Criteria for Crack Branching in Cylindrical Rods: I, Tension

The angular and radial dependencies of the mirror‐mist boundaries predicted by the stress intensity and Johnson and Holloway (JH) criteria were compared with experimentally determined shapes of the boundaries in cylindrical specimens fractured in tension. At the front surface, for relative mirror radii up to at least 0.2, boundary correction factors based on a recently available finite‐element analysis provided the best predictions, showing among other things that the so‐called mirror constant is a variable. In this size range, the stress intensity criterion provided better predictions of the boundary shapes than the Johnson and Holloway criterion. For large relative mirror sizes, neither the JH criterion nor the stress intensity criterion assuming semicircular cracks provided accurate predictions.