Fracture Mechanics based Remaining Life Evaluation of the Brake Clamp Seat of Bogie Frames

Lack of fusion and pores for the welded bogie frames have become the most fundamental source of fatigue crack initiation and propagation. Taking the fatigue life of the cast parts of a passenger car non power bogie frame as the investigation object, firstly, the high cycle fatigue test and fracture mechanics test of G20Mn5 cast steel for the brake clamp suspension seat are carried out, and then the measured level 8 load spectrum under the braking condition is taken as the input. The residual life of the brake clamp hanger with defects is predicted and analyzed by using the classical Paris fatigue crack growth rate model and the damage tolerance evaluation method. It is found that when the original casting defect at the weld between the brake clamp hanger and the beam is less than 0.5 mm, it will not expand. However, when the crack extends from initial depth of 1 mm to final depth of 14 mm, the remaining life can reach 70.98 million km, exceeding the design life of in service welded bogie frames. It can be seen that the fatigue life can meet the design life index and has a certain safety margin.