On the Frost–Dugdale plot for non‐propagating cracks

The Frost–Dugdale plot is re‐examined and the subject of the non‐propagation of fatigue cracks is updated to emphasize that fatigue crack closure is the principal factor responsible for the non‐propagation of fatigue cracks which originate at notches. The limitations of the original Frost–Dugdale plot with respect to notch depth are also discussed.