Comprehensive Test And Analysis On The Force Of The Tarpaulin Of Railway Freight Car Under Complex Condition

Tarpaulin of the freight car is an important tool for railway freight transportation, which plays an important role in Chinese railway transport. As the train speed rise, the traditional cover ways and the tarpaulin types can not meet the requirements of the railway development. In order to adapt the needs of the passenger and freight rail vehicle acceleration, new type of tarpaulin, tarpaulin rope and net have been put into actual operation. Because of the adoption of new materials, the structural and force of the tarpaulin, tarpaulin ropes have been changed. New standards and technical conditions of the tarpaulin and tarpaulin rope should been put forward.The standards and technical conditions of the tarpaulin and tarpaulin rope in Chinese railway had been set primarily based on the international standards and field experience at present. So far, domestic and foreign scholars have never carried out the systematic research and comprehensive test on the tarpaulin and tarpaulin rope when they had been used under the complex transport condition. With the development of the railway transportation in China, it is urgent to carry out a comprehensive analysis and assessment on the force of the tarpaulin and tarpaulin rope when the freight vehicle runs in all kinds of the worst working conditions. It should provide scientific basis for setting reasonable technical standards on the tarpaulin and tarpaulin rope of the freight vehicle in China.In this paper, the author have carried out a comprehensive study on the force of the tarpaulin and tarpaulin rope used the real vehicle test and numerical simulation method, when the tarpaulin and tarpaulin rope are used in different operating conditions, different loading conditions and different cover ways. The main contents and contribution of the dissertation are as follows:1. Real train test study(1) A real train testing system, which can test the aerodynamic force of the tarpaulin and tarpaulin rope, is developed. The author has carried out a real train test on aerodynamics force of the tarpaulin and tarpaulin rope for the first time at home and abroad. The maximum pull force of the tarpaulin rope and net and the maximum tarpaulin stress have been gained by real train test, when the freight vehicle covered with the tarpaulin run through the wind areas and the tunnel, pass by the other passenger vehicle in open air and in tunnel. It should provide scientific basis for setting reasonable technical standards on the tarpaulin and tarpaulin rope.(2) An effect law of the pull force of tarpaulin rope and the stress of the tarpaulin were gained, which caused by the scheme of the cargo loading, the type of the tarpaulin (D type tarp and X type tarp), the train speed, the speed of the side wind, the tunnel section, the tunnel length and the wind-break facilities.2. CFD numerical simulation(1) The complex three-dimensional flow field model around the tarpaulin were built when the fright vehicle runs through the wind area, runs and passes by the other passenger vehicle in the open air, runs through the tunnel and passes by the other passenger vehicle in tunnel. The zero-thickness wall was used to simulate the tarpaulin in those models.The aerodynamic lift forces were gained by CFD numerical simulation when the freight vehicle coved with tarpaulin operated in different conditions, such as wind area, passing by other passenger vehicle and through the tunnel et al. These lift force data would be used when the author studied the tarpaulin strength.(2) When the freight vehicle covered with tarpaulin run through the wind area, the effect laws of the tarpaulin aerodynamics force were gained which caused by the train speed, the speed of the side wind, the height of the cargo loading and the figure of the cargo loading, the sedimentation of the cargo and the wind-break facilities. When the freight vehicle covered with the tarpaulin run and passed by other passenger vehicle in the open air, the effect laws of the tarpaulin aerodynamics force were gained which caused by the train speed, the speed of passenger vehicle and the tunnel section. When the freight vehicle covered with the tarpaulin run and passed by other passenger vehicle in the tunnel, the effect laws of the tarpaulin aerodynamics force were gained which caused by the train speed and the speed of passenger vehicle.3 Tarpaulin structural strength study(1) A tarpaulin structural strength model influenced by the aerodynamic force was established. At the same time, the FEM solving equation of the cable and the membrane was derived when the cable and membrane structure strength analysis was studied. In the model, the triangle isoperimetric membrane unit was used to simulate the tarpaulin and the space two nodes cable element was adopted to simulate the tarpaulin rope.(2) The quasi static coupling method based on the CFD and CSD were used to study the tarpaulin structural strength. Firstly, the surface pressure distributions of the tarpaulin when freight vehicle operated in different conditions were gained by CFD numerical simulation. Secondly the numerical simulation on the tarpaulin structural strength caused by aerodynamic force were conducted when the freight vehicle covered with tarpaulin operated in different conditons.When the numerical simulation were done, the tarpaulin structural strength model influenced by the aerodynamic force was used and the tarpaulin surface pressure distribution were loaded on the model. Thirdly, the effect laws of the tarpaulin stress were gained which caused by the speed of passenger vehicle and the train speed.(3) The theory of the cable and membrane structure was used to check the tarpaulin strength under different operating conditions. When the freight vehicle run in the open air and through the tunnel with the speed of 160km/h, the maximum main stress of the tarpaulin without the cord is less than the allowable stress of the tarpaulin. When the freight vehicle speed was 160km/h and passed by the CRH2 EMU with the speed of 250km/h in the open air and in the tunnel, the maximum main stress of the tarpaulin without the cord is less than the allowable stress of the tarpaulin, which can meet the requirement for safety operation. When the freight vehicle speed is 120km/h and the side-wind speed is less than 41.4m/s, the tarpaulin stress used the doubled-welded without the cord is less than the allowable stress of the tarpaulin, which can meet the requirement for safety operation. When the freight vehicle speed is 120km/h and the side-wind speed is less than 54m/s,the tarpaulin stress used the doubled-welded with the wind-break cord is less than the allowable stress of the tarpaulin, which can meet the requirement for safety operation. (4) The effect laws of the maximum main stress and the maximum displacement of the top of the tarpaulin were gained which caused by the Poisson's ratio and the pre-tension force of the cord through the analysis method of cable and membrane.