Study On Strength Of Aluminum Alloy Column In Cooling Unit Of EMU Traction Converter

The cooling unit of EMU traction converter is arranged with cooling plate and cooling fan,so as to cool off the under-vehicle equipment such as traction converter and ensure the safety of train operation.The cooling unit and other equipment are fixed under the train and inside the equipment cabin in the form of hoisting.With the increase of highspeed train speed,the working environment of the equipment under the train becomes worse: due to the irregularity of the track,the hoisting equipment is subjected to the vibration load transmitted by the body for a long time.When the train meets and passes through the tunnel,the hoisting equipment will be affected by strong aerodynamic load,so the support structure of the suspension equipment under the train often occurs fatigue failure.The structural reliability of key equipment directly affects the operation safety of the train,so it is increasingly important to study the cracking reason and strength reliability of the support structure of the undercarriage equipment.In this paper,the cause of aluminum alloy column cracking of traction converter cooling unit frame is the research goal.Starting from two aspects of test and finite element simulation,through line test and finite element analysis,the real cause of aluminum alloy column cracking of cooling unit is obtained,and whether the fatigue strength of the improved structure meets the requirements is analyzed.The specific research contents are as follows:(1)Based on the actual measurement of the Beijing-Shanghai railway line,the line test scheme is introduced.By processing the measured data of each measuring point of the cooling unit frame and column,the variation rules of dynamic stress and vibration acceleration of each measuring point in different running states of trains are obtained,and the influence of sudden change of air pressure value on dynamic stress and vibration acceleration of measuring points is also obtained.(2)The finite element model of the cooling unit frame is established,and the static strength,modal and harmonic response of the cooling unit frame under vibration acceleration and aerodynamic load are analyzed.Combined with the spectrum of the measured data,the main reason for the cracking of the aluminum alloy column of the cooling unit of the traction converter is obtained.(3)The finite element model of three-car EMU and under-car equipment is established,and the flow field analysis area and boundary conditions are determined according to the actual line conditions.Through the static analysis of the air flow field of the train model,the different positions of the equipment compartment,the air flow movement and air pressure distribution inside and outside the equipment compartment when the train is running at different speed levels are obtained.At the same time,the influence of aerodynamic load on the frame structure of cooling unit is verified by fluid-structure coupling simulation.(4)The equivalent stress values of the original structure column and the improved structure column are calculated based on the measured data of the line.The stress spectrum and fatigue damage value of the column are obtained by rain flow counting method,and whether the improved structure column meets the requirements of static strength and fatigue strength is judged.