中文摘要：

螺栓球节点往往是网架结构疲劳破坏的薄弱环节.本文利用螺栓螺纹应力集中系数结合线弹性断裂力学对螺栓球节点的疲劳极限强度进行估算.在S-N曲线法基础上推导了螺栓球节点的疲劳寿命估算公式,该公式结合等寿命曲线综合考虑了应力幅和应力比的影响.将估算结果与国内已有的实验数据进行对比,结果表明该公式能够满足工程设计要求.在此基础上本文研究了初始裂纹长度对高强螺栓疲劳寿命的影响,并给出了影响规律.

英文摘要：

Bolted sphere joints in spatial grid structure are always susceptible to fatigue failure.Based on linear elastic fracture mechanics,the stress concentration factor of bolt thread was used to estimate the fatigue ultimate strength of bolted sphere joints.Based on S-N curve method,a simplified formula to estimate fatigue life of bolted sphere joints was derived by considering the effects of stress amplitude and stress ratio on fatigue life in combination with equilife curve.Compared with the existing experimental results,the predicted formulas can satisfy the engineering design requirements.On this basis,the effects of initial crack length on the fatigue lifetime of high strength bolts were studied and the influence rule was given.