Kinetics of the power exponent of material cyclic hardening in view of the forms of cycles of high-temperature low cycle loading

It is noted that experimental and computation studies of kinetics of stresses and strains and properties of materials are an essential principle for working out and application of criteria of cyclic fracture, and also for carrying out of the refineded computations of structures parts on low cycle strength. Improvement and evolution of these methods in the direction of the accounting of factors of various service conditions, including forms of the loading cycles influencing on characteristics of hardening or softening of material is based on establishment of patterns of relationship of change of basic parameters of the state equations describing a kinetics of local cyclic elastic- plastic strains depending on parameters of service cycles of a loading. At the same time the relation between stresses and strains at a cyclic loading outside elasticity is characterized by diagrams of a cyclic elastoplastic deformation in the parameter of number of half-cycles (cycles) of a loading. The greatest distribution for the description of diagrams of a cyclic deformation outside elasticity in established practices was gained by their power approximation which key parameter is the module of cyclic hardening — an exponent of power dependence between relative values of cyclic stresses and strains in a cycle. For the choice of basic parameters of the state equations in this case along with characteristics of stress-strain states the data on mechanical properties of materials received at their short-term and long static and cyclic tests are initial. The analysis of the obtained computation and experimental data shows that consideration and establishment of patterns of relationship of a kinetics of the cyclic hardening module in relation to the diagrams of a cyclic elastoplastic deformation of austenitic stainless steel received experimentally in a wide range of temperatures and parameters of a deformation allows to characterize its kinetics in view of forms of cycles of a loading including effect both hardening, and softening of material owing to action of high-frequency strain at the two-frequency mode of a loading with the level of cyclic stresses, equal with the single-frequency forms of a cycle.

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