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Fatigue tests have been carried out on mild steel specimens containing edge cracks of various lengths and the alternating stress just insufficient to cause the cracks to grow obtained. It was found that the relation between this critical alternating stress σ and the crack length l was given by σ 3 l = constant. By means of this relation it was possible to correlate a wide variety of hitherto unrelated notch fatigue data.
Nancy Frost (Mon,) studied this question.