13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Fatigue performance analysis of frictional type high strength bolts of overlapped joints Huili Wang1,*, Hongjian Yin1, SIfeng Qin2 1 Bridge Science Research Institute Dalian University of Technology, Dalian, 116023,China 2 Research Center for Numerical Tests on Material Dalian University, Dalian, 116022,China * Corresponding author:: whl7997@163.com Abstract: According to the fatigue crack extension theory of the fracture mechanics, this paper analysis the relationship between the property of the high-strength bolts and the connection surface friction coefficient, as well as the relationship between the property of the high-strength bolts and temperature. The fatigue life and fatigue damage degree under different anti-friction coefficient and different temperature are calculated by high-strength bolt three-dimension FEM model. After recycling for the same times, the fatigue life will decrease with the increase of the anti-fiction coefficient as well as the temperature. The bigger the anti-friction coefficient is, the more serious the fatigue damage is. The higher the temperature is, the more serious the fatigue damage degree is. With the increase of the anti-friction coefficient, the structure safety factor will decrease, for the increased anti-friction coefficient makes the connection surface geometric discontinuities degree become serious, then the crack extension rate will be faster. With the increase of the temperature, the structure safety factor will also decrease. The conclusions can be used as a reference for the afterwards fatigue design about such components. Keywords: Fatigue Life, Fatigue Damage, Safe factor, Fracture mechanics 1. Introduction Because of convenient installation, high-strength material of steel bridge, it was adapted by engineer, as the main form of the structure of large- span bridge design. Factory welding and construction site bolt connection as the general connection between Steel components. As welding connection mode restrictions by welding process and construction environmental, it was difficult to ensure the construction quality when the construction site in the way. So components on site installation connected often use high strength bolt connection. Because bridge often bears car live load function etc, as a result the bridge always under repeated load, will eventually cause fatigue damage of steel bridge. Now a lot of research on the fatigue of the connection method for welding, but for the high strength bolts of fatigue performance opposite less, but bolt-connection structure also had fatigue problems. In this article we use three dimension finite element model of double plate joints connected by high strength friction type bolt, and analysis the node fatigue performance under different temperature and different interface handle methods. 2 Fatigue crack expansion and estimate fatigue life of structure Fatigue phenomenon produced when the cyclic stress impact on the structure, caused by the subtle crack and steady state expansion, most components considered having the internal defects, having the propagation of the crack which eventually leads to fatigue damage. The maximum stress reached probably in t elastic deformation range in the entire stress object, so effective prediction of fatigue life is the key to guarantee the safety of component. Fracture mechanics applied to solve the problem of the fatigue crack propagation law made well. Etc of variable load in the fatigue crack propagation characteristics can be made by Pairs formula says:
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