Fracture Analysis of Setting Bolt for Shimmy Stopper

In allusion to the phenomenon that the setting bolt of a helicopter shimmy stopper is prone to fracture during service, the reason for the bolt fracture is analyzed in this paper. The heat treatment process parameters for the fractured bolt were verified by macroscopic and microscopic observation of the fracture, chemical composition analysis and hardness test. And on this basis, the bolt tightening torque, the tensile, and the impact toughness tests were used to ascertain the cause of the failure of the bolt helicopter shimmy stopper. The results show that bolt fracture is the tempering brittleness caused by the improper heat-treatment process. To solve the bolt failure problem, a method for improving the tempering brittleness is proposed in this paper. The decrease in tempering temperatures is expected to reduce the fracture risk of the shimmy stopper caused by the impact of the blade on the bolt during flight and ensure the safety of the helicopter operations.