Numerical Analysis And Experimental Study On Vibration Fatigue Of Freight Car Body Of Railway Vehicle

Welding is a kind of effective and economical way to connect metal structure,and it is also one of the most important connection modes in modern manufacturing industry.In the car body structure,because of the stress concentration,the weld is the most prone to fatigue damage.Therefore,it is of great significance to predict the fatigue life of the car body under vibration load in order to design,produce and improve the welding quality.In this paper,the truck C70 body is taken as the research object,and the dynamic structural stress method is used to evaluate the vibration fatigue of the car body:First of all,the development status and trends of vehicle and research significance are introduced.The fatigue evaluation method of vehicle structure and the research of vibration fatigue at home and abroad are briefly summarized.Secondly,this paper introduces the existing methods of vehicle evaluation in detail: BS standard,IIW standard,AAR standard.The principle of the algorithm is deduced systematically.It is found that the new mesh insensitive S-N curve method in the ASME standard can predict the fatigue life of welded joints more accurately.However,these standards cannot fully consider the effects of the vibration acceleration and the natural frequency of the body on the structural stress.In addition,the basic theory of random vibration is introduced from the following aspects: single degree of freedom or multi degree of freedom system,with or without damping effect,whether the forced vibration.After that,through the analysis and simplification of the existing geometric model in HyperMesh software,we can get rid of the complex structure which has little influence on the stress of the car body.Extract the geometric structure of the middlesurface,mesh the division of finite element,establish grid properties and establish condition.Export.cdb file to ANSYS software for modal analysis and static analysis.By analyzing and comparing the yield strength of the car body material,all accord with the design requirements.What needs to be pointed out is that: In order to ensure the accuracy of the calculation,the mesh size of the grid is 40 mm,which saves space and workload for the transient analysis.Then,the method of data processing for the experiment platform to be applied to the car body is described.After that,Adams software is used to solve the dynamic equation of the car body and output the load time history data of eight points.These data are read into the ANSYS.The dynamic analysis of the car body is carried out by using the transient analysis in ANSYS.The direction stress of the point of the four parts on the chassis is changed with time.It is concluded that the transient dynamic analysis can be used to analyze the response of the structure under dynamic loads by compared with the experiment table of load points obtained by the patch spectrum.Finally,the dynamic structural stress method based on the main S-N curve method is applied to the fatigue life evaluation of C70 body structure.The reliability of this method is verified by transient analysis of a typical welded joint.And then select a larger weld from the C70 body as the object of evaluation.According to the dynamic structural stress method,the equivalent stress of each node is calculated from the dynamic analysis and calculate the fatigue life of the weld.