Measurement of the full wave field on a shell using a single-point laser Doppler vibrometer

To experimentally measure the complicated vibration and wave characteristics of a shell, a 3D scanning laser Doppler vibrometer is a competent but costly instrument due to the requirement of exactly aligning each point when scanning the shell. Here we propose a simplified measuring method just by utilizing a single-point laser vibrometer fixed on a motorized positioning system. The clamp can be rotated to adjust the incident angles and translated to capture the whole tested region. During each test in a specific incident angle, the signals are interpolated to generate a continuous wave field in both the time domain and the frequency domain, eliminating the need for alignment. The in-plane and out-of-plane wave fields are obtained from the measured 3D signal using the projection relationship, and then verified both experimentally and numerically. Furthermore, we show that the present method can be used to test complex wave fields, such as the scattering field by obstacles on a cylindrical shell. The present work may stimulate systematically experimental studies on the wave propagation and vibration on shells.