Research on bolt axial force measurement method based on the combination of ultrasonic longitudinal wave and trailing pulse

High-strength bolts are widely used in applications such as fans, sealed containers, and mechanical transmission devices, where ensuring the consistency of axial pre-tightening force is crucial for enhancing connection and seal reliability. Traditional torque methods for measuring bolt axial force often face challenges due to various industrial friction factors, resulting in significant measurement discrepancies. To overcome these limitations, this paper introduces an ultrasonic method to precisely measure bolt axial force, utilizing a novel approach that combines ultrasonic longitudinal waves with trailing pulses. This method notably simplifies the measurement process by eliminating the need to account for bolt length and reduces the complexity of transducer design, requiring only the design of a longitudinal wave transducer. The propagation characteristics of trailing pulses are analyzed using ray tracing techniques, and the study further explores the relationship between the travel time ratio of trailing pulses and longitudinal waves and the bolt axial force. The viability of this approach is validated th rough both simulation and experimental methods, revealing a linear correlation between ultrasonic time measurement (D) and bolt axial force (F), with a measurement error under 5%.