基于超声模式转换的螺栓轴向应力测量方法

Measurement method of bolt axial stress based on ultrasonic mode conversion

针对目前螺栓轴向应力超声测量技术中存在的测量繁琐、测量限制条件较多等问题,提出基于超声模式转换的螺栓轴向应力测量法。在分析加载螺栓中的超声波传播规律的基础上,通过非线性声学理论和弹性力学理论推导了使用纵波与模式转换波声时比计算螺栓轴向应力的表达式,采用基于Gabor变换和高斯经验模型的渡越时间计算方法得到了纵波和模式转换波的准确渡越时间,克服了信号中的混叠和畸变。搭建了螺栓轴向应力超声测量试验平台,使用上述方法以及常用的纵横波声时比法对多组不同材料和规格的粗牙半螺纹螺栓进行对比标定和测量试验。试验证明,该方法具有测量精度高、测量流程简洁的特点。

Here,aiming at problems of tedious measurement and many restrictions in current ultrasonic measurement technology of bolt axial stress,a bolt axial stress measurement method based on ultrasonic mode conversion was proposed.Based on analyzing propagation law of ultrasonic wave in loaded bolts,the expression for bolt axial stress was derived by using the acoustic time ratio of P-wave and mode conversion wave through the nonlinear acoustic theory and elastic mechanics theory.The accurate transit time of P-wave and that of mode conversion wave were obtained by using the transit time calculation method based on Gabor transform and Gaussian empirical model to overcome aliasing and distortion in signals.The test platform for ultrasonic measurement of bolt axial stress was built.The proposed method and the commonly used P-wave and S-wave acoustic time ratio method were used to conduct contrastive calibration and measurement tests for several groups of coarse thread bolts with different materials and specifications.Tests showed that the proposed method can have characteristics of high measurement accuracy and simple measurement process.