A PLASTIC FLOW-INDUCED FRACTURE THEORY FOR FATIGUE-CRACK GROWTH

A plastic flow-induced fracture theory for fatigue crack growth is pre sented. A new formulae for the fatigue stress intensity threshold and the fatigue crack growth rate law are derived by applying the principl e of energy conservation in considering the fatigue crack growth proce ss in the presence of local plastic flow ahead of the crack-tip. The p resent theory predicts not only the fatigue crack growth rate being ju st proportional to the rate of creation of dislocation at the crack-ti p, but also the fatigue stress intensity threshold, which can be deter mined according to the applied fatigue stress amplitude and the charac teristic size of microstructural fracture process ahead of the crack-t ip, and can account for the fatigue crack growth characteristics at bo th low and high levels of applied fatigue stress intensity amplitude. All the results are universal and agree with the existing empirical re sults and experimental observations.