Research On Methods Of Establishing Test Load Spectrum For The Bogie Frame Of High-speed EMU

The load spectrum of the bogie frame is the foundation of standard and design specification for vehicle reliability assessment.The basic work of the load spectrum is studying on the type and mode of the input loads.At present,the major specifications are UIC 615-4,EN 13749 and JISE 4207.These specifications predict structure strength of the bogie frame via the effective load values applling the specified loading times.The load values are obtained according to the traditional load calculation method substitute the technical parameters of bogie.However,the service loads are significantly different from the standard loads when evaluating fatigue strength according to the traditional load design specification.The evaluation results often cannot reflect the real service damage.Therefore,in order to correctly predict the service fatigue damage of the bogie frame,it is necessary to obtain the realistic design loads in the service line.In this dissertation,studying on the type and mode of the input load on the bogie frame of the high-speed EMU is necessary based on the structure form and motion characteristics.The research about the mode and behavior of bogie is to establish a load spectrum which can predict the fatigue damage in service.The main research contents of this dissertation are as follows:(1)The main input loads of the frame are determined according to the motion characteristics of the high-speed EMU bogie frame via studying the structure type and bearing condition.According to the structure strain response characteristics,the load test is carried out on the test rig using real framework.The transfer matrix between load and response is decoupled by means of diagonalization,which rely on strain gage group bridging technology.In the event of this problem,a high-precision load decoupling and low-deviation test dynamometric frame was developed to obtain the service load installed in the train.At the same time,it is made to undertake both the use function and the force measurement function.(2)The load characteristics of the frame under different typical working conditions are analyzed by the load and stress-time history in the long-term on-track test.In the meantime,it is combined with GPS and gyroscope aided identification tool to analyze the change of load trend for the axle-box vertical force and lateral wheelset force.The results indicate that there are passive force component in the axle-box vertical force and lateral wheelset force.The vertical bouncing load systems,rolling load systems,the torsion load systems and the transverse load systems are obtained by decomposing the vertical force of the axle-box and the transverse force of the wheelset,which are suitable for the platform loading are obtained.(3)According to the balance principle of space force system,this dissertation proposes that the bogie load systems are formed by active force and passive force.The feasibility and correctness of the force balance systems are verified by theoretical calculation,finite element simulation and test rig loading from vertical load system and plane load system of the frame in two ways.Furthermore,the frequency domain coherence and load damage ratio are proposed to identify and confirm the load systems.At the same time,the main deviation of load spectrum occurs in the root region between longitudinal-beam and lateral-beam,side-beam and lateral-beam.(4)In this dissertation,a fatigue damage model of the frame based on time-domain linear cumulative damage theory is suggested to predict the fatigue life.The contrast analysis according to the measured equivalent stress,the calculation stress of load timehistory and the calculation stress of standard EN 13749 shows that realistic design loads are necessary.Meanwhile,the stress calculated by time-domain load is closer to the measured equivalent stress.Then the integrity of load spectrum is confirmed by load damage ratio.Finally,a total of 16 loads are applied including vertical bouncing loads,rolling loads,torsion loads,motor vertical synthetic loads,motor vertical reverse loads,gearbox synthetic loads,gearbox reverse loads,anti-roll loads,braking loads,secondary suspension vertical damper loads,transverse loads,lozenge loads,anti-snake damper loads,motor transverse loads,secondary suspension transverse damper loads and traction rod loads.(5)In order to accurately predict the fatigue damage of the bogie frame in service,it is necessary to establish the test load-spectrum that conforms to the load of the test rig.The establishment of effective test load-spectrum needs to include the load amplitude,load frequency and load phase on the basis of confirming the load type.Therefore,a loadspectrum loading model aiming at minimizing the damage is proposed in this dissertation.The phase information lost in the load spectrum conversion process is defined by Pearson correlation coefficient in the whole load-time history,and the load coupling relationship on the bogie frame is simulated by means of co-loading and reverse loading.At the same time,load frequency is determined by means of proportional reduction in the realistic load-time history,then Latin hypercube sampling is further used to determine load action mode of compression spectrum.Finally,the damage of measured spectrum after rain-flow counting is converted into the load amplitude corresponding to the load frequency.The contrast analysis based on the measured spread damage,the calculation damage of loadtime history,the calculation damage of test load-spectrum and the calculation damage of EN 13749 shows that the test load-spectrum established in this dissertation can better restore the realistic loads,and is closer to the real service damage of the bogie frame compared with the load specification EN 13749.