Ya. S. Matychak, V. S. Pavlyna, and V. M. Fedirko UI~539.2 Within the framework of continuum mechanics, we investigate the interdependent processes of strain and diffusion. By solving a wide class of initial-value and boundary-value problems concerning a physicomechanical state of elastic and viscoelastic bodies, we establish kinetic regularities of the interaction of structural and functional materials with working and technological media. We propose approaches to the calculation of residual stresses under conditions of multicomponent diffusion, phase transformations, and chemical reactions. We emphasize the importance of a consistent and rigorous consideration of properties of structural materials for the construction of their physicomathematical models. Tendencies and prospects of the development of investigations in this direction are evaluated.The problem of the interconnection of diffusion and mechanical processes is somewhat unusual for continuum mechanics. On the one hand, we observe discrete motions of individual atoms or ions and, on the other hand, strain and fracture of a body as a continuous medium. At first sight, these processes as objects under investigation relate to different fields of solid-state physics and can be considered independently (to some extent) of one another. Numerous available theoretical and experimental results enable one to make a versatile consideration of diffusion and mechanical processes in view of their interdependence and interconditionality.Pidstryhach laid the foundations of principles and methods for the construction and development of models of continuum mechanics which involve diffusion processes [1][2][3]. Later, these ideas were developed by his disciples. In particular, Burak generalized certain model representations concerning the interdependence of the processes of strain, heat conduction, electric conduction, and diffusion [4,5], Shevchuk investigated mechanical and diffusion processes in inhomogeneous structures [6,7], and Shvets' studied the processes of strain, heat conduction, and onecomponent diffusion in thin-walled elements [8].In the present paper, we attempt to establish methodological features of the union of physicochemical and mechanical phenomena in a theoretical simulation, to describe some regularities of changes in the properties of structural materials caused by interaction with the environment at high temperatures in the process of treatment of these materials and their service, and to show possible ways for the construction of models of deformable materials for the prediction of their behavior and, in perspective, for the development of elements of high-temperature physicochemical mechanics of materials. General StatementsMaterials of parts of modem machines, devices, and instruments are subjected to the action of various mechanical loadings, elevated temperatures, corrosive media, etc., both in the process of their production and under service conditions. It is natural that their properties (in particular, strength, deformability, and, wh...

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The phenomenological theory for describing high-temperature interaction between metal and diluted gaseous medium has been developed. The theory is based on the assumption of duplex contact layer existence in the vicinity of interface (with relative thickness 2 d), where chemical reactions and processes of gas component migration occur. The non-stationary conditions of mass transfer at the interface are described involving effective average parameters. These conditions allow considering a wide spectrum of boundary diffusion phenomena (in a short and prolonged time ranges), in order to describe the kinetics of accumulation of diffusing component close to the interface. The description of the kinetic of gaseous saturation of metal (nitriding and borating) in the diluted medium becomes a partial proof of the suggested models. In order to approach the diffusion phenomena, boundary conditions, which contain, besides the coordinate derivative of concentration function, also the time derivative, were suggested. The derived equations describe the time dependence of change of surface concentration of gaseous component, the kinetics of its accumulation owing to chemical reaction, the specimen mass change owing to both, the diffusive addition dissolution in metal and its chemical interaction. The role of temperature is also discussed.

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