激光超声表面波检测薄板残余应力的数值模拟

应用ABAQUS有限元软件模拟了脉冲激光激发的超声表面波在半无限大弹性薄板内的传播.首先把激光激励等效为作用在薄板表面的高斯分布的脉冲载荷,模拟输入的超声信号,在边界处采用无限单元来消除边界反射波对接收信号的干扰,接收到的表面波信号具有典型的表面波特点.其次,通过修正弹性模量的方法得到薄板在单向应力状态下的应力场,采用时差法得到表面波在应力区的传播速度,所得的数值结果和理论解与实验结果拟合良好,为激光超声检测残余应力提供了一种有效的数值方法.

Numerical Simulation of Laser Ultrasonic Surface Wave Measurement of Residual Stress

The propagation of surface wave which induced by the laser ultrasonic shock processing was simulated in half-space elastic materials by ABAQUS software. First， the effect of laser shock processing was equivalent to a modulated Gaussian pulse. To eliminate the undesirable reflections from boundary edges， the infinite elements were placed along the appropriate edges of the model. The received waves agree with the Rayleigh surface waves. Secondly， the effective elastic modulus method was introduced to simulate the initial residual stress in the surface region. Detection of surface velocity based on ultrasonic time-difference method was introduced. The numerical value and theory well fit experimental datas， which provid a way of using laser ultrasonic to measure of the residual stress.