Fracture analysis of surface- and through-cracked sheets and plates

The Neuber stress-concentration relation for notches in an elastic-plastic material subjected to shear loading was generalized for a crack in a finite plate subjected to tensile loading, similar to the way in which Kuhn modified the Hardrath-Ohman notch equation for a cracked plate. An equation was derived which related the linear elastic stress-intensity factor, the applied stress, and two material parameters. The equation was then used as a two-parameter fracture criterion for surface- and through-cracked specimens. Fracture data from the literature on surface- and through-cracked sheet and plate specimens of steel, titanium alloy, titanium weldment, and aluminum alloy tested at room and cryogenic temperature were analyzed according to the proposed equation. For surface cracks, wide ranges of crack-depth to crack-length ratio and crack-depth to specimen-thickness ratio were considered. For through cracks, wide ranges of crack length and specimen width were also considered. An empirical equation for the elastic magnification factors on stress intensity for a surface crack in a finite-thickness plate was also developed. The fracture stress predictions computed from the two-parameter fracture criterion for both surface- and through-cracked sheet and plate specimens are consistent with experimental failure stresses.