Fatigue Property of Hard Drawn Steel Wire under Double Repeated Bending Stress in Two Stress Levels

Abstract

The present writers have investigated about the property of fatigue damage of hard drawn steel wire and the fatigue property under double repeated bending stress in two stress levels. For the testing materials, 0.6% carbon steel wires drawn with three reductions of 25%, 50% and 85% were used and their diameters were 2.5mm.
The principal results of this investigation can be summarized as follows:
(1) When the 10% over primary stress is loaded to lower cycles than the maximum cycle of no fatigue damage n_d, the fatigue limits of wires drawn with reductions of 50% and 85% increase slightly. And when that primary stress is loaded to higher cycles than n_d, the fatigue limits of all wires decrease and those decrements decrease with the increase of the reduction by drawing.
(2) When the 10% over primary stress is loaded to lower cycles than n_d, the cumulative cycle ratio Σ(n/N) exceeds unity in both cases of secondary stress is larger and smaller than primary stress. And when that primary stress is loaded to higher cycles than n_d, the cumulative cycle ratio exceeds unity or nearly equals unity.
(3) When the 50% under primary stress is loaded to 10⁶ or 10⁷ cycles, the fatigue limits of all wires increase slightly and those increments increase with the increase of the reduction by drawing.