The Behavior of Fatigue Cracks in Pure Iron Subjected to Rotary Bending and Cyclic Torsion : 1st Report, Stress-Concentration Factor and Fatigue-Notch Factor due to Fatigue Cracks

Abstract

In order to examine the behavior of fatigue cracks in pure iron subjected to rotary bending and cyclic torsion, the copper electroplating method of stress analysis and slip phenomena in the material was applied. The charge in metal properties caused by fatigue cracks had no effect on the propagating stress of cracks. The difference of the fatigue-notch factor between bending and torsion was due to that of both the strain-concentration factor and the strain gradient at crack tips. It was found that in torsion the fatigue cracks propagated when the cyclic shear stress over one grain reached cracks depended on the tensile stress exerted over more than one grain size.