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Tbilisi, Georgia

Kecskes L.,U.S. Army | Butler B.,U.S. Army | Oniashvili G.,Tavadze Institute of Metallurgy and Materials Science | Aslamazishvili Z.,Tavadze Institute of Metallurgy and Materials Science | And 2 more authors.
Materials and Manufacturing Processes | Year: 2011

Bi- and trilayer composites of titanium aluminides (Ti-Al) and substoichiometric titanium boride (TiB0.6) have been fabricated from green compacts placed under pressure. Ti-Al blends with ratios of 3:1, 1:1, or 1:3 have been prepared by ball milling. Subsequent to the preparation of the precursor blends, plate-shaped green compacts of Ti-Al and Ti-B0.6 were pressed at room temperature. Green compacts were stacked in a layered geometry and were heated rapidly under a static pressure of about 10bar. After the temperature reached 1300-1400°C, the Ti-Al and TiB0.6 phases were synthesized by the conversion of the reactants into the product phases (also known as "thermal explosion" processing) and simultaneously consolidated and joined under a pressure of 80-100bar. Scanning electron microscopy (SEM) examination showed that the Ti-Al layer was highly heterogeneous, and the extent of heterogeneity depended strongly on the respective elemental ratio of Ti to Al. Furthermore, the conversion from reactants to products was found to be determined by the overall heat available during the thermal explosion processing step. Unlike the Ti-Al, the TiB 0.6 layer was more uniform; however, the combination of heat and pressure was found to be insufficient to fully densify the aluminide layer. These and other features of the layered intermetallic structures will be discussed. Copyright © Taylor & Francis Group, LLC. Source

Groppen V.O.,Mining Institute of Georgia
International Journal of Mathematics and Computers in Simulation | Year: 2011

Proposed approach is based on the idea of variability of measurement standards. This approach permits us to predict some features of the Universe: spontaneous growth of distance between two resting objects detected by an observer at one of these objects, velocity/distance dependence is known to meet the Hubble Law, constancy of any solid body linear dimensions in time and equality of absolute values of gravitational braking and of illusive acceleration of galaxies is believed to be caused by linear measurement standard shortening some 6-8 billion years ago, as well as by mass loss by physical objects. The latter permits us to propose simulators, describing gravity and inertia as different manifestations of reaction forces. Source

Japaridze L.,Mining Institute of Georgia
Journal of Rock Mechanics and Geotechnical Engineering | Year: 2015

In this study, the interaction between cylindrical specimen made of homogeneous, isotropic, and linearly elastic material and loading jaws of any curvature is considered in the Brazilian test. It is assumed that the specimen is diametrically compressed by elliptic normal contact stresses. The frictional contact stresses between the specimen and platens are neglected. The analytical solution starts from the contact problem of the loading jaws of any curvature and cylindrical specimen. The contact width, corresponding loading angle (2θ0), and elliptical stresses obtained through solution of the contact problems are used as boundary conditions for a cylindrical specimen. The problem of the theory of elasticity for a cylinder is solved using Muskhelishvili's method. In this method, the displacements and stresses are represented in terms of two analytical functions of a complex variable. In the main approaches, the nonlinear interaction between the loading bearing blocks and the specimen as well as the curvature of their surfaces and the elastic parameters of their materials are taken into account. Numerical examples are solved using MATLAB to demonstrate the influence of deformability, curvature of the specimen and platens on the distribution of the normal contact stresses as well as on the tensile and compressive stresses acting across the loaded diameter. Derived equations also allow calculating the modulus of elasticity, total deformation modulus and creep parameters of the specimen material based on the experimental data of radial contraction of the specimen. © 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Source

Chikhradze N.,Georgian Technical University | Chikhradze N.,Mining Institute of Georgia | Abashidze G.,Mining Institute of Georgia | Pkhaladze G.,Mining Institute of Georgia
International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM | Year: 2014

With the advent of 21-st century the intensive investigations carried out all over the world for preparation of technical purpose fibers of new type. Among them is basalt fiber which may be considered as an alternative of glass fiber. Basalt fiber is distinguished from glass one by improved physical-mechanical characteristics, especially by elasticity module, enhanced heat resistance and stability against various aggressive media. Taking into consideration the fact that the technology of preparation of basalt fiber is not much different from the technology of preparation of glass fiber and their cost is the same order, the technologies of preparation of the products from basalt fiber occupy a highly important place in advanced industrially developed countries. There are large resources of basalt raw material in Georgia. In presented work the characteristics of basalt rocks of three deposits (Marneuli, Tetritskaro, Bolnisi) are given as well as such properties of obtained melt as viscosity and crystallization ability, the conditions of fiber formation, fiber physical-chemical and mechanical characteristics, including short-term resistance and long-term strength at tension. © SGEM2014. Source

Chikhradze N.M.,Georgian Technical University | Chikhradze N.M.,Mining Institute of Georgia | Marquis F.D.S.,Naval Postgraduate School, Monterey | Abashidze G.S.,Mining Institute of Georgia | Kurdadze L.,Mining Institute of Georgia
JOM | Year: 2013

The theoretical design and the experimental design and development of multifunctional radiation-absorbing composite material systems based on gadolinium, boron, tungsten has been carried out. Based on theoretical calculations, the effective compositions of these composite subsystems were established for the enhanced absorption of neutron and γ irradiation in various energy spectra. In addition, the systems and systems compositions were designed and processed for enhanced multifunctional performance. Selected and optimized compositions of Gd-B-W system were densified by shock wave consolidation technology. The technological parameters for the explosive consolidation processes and the structure-properties relationships are presented and discussed. The radiation-absorbing properties of the bulk samples were investigated and measured under neutron and gamma irradiation. The theoretical design and the optimization of these composite systems were carried out by the Monte Carlo method with a GEANT 3 program, which contained a special GCALOR package for the simulation of the interaction of thermal and fast neutrons with the composite material systems. During the neutron passage through the samples, the main processes of the interaction of neutrons with matter were considered including elastic and inelastic scattering, neutron fission of nuclei, radiation capture. The attenuation factor of the irradiation flux is determined as a criterion of efficiency of radiation absorption. For the energy of 0.025 eV (thermal neutrons), gadolinium-containing composites have the maximum absorption capability. In the range of energy spectrum from 1 eV to 10 eV, the boron-containing composites have better absorption performance. For the capture of neutrons in wide energy spectrum, the (n, γ) reaction takes place and tungsten provides enhanced absorption of radiation. In the presence of mixed radiation sources (neutron and γ quanta), the boron- and gadolinium-containing composite materials prepared on the tungsten basis have the best performance. In addition to enhanced radiation absorption properties, these composite systems show also enhancement on other properties such as corrosion resistance in aggressive media. © 2013 TMS. Source

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