Relation between Low Cycle Fatigue Life and Fracture Ductility in Various Aluminium Alloys.

Abstract

In this paper, the relation between low cycle fatigue life and fracture ductility was investigated in various aluminium alloys. Low cycle fatigue tests were carried out using cylindrical specimens, and the propagation of small cracks were measured and observed. As a result, it was clear that there was no consistent relation between low cycle fatigue life and fracture ductility. In materials with large fracture ductility, fracture ductility can be considered as low cycle fatigue which has fracture at N=1/4, and fatigue life can be estimated from fracture ductility. However, in materials with small fracture ductility, experimental fatigue life is larger than estimated one from fracture ductility. In materials with large fracture ductility, the cause of decrease of experimental fatigue life is that the crack growth rate is accelerated by the connection of each crack in the early stage of fatigue life.