Effects of expanded and non-expanded hole on the delay of arresting crack propagation for aluminum alloys

The purpose of this paper is to study the effects of inserting an expanded hole or a non-expanded hole at the tip of a fatigue crack on the subsequent delay of fatigue crack propagation. Single edge pre-cracked specimens of t wo aluminum alloys were used to perform the crack arresting tests under cyc lic stress loading. An obvious increase in the delay of crack propagation i s obtained for the specimens with expanded hole. The compressive residual s tresses produced by the hole expansion process play an important role in in creasing the fatigue resistance of the material. The observation of micro-s tructure at the fatigue failure section reveals that the hole expansion pro cess modifies the condition and properties of the surface layer of material s and affects, significantly the length of the nucleation stage of the fati gue process. (C) 2000 Elsevier Science S.A. All rights reserved.