On October 9, 2015, Professor Deng Mingxi from the Logistics Engineering College of the Chinese People's Liberation Army visited and did "Study on the Surface Acoustic Wave Nonlinear Detection of the Roll Surface Hardening Layer" Academic report.

The following is a summary of the report:

Theoretically studied the nonlinear effect of surface acoustic waves, analyzed the influence of the surface hardened layer of the roll on the second harmonic generation effect of surface acoustic waves, and proposed The basic principle of the second harmonic detection of the surface acoustic wave of the hardened layer theoretically demonstrates the feasibility of using the nonlinear surface acoustic wave to detect the hardened layer of the roll surface. A nonlinear surface acoustic wave experimental measurement system was established, and the experiment accurately measured the transverse and longitudinal sound velocities of the roll material. An experimental measurement method for spontaneously and self-received SAW second harmonics is proposed. The established nonlinear SAW experimental measurement system has stable performance and good measurement repeatability. With the aid of the established experimental system, for the case where the surface acoustic wave propagates along the roll surface texture direction (rolling direction), a significant and stable time-domain echo signal of the second harmonic of the surface acoustic wave can be observed. Experimental studies have proved that when the surface acoustic wave propagates along the surface texture direction of the roll, the amplitude of the fundamental frequency surface acoustic wave hardly changes with the thickness of the hardened layer, but the second harmonic occurs with the propagation of the fundamental frequency surface acoustic wave. The amplitude of the wave decreases monotonously with the decrease of the thickness of the hardened layer; similarly, the relative nonlinear acoustic parameter R of the surface acoustic wave also decreases monotonously with the decrease of the thickness of the hardened layer. With the help of the relatively non-linear acoustic parameter R with the decrease of the thickness of the hardened layer and the monotonous decrease of the relationship curve, the thickness information of the hardened layer can be obtained through the actual measurement of R, which can be used to solve the problem of important practical significance in the detection of the thickness of the hardened layer. Provide a feasible method and technical means.