激光在热弹效应下激发出的声表面波，在柱状材料表面传播过程中发生相移现象。通过有限元方法对铝材圆柱中表面波相位变化规律以及表面波与缺陷作用机理进行数值模拟。数值研究表明: 激光产生的表面波负相位最强，传播过程中负相位向正相位移动，相位差逐渐减小，180°左右正负相位强度大致相等，之后正相位继续增强、负相位持续减弱，并且沿圆周每传播一周，其相位发生一次翻转，缺陷产生的表面反射波有同样的相位变化现象；通过B扫图发现RRcw随缺陷角度增大变得模糊，RRccw随缺陷角度增大变得明显。说明反射波产生时间的长短与受干扰程度成正比，针对柱状材料表面缺陷提出了合理的检测范围；对不同深度缺陷数值模拟发现，深度变化使得P波峰在接收时间上发生延迟，推测P波峰传播路径并提出相应公式进行证明，计算结果与模拟结果吻合度较高，可通过此公式定量缺陷深度信息。以上研究结果为超声波检测柱状材料表面缺陷提供了有效参考。

The phase shift phenomenon occurs in the propagation process of surface acoustic waves excited by laser under Thermoelastic effect. The phase variation law of surface wave and the interaction mechanism between surface wave and defect in aluminum cylinder are numerically simulated by finite element method. Numerical results show that the negative phase of the surface wave generated by laser is the strongest, the negative phase moves to the positive phase in the propagation process, and the phase difference gradually decreases. The intensity of the positive and negative phases is roughly equal at about 180°. After that, the positive phase continues to strengthen and the negative phase continues to weaken, and its phase reverses once every time it travels around the circle. The surface reflection wave produced by the defect has the same phase change phenomenon. Through scanning diagram B, it is found that RRcw becomes fuzzy with the increase of defect Angle, and RRccw becomes obvious with the increase of defect Angle. It shows that the length of reflection wave generation time is proportional to the degree of interference. Based on this, a reasonable detection range is proposed for the surface defects of cylindrical materials. The numerical simulation of defects with different depths indicated that the change of depth made the P-wave peak delay in receiving time. The propagation path of P-wave peak was speculated and the corresponding formula was proposed to prove it. The calculated results were in good agreement with the simulated results, and the defect depth information could be quantified by this formula. The above research results provide an effective reference for ultrasonic detection of surface defects of columnar materials.