Research On Welds Defect Rate Of Side-wall For Stainless Steel Subway Car

The stainless steel bodies are widely used in the manufacturing of subway cars,because it has high quality,and good security,good corrosion resistance.Stainless steel subway cars generally use resistant spot welding,because it reduces welding deformation.However,Because side walls have many spots and obvious indentations,the deformation agglomerations are easily caused.Therefore,the outward appearance and quality of the vehicle can be affected.The lap laser welding of stainless stell is beginning to replace resistant spot welding with the aim to solve this problem.Due to the limitations of the non-penetration laser lap welding,there will appear to be weld defects on both the inside and outside of the due to incomplete penetration.When the vehicle is running,the weld is easily to damaged.Strength and fatigue resistance of welding parts is important.So not only is the overall strength a concern,but also the strength and durability of the weld must be considered.In short,weld defects and how they affect the structural integrity of the body are worth studying.Taking a stainless steel metro vehicle laser welding vehicle as the research object,the research was mainly on the numerical analysis of strength of laser welding stainless steel body side wall structure under the condition of different degrees of defects exist mainly on joint.Combined with the evaluation of the side wall weld shear stress,the maximum of weld defect rate which ensure the strength and safety of vehicles was determined.The main research contents are as follows:(1)Preparation of the welding laser specimen with different welding defect rate,the tensile shear strength test was done with reference to the relevant standards for laser lap welding specimen with different defect rate.According to the minimum tensile shearing load of the laser welded specimens,the minimum defect was determined.(2)Studying on the methods is carried out to establish finite element model of laser welding car body.According to different welding processes of side wall,the establishment of finite element model for weld defect as well as the processing method for the degree of weld defect was confirmed.The effects of weld defect on the strength of laser welding stainless steel car body were valuated based on the finite element method.(3)The standard of body side wall weld shear strength is determined by the minimum tensile shear load of side wall inner plate material.Through the analysis of car body welding of different weld defect rate under eight shear stress,the rule of the influence of weld defects on the shear strength of weld was obtained.The results showed that as the rate of weld defects grow,stress on car-bodies and shear stress on welds show an upward trend.In the five conditions,shear stress exceeds the shear weld ultimate strength.Based on the calculation of static welds for car-bodies with different weld defect rates and comprehensive analysis calculated from a safety perspective,the maximum tolerance of the laser weld defect rate should not exceed 5%under static loading conditions.