Theory of rate of growth of fatigue cracks under combined static and cyclic stresses

An equation is derived that describes the rate of growth of fatigue cracks under combined static and cyclic stresses. The equation predicts that a static tensile stress has very little influence on the rate of growth of fatigue cracks, even if the static stress is very much larger than the amplitude of the cyclic stress, unless the maximum total applied stress is comparable to the (static) fracture stress.