Effect of different surface conditions on fatigue properties of 7N01 aluminum alloy and the behavioral mechanism of crack of the alloy under alternating load

Abstract

Abstract In this paper, the surface of 7N01 aluminum alloy profile is sandblasted or electropolished. The influence of different surface conditions on its conditional fatigue strength and fatigue mechanism under the alternating load after prefabricated short crack are studied. Results show that the 7N01 aluminum alloy with sandblasting treatment has formed a work hardened layer and its fatigue strength is increased by 42.9% comparing with the original surface specimens. The fatigue strength of the 7N01 aluminum alloy after electropolishing is almost unchanged compared with the original specimen. The fatigue behavior of the 7N01 aluminum alloy after prefabricated side straight through the notch deviated from the theoretical smooth specimen law and long crack propagation law in which is a ‘shortage effect’. When the notch size is smaller than the transition crack size a0, the fatigue limit of the notched specimen is lower than the fatigue limit of the smooth specimen. When the notch size is larger than the transition crack size, the fatigue limit of the long-notched specimen is still lower than that predicted by linear elastic fracture mechanics. Due to the ‘short notch effect’, the effective notch propagation threshold ΔKeff.th of the long crack is 0.39 Mpa m1/2 based on the effective notch propagation size a0 eff of the alloy.