Yan Bingsheng, Song Yuzhou, Nie Shijie, Yang Mingchao, Liu Ziran
School of Mechanical and Electrical Engineering, Henan University of Technology, Zhengzhou 450001, China.
Sensors (Basel). 2020 Mar 31;20(7):1955. doi: 10.3390/s20071955.
The acoustic non-linearity parameter of Rayleigh waves can be used to detect various defects (such as dislocation and micro-cracks) on material surfaces of thick-plate structures; however, it is generally low and likely to be masked by noise. Moreover, conventional methods used with non-linear Rayleigh waves exhibit a low detection efficiency. To tackle these problems, a method of exciting reversed-phase Rayleigh waves in opposite directions is proposed to measure the acoustic non-linearity parameter of materials. For that, two angle beam wedge transducers were placed at the two ends of the upper surface of a specimen to excite two Rayleigh waves of opposite phases, while a normal transducer was installed in the middle of the upper surface to receive them. By taking specimens of 0Cr17Ni4Cu4Nb martensitic stainless steel subjected to fatigue damage as an example, a finite element simulation model was established to test the proposed method of measuring the acoustic non-linearity parameter. The simulation results show that the amplitude of fundamentals is significantly reduced due to offset, while that of second harmonics greatly increases due to superposition because of the opposite phases of the excited signals, and the acoustic non-linearity parameter thus increases. The experimental research on fatigue damage specimens was carried out using this method. The test result was consistent with the simulation result. Thus, the method of exciting reversed-phase Rayleigh waves in opposite directions can remarkably increase the acoustic non-linearity parameter. Additionally, synchronous excitation with double-angle beam wedge transducers can double the detection efficiency.
瑞利波的声学非线性参数可用于检测厚板结构材料表面的各种缺陷（如位错和微裂纹）；然而，该参数通常较低，且容易被噪声掩盖。此外，传统的非线性瑞利波检测方法效率较低。为了解决这些问题，提出了一种在相反方向激发反相瑞利波的方法来测量材料的声学非线性参数。为此，将两个斜探头放置在试样上表面的两端，以激发两个反相的瑞利波，同时在上表面中间安装一个直探头来接收它们。以承受疲劳损伤的0Cr17Ni4Cu4Nb马氏体不锈钢试样为例，建立了有限元模拟模型，以测试所提出的测量声学非线性参数的方法。模拟结果表明，由于信号偏移，基波振幅显著降低，而由于激励信号反相叠加，二次谐波振幅大幅增加，声学非线性参数因此增大。采用该方法对疲劳损伤试样进行了实验研究。试验结果与模拟结果一致。因此，在相反方向激发反相瑞利波的方法可以显著提高声学非线性参数。此外，使用双斜探头同步激励可以使检测效率提高一倍。
