Construction Of An Experiment Device About Body Of High-speed Train On Alternating Aerodynamic Loads

When a high-speed train enters a tunnel alone, and passes in tunnel and in open air, there will be great changes in air pressure.Under the alternating aerodynamic loads, a high tension often appears on the regions of the vicinity of welded joints, the structural discontinuity regions and the diameter nozzle, which will make the material crystal slide and dislocate, and gradually form the micro-cracks.Along with the constant cycle of the loading, the micro-cracks are also expanding, thus forming the macroscopic fatigue cracks.The cracks will lead the car body to turn out fatigue fracture finally, and affect the safety of trains.In order to study the fatigue properties of the car body and components under the alternating aerodynamic loads,a detailed study on the internal flow field of the car body was conducted based on the Navier-Stokes equations with three dimensional,compressible and unsteady viscous fluid. Then, an experiment device about the body of high-speed train under the alternating aerodynamic loads was designed and constructed, which can make the pressure in the car body change as triangular waveforms.Through the three-dimensional flow field numerical simulation, the car body inflation and extraction processes under different aperture was simulated, and the pressure distribution uniformity of the car body flow field and the processes of the pressure changed with time was analyzed.The results of numerical simulation show that:the influence of the pore size to the pressure inside the vehicle can be ignored on the condition of the car body inflation and extraction flow constanting; the pressure in the car body changes linearly with time;and with the repeating processes of inflation and extraction, the pressure in the car body will change as triangular waveforms with time achieving the test requests."An experiment device about the body of high-speed train on the alternating aerodynamic loads "was constructed by the design and comparison of simulating car body, pneumatic system, control system and data acquisition system.And the repeatability and reliability of tests on this experiment device were done.The experimental results show that:the pressure in the car body changes as triangular waveforms with time;the amplitude and period of pressure waveforms can be arbitrarily adjusted; the positive and negative amplitude of the pressure wave are symmetrical;the pressure distribution are uniform; the test data has good repeatability; and the experiment device runs reliably. The test results are consistent with the numerical simulation results, which can meet the fatigue test requirements of the car body.