Study On Fatigue Characteristics Of Crucirorm Wel Ded Joints Of High Strength Al Uminum All Oy

In the connection of the bogie of the high-speed railway train the crucirorm welded joint of the 7N01 aluminum alloy material is used to study the fatigue fracture and the fatigue fracture.The two stages of expansion are studied,and the fatigue crack initiation and fatigue crack propagation life are calculated by the combination of experiment and finite element method.Through the low cycle fatigue test of 7N01 base metal and weld material,the cyclic strain amplitude-life curve of the base metal and the weld is fitted.Through the analysis of the experimental results,it is found that under the condition that the load level is low and the life is longer The elastic strain has a great influence on the fatigue process of the specimen.The plastic strain has little effect.With the increase of the load,the proportion of plastic strain will increase rapidly.When the load level is high,the plastic strain will be the main And the stress distribution of the cross joint was simulated by finite element method.It was found that the stress concentration position coincided with the crack location in the actual fatigue process,and the stress concentration factor was obtained by obtaining the fatigue failure position.Considering the process of rapid heating and rapid cooling,the relaxation of the residual stress in the welding process is analyzed,and the effect of the asymmetric load on the cyclic stress is discussed.Cyclic strain-strain equation and Neuber hyperbolic equation are used to solve the local strain.After the correction of the cyclic strain-life formula,the fatigue initiation life of the specimen at the toe and the weld is obtained The In this paper,the expression of stress intensity factor of plate edge crack is deduced.The finite element method,membrane stress,bending stress method and nodal force method are used to solve the stress field distribution of the joint of the cross joint The stress intensity factor derived from the weight function is used to calculate the stress field strength factor of the specimen.Through the analysis of the results,it is found that the stress intensity factor of the stress field is more in line with the real result.The stress field strength factor is introduced into the Pairs formula to solve the fatigue life of the specimen.The principle of structural stress method is introduced,and the total fatigue life of the cross joint is solved by using the structural stress method.The total fatigue life of the fatigue joint obtained by the structural stress method,the fatigue initiation life and the fatigue life Life expectancy and the fatigue life of the specimen recorded in the experiment.It is found that the three methods are basically well matched,thus verifying the rationality of the calculation method used.