Research On Fatigue Life Evaluation Method Of Magnalium And Its Application In Train

Magnesium-aluminum alloy is the lightest metal material today,and has been involved in product design as a lightweight material in many fields.The use of magnesium-aluminum alloys in the lightweight design of rail vehicles can significantly reduce the mass of the car body,increase the speed of trains,and reduce operating energy consumption.After the magnesiumaluminum alloy is applied to rail vehicles,the fatigue resistance of the welded structure of magnesium-aluminum alloy is different from that of the commonly used metal materials at this stage.There are few studies on the main structure,which cannot guide the wide application of magnesium-aluminum alloys to rail vehicles.In this article,a rail vehicle body is taken as the research object,and the method of combining theoretical calculation,elastic mechanics principle and numerical simulation is used to study the fatigue life evaluation method of magnesium-aluminum alloy welded structure,and the application of magnesium-aluminum alloy to the rear structure of rail vehicle body.Static strength,stiffness and fatigue strength,the main research results are as follows:First,considering the difference between the fatigue strength of the weld and the base metal,the application range,calculation difficulty and calculation accuracy of various types of working stress at the weld are compared and analyzed,and the work suitable for the fatigue strength assessment of magnesium-aluminum alloy welded structures is obtained.Stress,which is the nominal stress and the equivalent structural stress.Secondly,on the basis of the nominal stress method and the equivalent structural stress method to evaluate the fatigue strength of welded structures,combined with the corresponding IIW standard and the ASME standard in the fitting specification of the fatigue test data of the joint specimens,the typical welded joints of magnesium and aluminum alloys are analyzed.The fatigue resistance S-N curve fitting was performed on the fatigue test data,and the FAT value of the magnesium-aluminum alloy welded joint and the main S-N curve parameters of the magnesium-aluminum alloy welded joint were obtained.The fatigue strength evaluation method of the magnesium-aluminum alloy based on the nominal stress and equivalent structural stress was proposed.Finally,according to the theory of elasticity,the parameters of the car body after the magnesium-aluminum alloy is applied to the lightweight design of the rail vehicle body are calculated.Based on the finite element number theory,a finite element model of the car body with magnesium and aluminum alloys as the main body is established.According to the strength design standard of the vehicle body,the representative evaluation conditions of static strength,stiffness and fatigue strength are selected,and the strength numerical simulation of the vehicle body is carried out.The static strength,stiffness and fatigue strength of the car body are analyzed,and the fatigue strength is evaluated by the nominal stress and the equivalent structural stress respectively for the welded structure of the car body.The calculation results of the car body are compared with the calculation results of the car body using aluminum alloy,and the changes of various strengths of the car body after the application of magnesium aluminum alloy are analyzed,and the advantages and disadvantages of magnesium aluminum alloy applied to the car body are obtained.