Study On Stiffness Performance For Vehicle Body Of Underframe Bearing Type Locomotive

High-speed and heavy-duty have been important development direction of the railway construction. To obtain an optimal underframe, the underframe bearing type locomotive needs to balance the relation among weight, strength and stiffness of the vehicle body, on the premise that the strength and stiffness have met the demand of the standard. Many scholars have started the research in this field, but most of their studies are based on the finite element model, it belongs to evaluation work. We attempt to obtain an excellent locomotive vehicle body by means of control on stiffness characteristics at a preliminary design stage, it has important engineering significance.Deflection of the longitudinal beam and first vertical bending frequency are the major evaluation indicators of the vehicle body stiffness. Lack of rigidity can cause problems such as the large deformation of windows and doors, low vibration frequency and even the crack of the longitudinal beam. When the stiffness is excessive, weight of the vehicle body will increase, running condition of the train will deteriorate, reliability and safety of the train operation will be threatened directly. Besides, when the vibration frequency is too low, fatigue life of the vehicle body will decrease.In order to control and improve the vehicle body stiffness performance of the underframe bearing type locomotive at a preliminary design stage, we studied the stiffness characteristics based on the 3D solid model, in stead of the finite element model.The integral method and the equivalent stiffness method were derived. To get the advantage, disadvantage and scope of application of the two methods, some typical cases were analyzed and compared with each other. The vehicle body was equivalent to the simply supported beam. Using the equivalent stiffness method, the cross section parameters were analyzed. The moment of inertia and loads were equivalent to get the deflection of the longitudinal beam. The error between the analytical result and the FEA result was 8.43%. Traditional integral method was used to calculate the deflection of the longitudinal beam subjected to the diesel generator load. Maximum height of the cross section, starting point of variable cross section and span of variable cross section were presented as the basic variables. Optimization design of the longitudinal beam was calculated by the Matlab program. Three formulas were presented to calculate the bending natural frequency of the vehicle body. Based on the underframe model, errors among the three formulas were analyzed and compared. The results showed that:the error of revised formula was obviously decreased. Finally, strength analysis of the optimized vehicle body was calculated, and the results met the demand of standard.The results show that the equivalent stiffness method can be used to calculate the deflection and the first vertical bending frequency in the preliminary stage, it is feasible to control the vehicle body stiffness at a preliminary design stage. The integral method can be used in the precise calculation of the variable cross-section beam deflection and the optimization design of the longitudinal beam.