Description of short fatigue crack growth in a shot-peened medium carbon steel

A probabilistic and simplified approach to the description of short crack growth in shot-peened, medium carbon steel specimens is presented. In order to model the dynamics of short crack growth, a difference equation has been formulated with coefficients originating from a two-parameter Weibull distribution of crack advance. The Fokker-Planck partial differential equation is the source of a solution based on the form of a probability density function of crack length. The resolved function allows one to calculate the expected crack length, crack growth rate and standard deviation of crack length. The viability of the probabilistic method has been verified using experimental data gained for shot-peened specimens fatigued under reversed torsion.