Research on Bolt Axial Stress Measurement Method Combining Longitudinal Wave and Trailing Pulse With Temperature Compensation

In addition to the axial stress, temperature also affects the velocity of ultrasonic waves in the bolt. Ignoring the influence of temperature leads to inaccurate bolt axial stress measurements. In this article, a method that combines the longitudinal wave and trailing pulses is proposed to measure bolt axial stress. Compared to the longitudinal-transverse wave method, the proposed method is sensitive to stress change but less sensitive to temperature change, which is more suitable for measuring bolt axial stress. Through theoretical analysis and experiments, the relationship between temperature, axial stress, and the time-of-flight (TOF) coefficient corresponding to the longitudinal wave and trailing pulses is explored. Based on this, the temperature compensation technique is developed, enabling accurate bolt axial stress measurements across a wide temperature range. The measurement error of the proposed method is lower than that of combining the transverse and longitudinal waves.