Simulation Analysis Of Brake Shoe In Freight Train Under Different Conditions And Wear And Tear Research

To meet the needs of national economical development, improving the transport capacity of railway freight trains has become the inevitable trend of development and quick and overloads of freight trains has become two important directions of development of railway transport of goods. With the continuous development of heavy-duty and rapid transport, Security issues of whether the braking capability can ensure that the train is safe and reliable operation has become more important. So it demands a higher braking capacity on the train. However, freight train braking is tread brake mainly in China. The brake shoe is high friction coefficient synthetic brake shoe. The synthetic brake shoe will have a greater heat load in the process, such as long ramps velocity modulation braking on the long slope in Datong-Qinhuangdao line and several continuous slopes length 300km in Shenmu northern section to Huanghua line (total length 815km), the gradient reaches -12‰, which can causes varying degrees of thermal cracks and wear on the wheel and brake shoe. With the construction of the Sichuan-Tibet railway, which the long ramp road conditions will occur more frequently, it is necessary to study the thermal- structural coupling behavior and wear conditions of shoe in harsh conditions.On the basis of the domestic and foreign studies about effects of the heat generated by tread braking on wheels, this paper researches the influence on the brake shoe from friction heat. It uses Finite Element Analysis Software ANSYS to make a simulation analysis about the temperature and stress field on brake shoe in different braking conditions and compares with some related tests. Also, it needs microscopic analysis on frictional surface of brake shoes during the braking process and defines the limited temperature value by some relevant standards, which the brake shoes can withstands. Based on the above analysis, calculating the limit amount of wear on the brake shoe in some harsh conditions theoretically and comparing with some existed results Of real vehicle tests.The main conclusions drawn in this paper are:(1)The maximum temperature of the brake shoe rises sharply and then slowly to the maximum value and finally drops slowly, which is 206.2℃ in the 28 second of the whole braking process. The trend of the maximum stress and the temperature is similar, the maximum value is 15.4MPa at the 32 second of the whole braking process, the time delays 4 second than the maximum temperature. The maximum temperature and stress of brake shoe in varying degrees of wear don’t reach the damage value.(2)The temperature and stress increases in the whole braking process of the long slope continuously, but the trend rises slowly gradually. The maximum temperature and stress appear at the end of the braking process. Compared the maximum temperature with some relevant standards, The maximum temperature of shoe of greater degree of wear exceeds the limit. For using on the project easily, it is necessary to fit curve for the trend of maximum temperature.(3) Based on the different temperatures occurred during braking, the friction state of brake shoe’s friction surface were microscopic analyzed preliminary with existing data. Due to abrasive wear, friction surface produced different degrees of furrows and defects. From the beginning of the fiber breakage to the base material drops caused by fiber fracture, and then to fiber was been cut to a plane, which leads to the fibers are worn and fall off eventually, then the surface forms defects and tiny hot cracks.(4) According to the relevant standards, the limit amount of wear on the brake shoes is calculated theoretically in some extremely harsh conditions. It shows that the amount of wear on the brake shoe reaches 20.96mm per ten thousand kilometers on the condition of the gradient is-12%o and the limit speed is 80km/h.