Failure Analysis and Treatment Process of Traction Center Pins for Urban Rail Transit Vehicles

[Objective] In view of the problems found during the secondary overhaul of a subway vehicle, such as local cracks on cone surface of the traction center pin, the reduced fit with the traction center pin seat, and thus generated potential safety hazards to the subsequent operation of the vehicle, it is necessary to conduct a failure analysis on the traction center pin of urban rail transit vehicles. [Method] Combined with finite element software, the hypothesis analysis method is adopted to study the random vibration, shock vibration, local contact extrusion and torsional deformation issues under special conditions of the traction center pin during the heat treatment stage and daily vehicle operation, a corresponding finite element model is established. The stress distribution characteristics of traction center pins under different confidence intervals and its deformation degrees along different directions are analyzed. [Result & Conclusion] Residual stress accumulated in traction center pins during the heat treatment stage is one of the main reasons for subsequent local cracks, and its coupling with vibration, extrusion, torsion and other factors generated during vehicle daily operation, may induce plastic flow on the cone surface and then form cracks. Implementing a reasonable maintenance process during frame overhaul can eliminate local cracks, extend the service life of traction center pins, and reduce the possibility of local crack propagation on the cone surface.