laser ultrasonic was applied to monitor the looseness of a bolt, aiming at the phenomenon that bolts can be loose after being assembled in a machine. We expound the experimental principle to monitor the bolt looseness by wave energy dissipation based on Hertzian theory of contact, taking only the asperity elastic deformation into account in our research. In the experiment, guided wave was induced by the laser, which was stimulated on the plate, to realize the goal of non-contact excitation. A piezoelectric sensor was used to receive the guided wave signal in the experiment. The distribution of guided wave power with frequency was observed by a Welch power spectral density (WPSD) image, and then the power of guided wave was calculated by power spectral density(PSD). We found that the power of guided wave is positively correlated with bolt torque. This conclusion is feasible for plates of different roughness (Ra0.5 ∼ Ra1.5), clamped by a bolt, verifying the efficiency of the metho...

中文翻译：

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通过激光超声波监控螺栓的松动

激光超声波被用来监视螺栓的松动，以解决螺栓在机器中组装后可能松动的现象。我们阐述了基于赫兹接触理论通过波动能量消散来监测螺栓松动的实验原理，在研究中仅考虑了粗糙弹性变形。在实验中，通过激光诱导导波，并在板上激发，以实现非接触激发的目的。实验中使用压电传感器接收导波信号。通过Welch功率谱密度（WPSD）图像观察导波功率随频率的分布，然后通过功率谱密度（PSD）计算导波功率。我们发现导波的功率与螺栓扭矩成正相关。