表面性质变化材料中激光声表面波的数值计算

Numerical calculation of laser induced surface wave in material with changes of near-surface properties

激光激发超声波为评价材料近表面弹性性质提供了有效的手段,考虑到由于冲击硬化、表面热处理、表面氧化等引起的金属材料近表面层弹性性质的变化,建立了一种激光在基底上的梯度材料中激发超声波的理论模型,用有限元方法(FEM)模拟了热弹条件下脉冲激光作用于材料上表面激发出的声表面波及其传播过程。当表面层"变硬"时,讨论了不同的硬化层厚度和不同的弹性性质的变化对激光声表面波的影响。为进一步研究近表面层的弹性性质及材料性质的反演提供了理论依据。

Laser-generated ultrasonic waves is effective for evaluating near-surface elastic property.Taking accounting of the gradient changes of the near-surface elastic property caused by surface heat treatment,laser shocking peening,a finite element method is developed to simulate the laser thermo-elastic generation and propagation of acoustic waves in the system of multiple gradient layers on the substrate.The regular phase velocity dispersion are obtained and analyzed in the systems with different spatial variation of the material elastic properties and different affected layer depth when the layer loads the substrate.The phase spectrum method has used to attained the phase velocity dispersion.The conclusion could be useful to the further study of the near-surface elastic property.