Research On The Partical Load Spectrum Of Carbody Structure Under Wind-Induced Loads

When the train runs at low speed, the influence of aerodynamic load on the strength of the car body is generally not considered, along with the increase of the running speed, the dynamic environment of the train is deteriorating, and the influence of the aerodynamic force on the strength of the car body is increased, which has become one of the factors that must be considered in the study of the load spectrum. As the train passes through the tunnel or intersection at high speed, or passing each other, air pressure between the inside and outside of car body, the car body and the tunnel, and the car body and the car body Changes periodically, causing the side wall of the car body a large periodic deformation; The continuous alternating dynamic loads lead to repeated expansion and contraction of the vehicle body, and the internal stress of the car body changes with time. So the influence of internal and external pressure difference on the fatigue strength of the car body structure should be considered. And also, when the train running in the open air, encountering random natural wind, continuous stochastic aerodynamic loads act on the car body, cause the continuous vibration of the car body structure. The accumulation of the load cycle may lead to crack initiation, propagation and even fatigue fracture.The superposition of various loads in the process of high-speed train is a complicated stochastic process. Therefore, it is necessary to fully understand the service load environment of the train body, and mster the typical line characteristics and operating conditions that impact the fatigue of the structure of the car body more, and then build up a larger area of the body load spectrum, so that to evaluate the fatigue design and test of the vehicle body scientifically and reasonably, providing theoretical support for the reasonable arrangement of maintenance period.In this paper, the research object of a high-speed train based on CRH, considering the influence of random wind load on the vehicle dynamic characteristics and strength of body structure, using spectral method to calculate the random aerodynamic load. The research focuses on the typical load spectrum of carbody structure wind-induced loads and the main work includes:(1) The basic characteristics of the line spectrum of Beijing and Tianjin are studied, including the curve radius distribution, the curve super high, and the length of the transition curve length and so on; Based wind spectrum information of Beijing Tianjin line provided by the literature, The dominant wind direction and the maximum instantaneous wind speed along different time periods is anayzed. And then, select Cooper wind speed spectrum as the target spectrum, the time history of fluctuating wind speed of the moving point shifting with high-speed trains is simulated using the linear filtering method. The calculation method of aerodynamic load is analyzed based on the relationship between wind speed and wind pressure and the aerodynamic weight function is introduced to calculate unsteady aerodynamic force of high speed train under crosswind. At last, the simulation of unsteady aerodynamic force is realized by MATLAB programming.(2) Based on the theory of multi-body dynamics and vehicle dynamics modeling, a prototype of a high-speed train based on CRH, combining with the main performance parameters of the actual vehicle dynamics, vehicle dynamics model is established. And according to the characteristic of the Beijing Tianjin route and the relevant information of the instantaneous maximum wind speed to determine typical vehicle operating conditions, develop a detailed study of the wind load transient loading method, the dynamic load is applied to the vehicle, the running safety of the high-speed train in typical load conditions is evaluated.(3) With the high speed train vehicle dynamics model in typical conditions under the crosswind as the main research object, Through the simulation calculation method, the load time history of the car body structure is extracted; The simulate load time history and the simulation data of unsteady aerodynamic force is statisticed based on the rain flow counting method, the typical wind load spectrum of the body structure is formed.Research results show that, the wind speed power spectrum and the target spectrum obtained by the linear filtering method have high accuracy in the simulation frequency range, the energy concentration of random wind speed is distributed in the range of 0.001-3Hz; In the process of aerodynamic calculation, the weight function is introduced, and the pulsating component of the high frequency aerodynamic force is filtered, and reflects the effect of the aerodynamic effect of the delay; Dynamic simulation analysis, when the wind speed is 20.6m/s, Model vehicles pass a track with excitation at 200-300km/h speed, all safety indexes of vehicles meet the requirements of safety driving; Finally, the rain flow counting method is used to form the load spectrum of the vehicle body structure and the load spectrum of the random aerodynamic load.