State-of-the-art review on extended stress intensity factor concepts

The stress intensity factor concept for describing the stress field at pointed crack or slit tips is well known from fracture mechanics. It has been substantially extended since Williams' basic contribution (1952) on stress fields at angular corners. One extension refers to pointed V-notches with stress intensities depending on the notch opening angle. The loading-mode-related simple notch stress intensity factors K-1, K-2 and K-3 are introduced. Another extension refers to rounded notches with crack shape or V-notch shape in two variants: parabolic, elliptic or hyperbolic notches (blunt notches') on the one hand and root hole notches (keyholes' when considering crack shapes) on the other hand. Here, the loading-mode-related generalised notch stress intensity factors K-1, K-2 and K-3 are defined. The concepts of elastic stress intensity factor, notch stress intensity factor and generalised notch stress intensity factor are extended into the range of elastic-plastic (work-hardening) or perfectly plastic notch tip or notch root behaviour. Here, the plastic notch stress intensity factors K-1p, K-2p and K-3p are of relevance. The elastic notch stress intensity factors are used to describe the fatigue strength of fillet-welded attachment joints. The fracture toughness of brittle materials may also be evaluated on this basis. The plastic notch stress intensity factors characterise the stress and strain field at pointed V-notch tips. A new version of the Neuber rule accounting for the influence of the notch opening angle is presented.