Analysis & Research On Failure Of Frame Braced Bogie For Higher Speed Railway Freight Car

A new type of speed-up wagons equipped with type K2 bogie and 8G bogie developed and manufactured by QRRS were found to some extent, collapsing and cracks due to the quality issues on some of the frame braced devices of both two types of bogies during the fatigue test of the complete car and actual operating. As this is the latest technology related to the safety of the freight car transportation, it is very important to analyze and finalize the reasons for failure, and take the necessary corrective actions for improvement. On the basis of high-tech analyzing methods and the relevant technical theories, a further study on the collapsing of center bonded bushing, which is part of the frame brace device of K2 bogie, caused by fatigue is performed. The toe cracks are mainly occurred along the welding joint at the ends of the frame brace and also the molten drops fallen between steel pipe and bonded bushing where the fused bead gathered while welding is performed, and extending to the inner side of the pipe. The cracks occurred at the butted round welding seam were mainly occurred in the inner boss of the welding seam and the un-penetrated edge. In addition, the simulative fatigue test is performed at the welding joint of the ends of bonded bushing, loaded case, obtained detailed data of the test, and provided the basic theory for the further improvement. On the basis of advanced measuring methods and the relevant technical theories, a deeply study on cracks due to the quality occurred at the upper and lower bonded bushing of the frame brace devices of 8G bogie during the operating, and presented the reasons in this passage, that is the top and bottom flanges are too close to the backward arch area of the vertical localizing welding seams and the circle fringe R100, the dimension of the transverse section of the joint area of top and bottom flanges connected with the location seat are greater excessive, all these caused the accumulation of the stress and resulted in fatigue cracks and then damage occurred , further more, the dissymmetry of the opposite frame brace cause additional curving stress, the area of the backward arch of the welding seam affected by heat are too thick, this also lessen the strength of fatigue resistance. In addition, an over-all analyze of the strength and stress condition of the localizing pad and bonded bushing are carried out, then present the proposals for improvement and reduce the stress distributed around this area.