This review is a brief survey of three‐dimensional effects at cracks and sharp notches. The overall aim is to review developments over the past 50 years leading up to the current state of the art. The review is restricted to linear elastic, homogeneous, isotropic materials, with any yielding confined to a small region at a crack or notch tip. It is also restricted to static loading and to constant amplitude fatigue loading. An enormous amount of theoretical and experimental information relevant to three‐dimensional effects has been published in the past five decades, so the review is, of necessity, highly selective. Theoretical topics covered are linear elastic fracture mechanics, including Volterra distorsioni, stress intensity factors, corner point singularities, crack front line tension, displacement analysis of cracks and notches, and through thickness distributions of stresses and stress intensity factors. Crack path topics covered are fatigue crack path constraints, determination of fatigue crack paths, oscillating crack fronts in thin sheets and the transition to slant crack propagation in thin sheets. Plane strain fracture toughness testing, including standards, is covered. Overall, it can be concluded that the existence of three‐dimensional effects at cracks and sharp notches has been known for many years, but understanding has been limited, and for some situations still is. Understanding improved when the existence of corner point singularities and their implications became known. Increasingly powerful computers made it possible to investigate three‐dimensional effects numerically in detail. Despite increased understanding, three‐dimensional effects are sometimes ignored in situations where they may be important.

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a b s t r a c tThe existence of three-dimensional effects at cracks has been known for many years, but understanding has been limited, and for some situations still is. Despite increased understanding, three-dimensional effects are sometimes ignored in situations where they may be important. The purpose of the present investigation is to study a coupled fracture mode generated by a nominal anti-plane (Mode III) loading applied to linear elastic plates weakened by a straight through-the-thickness crack. With this aim accurate 3D finite element (FE) analyses have been performed. The results obtained from the highly accurate finite element models have improved understanding of the behaviour of through cracked plates under anti-plane loading. The influence of plate bending is increasingly important as plate thickness decreases. It appears that a new field parameter, probably a singularity, is needed to describe the stresses at the plate surfaces. Discussion on whether K III tends to zero or infinity as a corner point is approached is futile because K III is meaningless at a corner point. Calculation of the strain energy density (SED) in a control volume at the crack tip allows us to predict the most critical point through the plate thickness.

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