Abstract
In order to examine the behaviour of fatigue cracks in carbon steel subjected to rotary bending and cyclic torsion, both the technique utilizing slip-initiation phenomenon in the material and the copper electroplating method of stress analysis are applied. Based on the above results, the fatigue-notch factor of cracked specimens is compared with the stress-concentration factor at crack tip. It is found that more accurate results can be obtained by the slip-initiation technique than by the electroplating method, if the measuring region at the crack tip is identical. The change in metal properties caused by the formation of fatigue cracks has no effect on the crack propagating stress in pure iron, but it affects notably the crack propagating stress in eutectoid steel.
