Study On Fatigue Properties Of Laser Welded Joint With Penetrating Vertical Weld

With the development of the times,the transportation system formed by high-speed rail vehicles has become the lifeblood of social progress and national economy.The convenience it brings also gradually enters the hearts of the people and is accepted and respected by everyone.In recent years,China's progress in the design and production of high-speed passenger cars is extremely rapid.Not only does it have a fully independent property rights,it also exports a number of countries and regions to the outside world,giving a boost to the country's economic growth.When the demand for rail passenger vehicles continues to increase,we must consider factors such as lightweight body material,higher welding strength of the body,and stronger carrying capacity.Therefore,it is urgent to solve problems such as improving the welding strength of laser welding,anti-fatigue strength,and researching new type of laser welding to replace the old spot welding.In this paper,the fatigue properties of the new penetration type vertical weld laser welded joints are further explored.Through welding different sizes of laser welded joints,we study the relationship between their corresponding fatigue properties and fracture mechanisms,and summary laser welding fatigue fracture mode.Through the ABAQUS simulation,we get the fracture form and fatigue strength corresponding to the plate strength and the different thickness,and finally achieve the purpose of optimizing the fatigue properties of the laser welding structure.In this paper,AISI301LN-1/4H stainless steel plate is selected as the USA standard.Plate type combination is 0.6mm+1.0mm penetration type vertical seam laser welding structure.At present,the research on the stainless steel laser welding of vehicle body is mainly reflected in the optimization of parameters of the laser welding process of the horizontal weld.However,there are only a few the related research on vertical weld laser welding.We have done a series of inductive research on vertical seam stainless steel laser welding.The details are as follows:(1)According to the mechanical properties of AISI301LN-1/4H series stainless steel sheet,tensile tests of 30 mm single vertical weld,30 mm double vertical weld and 15 mm double vertical weld specimen are carried out.We obtained force displacement curves,and compared the differences between tensile strength,fracture plasticity and structural differences.(2)According to the static tensile load,fatigue tests of three specimens are carried out,and the fatigue limit of different welding modes is obtained.We obtain the corresponding data to draw the median S-N curve and divide the high and low cycle fatigue life,and Compare differences in fatigue performance between different specimens.(3)We study the fatigue properties of test specimens from the perspective of specimen material and weld microstructure.Using scanning electron microscopy,metallographic microscopy,and other observational methods,the crack initiation sites,fatigue fracture locations,crack initiation,etc.of AISI301 LN sheet material were analyzed from the microscopic level,and the fracture mechanism was studied.(4)Useing ABAQUS and other software for modeling and modeling,we build a vertical weld laser welding model,simulate the tensile test of the model and verify the reliability of the simulation model.A comparative analysis of experimental phenomena is combined with the observation of the stress distribution of lap welding tissue during fatigue loading.It can provide reference for the actual body design application.