Enhanced model of partial crack closure for correlation of R-ratio effects in aluminum alloys

In this paper, an enhancement of Donald and Parisʹ partial crack closure model is proposed. The enhancement is based on the argument that an apparent effectiveness of the crack closure phenomenon is dependent upon Kmax and the crack tip opening profile. A transition function is used in order to evolve from Donald and Parisʹ partial crack closure model at the near-threshold region to the conventional Elberʹs closure approach at the Paris region. The model correlates fairly well the R-ratio effects on fatigue crack growth rate at low and intermediate stress intensities for aluminum alloys.