sensing element. A roving set of hammer tests as inputs was done on every structure which was marked by 9 grid points, whereas piezo-film was fixed on 3 locations to measure the outputs. Signals’ input and output were combined to compute the frequency response function (FRF) and afterwards used to estimate and extract the modal parameter. On the other hand, theoretical values were derived by using Euler Bernoulli beam theory. As a result, the first 5 mode shapes with corresponding frequencies were determined and evaluated in both experiment and theory, and later on, compared for data’s stability and validity. The outcome suggested satisfying experimental modal data which was in good agreement with theoretical’, delivering an average of mean absolute percentage error (MAPE) of approximately 7.3%.