Analysis of circular cross-section element, loaded by static and cyclic elastic–plastic pure bending

Abstract

Data of theoretical and experimental investigation of a circular cross-section element subjected to monotonic and cyclic elastic–plastic pure bending is presented in the paper. Linear approximation of monotonic and cyclic tension–compression curves was applied, what allowed to simplify analysis and to obtain satisfactory conformance of theoretical data with experimental results. Grade 45 structural steel specimens were subjected to low cycle stress or strain-controlled reversed tension–compression and cyclic pure bending. In case of strain-controlled loading low cycle fatigue life curves for both loading models (tension–compression and bending) coincide. In case of stress-controlled bending elastically deformed internal fibers of the element impede the plastic–strain accumulation in the external fibers, and in such a way decrease the quasi-static damage accumulation, and increase the lifetime. In this research specimens lifetime was calculated by use of fatigue damage fraction and quasi-static damage fraction summation rule. The damage calculations allowed to establish the increase of fatigue life at stress-controlled low cycle bending.