Key Engineering Materials Vol. 887

Abstract: This paper dwells upon finding the specific surface area of cake, a coal enrichment waste, exposed to electroplasma treatment; the goal is to make an organomineral porous material to be used as a sorbent for wastewater treatment. The research team used a monomolecular Langmuir adsorption model and surface tension of the surfactants before and after adsorption at the interface of solution and solid adsorbent. Another process considered herein was thermal activation of substances in the electroplasmic reactor for making organomineral porous materials from coal cakes. The paper presents the resulting specific surfaces area of the organomineral sorbent thus produced. Thus, the waste of flotation, i.e. coal cake, is fundamentally suitable for making porous substances by thermal destruction in an electroplasma reactor.

Abstract: Bending vibrations of a mixed dislocation in ferroelastics near structural phase transition were considered. It was assumed that the dislocation line performs small bending vibrations near equilibrium position. Complete system of equations describing the vibrations of a mixed dislocation near the structural phase transition is written. Based on these set of equations describing the vibrations of a crystal with a dislocation near the structural phase transition, written equations for dynamics of the mixed dislocation in linear approximation of dislocation displacement. Fourier transform of these equations is satisfied. Expression for Peach-Kohler force acting on the dislocation is obtained, and linear response function (generalized susceptibility) of the mixed dislocation in ferroelastics is found.

Abstract: The paper presents the results of the study of fragments of the electric engine rotor shafts of the air-cooled units in order to establish the causes of its destruction. Chemical composition, type of the fracture, macro-and microstructure, as well as the mechanical properties of the metal are studied. Structural and technological factors contributed to the destruction are identified.

Abstract: In this study, a structural-deformation analysis of the process of crack development is performed, on the basis of which an engineering methodology is developed for assessing the endurance limit and resource of large-sized structures. A simple analytical dependence (correlation аналитическая зависимость) was obtained, which allows one to determine the critical size of macrocracks for ferritic-pearlitic steels without using the well-known Griffith formula. The results of calculating the cracks critical lengths of various steels depending on their yield strength are presented. The analytical dependence of the calculation of the fatigue limit for the most dangerous symmetric loading cycle according to the standard set of mechanical characteristics of ferrite-pearlite steel is presented. The obtained results make it possible to calculate the endurance limit of structural elements of marine equipment and other structures subject to cyclic loads

Abstract: The paper discusses the results of mathematical modeling the two-dimensional nonlinear dynamics of heteromodular elastic materials. The resistance of these materials under tension and compression is various. The deformation properties of the heteromodular medium are described within the framework of the isotropic elasticity theory with stress-dependent elastic moduli. In the plane strain case, it is shown that only two types of the nonlinear deformation waves can appear in the heteromodular elastic materials: a plane-polarized quasi-longitudinal wave and a plane-polarized quasi-transverse wave. Basing on obtained properties of the plane shock waves, two plane self-similar boundary value problems are formulated and solved.

Abstract: The problem of uniaxial tension of a hollow cylinder made of a rigid-plastic material is considered. Within the framework of the theory of an ideal rigid-plastic body, this problem has many solutions. Based on the Strain-Energy Criteria of choosing the preferred solution, this problem can be solved unambiguously.

Abstract: It is possible to explain the phenomenon of fatigue destruction and the patterns that are observed only in the deep study of the processes taking place in the material under conditions of repeated-variable loading, i.e. in the development of the physical theory of metal fatigue. Despite the large number of work on this issue, there is currently no single interpretation of the process of fatigue destruction of metals, which is primarily due to the exceptional complexity of the problem. The purpose of the study is to study low-cycle corrosion fatigue of steel using the example of A 414 Grade A steel. The work solved problems, such as research of kinetics of crack development in conditions of low-cycle loading of metal structure made of carbon structural steel A 414 Grade A. Regression analysis has also been applied to predict a change in the thermodynamic stability of the metal during cyclic loading. Analysis of fatigue crack development at alternating loading cycle was carried out. The results of calculations based on the proposed model of elastoplastic deformation near the top of the crack at the sign-alternating loading cycle can be described by non-linear dependence. The regression analysis revealed that the correlation coefficient of the selected model is-0.93, which indicates a relatively strong relationship between the variables. In experimental way it has been proved that reduction of thermodynamic stability of metal in corrosive medium is connected with increase of number of loading cycles, which leads to accumulation of fatigue damages.

Abstract: On the basis of previously accumulated irreversible deformations, and, consequently, residual stresses, the process of removing residual stresses in metal workpieces under the action of low and high temperatures is simulated. Boundary value problems are solved and here are described regularities that are responsible for removing residual stresses for processing modes: high-temperature heating - cooling, high-temperature heating - holding - cooling, low-temperature heating - holding - cooling. The holding stage is modeled, taking into account the creep properties of materials under Norton creep conditions. According to the dependences of the obtained exact solutions, it is shown that it is the holding process that leads to the relaxation of residual stresses.

Abstract: Geometrically non-linear problem of orthotropic thin rectangular panel post-buckling behavior with shear is solved. Deflection function takes all-boundary rigid support conditions into account. Based on derived solution method of smooth panels design which can be used for aircraft structures rib and spar webs optimal parameters is suggested.

Abstract: The use of the nonlinear deformation model in computer calculation methods involves the use of time-consuming step-iteration methods for solving systems of resolving equations with problems of convergence. To eliminate these difficulties, the physical relations of the deformation model are established in finite increments. The article considers the construction of such a model in finite increments as applied to the calculation of the core reinforced-concrete structures in the overall case of oblique bending and oblique eccentric compression or tension, taking into account the action by the cross sections of low subzero temperatures.