Fatigue Analysis Method And Application For High-speed Train Body Spot Welding Structure

Nowadays,with the improvement of the performance requirements of the rail vehicles,the designers try to make the vehicle run faster with less weight and longer fatigue life.The existing railway body is divided into three types:ordinary carbon steel body,aluminum alloy car body and stainless steel car body.Stainless steel body with strong corrosion resistance,high strength,light weight,but also high temperature resistant,strong flame-retardant,free coating,less maintenance,and low total life cycle cost,is widely used in the railway industry at home and abroad.But confined to the limitation of processing technology and aesthetic requirements,stainless steel car body sheets mainly rely on the spot welding.Under the premise of satisfying the strength requirement,the fatigue performance of spot welding structure becomes more and more important.So the solution of improving the fatigue life of the welded structure is an urgent problem to be solved.Based on the above background,this thesis mainly studies the following aspects:First of all,this paper introduces the domestic and foreign stainless steel car body development and spot welding structure fatigue research both at home and abroad,analyzes the difference and application range of spot welding,plug welding and arc welding.The advantages and disadvantages of stainless steel car body connected by spot welding are also studied.Secondly,the fatigue theories and methods of various spot welded structures are researched.The advantages and disadvantages of various methods of fatigue assessment are studied by using different methods to evaluate the fatigue life of spot welded structures.In view of the same material and the geometry of tensile shear specimens and coach peel specimens,respectively,five kinds of fatigue analysis method:Nominal stress method,LBF method,LMS method,main S-N curve method,main S-N curve method and LBF method combining method,are used to assess the fatigue life of spot welding specimens.What is more,according to the experimental results,it is found that the main S-N curve method and LBF method combining method has the advantages of both modeling efficiency and accuracy.Finally,take a high speed train stainless steel spot welding of car body for example,main S-N curve method and LBF method combining method are used to analyze eight selected areas of the solder joint fatigue life assessment.The evaluation results show that the fatigue life of the minimum value is 2.13×107 times,in line with the design requirements of the stainless steel body in terms of fatigue life.