Book Description

At room temperature the fatigue strength of high-purity aluminum approaches a lower limiting value in accord with the usual observations on nonferrous metals. But at 250 C its fatigue strength continues to decrease abruptly with increasing cycles of stress without exhibiting any trend toward reaching a limiting value even at 107 cycles. Whereas finer grain-sized specimens exhibit higher fatigue strengths at room temperature, grain size has no effect on the fatigue strength at 250 C. Such insensitivity of the fatigue strength to grain size is undoubtedly due to the fact that both grain sizes yield identical structures consisting of extensively disoriented polygonized subgrains which completely obliterate the original grain size following brief cycling at a given stress at 250 C.