Peculiarities of Short Fatigue Crack Growth from a Blind Hole in Specimens Made of Steel 45. Part 2. Model of Short Fatigue Crack Growth from a Notch

A model to describe the kinetics of short fatigue crack growth from an obtuse stress raiser (notch) is proposed. The model makes it possible to calculate the kinetic diagram of short fatigue crack growth rate from a stress raiser and to estimate the number of loading cycles from the moment of crack initiation up to the moment when the crack reaches the specified size at a constant range of applied nominal stresses. Apart from the loading parameters and geometrical dimensions of the stress raiser, the input data for calculations are the static strength characteristics (elastic modulus, Poisson’s ratio, and yield stress, which are determined from short-term tensile tests on standard specimens of the material) and microstructural characteristics (grain size, Taylor factor, and Buergers vector, which are determined from microstructural analysis of the initial material). Calculations according to the proposed model of kinetic curve of crack growth rate and number of loading cycles during its growth for tested 45 grade steel specimens exhibited a good agreement with the experimental results.