An Anticipativelncrease of Endurance Limit in SteeI Subjected to Sequentia1 Repeats of Various Understresses

An experimental and analytical investigation was undertaken to study the coaxing effect in a low-carbon steel specimen during and after repeated loading of various understresses in the order of their magnitude. Based on a fatigue energy concept covering its transition and convergence，indexes were derived to calculate and predict the enhanced endurance limit of the material of which the understressed career was known. The understress ratio and the sequence of the repeated stress magnitude were taken as the parameters. The mode of fracture and the macrocopic hardness of thus fractured specimen，not only revealed that the energy model postulated at the start was of considerable probability，but also suggested that a macroscopic fatigue criterion led from this experiment could reflect some microscopic or super-microscopic behaviors of the tested specimen，above an just prior to the fracture. While it is widely insisted that a material-steel in this case，hough一steel in this case, though-cannot show a behavior around what are called fatigue phenomena，other than that， more or less influenced by the past it experienced，as heat treatment，nitriding or machining， a positive step to materialize the raise of the endurance limit characterized in this paper， may be recommendablere to the up-to-date manufacture and usage of machines and structures dashing for all the more severer designing or service conditions