The effect of temperature on the stress range diagram is discussed and the particular characteristics of the curves for unnotched and notched specimens are analyzed. Excluding metallurgical factors from consideration, it is suggested that relaxation is the principal mechanism which influences the behavior of polycrystalline metals under combined alternating and static stress. Two parallel nonlinear Maxwell units are used to represent the relaxation mechanism at elevated temperature. An analysis of this model shows that relaxation occurs to an asymptotic finite value of stress which is a function of the initial stress. The same model is applied for representing the behavior in the stress range diagram with the assumption that a linear relationship exists at low temperature between the fatigue strength and the normal stress acting on the planes of reversed slip.

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