Strength of structural elements with cracks

Abstract

Abstract In almost every detail, despite careful control at all stages of production, there may be cracks. The reasons for their occurrence can be very different, including the shape and size of the part, the conditions and nature of loading, the nature of the environment, defects of a crystal lattice, the possible presence of non-metallic inclusions adverse forms, structure and grain size, depending on the technology upstream processing, fatigue, etc. The reliability of the equipment is determined by the correct choice of material and taking into account the operating conditions, including the level and nature of loading. The paper provides a comparative review of the main approaches for selecting strength criteria for structural elements with cracks. The energy and power strength criteria are considered. The energy criterion of A. A. Griffiths considered a perfectly brittle material without taking into account the plasticity reserve of real metal materials. The force criterion allows us to estimate the value of the stress taking into account the critical moment of loading, at which unstable destruction begins due to the reserve of elastic energy. It is shown that the transition of steel from a plastic state to a brittle one is influenced by the test temperature, the type and speed of deformation, and changes in the chemical composition and mode of heat treatment. Thus, when choosing a certain strength criterion, you should take into account the operating conditions and the degree of responsibility of the structure.