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基于等效载荷法,应用有限元软件Abaqus模拟了脉冲激光激发的超声表面波在预加裂纹的半无限大弹性薄板内的传播,并探讨了微裂纹的尺寸对超声信号的影响。将脉冲激光激励等效为作用在薄板表面的在时间和空间上均满足高斯分布的脉冲载荷,并通过引入修正系数建立了激光的物理参数与峰值载荷的定量关系。在实验验证了有限元模型和等效载荷法正确性的基础上,探讨了裂纹的宽度、深度对反射波和透射波声学特性的影响。结果表明,所建立的等效载荷法能有效地模拟激光超声检测裂纹的实验过程,对激光超声的数值模拟研究以及在裂纹检测方面的应用具有重要的意义。
Based on the equivalent load method, the finite element software Abaqus was used to simulate the propagation of pulsed laser-induced ultrasonic surface waves in pre-cracked semi-infinite elastic thin plates. The effect of microcrack size on ultrasonic signals was also discussed. The pulsed laser excitation is equivalent to the pulse load satisfying the Gaussian distribution in time and space on the surface of the thin plate. The quantitative relationship between the physical parameters of the laser and the peak load is established by introducing the correction coefficient. Based on the experimental verification of the finite element model and the correctness of the equivalent load method, the influences of crack width and depth on the acoustic characteristics of reflected and transmitted waves are discussed. The results show that the established equivalent load method can effectively simulate the experimental process of laser ultrasonic flaw detection and is of great significance to the numerical simulation of laser ultrasonic and the application in crack detection.