Study On Fatigue Fracture Mechanism Of Non-Penetrating Laser Welding

Austenitic stainless steel 301L series of sheet metal is used to manufacture lightweight main material,which has good mechanical properties and corrosion resistance.When the train speed of 250km or more,by the spot welding of the body because of its poor sealing characteristics are no longer meet the needs.Non-penetration laser welding not only meet the strength and safety requirements,but also has good air tightness and surface finish.In this paper,through the fatigue test,the fracture mode analysis,stress intensity factor calculation and stress analysis method,the 0.8mm+1.5mm,0.8mm+2.0mm,1.5mm+1.5mm and 2.0mm+2.0mm these four different The fatigue properties and fatigue fracture mechanism of the plate combination are studied,and the scheme of optimizing the fatigue performance of the sheet is put forward.The results show that the fatigue failure mode and the fatigue crack propagation path have a great influence on the fatigue performance of the specimen.When the fatigue fracture pattern is the same,the different plate combinations with the same thickness of the external wall board have similar fatigue properties.When the external wall thickness And the S-N curve of the combination of different plates is similar or the same when the fatigue fracture pattern is the same.The calculation of the stress intensity factor of the specimen shows that the stress intensity factor is the reason of the fatigue fracture model.And the logarithm of the equivalent stress intensity factor has a good linear relationship with the logarithm of the fatigue life of the specimen,and the fatigue life of the specimen can be predicted according to the equivalent stress intensity factor.The fatigue crack initiation phase is the main part of the fatigue life of the specimen by the local stress intensity factor calculation.The stress analysis of the specimen shows that the fatigue fracture occurs at the stress concentration,and the stress concentration is the main cause of the fatigue damage.For the same plate combination,the greater the maximum stress concentration,the smaller the fatigue life.The change of the thickness of the inner plate is the main reason for the stress distribution and the change of the size.