Abstract
Short crack fatigue growth was studied using a method of plastic replication on specimens of rail steel that were subjected to fully reversed fatigue loading at ambient temperature. Crack lengths were measured from replicas using an optical microscope from which the growth rate could be calculated. Based on the growth data and adopting the Hobson model, a crack growth equation has been derived in an attempt to describe the physically small crack growth behavior. The equation for the crack growth is presented for the form: (da)/(dN)=Ca_s+D where a_s is the surface length of the crack, N the number of cycles, C the function of the total strain range and D is a constant. By obtaining short crack growth data for different stress levels, a quantitative expression of the equation was obtained.
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