Optimization Study Of Stainless Steel Car Body Laser Welding Structure Based On Fatigue Performance

301L austenitic stainless steel is the main material to manufacture lightweight stainless steel passenger cars. Based on the research about fatigue properties of lap vertical laser welding structure, this paper designs lap tilt laser welding structure. Through the fatigue testing, fatigue fracture analysis, finite element simulation toward welded joints of the combination of 5 kinds of plates, this paper provide theoretical and experimental basis for optimization of fatigue properties of laser welded structures and secure and reliable applications.Research indicates that, if change lap vertical laser welding structure to lap tilt laser welding structure, the fatigue performance of 2mm+2mm andl.5mm+0.8mm plate combinations don’t increase, the study about engineering feasibility need to be continued; while the performance of 1.5mm+1.5mm,1.5mm+2mm and 0.8mm+2mm increase significantly and can be applied in engineering. When changed to tilt welding, the fatigue fracture mode of lap tilt laser welding structure do not change significantly, all fractures happen in outer plate loading end wear plate near welded joints. Specially, the fatigue of 1.5mm+1.5mm happen in outer and inner plate loading end wear plate near welded joints.Fatigue fracture analysis studies show that, for plates combinations with good fatigue performance, fatigue main crack first go through the welding structure then the plate structure, and finally facture when extending. While for vertical welding structure, it only goes through the plate structure, but not touch the welding structure. Plus, that the expansion degree of plate structure is greater than that of welding structure, we conclude that the fatigue resistance of welding structure is better than that of plate structure. Otherwise, the tensile strength and fracture ductility of the tilt welding joint are also improvedABAQUS finite element analysis indicates that, the most dangerous area of fatigue loading (with greatest stress) matches the actual fatigue sample fractures. But There are differences in the direction of crack propagation. Combined with the effect of improving fatigue properties, the fatigue crack extends near the end of the outer plate weld load, due to the existence the welding structure, the fatigue resistance performance improved. This optimization is achieved by lap tilt laser welding structure.