An alternative method of decreasing ΔK FCGR testing

Abstract

The conventional technique of decreasing ΔK FCGR testing often presents experimental difficulties in terms of the length of crack that must be accommodated and the time required to reach low values of ΔK. Addressing these issues, an alternative method of conducting such tests has been proposed. A relation according to which ΔK must be decreased has been derived assuming that the monotonic plastic zone size can be decreased at a constant rate with increase in crack length without adversely affecting the integrity of the FCGR data. Through experimental assessment of the alternative method and examination of crack closure effects, such an asumption has been vindicated. It has been shown that this method is particularly suitable for high strength materials and that it provides great advantages when conducting FCGR tests at low frequencies. The employment of the method for obtaining threshold regime corrosion fatigue crack growth data has been demonstrated for HSLA steels.