Abstract: A piezoelectric impedance shift method was proposed to detect bolt looseness based on changes of piezoeletric impedance frcquency. A piezoelectric patch was bonded on the head of the bolt, and a material testing machine was adopted to apply tension force precisely on the tested bolt to simulate pre-tightening forces of bolts. The shift of a specified peak frequency in piezoelectric admittance spectrum was measured by a precision impedance analyzer in clean environments and oil pollution environments. The experimental results show that the specified peak frequency decreases while bolt preload increases, and the frequency shift has a linear relationship with the preload on the bolt, and oil pollution has a little effects on the experimental results.

Key words: bolt looseness, piezoelectric impedance, impedance frequency, preload measurement

摘要： 针对螺栓松动问题，提出基于压电阻抗频率变化的螺栓松动监测方法。在螺栓头部安装压电材料，采用材料试验机拉伸螺栓来精确模拟螺栓所受预紧力；研究了洁净环境和油污环境中，压电材料导纳谱中的峰值频率随螺栓预紧力的变化。结果表明：随着螺栓预紧力的增大，压电导纳谱中的峰值频率降低，且两者间具有较好的线性关系；油污对测试影响较小。

关键词: 螺栓松动, 压电阻抗, 阻抗频率, 预紧力检测