Elastic–plastic finite element analysis and experimental study of short and long fatigue crack growth

Abstract

A detailed elastic–plastic finite element analysis of cracks under mode I loading is presented under both small- and large-scale yielding conditions. Five centre-cracked panel specimens with different crack lengths are analysed. The size of the crack tip plastic zone, the crack opening profile and the plastic strain distribution in front of the crack tip for short (0.1 mm) and for longer cracks (0.2, 0.4, 1 and 2 mm) have been studied. The analysis shows that the crack tip plastic zone size, crack tip plastic strain and crack tip opening displacements are larger for a short crack than for longer cracks at the same nominal stress intensity factor. Experimental study of both the short and long fatigue crack growths for an ultra-fine grain aluminium alloy IN9052 has also been performed. The experimental results show that the short fatigue cracks propagate faster than the long fatigue cracks under the same stress intensity factor ranges. However, if the short and long fatigue crack growth rates are correlated by the plastic zone size, the short and long fatigue crack growth rates fall in the same band.