The Fatigue Life Analysis With FEM On Welded Body Of The Freight Car

Heavy-duty,fast and multimodal transport plays an important role in China's transportation sector and plays an extremely important role in the development of the "Belt and Road" railway construction.On the other hand,fatigue fracture of railway welded car body is always an important technical issue affecting the safety of railway transportation.In this paper,the C70 welded structure car body is taken as the research object,and the fatigue life finite element analysis is carried out.The research proposes a finite element modeling method that can reasonably take into account the details of the welded joints,and more accurately and reasonably evaluate the fatigue life of the welded car body.The research results can guide the fatigue strength design of the railway truck welding car body and the prevention of fatigue damage accidents.At the same time,it also provides reference for the study of the finite element evaluation method for the welding body of railway wagons and even the fatigue life of welded structures.The main research contents are as follows:1.Based on the main parameters and structure of C70 car body,the finite element model of car body structure is established by using HyperMesh finite element pre-processing software according to AAR standard.The ABAQUS finite element software is used to analyze the structural strength of static load conditions,coupler tensioning conditions,coupler compression conditions,torsion conditions and roll conditions,and the boundary between the upper and middle beams of the bolster is determined.The main stress concentration areas are determined,such as the junction area between the upper cover plate and the middle beam of the pillow beam,the junction area between the front cover plate and the middle beam,the junction area between the lower cover plate and the middle beam of the pillow beam,and the junction area between the upper cover plate and the web plate of the cross beam.2.According to China's "Code for Design and Test Identification of Railway Vehicles",the finite element analysis of the finite element model of the vehicle body structure is carried out.On this basis,the maximum principal stress of each stress concentration part is extracted according to the AAR standard,and the fatigue stress amplitude is calculated and determined.Comparing the results under the two standards,it is concluded that the portion with the largest fatigue stress is generated at the junction of the front plate and the middle beam.3.Based on the results of structural strength analysis,fatigue life of fillet weld 6 mm high finite element model,fillet weld 12 mm high finite element model and finite element model without considering welded joints are analyzed by dangerous point stress method and nominal stress method.The results show that the influence of the weld joint details should be considered in the finite element modeling process.4.The fatigue life of fillet weld with 6 mm height,12 mm height and finite element model without considering the effect of average stress are higher than that of the fatigue life with the effect of average stress.When evaluating fatigue life,it is more reasonable to consider the average stress component in random load.5.Based on the finite element model with a fillet weld height of 6 mm,the equivalent structural stress method,the dangerous point stress method and the nominal stress method are used to evaluate the fatigue life of the modified fillet weld height 6 mm finite element model.The fatigue life results were compared with the railway truck segment repair standards.The results show that the equivalent structural stress method is conservative and the nominal stress method is dangerous,while the dangerous point stress method considering the details of welded joints is more reasonable.