Research On Wheel Fatigue Crack Of High-Speed EMU

In recent years, the rapid development of our country’s High-speed railway business has greatly promoted the growth of the national economy. The Jing-Hu High-speed railway and Jing-guang High-speed railway opened one after another greatly strengthen the between Beijing-Tianjin-Hebei economic circle and the Yangtze River Delta, Pearl River Delta, promoting the rapid flow of factors of production,It is expected that by 2020, "Four Vertical and Four Horizontal" railway network planning will have been fully through, which will drive the economic development of the eastern, central and western regions. And with the implementation of the "The Belt and Road" strategy, Chinese High-speed rail technology will go towards the world market. Compared with other means of transportation, High-speed railway has the following advantages: being fast and comfortable, being safe and stable, saving energy and environmental protection, and high carrying capacity, also the High-speed railway transportation facilities set can promotes the forward development of China’s equipment manufacturing industry.EMU’s actual speed can achieve 250~380 km/h today, we will see a lot of fatigue crack on the wheel tread and rail after running a period of time,and many of pits will be formed after the crack coalescence,and because the wear caused the wheels tread contour deformation, the wheel losses round, the damage will deteriorate the wheel/rail contact state and cause impact load, then the wheels need to carry into the factory to repair or replace the rails, by rotary repairing technology or grinding technology to recovery the wheel performance. Research found that fatigue crack is often less on the smooth wheel tread; But there is lots of fatigue crack on the rough surface. This suggests that there is competition between the wheel/rail wear and fatigue, and to some extent, the wear will undercurrent some fatigue crack, inhibitting the further extension of crack. So during a certain running mileage, researching the competitive relationship between wheel/rail contact fatigue and wear will have an important significance for correctly maintaining the wheel and rail.The forming mechanism of wheel tread contact fatigue is very complicated, involving many crossing disciplines, so far the reasons of such destruction phenomenon formed still being explored. This article widely draws on the study about rolling contact fatigue problem from the domestic and foreign. Firstly simulating the wheel/rail contact stress and strain state in different axle load, lateral displacement, attack angle, rail bottom slope, and finding out the biggest factor influencing on the wheel/ rail contact state for the further analysis of contact fatigue to lay the foundation.Secondly analyzing qualitatively the extention of artificial crack on the wheel tread, investigating the influence of bend radius, operating mileage and impact load on the fatigue crack of wheel tread, experimental operation was that installing the wheel sample on the test bench, according to the motion state signal collected, and the hydraulic on the test bench would impose force on the wheel, making artificial crack evolute. At the end of the experiment, using Scanning Electron Microscopy, Energy Spectrum Analyzer, Ultrasonic Detector, tread profile tester and other equipment to teste and analyze the wheel sample artificial crack.The results show that the running mileage and contact state have a great influence on the wear and fatigue, and due to the presence of wear, during the experimental mileage, the artificial crack ultimate expanding depth is less than its original depth on the wheel surface. Therefore, we can draw on that the wheels carried into the factory to repair is feasible after running for 20~30 million kilometers.