测量距离对超声表面波评价不同组织的材料表层硬度的影响

Effects of Measurement Distance on Hardness Evaluation of Material Surface with Different Microstructure by Acoustic Surface Wave

通过搭建高精度的超声表面波检测系统,采用双探头法测量不同热处理45钢标定试件超声表面波的传播声时和接收声波幅值,分别计算超声表面波的传播声速和衰减系数;在测量过程中,改变发射探头和接收探头之间的距离,研究不同测量距离及微观组织对超声表面波声速测量的影响,由此建立材料表层硬度、微观组织及超声表面波特征值之间的映射关系,得到超声表面波评价45钢试件表层硬度指标的标定模型,并对标定模型进行验证。研究表明,采用超声表面波声速评价45钢表层硬度可行,标定模型预测硬度误差满足工程应用误差10%的要求;超声表面波衰减系数与材料表层硬度没有明显的映射关系,不能作为评价45钢试件表层硬度指标评价参量。

Employing acoustic surface wave for surface hardness quantitative evaluation faces many challenges now. By setting up high-precision acoustic surface wave detection system, the surface wave amplitude and propagation time of different heat treated 45 steel calibration specimens were measured by double probes method, calculating attenuation coefficient and acoustic surface wave velocity, respectively. The distance between the transmitting and receiving probes changed during the measurement, and the effects of different microstructure and measuring distance for surface wave velocity were studied. The mapping relationship of material surface hardness, microstructure and acoustic surface wave test characteristic value was set up, and a acquiring calibration model for evaluating surface hardness of 45 steel specimens by acoustic surface wave method was acquied and verified. The results show that it is feasible to evaluate the surface hardness of 45 steel by using surface wave velocity, and the predicting hardness error meets the requirement of 10% size for the engineering application. There is no obvious mapping relationship between the attenuation coefficient and the surface hardness, therefore, the attenuation coefficient cannot be used to evaluate the surface hardness of 45 steel specimens.