Effect of single tensile overload on fatigue crack growth behavior based on plastically dissipated energy and critical distance theory

The paper systematically investigates the fatigue crack growth (FCG) behavior of Q345 steel under a single tensile overload during constant amplitude cyclic loadings by combining the experimental, numerical and theoretical methods. Compact tension specimens are applied to explore the retardation effect of FCG rate after the overload application. A predictive technique based on plastically dissipated energy method, critical distance theory and node-release technology is developed to characterize the FCG behavior following the overload. Crack opening displacement and crack opening load level along the crack flank are obtained to explore the effect of overload on plasticity-induced crack closure. Additionally, the stress-strain response at critical distance and compressive residual stress field ahead of crack-tip are further explored to reveal the intrinsic mechanism and accumulative damage. Results show that the magnitude of residual stretched material wedge and value of maximal crack opening load level increase obviously with the increasing of overload; discontinuous closure takes place behind and before plastic wedge at overload location, which limits the stress/strain ranges at crack-tip and thereby retards crack growth. The magnitude of compressive residual stress and size of stress field ahead of crack-tip increase with increasing overload ratio, which aggravates the retardation effect after overload.