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In a previous study, Newman's modified strip-yield model which estimates the plasticity-induced crack closure was modified to estimate the crack growth behavior in a residual stress field. The results showed that the model gave good predictions when compared with experimental data reported in literature. However, it was also found that the model failed to predict Glinka's experimental data. In the current study, this difficulty was explained by the unusual crack growth behavior in Glinka's specimens which were made of 18G2AV steel, that is, the crack closure concept cannot be used to explain the crack growth behavior in 18G2AV steel at various load ratios. Hence, it was assured that the modified strip-yield model can be used for the residual stress problems. In addition, it was found that the crack growth behavior in an overload or a notch plastic zone can be solved by treating the crack growth in a way that the crack propagates in the residual stress field caused by the overload or the notch plasticity. This approach successfully captured the crack growth behavior in these pre-existing plastic zones, and the phenomenon that the measured overload affected distance in thin plates being much larger than the overload plastic zone size could be possibly explained by the residual stresses induced by the overload plasticity.
crack growth behavior, residual stresses, crack closure, overload, notches, modified strip-yield model
Visiting scholar, State Key Laboratory of Fatigue and Fracture of Materials, Institute of Metal Research, Shenyang,
Associate professor, National Cheng Kung University, Tainan,