Simultaneous Measurement of Plate Natural Frequencies and Vibration Mode Shapes Using ESPI

Abstract

AbstractThe natural frequencies and vibration mode shapes of flat plates are simultaneously measured using ESPI. The method involves measuring the surface shape of a vibrating plate at high frame rate using a modified Michelson interferometer and high-speed camera. The vibration is either excited by white (random) noise or by impact. Fourier analysis of the acquired data gives the natural frequencies and associated mode shapes. The analytical procedure used has the advantage that it simultaneously identifies full-field images of all vibration modes with frequencies up to half the sampling frequency. In comparison, the ESPI time-averaging and the traditional Chladni methods both require that the plate be excited at each natural frequency to allow separate measurements of the associated mode shapes. The Instrumented Hammer method and Laser Doppler Vibrometry require sequential sampling of individual points on the test surface to provide full-field results. Example measurements are presented to illustrate the use and capabilities of the proposed plate natural frequency and mode shape measurement method.KeywordsModal analysisESPIFull-fieldChladniInterferometry