A method is presented for assessment of effects of main plastic factors – reversed plastic yielding of the material and plasticity-induced crack closure – on small fatigue crack behavior. The method uses the closed form analytical solution of the elastic-plastic problem for a rectilinear crack in a plate on the basis of plasticstrip model. This allowed to simplify significantly the calculation of the stress-strain parameters at the crack tip (the effective stress intensity factor range and crack tip opening displacement range). It was shown that the calculated results agree well with those obtained by the more complicated methods, including a method of finite elements. Using the proposed method, the dependence of the small crack growth rate on the loading amplitude and stress ratio, initial crack size and other parameters, has been analyzed. The revealed regularities and tendencies are proved experimentally. In particular, the method is successfully utilized to predict the small fatigue crack growth rate in Fe-3% Si alloy under high amplitude loading.
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