No abstract

The mechanical connection was the main connection means of composite structures. In this paper, a three-dimensional finite element model of progressive failure was established by business software ABAQUS. The model considered the contact between bolt and hole, progressive damage, large deformation theory, and nonlinear shear stress/strain relations. HASHIN failure criterion and TAN material property degradation criterion were adopted to study the progressive failure process of mechanical connection structure, and the effects of different interferences (0%, 0.5%, 3%) on the strength and stiffness of mechanical connection structures were investigated. The results showed that the proper interference fit could improve the bearing strength of the mechanical connection, while the excessive interference fit could reduce the bearing strength of the connection, which was in consistent with the test results.

According to the two failure mechanisms of fatigue fracture of fasteners, the fatigue damage evolution equation of microcrack initiation and propagation of fasteners is proposed, and the crack initiation life and crack propagation life models are deduced. After superposition, the fatigue model of fastener fracture failure is obtained. Based on the fatigue test results, two widely used fatigue life models (exponential and power functions) are compared. The results show that the exponential type and power function type only fit the test data without considering the different failure modes of the structure. Based on the failure mechanism, the fitting results of the model are in good agreement with the experimental results, and have great reference value in the design of fatigue structure.