The Influence Of Cracks Around Rivet Roles On Mechanical Property Of Aluminum Sheets

Due to pre-damage,outer loading and other reasons,there will be multi-site damage(MSD)on outer skin of aircrafts,and the existence of MSD will decrease structural fatigue life and residual stress,which may result in catastrophic damage.The influence of MSD on mechanical performance of 2024 aluminum sheet is studied by combination of digital image correlation(DIC)and fatigue tests.Firstly,the influence on fatigue performance is studied by combination of DIC and fatigue tests.In order to make sure the accuracy of DIC analysis result,the accuracy control on DIC method was studied based on orthogonal test.By analyzing and summarizing the orthogonal results,the optimal combination of those four factors is proposed.Secondly,based on fatigue test,2024-T4 specimens are subjected to cyclic flight spectrum,the fatigue life and strain information can be obtained from DIC results.According to results,the influence of hole spacing and intercrack angle on fatigue life,the crack propagation path and the damage theory are analyzed.In addition,the numerical results of fatigue life and residual stress are calculated by combining ABAQUS and Paris fomula,and two other crack configurations are calculated and analyzed based on this method.From the result,we can conclude that the fatigue life of MSD will increase with the increase of hole spacing and the fatigue life of specimen with non-collinear cracks is larger than that with collinear cracks.Finally,based on tensile tests and DIC,the influence on residual stress is discussed.the influence of hole spacing and intercrack angle on residual stress is analyzed.The numerical residual stress is computed based on net-section yield criterion and plastic zone connection criterion,results are compared with experimental results.Furthermore,by the help of ABAQUS,the one with a large error is modified,two other crack configurations are calculated and analyzed based on this method.The result also indicates that the residual stress of MSD will increase with the increase of hole spacing and the residual stress of specimen with non-collinear cracks is larger than that with collinear cracks,which is coincident with the trend of fatigue life.