An unreported phenomenon of phase evolution of Rayleigh ultrasonic waves with subsurface defects is observed and systematically explored for detection of subsurface defects using non-contact line laser ultrasonic technique and numerical simulation. The mechanism of phase evolution of Rayleigh wave signals is explained by the interference of the reflected and direct Rayleigh wave, explored by finite element analysis. Both experiments and simulation show distinct peak evolution of the Rayleigh wave signals with the width and depth of subsurface defect. A dimensionless parameter (|Neg|/Pos), defined by the ratio of absolute negative peak to positive peak of Rayleigh wave, is proposed to evaluate the phase evolution of Rayleigh wave with defect width and depth, which is further used to quantify the subsurface defects. The phase evolution of Rayleigh waves can act as a robust and sensitive feature to detect subsurface defects using laser-generated ultrasound, which has promising applications in life prediction and health monitoring of various engineering structures.

观察到了具有表面缺陷的瑞利超声波相变的未报告现象，并系统地探索了使用非接触线激光超声技术和数值模拟检测表面缺陷的方法。瑞利波信号的相位演化机理是通过反射和直接瑞利波的干涉来解释的，并通过有限元分析来探索。实验和仿真均显示了瑞利波信号随表面缺陷的宽度和深度而出现的明显峰值演化。提出了无量纲参数（| Neg | / Pos），由瑞利波的绝对负峰值与正峰值之比定义，以评估具有缺陷宽度和深度的瑞利波的相位演化，并进一步用于量化地下缺陷。