Factors relevant to fatigue strength of eutectoid steel wires

The factors relevant to the fatigue strength of cold-drawn eutectoid steel wires were examined. Results were summarized as follows: The fatigue limit of eutectoid steel wires increased with drawing strain (Ε = 2lndo/d), where do and d are diameters before and after drawing) until about 2.5, and then decreased. In the case of ferritic steel wires, however, the fatigue limit was almost constant, while the fatigue life increased with drawing strain. The fatigue limit increased with decrease of specimen diameter. The interlamellar spacing did not influence the fatigue limit. With an increase of drawing strain, the ratio of the period of crack initiation and initial propagation to the fatigue life increased. This ratio in eutectoid steel with larger drawing strain was high as compared with that in farritic steel.