Ductile crack growth emanating from Sharp Notes in a low Alloy Steel

Stable crack growth behavior emanating from a sharp notch is investigated. Material chosen for tests was EN 34 NiCrMo6 low alloy steel (akin to 4340/4330). Tests were carried out on CT specimens for various angles and ratios to obtain load vs, load-line displacement, Ρ-ΔLL, curves. Experimental results were analyzed. A normalization approach of Ρ-ΔLL curves has been attempted and all experimental curves were represented as a single characteristic curve. Such approach has been also applied on experimental data available from other experimental investigations and results were encouraging, as it may address transferability issue. Fracture surfaces were also examined; crack-front tunneling was obtained using dye penetrant technique to determine extent of stable crack growth. Tests on various notch sizes were also carried out and show that despite more than ten folds increase in notch radius, the maximum load increase recorded for CT was not more than 15%