1986 Volume 35 Issue 394 Pages 785-790
In this paper the model of crack closure is developed to analyse the experimental results of the previous report.
The plasticity induced crack closure is simulated by leaving residual stretch in the wake of the advancing crack tip, and the roughness induced or the oxide induced crack closure is modeled by the debris whose thickness is assumed to be constant along the crack surface. The method of analysis used here is the extended body force method.
It is shown by the present model that the effective stress range ratio Uop(=1-σop/σmax) or Ucl(=1-σcl/σmax) of fatigue crack in the stabilized state is mainly controlled by the Kmax (when stress ratio R is constant) and that the reversed crack tip opening displacement can be expressed unifyingly by the effective stress intensity range ΔKeffop(=Kmax-Koq) or ΔKeffcl(=Kmax-Kcl), independently of the loading history and the stress ratio. These are in good agreement with the experimental results of the previous report. Moreover, the transitional behavior of the crack closure observed in the experiment of the previous report, when load is changed, can be illustrated as well by this model.