基于超声双波法测量高强螺栓预拉力试验研究

Experimental study on pretension measurement of highstrength bolt based on ultrasonic dual-wave method

为了降低高强螺栓脱落或断裂对结构性能的影响,研究了高强螺栓预拉力的超声双波检测方法,通过及时判别出欠扭和过扭螺栓,来降低螺栓预拉力失效的概率。基于超声双波法原理,研究了螺栓有效应力长度对螺栓预拉力超声测量的影响,进行了已紧固高强螺栓预拉力的测量试验。结果表明:螺栓有效应力长度取L_(g)+d/6或L_(g)+d/3时,测量值与实际值的相对误差小于10%。修正了螺栓有效应力长度的经验公式,可将其应用于工程实践。

In order to reduce the impact of falling off or breaking high-strength bolts on structural performance,the ultrasonic dual-wave detection method of pretension of high-strength bolts was studied.This is an effective way to identify the under-torsion or over-torsion bolts in time that enables to reduce the probability of failure of pretension of bolts.Based on the principle of the ultrasonic dual-wave method,the effect of effective stress lengths on ultrasonic measurement of bolt pretension was evaluated.Meanwhile,the pretension of high-strength bolts in service was measured.The results show that the relative error of the ultrasonic measured values and the actual values is within 10%when the effective stress length of the bolt is taken as L_(g)+d/6 or L_(g)+d/3.This paper theoretically and practically contributes to the validation and modification of the empirical formula for effective stress length of bolts.