Experimental determination of the stress intensity factor for a part-through thickness crack

Based on the relationship between the stress intensity factor and the plastic zone size at the crack tip, an experimental method for the evaluation of the stress intensity factor for a part-through thickness crack is proposed. Approximating the geometrical shape of the crack to a semi-elliptical surface crack, an empirical K-expression for the surface crack in a plate under bend loading configuration is derived and verified experimentally where the new K-expression contains both crack depth and length as a crack tip singularity parameter. The experimental work makes use of newly developed etching techniques to reveal the plastic zone size in deformed A533B pressure vessel steel.