Effects of characteristic parameters of corrosion pits on the fatigue life of the steel wires

To study the influence of corrosion pits on fatigue life of high-strength steel wire, 69 cable steel wires with different characteristic parameters of pits were obtained by manual prefabrication. The effects of pit depth, width, location and stress amplitude on the fatigue life of steel wires were investigated through the fatigue test. Then, the prediction model of fatigue life of steel wire with corrosion pits was established. Finally, 236 finite element models (FEM) of steel wire with corrosion pits were established by the software ANSYS and nCode designLife, and the S-N curves of steel wires with different sizes of pit and stress ratios were also analyzed. The results showed that the fatigue life of steel wire decreased significantly when the depth of pit was in the range of 0.2-0.6 mm, with a maximum reduction of 99.25%. The slight change of stress amplitude would result in the fatigue life by several times or even ten times. The superposition effect of pits would slightly increase the fatigue life of steel wire. In addition, when the stress ratio increased from -1 to 0.44, the S-N curve of steel wire with 0.16 of depth-width ratio of pits would move down more than twice than that of steel wire with 0.75 of depth-width ratio of pits. For finite life design, the fatigue life of steel wire changed from high cyde fatigue to low cycle fatigue with the increase of depth-width ratio of pits. When the depth-width ratio was >1, the corresponding stress amplitude was not affected by the pit sizes under the same fatigue life. The effect of stress ratio on wide-shallow pits was greater than that on deep-narrow pits. (C) 2019 Elsevier Ltd. All rights reserved.