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激光冲击硬化通过在材料的近表面产生残余压应力来提高材料的表面硬度和抗疲劳寿命。材料近表面性质的变化能够导致在其中传播的声表面波发生色散。为了研究激光冲击硬化后金属Al合金样品中的激光声表面波(SAW)的传播,提出一种合理的宽带激发和接收方法,搭建了由激光激发、聚偏二氟乙烯(PVDF)传感器接收超声信号的实验装置。分别对不同条件下激光冲击的Al合金样品中的激光声表面波进行了探测,通过对接收到的超声信号进行时频分析得到了信号的频谱以及声表面波的相速度色散曲线,速度色散主要是由于晶粒方向改变和错位密度的增加引起的。
Laser shock hardening increases the surface hardness and fatigue life of the material by generating residual compressive stresses at the material’s near surface. Changes in the near-surface properties of the material can cause dispersion of the SAW propagating therein. In order to study the propagation of laser surface acoustic wave (SAW) in metal Al alloy samples after laser shock-hardening, a reasonable method of wideband excitation and reception was proposed. The laser-excited, PVDF (Polyvinylidene fluoride) Signal experimental device. Laser surface acoustic waves in Al alloy samples under different laser shock conditions were detected respectively. The frequency spectrum and the phase velocity dispersion curve of SAW signals were obtained by time-frequency analysis of the received ultrasonic signals. The velocity dispersion mainly Is due to changes in the direction of grain and dislocation density caused by the increase.