基于阈值和互相关的螺栓超声轴向应力测量算法

Ultrasonic axial stress measurement algorithm for bolts based on thresholding and cross-correlation

准确获取超声波的渡越时间是螺栓轴向应力测量的最基本要求。介绍了两种常用的获取超声波传播时间的方法——阈值法和互相关算法,并将两种算法结合提出了阈值互相关算法,辅以小波降噪算法提高渡越时间计算的准确性,使用碳钢螺栓对算法可靠性进行了验证。试验结果表明,阈值互相关算法受噪声信号影响小,平均误差均可控制在5%内,具有良好的抗噪性能和稳定性,在噪声较大的工程环境中实用性较好。

Accurate acquisition of the ultrasonic transit time is the most basic requirement for the measurement of axial stresses in bolts.This paper introduced two commonly used methods to obtain the ultrasonic propagation time-threshold method and mutual correlation algorithm,threshold mutual correlation algorithm proposed by the combination of the two algorithms,wavelet noise reduction algorithm supplemented to improve the accuracy of time-of-flight calculation.8.8 grade M20×100 carbon steel bolts were used to verify the reliability of proposed algorithm.The study showed that the threshold cross-correlation algorithm was little affected by the noise signal,and the average error was controlled within 5%,which had good anti-noise performance and good stability,and had greater practicality in engineering environments with large noise.