Study On Safety Of High-speed Train Curve Passing Under Sudden Wind

When the train passes through the curve segment,the mechanical properties between wheel and rail will change compared with the straight section,and the dynamic coefficients will also change.Under the action of wind load,the wheel-rail force changes more complex when the train passes through the curve segment,and the train may derail or overturn.Therefore,it is of great significance to study the mechanical properties of trains between wheels and rails under wind loads,to analyze the influence of wind loads on mechanical properties,and to formulate safety speed limit schemes for preventing train safety accidents caused by strong winds.In present thesis,numerical method is used to study the effect of mutation wind on a certain type of CRH high-speed train.The aerodynamic performance and the surrounding flow field of the train are analyzed.The time-domain and frequency-domain characteristics of aerodynamic loads on different track conditions(flat ground,embankment and bridge)at different driving speeds of trains are studied.The influence of cross-wind catastrophe characteristics on aerodynamic loads and flow field around trains is also briefly analyzed.The aerodynamic simulation results are loaded into the dynamics software in the form of a function to realize the fluid-solid coupling simulation..According to the theory of Vehicle Multi-body dynamics,the safety of train curve passing under the influence of mutation wind is studied.The effects of wind direction,curve radius,transition curve and running speed on train dynamics are analyzed.Finally,the safety of train curve passing is analyzed and evaluated by derailment coefficient and wheel weight reduction rate.The study reveal that by comparing the sudden wind and the constant wind with the same extreme speed on the flat ground,the difference of aerodynamic loads of trains can be as high as 81.3%,and the higher the speed,the samller the difference;under the same speed,the aerodynamic loads of trains are the smallest on the flat ground,the difference between the extreme lift of embankments and the maximum lift of embankments is 769.8%,and the difference between the maximum lift of bridges and embankments is 467.6%.The maximum difference of lateral force between embankment and flat land is 71.5%,and that between bridge and flat land is 54.9%.The maximum difference of overturning moment between embankment and flat land is 83.7%,and that between bridge and flat land is 118.6%.The distribution frequencies of peak power spectral density of unsteady aerodynamic loads on trains under different conditions are concentrated in the range of 0.125 Hz to 0.75 Hz,which is similar to the distribution frequencies of natural vibration modes of train system itself,and resonance may occur,which may lead to train instability.Under the action of transient wind,the safety of train passing on the flat curve is the best,then are embankment and bridge.While the safety factor of near wind side of embankment and bridge is higher than that of far wind side.The maximum speed on flat ground can reach 300 km/h and pass any radius curve safely.The speed on embankment can reach 250 km/h to pass some curves,and the driving speed on the bridge can reach 200 km/h to pass some curves.