Reliability Analysis Of Heavy Freight Couplers Based On Small Set Of Fatigue And Fracture Test Samples

With the rapid development of Chinese economy, the demand for industrial electricity grows rapidly, which leads to require coal volume more and more. As the main line for the coal transport, the freight volume of Da-qin railway has a substantial growth with the heavy haul train of twenty thousand tons opened in 2006, and the number is up to 4 hundred million tons just in the whole year of 2010. However, a lot of problems were discovered such as the fatigue of the couplers which would lead to the safety accident. So in this paper, it analyzed the fatigue life and reliability of the No.17 couplers according to the relative test.First of all, three special couplers were made and calibrated to measure the longitudinal force. The sensor system of the couplers was composed with the bridge circuit of resistance strain gauge. The third position both in the former and latter 10,000 tons was measured twice as well as the thirty and the eighty-forth position. In order to apply in the fatigue rig, the data were dealt with the principle of the rain-flow counting. The relative data were got such as amplitude,mean value and frequency.In the real situation, the train was marshaled periodically, so the longitudinal force of a single position could not stand for the whole load of couplers. Accord to the test schedule and test result, the grade five loading spectrum was edited to carry out small sample fatigue test. From the test, some appearance could be discovered. One is that the cracks of No.17 couplers are the lower traction Table as the same as the real situation. The fatigue life between the two kinds of data is alike. So the test spectrum could be proved as a good response to the real load. The other is that the fracture position of coupler knuckle is traction Table and pull S plane, and the obvious fractography could be found. It could be as the base of fatigue performance of coupler knuckle analyzed.At last of this paper, the reliability was analyzed because of the dispersion of the couplers. Based on the Bootstrap method, the relationship among operation mileage,reliability and confidence level. The conclusion could be drawn that the fatigue life of the couplers is longer than that of coupler knuckle. However, for the coupler knuckle, the life of traction Table fracture is lower than that of pull S plane fracture, so the whole life of coupler knuckle could be improved by modifying the structure of the traction Table.The research of the fatigue life and reliability about the couplers can be a basis for formulate the repairing cycle. It is helpful to reduce the safety accidence caused by the fracture of the couplers.