The effect of copper grain size on laser ultrasonic backscattered signal

Abstract

Grain size has an essential influence on the serviceability of metallic materials. In this paper, a noncontact laser ultrasonic testing platform is built to study the effect of copper grain size on the laser ultrasonic backscattered signal. According to the correlation between grain size and ultrasonic wavelength, the ultrasonic scattering by copper grains in the experiment contains not only Rayleigh scattering but also the transition region from Rayleigh scattering to stochastic scattering. Using time–frequency analysis, the influence of copper grain size on the characteristic parameters of backscattering was explored, and a prediction model of grain size was established, which was compared with the prediction model based on the attenuation method to verify the accuracy of the backscattering model. The results show that the backscattered signal can adequately characterize the grain size information and laser ultrasonics is a method that can realize on-line detection of grain size.

Laser Ultrasonic Automatic Detection Method for Surface Microcracks on Metallic Cylinders

“…Compared with piezoelectric ultrasonic testing, laser ultrasonic (LU) testing can realize the long-distance excitation and detection of ultrasonic waves, and has a higher temporal and spatial resolution; it is therefore a method that can achieve online ultrasonic testing [13][14][15][16].…”