利用非线性Rayleigh波检测镁合金厚板疲劳损伤的仿真和试验研究

Simulation and Experiment of Fatigue Damage Detection in Magnesium Thick Plate Using Nonlinear Rayleigh Wave

为在波结构上扩展非线性超声无损检测技术的工程应用范围,提出一种将压电传感器直接安装在试件的边缘激发和接收Rayleigh波的方式,通过有限元数值仿真验证了此方法是有效的。利用此试验系统和方法验证非线性Rayleigh波的累积效应,非线性系数随Rayleigh波传播距离的增加近似线性增长,表明Rayleigh波的非线性特征参数对于材料内部微观缺陷的变化是敏感的,同时也表明该试验方法和系统是可靠的。利用非线性Rayleigh波检测AZ31镁合金厚板的表面疲劳损伤,虽然试验结果具有一定的分散性,但超声非线性系数整体随疲劳周数增加呈明显增长趋势,所以Rayleigh波的非线性系数对于厚板结构的疲劳寿命预测有潜在的工程应用价值。

In order to extend engineering application of nonlinear ultrasonic nondestructive testing technique in wave structure,an experimental technique for excitation and reception directly of Rayleigh wave by fixing piezoelectric sensor on the edge of the specimen is presented,this method is verified by simulation of the finite element method（FEM）.By using the experimental system and procedure,cumulative effect of nonlinear Rayleigh waves is proved,nonlinearity parameters nearly linear increase with Rayleigh wave propagation distance increasing,which demonstrates the Rayleigh wave nonlinearity parameters are sensitive for the changes of microscopic defects in the materials internal,and the experimental system and procedure are reliable.Finally,the surface fatigue damage of AZ31 magnesium thick plate is detected by nonlinear Rayleigh waves.Although the experimental results have some dispersion,the ultrasonic nonlinearity parameters overall increase apparently with the fatigue cycles increasing,which shows the Rayleigh wave nonlinearity parameters for the thick plate structure fatigue life prediction have potential engineering applications.