Analysis of machine beam fracture fault

In order to investigate the cause of beam fracture in the piston rod end connection of a certain type of aircraft engine’s intake and expansion nozzle actuator, combined with the fracture surface, assembly process, and service status, an analysis was conducted. The results showed that the material of the faulty beam was not abnormal,and its fracture mode was overload fracture. At the same time, it was found that the external nut safety lock of the actuator connected to the beam was not tight enough, causing circumferential loosening, resulting in abnormal eccentric wear between the inner wall of the lining cylinder and the piston. The comprehensive analysis results show that the abnormal eccentric wear between the faulty piston and liner causes the piston rod to move and become stuck.When the faulty component is discharged from the nozzle, the piston rod cannot contract, and the middle part of the beam connected to it is subjected to abnormal large stress, resulting in fracture.