Papers by Keyword: Elastic Interaction

Abstract: The solution behavior of oxygen atom in Nb-Cr alloys was investigated by employing the density-functional theory. The solution behavior mainly depends on two factors, namely, the elastic and chemical interactions. We proposed a method to separate these two parts and applied it in Nb-Cr-O system to investigate the effect of alloying Cr concentration on the solution behavior of interstitial oxygen atoms. This method can be useful for understanding and predicting the solution behavior in ternary alloys which contain interstitial elements.

Abstract: With the development of the contemporary industry, a need arises in the production of high - strength steels that can withstand heavy loads and work in harsh conditions. Industrial equipment (in particular, a hot-rolling mill) is subject to high loads that are close to critical. Therefore, the issues related to the development and applications of methods aimed at reducing of energy consumption during rolling are being solved before the product output. One of the efficient ways to reduce energy-power parameters of the process is the use of the rolling lubrication feed systems (RLFS) in the production of hot-rolled products. Accordingly, it is necessary to consider the method of supplying lubricating material (LM), its quantity, shared contact surfaces nature. Currently, one of the significant drawbacks in the RLFS is the lack of correlation between the quantity of fed LM and properties of the rolled material. As a result, RLFS are used in a restricted mode, and power consumption reduction is not significant: 3-6%.

Abstract: The solution of boundary-value problem in mechanics of polycrystalline materials is represented as perturbation series upon intergrains interaction like it is made in quantum fields theory. The terms of this series satisfy the infinite set of integral equations that reduced to systems of linear algebraic equations if to neglect the heterogeneities of strains within domain of individual grain. The method allows to take into account a microstructure of materials. Few examples of method application are demonstrated.

Abstract: The proposed dislocation model describes the orientation dependence of the critical resolved shear stress (CRSS) and deformation mechanisms on the yield point in single crystals of austenitic stainless steel with nitrogen impurities. The model takes into account the following: the change of the interstitial atom position in the lattice from octahedral interstice to tetrahedral site owing to passage of a leading Shockley’s partial dislocation; the change in the separation width between two partial dislocation in external stress field; the relationship between the width of the extended dislocation and the elastic interaction of the extended dislocation with the impurity atoms.

Abstract: We have elucidated the elastic interaction between the 90° domains and misfit dislocations in PbTiO₃/SrTiO₃ (001) epitaxial thin films by the local strain mapping based on high-resolution transmission electron microscopy. The novel mechanism of the nucleation and growth of 90 ̊ domain has been proposed based on the results, including the introduction of the additional dislocation perpendicular to the misfit dislocation and the dissociation of these dislocations into two pairs of partial dislocations with an anti-phase boundary.

Abstract: Disc-rotor is composed of certain number of discs which are fastened as a single-shaft rotor by tie-rods. The rods must be very carefully tensioned in the course of rotor assembly to ensure a circumferentially uniform prestress, thus acceptable run-out value, as otherwise the rotor will be susceptible to vibrations particularly during start-up. Uniform prestress is also beneficial to improve the fatigue life of the rods. Initial preload for one rod is calculated and the appropriate tightening scheme is determined by finite element analysis, considering relaxation and elastic interaction. A kind of hydraulic tensioner is designed to assemble the disc-rotor. The experiment to fasten the disc-rotor by the tightening scheme above mentioned is presented.

Abstract: We present the linear stability analysis for the epitaxial thin film growth on the vicinal surface of strained Si and the growth mode diagrams of the epitaxial growth under various operation conditions. Competition between step-step elastic interactions and the asymmetry of incorporation of adatoms from the terraces to step edge is considered. Force monopoles at steps and their interaction lead to it on the vicinal surface while kinetic asymmetry of the adatom incorporation at steps due to Ehrlich-Schwoebel barrier prevents the step bunching instability. Growth mode on the vicinal surface is determined by the competition between elastic step-step interactions and Ehrlich-Schwoebel barrier.

Abstract: The H(D) atom’s interaction with one another, ‘heavy’ interstitial atoms (O, N, C), and substitutional atoms is analyzed on the basis of strain-induced (elastic) interaction. The interaction energies are calculated for bcc, fcc, and hcp metal solid solutions with regard to the discrete atomic structure of the host lattice. The elastic constants, Born-von Karman constants of the host lattice, and concentration expansion coefficients of the solid solution lattice due to solute atoms, are used as the parameters for numerical input. It is shown that the interaction is long-range, oscillating, and anisotropic. In all cases, the coordination shells of both types - with attraction and with repulsion - exist. The interaction energy dependence on the distance is due mainly to the crystal lattice type. The strain-induced interaction should be supplemented by repulsion in the nearest coordination shells for the case of interstitial-interstitial interaction and by chemical interaction in the case of H-substitutional interaction. Two examples are given for the use of the strain-induced interaction energies in calculations relaxation processes.

Abstract: The morphological changes and the coarsening kinetics of B2 particles in A2 matrix in the elastically constrained Fe-16at%Al-18at%Co alloy were investigated by means of transmission electron microscopy (TEM). The mean particle radius increases in proportion to the cube root of ageing time at early stage, then the coarsening of B2 particle decelerate at late stage of aging. And it clarified the decelerated coarsening in Fe based alloy also is related to the change in PSD and is caused by the elastically strained effect.