Fatigue damage accumulation in cold-drawn patented steel wire under variable loading

In this work cumulative fatigue damage characteristics of patented steel wire has been studied in the form of stepped loading and block loading under tension–tension load control condition. The experimental results were modeled utilizing three commonly used fatigue damage accumulation rules namely linear damage rule, double linear damage rule and damage curve approach. The results obtained showed that among these three damage accumulation rules damage curve approach gives the best agreement with the experimental results. Although double linear damage rule reveals better results under stepped loading condition, nevertheless under block loading the results are not promising. The linear damage approach gives acceptable results only under block loading, however damage curve approach is more reliable in either stepped loading and block loading. Fractography examinations revealed unusual oblique fracture surface seemingly due to inhomogeneous deformation pattern of pearlite colonies in the cold-drawn patented steel wires.