基于超声波技术，通过对螺栓进行拉伸试验，研究了不同外载下螺栓轴向力-伸长量特征曲线的差异，分析了螺纹摩擦对螺栓轴向力-伸长量特征曲线的影响。结果表明：螺栓的单向拉伸与扭转拉伸因受到的载荷方向不同而导致其屈服点不同；螺栓前期拧紧标定过程中螺纹摩擦对螺栓轴向力有很大影响，会影响后续子系统螺栓夹紧力的大小；不同的螺纹摩擦状态导致拧紧过程中螺栓轴向应变速率不同，会产生不同的特征曲线，且螺纹摩擦因数越大，扭转应力就越大，螺栓屈服点就越低；若能保证轴向拉伸速度相同，不管是涂层之间的正常螺纹摩擦还是使用机油降低摩擦，获得的特征曲线斜率是相同的；无涂层的金属间摩擦会导致螺纹尖端产生塑性变形，形成的特征曲线弹性段斜率有较大差异。

Based on ultrasonic technology, through the tensile tests of bolts, the differences of bolt axial force-elongation characteristic curves under different external loads were studied, and the influences of different thread frictions on bolt axial force-elongation characteristic curves were analysed. The results show that the yield points of bolts under uniaxial tension and torsional tension are different due to different load directions. In the process of bolt pre tightening calibration, the thread friction has a great influence on the bolt axial force, which will affect the bolt clamping force of subsequent subsystem. Different thread friction states lead to different axial strain rates during tightening and different characteristic curves. The greater the thread friction coefficient is, the greater the torsional stress is and the lower the yield point is. If the axial tensile speeds are the same, the slopes of characteristic curves are the same, whether it is the normal thread friction between coatings or the use of oil to reduce friction. The friction between metals without coating will lead to the plastic deformation of thread tip, and the slope of the elastic section of the characteristic curve is quite different.