Non-contact measurement of particle velocity distribution of ultrasonic waves along an elastic bar using laser Doppler velocimetry

A new method is described for non-contact measurement of particle velocity distribution along an elastic bar excited by a PZT transducer. By analyzing two signals measured by a laser Doppler velocimetry (LDV) from two incident angles, the particle velocity distribution for each of the two components, normal and parallel to the bar axis, is separately obtained. The principle of the proposed measurement method is confirmed by the experiments using a Langevin type PZT transducer having a resonant frequency of 17 kHz. The sensitivity of this method is enough high to measure the particle velocity less than 12 μm/s at the resonant frequency of 17 kHz.