Research On Safety Assessment Method Of Car Body Structure With Damaged EMU

With the advancement of science and technology and the improvement of manufacturing level,the rail transportation industry has developed rapidly.China’s research and manufacturing of high-speed EMUs are relatively late,but through the continuous efforts of researcher,the level of design and manufacturing technology has been greatly improved,and has gradually reached the forefront of the world.The car body is an important bearing structure of the EMU,and it is very important in the design of the body structure.Due to the effects of processing technology,welding process,service load and environment,the car body may appear crack in local areas after a period of service.This article takes the middle body of a certain type of EMU as the research object,and the safety assessment method of the EMU body structure with damage is studied.The main research contents of the paper include:(1)The structural characteristics of the car body are analyzed,and a finite element model of the intermediate car body is established by HyperMesh software.This article establishes five typical working conditions by analyzing the force state of the vehicle during actual operation and referring to the Japanese "JIS E7106:2006 Railway Passenger Car Design Standard".Several typical vulnerable parts of the car body are determined through the simulation results of each working condition,actual engineering conditions and related literature.(2)By comparing several calculation methods for calculating the stress intensity factor,it is concluded that the J-integral method is relatively reasonable for car body damage structures.Based on the analysis of the stress characteristics of the car body structure,a method for establishing a simplified model of the fracture mechanics of key parts of the car body is proposed.For indirect load-bearing structures,a sub-model method is used to establish a simplified model,and for direct load-bearing structures,a solid model method is used to establish a simplified model.Both methods meet the engineering requirements by comparing with the vehicle model.(3)The principle of the failure assessment chart is introduced and the determination methods of key parameters are analyzed,including the selection of the evaluation curve and the calculation method of the evaluation points.Then the 3C and 2A evaluation curves of the typical structure of the car body are constructed,and the failure assessment chart method can be applied to the car body structure.In addition,the 2A rating curve is more suitable for engineering applications due to the simple operation and the evaluation results are too safe.The 2A rating curve is used to evaluate the safety of the traction beam structure.(4)Based on the failure assessment diagram and reliability theory,the method of probabilistic safety assessment of the car body structure is analyzed.Probabilistic failure model is proposed and Monte Carlo method is used to calculate the failure probability of damaged traction beam structure.The results of the probabilistic failure assessment chart method are biased towards safety by comparing with the traditional probabilistic fracture mechanics method.Finally,the sensitivity of key parameters is further analyzed.