Analysis On Fatigue Influencing Factors And Notch Effect Of High Strength Bolt Used In Grid Structure With Bolt-sphere Joints

Fatigue of grid structure with bolt-sphere joints mainly behaves fatigue in joints, the critical of which is fatigue of high strength bolt.Lots of fatigue influencing factors on high strength bolts is analyzed in this paper systematically, including materials, construction processing, fixing and working stress.The most important reason for fatigue fracture of high strength bolts is stress concentration. Based on ANSYS, this paper studies stress concentration on single notch of eight kinds of high strength bolts used in grid structure, obtaining their stress concentration coefficients, discussing the effect of ascending angle, bottom radius of screw thread and bolt-ball on stress concentration, introducing their effect coefficients of a1,a2,a3, putting forward the formulae of stress concentration coefficient. Based on stress concentration coefficient, fatigue notch coefficient, fatigue limit and range of allowed stress are obtained.Finally, theoretical results and the fatigue test data of equalamplitude are combined, which is introduced the conception of"range of hotspot stress" , and the method of fatigue designfor grid structure with bolt-sphere joints is obtained in this paper.