用振动声学方法检测螺栓松动，通过频率调制信号识别非线性特征。
Frequency-Modulated and Single-Tone Excitation to Reveal Vibro-Acoustic Nonlinearities in Loosened Bolted Joints
- 采用单频与频率调制信号激励结构，感知非线性响应。
- 松动状态在130Hz附近出现高频谐波峰，6阶谐波功率差达36.5dB。
- 适合铁路车辆等机械系统中螺栓状态的在线监测应用。
螺栓预紧力损失会导致结构刚度、阻尼和非线性的变化，但现有轨道车辆系统的监测技术难以同时实现受控激振与非线性特征感知。本文提出一种基于振动声学的螺栓松动检测方法，对演示结构施加受控激振以捕捉非线性特征。在三轴加速度计与近场麦克风同步采集下，测试了0%、20%、40%和80%预紧力条件下的螺栓状态。在130 Hz主固有频率（通过正弦扫频和窄带激励确定）附近施加单频与频率调制（FM）信号。单频130 Hz激励时，松动状态出现多个高频谱峰；频率调制（125–135 Hz）进一步区分状态差异。归一化载波的谐波带功率比可有效区分松动与80%预紧状态，其中第2阶谐波差值为17.5 dB，第6阶达36.5 dB。
原文摘要 · Abstract (English)
Preload loss in bolted joints results in alterations of the stiffness, damping, and nonlinearity of the structure, but existing monitoring techniques for rail-vehicle systems are often not capable of combining controlled shaker tests and sensing of nonlinear features. This paper proposes a method for detecting bolt loosening using a vibro-acoustic technique, where the structure is subjected to controlled shaker tests to sense the nonlinear features. A triaxial accelerometer was attached to the demonstrator, a microphone was placed in close proximity, and one of the bolts was tested under 0%, 20%, 40%, and 80% preload conditions. Single-tone and frequency-modulated (FM) signals close to the main natural frequency of 130 Hz, which was identified using sine sweep and narrow-band excitation, were applied to the demonstrator. When the structure was subjected to 130 Hz single-tone excitation, the loose state of the bolt exhibited several additional high-frequency spectral peaks. FM excitation between 125 and 135 Hz further distinguished between the states. Harmonic band power ratios, normalized to the carrier, distinguished between the loose state and the 80% preload state, where the difference between the loose and 80% preload states was 17.5 dB for l = 2 and 36.5 dB for l = 6.
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