Experimental study on fatigue performance of M30 high-strength bolts in bolted spherical joints of grid structures

A grid structure with bolted spherical joints (BSJs) is one of the large-span space latticed structures and has been widely used in industrial buildings. Under the alternating actions of the suspension cranes, fatigue failure of BSJs is liable to occur in a high-strength bolt. In this paper, the constant amplitude fatigue tests of 39 40Cr steel alloy M30 high-strength bolts used in BSJs were carried out using an MTS fatigue testing machine. The corresponding fatigue S-N curves were developed with the stress range as the parameter, and the test results were discussed with the theoretical values of the current specifications. Then, by means of the finite element analysis, the stress state and fatigue failure position of bolts in BSJs in tension were discussed. The analysis of fracture morphology was performed to investigate the fatigue fracture characteristics. Finally, on basis of fatigue damage theory, a high-cycle fatigue damage model was adopted to describe the development process of fatigue damage.