环形厚度线性变化薄板中Lamb波传播轨迹研究

The Propagation Trajectory of Lamb Waves on Thin Plates with Circular Thickness of Linear Variation

摘要: 本文利用激光激发Lamb波，对环形厚度线性变化薄板中Lamb波传播轨迹进行了研究。基于在金属材料中激发超声的热弹机制，分别建立激光线源和点源在环形厚度线性变化薄板中激发Lamb波的三维有限元模型。激光线源激发Lamb波进入环形厚度线性变化区域，向着厚度减小的方向传播，并在底部边界聚集，与声波波振面传播方向相交的底部边界传播的声波，能量最强，其他部分相对较弱。激光点源激发Lamb波沿半径方向传播进入环形厚度线性变化区域，声波能量持续在底边边界聚集，振幅逐渐增强，且以相同振幅、频率沿圆的两个方向传播。

Abstract: In this paper, the propagation trajectory of Lamb waves on thin plates with circular thickness of linear variation is studied by using laser ultrasonic technology. Based on the thermoelastic mech-anism, three-dimensional finite element model of Lamb wave excited by laser line source and laser point source is established, respectively. The Lamb wave excited by laser line source propagates into the area of thickness variation, and focuses at the bottom boundary. The sound wave propagates along the bottom boundary; part is strong, while the other parts are relatively weak. The Lamb wave generated by laser point source propagates along the radius into area of thickness variation. The acoustic accumulates continuously at the bottom boundary and the amplitude in-creases gradually. Moreover, the Lamb wave propagates along two opposite directions of the circle with the same amplitude and frequency. The results of this paper can be used to detect and evalu-ate thin plates with circular thickness of linear variation.