Study On Prediction Method Of Crack Propagation Life Of New Welded Siding Under Residual Stress

With the new welding technology in the aircraft fuselage wall structure of the increasingly widespread use of welding machine wall structure carrying capacity of a higher demand,in which fatigue failure affect the bearing capacity of the main factors,especially after welding residual stress on the components Fatigue life.The test method can accurately reflect the residual state and fatigue performance of welding components,but the factors are many,the test cycle is long and the repeatability is bad.Numerical simulation of welding residual stress by numerical method is of great significance to the application and development of new welding technology.In this paper,friction stir welding and laser welding of 2060-T8 Al-Li alloy plate are studied in this paper.Through theoretical analysis,Abaqus finite element simulation and experimental comparison,the fatigue crack propagation characteristics of welding components under residual stress are studied.A method for predicting crack propagation life is proposed.The crack is perpendicular to the central crack of the weld.In the presence of residual stress,a new stress intensity factor,(35)Keff,is defined according to the mechanical response of the crack tip to the linear elastic fracture mechanics.The crack propagation rate is estimated by the improved Walker formula.Comparison between the extended finite element method and the static fracture mechanics model shows that the theoretical value of the strength factor agrees with that of the finite element simulation in the presence of residual stress.The error between(35)Keffand experiment is less than 5%.The experimental data are compared with the fatigue data obtained by using the predictive method.It is found that the error of prediction is larger in the initial expansion and rapid expansion phase of the crack,and in the steady expansion phase The correlation between predicted curve and fitting curve is r = 89.7%.The method proposed in this paper is applicable to the prediction of the crackpropagation life of welding wall.The numerical simulation of the known residual stress field using the pre-defined temperature field method,the simulation results and experimental results error of less than 2.2%.The residual stress redistribution rule is the maximum value of the residual tensile stress along the crack propagation direction.The effects of residual stress on stress ratio and crack growth rate are studied.The effect of the stress ratio on the expansion rate is reduced.The results show that the fatigue life of friction stir welding components is larger than that of laser welding components,which is in accordance with the experimental results.The finite element method is used to analyze the fixture of the test fixture,and then the fixture suitable for the test is obtained.After the fatigue test,the fixture can meet the requirement of the experiment.