钢网架螺栓球节点用高强螺栓的缺口效应分析

On the Notch Effects of High Strength Bolt in Grid Structures with Bolt-sphere Joints

在悬挂吊车作用下,螺栓球节点网架的疲劳主要表现为节点的疲劳,而节点的疲劳关键是高强螺栓的疲劳.在影响高强螺栓疲劳性能的众多因素中,应力集中是其发生疲劳断裂的主要原因之一.本文从缺口效应出发,分析了高强螺栓疲劳裂纹的开展,并建立有限元模型,针对钢网架螺栓球节点常用的8种高强螺栓规格进行了单缺口应力集中分析,得到相应的应力集中系数,同时分析了螺纹牙根圆角半径对应力集中的影响,并提出了降低螺纹疲劳缺口敏感性的一些措施,为进一步以热点应力幅建立螺栓球网架疲劳设计方法奠定了基础.

Fatigue often occurs at joints for the grid structure with bolt-sphere joints（GSBSJ）loaded by suspension crane,especially for high strength bolts. Among many factors that cause fatigue fracture of high strength bolts, stress concentration is a dominant one. In this paper the fatigue crack growth in bolts is first presented. Then the single notch stress concentration for eight different kinds of bolts currently used in grid structures is studied based on finite element method. The influence of the bottom radius of screw thread on stress concentration is also discussed. To reduce the sensibility of notch in screw, some feasible methods are presented. The stress concentration coefficients obtained in the present study provide a foundation to further study and design GSBSJ using ＂hotspot stress amplitude＂.