Laws of the accumulation of fatigue damage in steels St. 45 and 1Kh13 under the influence of programmed variable loads

Abstract

1. The fatigue strength characteristics of steels St. 45 and 1Kh13 and the kinetics of the variation in cyclic inelastic strains of these materials were investigated; it was shown that the stabilized value of the inelastic strain per cycle is a measure of the intensity of the accumulation of fatigue damage under constant loading conditions. 2. A method based on taking into account inelastic strains was developed for determining the endurance of a specimen at various stress levels without testing it to fracture. 3. It was shown that the deviation of experimental data from the linear hypothesis of the summation of fatigue damage is attributable, firstly, to the disparity between the endurance of an individual specimen and the endurance determined from the averaged fatigue curve and, secondly, to the inherently nonlinear character of the accumulation of fatigue damage in a material under programmed loading conditions. 4. The accumulation of fatigue damage under programmed loading conditions can be characterized in terms of the inelastic cyclic strains. 5. A formula taking account of factors discussed in the item No. 3 of these conclusions and describing the accumulation of fatigue damage in metals was derived.