Fatigue lifetime model under a complex loading with application of the amalgamating safety indices rule
S. Belodedenko, V. Hanush, Oleksii Hrechanyі
Abstract
The problem of multiaxial fatigue is considered from the standpoint of amalgamating indicators of system reliability. The lifetime model is derived from the rule of amalgamating resource indices of safety. The load is represented as a combination of individual subprocesses of simple types of deformation with their amplitudes and stress ratio. A model of lifetime in multiaxial fatigue has been developed, which takes into account the parameters of the deformation cycle shape, the type of process (in-phase, disproportionate, constant static stress). The possibility is confirmed for obtaining the parameters of the model of multiaxial fatigue when tested for three-point bending under conditions of variation of the multiplicity of span. According to this scheme, fatigue tests were performed for prismatic steel samples 09G2 and 40Н. The fatigue resistance parameters were found for them, and also there were found the ratio of the fatigue limit for tangential stresses and the fatigue limit for normal bending stresses, which is equal to 0.385.