Effects of Hole Expansion Strengthening on Fatigue Properties of 7050 Aluminum Alloy Hole Structure
In order to investigate the effect of hole expansion strengthening of split mandrel with different relative expansion amounts on the fatigue properties of 7050 aluminum alloy,a finite element model of hole expansion strengthening of split mandrel was established,and hole expansion strengthening of split mandrel experimental was carried out.The residual stress on the hole wall of the hole expansion strengthening specimen and the distribution law of the stress on the hole wall of the loaded specimen were analyzed.In addition,the relationship among relative expansion amount,residual stress and fatigue life were explored.Finally,the fatigue resistance effect of hole expansion strengthening of split mandrel was revealed.The results show that when the relative expansion amount is 2％,3％,and 4％,the maximum residual compressive stress of the hole wall is 246.8,338.6,and 367.7 MPa at the inlet area of the hole wall of the specimen,respectively.The relative expansion amount is positively correlated with the maximum residual compressive stress of the hole wall.In inlet area of the hole wall of the loaded specimen,when the relative expansion amount is 2％,3％,and 4％,the maximum stress of the hole wall is 451.2,368.7,and 321.6 MPa,respectively;the relative expansion amount is negatively correlated with the maximum stress of the hole wall.The median fatigue life of specimens with relative expansion amount of 2％,3％,and 4％is 1.17,1.52,and 1.71 times of that of the specimens with relative expansion amount of 0,respectively.
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