Model of fatigue crack propagation rate based on crack tip opening displacement as the driving parameter

Abstract

To investigate the model of fatigue crack growth rate da/dN based on crack tip opening displacement (CTOD) as the driving parameter, the variation ranges [Formula: see text] by linear elastic fracture mechanics and [Formula: see text] by geometric principle of CTOD were deduced. The fitting relationships of [Formula: see text] and [Formula: see text] were attained through da/dN experiment by taking 17Cr16Ni2 stainless steel, and their discrepancies were compared. The results showed that at the early and middle periods, the relationships of [Formula: see text] and [Formula: see text] could be expressed by Paris law, and da/dN driven by [Formula: see text] was faster than that by [Formula: see text] notably; at the later period, the experimental data of [Formula: see text] and [Formula: see text] deviated from the fitted Paris curves and were above them with being crossed with each other; in the total variation range of CTOD, it was better to fit the relationships of [Formula: see text] and [Formula: see text] by polynomial method rather than Paris law.