Failure analysis of aviation hydraulic rotary joints

The aviation hydraulic rotary joint is an accessory of the aviation hydraulic system used to connect two pipelines in relative motion. The safety accident caused by the failure of the aviation hydraulic rotary joint occurred in engineering. The analysis of the potential failure causes of aviation hydraulic rotary joints can provide basic technical support for aircraft maintenance activities. In this study, a ground reliability experimental apparatus for an aviation hydraulic rotary joint was built, and a reliability test was conducted. The potential failure mode of an aviation hydraulic rotary joint was analyzed by observing the surface topography of each component. Finally, the failure mechanism was analyzed using the finite element method. To provide a basis for the maintenance and replacement strategy of the joints, the influence of the fit clearance on the reliability of aviation hydraulic rotary joints was analyzed. The results show that the wear of metal components and sealing components and the stress failure of sealing components are the main failure mechanisms of rotary joints; when the fit clearance increases from 0.02 mm to 0.12 mm, the maximum von Mises stress and maximum shear stress of the retaining ring were increased by 44.45% and 43.72%, respectively, and the maximum von Mises stress and maximum shear stress of the O-ring were increased by 131.89% and 123.64%, respectively. With the increase of the fit clearance, the stress damage probability of the retaining ring and O-ring will increase. The maintenance and replacement strategy of rotary joints can be made according to the size of the fit clearance.