This paper proposes a bolt looseness detection method based on the ultrasonic wavefield energy in the Lamb wave reflected from a target bolt. The full wavefield inside the area of the specimen containing the target bolt was first visualized. The ultrasonic wave propagation imaging (UWPI) approach was used for visualizing the interaction of the wavefield with the elements on the specimen such as the bolts and the boundaries of the specimen. The interaction between the ultrasonic wave and the airgap between the bolt head and the plate was interpreted based on the microcontact theory. This theory, when applied to the interface of two contacting surfaces such as those joined by a bolt, generally states that by increasing the fastening torque, the true contact area will increase and the wave will propagate across the interface with less energy loss. To apply the theory, the reflected wave from the target bolt was isolated from the incident wave and was further assessed to extract a feature indicating the looseness or tightness. The variation of the energy in the wave reflected from the target bolt with varying magnitudes of torque was determined by performing a continuous wavelet transform‐based energy computation. The reflected wave energies of the different torque values were first compared by considering single time instants starting with the moment the wave was first observed in the UWPI reflecting from the target bolt. Then, energy accumulation was used to obtain the overall energy differences that resulted solely from the torque differences.

中文翻译：

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基于Nd：YAG脉冲激光扫描系统基于超声场能量分析的螺栓松动检测

提出了一种基于目标螺栓反射的兰姆波的超声场能量的螺栓松动检测方法。首先可视化包含目标螺栓的试样区域内部的整个波场。超声波传播成像（UWPI）方法用于可视化波场与样本上的元素（例如螺栓和样本边界）的相互作用。基于微接触理论解释了超声波与螺栓头与板之间的气隙之间的相互作用。该理论在应用于两个接触面（例如通过螺栓连接的接触面）的界面时，通常会指出，通过增加紧固扭矩，真实的接触面积将增加，并且波将以较少的能量损耗在界面上传播。为了应用该理论，将目标螺栓的反射波与入射波隔离开来，并对其进行进一步评估，以提取出指示松动或密封性的特征。通过执行基于连续小波变换的能量计算，可以确定目标螺栓反射的波中的能量随扭矩大小的变化。首先考虑从从目标螺栓反射的UWPI中首次观察到该波的时刻开始的单个时刻，比较不同扭矩值的反射波能量。然后，使用能量累积来获得仅由扭矩差引起的总能量差。将目标螺栓的反射波与入射波隔离开，并进一步评估以提取出指示松动或密封性的特征。通过执行基于连续小波变换的能量计算，可以确定目标螺栓反射的波中能量随扭矩大小的变化。首先考虑从从目标螺栓反射的UWPI中首次观察到波浪开始的那一瞬间开始，比较不同扭矩值的反射波能量。然后，使用能量累积来获得仅由扭矩差引起的总能量差。将目标螺栓的反射波与入射波隔离开，并进一步评估以提取出指示松动或密封性的特征。通过执行基于连续小波变换的能量计算，可以确定目标螺栓反射的波中的能量随扭矩大小的变化。首先考虑从从目标螺栓反射的UWPI中首次观察到波浪开始的那一瞬间开始，比较不同扭矩值的反射波能量。然后，使用能量累积来获得仅由扭矩差引起的总能量差。通过执行基于连续小波变换的能量计算，可以确定目标螺栓反射的波中能量随扭矩大小的变化。首先考虑从从目标螺栓反射的UWPI中首次观察到波浪开始的那一瞬间开始，比较不同扭矩值的反射波能量。然后，使用能量累积来获得仅由扭矩差引起的总能量差。通过执行基于连续小波变换的能量计算，可以确定目标螺栓反射的波中能量随扭矩大小的变化。首先考虑从从目标螺栓反射的UWPI中首次观察到波浪开始的那一瞬间开始，比较不同扭矩值的反射波能量。然后，使用能量累积来获得仅由扭矩差引起的总能量差。