| In the new century,with the rapid development of urban rail transit industry,the urban rail transit mileage in major cities increases rapidly.Stainless steel car body is more and more widely used in urban rail transit.With the development of stainless steel cars,in addition to the traditional spot welding connection method,laser welding is also used in stainless steel car bodies due to its advantages such as small welding deformation and small heat affected zone.As the research object in this paper,the stainless steel car body is mainly connected by spot welding and laser welding,and analyzed its stiffness,mode,static strength,fatigue strength and crashworthiness.The main research contents was as follows:(1)By comparing the results of different simulation methods,the effective simulation methods of spot welding and laser welding was determined.The finite element model of the car body was established according to the given parameters,which provided experimental data for subsequent structural performance research.(2)According to the standard GB/T7928,the maximum vertical displacement of the lower flange in the middle of the side beam of the car body underframe under the vertical overload condition was 5.743 mm.According to the standard TB/T3550.1,the equivalent torsional stiffness under the torsion condition was calculated,which was larger than the recommended minimum value and met the requirements of the car body stiffness.It was calculated that the first-order torsional vibration frequency of the car body steel structure was16.39 Hz,the vibration frequency of the first-order vertical bending of the underframe was18.23 Hz,the first-order vertical bending vibration frequency of the car body chassis was9.16 Hz,and the first-order torsional vibration frequency of the car body was 10.83 Hz.(3)Based on the standard BSEN12663,12 working conditions for the static strength calculation of stainless steel car body were determined,and structural improvement were carried out continuously in the process of calculation.Finally,the safety factor of the static strength of the car body was at least 1.15,which met the requirements of the static strength of the car body structure.The synthetic shear force of spot welding was less than the minimum shear force of spot welding evaluation stipulated in GB/T 25343.3.The resultant shear forces of beam elements simulated by laser welding were all less than the minimum shear forces of laser welding lap joints specified in GB/T 37778.(4)Four working conditions of fatigue strength calculation were determined according to the standard BS EN 12663,and the structural improvement was carried out according to the unqualified position in the calculation process.According to the calculation of standard BS EN-1993-1-9-2005,the cumulative damage ratios of the selected locations in the four working conditions were all less than 1,which met the requirements of fatigue strength of car body structure.The maximum synthetic shear force calculated by spot welding fatigue was1450.91 N,which was less than the required minimum shear force 1690 N.The synthetic shear forces of beam elements simulated by laser welding were all less than the reference values of fatigue curves obtained from relevant references.(5)According to the standard EN15227,the working condition of stainless steel car colliding at 25km/h speed was designed.It was calculated by software that during the collision,the maximum change of the longitudinal displacement of the car body was 4.56%,less than the required 10%.The energy change trend was normal;the longitudinal speed gradually decreased.The maximum collision deceleration was 4.07 g,less than the required 5g.They met the requirements of the standard for car body crashworthiness.This paper studied the different simulation methods of welding simulation,and studied the performance of stainless steel car body which was mainly connected by spot welding and laser welding,in order to provided reference for the performance simulation of this kind of vehicle in the future. |
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