热处理及测量方式对纵波声速评价材料硬度的影响

硬度是材料力学性能的重要指标之一，目前采用超声无损检测方法评价材料的硬度指标存在诸多挑战。通过搭建高精度声时测量系统，采用超声纵波脉冲反射回波法测量不同热处理45钢试件沿厚度方向的超声波传播声时，计算超声纵波声速。同时改变门信号的测量方式，研究不同热处理及门信号测量方式对超声纵波声速评价材料硬度的影响。建立材料硬度、微观组织以及超声纵波声速之间的映射关系，得到超声纵波声速评价45钢试件硬度指标的标定模型，并对标定模型进行验证。标定模型预测硬度误差满足工程应用误差10%的要求。

Influence of heat treatment and measurement methods on material hardness evaluation by longitudinal wave velocity

Hardness is one of the important indexes of mechanical performance of materials, and employing ultrasonic nondestructive testing method for hardness evaluation faces many challenges now. In this paper, through setting up high-precision ultrasonic wave transmission time measurement system, the longitudinal wave propagation time in the thickness direction of different heat treated 45 steel specimens was measured by pulse reflected echo method, and the longitudinal wave velocity was calculated. Simultaneously, the gate signal measurement methods were changed, and the effects of different heat treatment and gate signal measurement methods on hardness evaluation by the longitudinal wave velocity were studied.On this basis, the mapping relationship among material hardness, microstructure and longitudinal wave velocity was obtained, and the calibration model for evaluating the hardness of 45 steel specimens by longitudinal wave velocity was established and verified. The hardness prediction error by the calibration model meets the error requirement of 10% for engineering application.