Study On Fatigue Life Of Frame Brace Of Railway Freight Car Bogie

In recent years, with implementation of railway rapid and sound development strategy, Chinese railway has entered into the sixth great speed increase with max. running speed above 160km/h on main lines. Thereafter, Chinese railway passenger cars will experience a further speedup. As in Chinese railway network, passenger cars and freight cars share the same railway lines, freight cars are required to speed up along with passenger cars. Therefore in the sixth great speed increase, freight cars are speeded up in the first time.ZK2 and ZK6 frame brace bogies are developed and produced by Qiqihar Railway Rolling Stock Co., Ltd (QRRS), and now become one of main types of bogies for speed increase of freight cars. Its max. commercial running speed can go to 120km/h. The frame brace of these bogies is introduced from American Standard Car Truck (SCT) with advantage of increasing bogie warp resistance, and consequently increasing freight car running speed and improving ride quality.The frame brace is the key component of the bogie to achieve speed increase. It is welded structure and mainly bears dynamic load when the freight car is running, including wheel track vertical and lateral dynamic force transmitted from wheelset and other complicated dynamic forces such as impact vibrations, which are born by left and right side frames, and alternative dynamic stress resulted from such as reverse nodding in twist track. Therefore manufacturing quality of frame brace, especially welding quality will directly influence the safety and reliability of freight car in operation.The essay finds the correlation between fracture mechanism and fatigue life by analysis on cracks on different locations such as girth weld at ends of cross rods and straight welds on plates. Based on the correlation, improvements are made on welding technology and other relevant aspects on frame brace, and respective processing parameters are determined after processing tests such as fine grain size welding, rod body polishing and forming. To evaluate results of improvements, main welds such as on rod body, plates and ends are analyzed for fatigue life, and fatigue tests on frame brace and trial operations are made. The effectiveness of frame brace manufacturing process is thus finally verified.