Failure analysis on the axial-connected bolts of the thin-walled cylinder under random vibration loading

Abstract The axial-connected bolts of the thin-walled cylinder structure product failed under random vibration loading acted in the transverse direction. The failure modes include pull-off of the thread on the nut as well as fracture of the bolt. The fracture appearance in fractographic study shows that the failure mechanisms of the bolt connections are shear strength failure of the thread on the nut and fatigue fracture of the bolt respectively. The FEM random vibration analysis was conducted on the overall structure, and the Power Spectral Density(PSD) of the axial force on the bolt was considered as the input loading of the shear strength failure life analysis on the nut as well as the fatigue life analysis on the bolt. Finally the fatigue experiment was conducted on the simplified bolt-connected structure for verification, which showed that the failure conditions and fatigue lives of the specimens were basically the same as those of the original product. Both the results of the fracture appearance analysis and the theoretical analysis are in accordance with those of the fatigue verification experiment, which confirms the failure mechanism of the product.