关键词: 螺栓预紧力；声弹性效应；超声波

Abstract: Bolt preload is one of the key factors affecting the reliability of bolt connection, and it is of great application value to measure bolt preload directly and accurately. Firstly, based on the principle of acoustoelastic effect, the relationship between ultrasonic propagation speed and axial stress of bolts is studied theoretically, and the calibration relationship between bolt preload and ultrasonic acoustic time difference is established in this paper. Secondly, the influencing factors of ultrasonic measurement of bolt preload are analyzed. Finally, the ultrasonic measurement method and application case of bolt preload are given. The MC900 ultrasonic measuring analyzer is used to monitor the preload attenuation of the dashboard beam and body bolts of a certain vehicle. The test results meet the durability and reliability requirements of the vehicle. The research results show that the ultrasonic preload measurement technology can well monitor the preload changing trend of bolt connection points during the endurance road test of the vehicle, and provide experimental basis for verifying the rationality of bolt tightening torque setting and analyzing the quality problem of torque attenuation.

Key words: Bolt preload; Acoustoelastic effect; Ultrasonic