激光冲击硬化层中激光声表面波的实验研究

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。

Experimental Study of Laser-Generated Surface Acoustic Waves in Laser Shock Hardening Metals

Laser shock hardening is a well-known method for prolonging the fatigue life of metals components by introducing near-surface compressive residual stresses.The surface acoustic wave can disperse when the material properties of near-surface change.The near-surface properties,such as elastic properties,residual stresses,can be analyzed by the phase velocity dispersion.An experiment method is presented to detect laser surface acoustic wave(SAW) of Al alloy by laser shock.Based on the advantage of broad bandwidth generation and detection,the experiment use laser excitating and polyvinylindene fluoride(PVDF) as transducer.The SAW signals in aluminum alloy material under different conditions by laser shock hardening were detected.The signals spectrum and phase velocity dispersive curves were obtained and analyzed.The SAW velocity dispersion is mainly caused by the near-surface grain reorientation and the increasing of dislocation density.