The effect of the amplitude of the first compression cycle on crack growth from notches under far-field cyclic compression was discussed in Section 14.13.1. Speculate about the effects of the following loading patterns on mode I fatigue crack growth from notches under cyclic compression:
(a) The fatigue crack is propagated ahead of a stress concentration under a constant amplitude of imposed cyclic compressive loads. The cracks arrest naturally after advancing a distance of ten times the notch-tip radius. At this point, the notched specimen is subjected to a 100% compressive overload. Will the application of the compressive overload result in the reinitiation of the crack? Why?
(b) The same situation as in the previous problem, except that the distance of total crack growth under constant amplitude cyclic compression is one-half of the notch-tip radius (instead of ten times the notch-tip radius). At this point, the notched specimen is subjected to a 100% compressive overload. Will the application of the compressive overload result in the reinitiation of the crack? If so, is the extent of crack growth following the overload greater than or less than that in part (a)? Explain.