Effects of Controlling Direction in Strain Cycling Fatigue of A 5083 P-O Aluminum Alloy

Abstract

Strain cycling fatigue tests were carried out of an A 5083 P-O aluminum alloy in order to investigate the effects of the anisotropic ductility on the low cycle fatigue properties. The hour-glass shaped specimen was used for the diametral strain controlled and completely reversed strain cycling tests. The diametral, total natural strain amplitude was controlled in the short transverse direction in one test series, while in the long transverse direction in the other test series. Considerable difference was observed between the test results on both test series, showing that the low cycle fatigue strength in the short transverse controlled condition is much higher than that in the long transverse controlled condition. By taking the experimental result that the ratio of Poisson's ratio in the long transverse direction to that in the short transverse direction was 0.52 into consideration, the diametral strain amplitude in each test series was reduced to the longitudinal total strain amplitude _??_ta, which was expressed as a function of the visible crack initiation life N, as follows : _??_ta=0.176 Nc-0.661+0.00773Nc-0.11 The Nc is related closely to the failure life Nf with an equation : Nc=0.654 Nf1.032