To the computation of the fatigue life of prismatic bars under uniaxial asymmetric bending

Abstract

An alternative approach to solving the fatigue life computing problems for material samples and structural elements under uniaxial asymmetric cyclic loading has been considered. This approach is based on the concept of equivalent stresses, which allows the asymmetric load cycle to be reduced to the equivalent symmetric cycle for the number of fracture cycles. The structure of equivalent stresses is obtained based on the hypothesis of the existence of single isochronous ultimate stress diagrams, which are invariant with respect to the number of cycles to fracture. As basic experiments, to determine the material constants in the original equations, easily reproducible standard tests of smooth samples of the material for short-term strength and fatigue under symmetric and asymmetric bending load cycles are used. Problems of multicycle fatigue analysis of prismatic rods under uniaxial asymmetric bending, considering the influence of mean stress, stress range, and amplitude coefficient, have been solved. Satisfactory agreement of calculation results with experimental data was obtained.