Papers by Keyword: Bulk Modulus

Abstract: In order to theoretically estimate the bulk modulus of granular composite materials (concretes: consisting of a binder and fine and coarse aggregates), the proposed model of the representative unit cell of a 3-phase concrete (with spherical gravel inclusion) is replaced by two 2-phase models: sand mortar (binder + sand) and concrete (mortar + gravel). The research paper substantiates the transition from the use of the Voigt – Reuss "fork" formulas (two models of 2-phase composites) to the generalized Voigt – Reuss "fork" formulas in cell models of 3-phase composites. A numerical and graphical analysis of the generalized formulas is made using the example of one of the possible subsets of 3-phase concretes. The graphic images of the Voigt – Reuss "forks" (of the analyzed subset of 3-phase composites) are characterized by their greater diversity in comparison with traditional images (in 2-phase composites). In this work, to choose out from the multitudes of possible compositions (3-phase composite) of the studied subset of 2-phase composites the authors employ and recommend for practical use the multistep dichotomy method.

Abstract: Nowadays there is a growing need to reduce or control wear, corrosion and fatigue in order to extend the lifetime of mechanical parts, to make engines and devices more efficient, to develop new advanced products, to conserve material resources, to save energy and to improve the safety. The surface properties of mechanical parts may be improved through Duplex treatments. A Duplex treatment is a sequence of two treatments, combining their advantages and leading to better surface properties. A Duplex treatment consisting in nitriding and work hardening through shot peening has been chosen as a solution for improving the properties of EN 34CrNiMo6 alloyed steel. This paper reports the results obtained for hardness and bulk modulus on treated and untreated samples. The samples were examined using a Dynamic Ultra Micro Hardness (DUH) tester under a set of maximum loads ranging from 100 to 1000 mN. Each sample was subjected to load-unload cycle under the same amount of maximum load and the loads vs. penetration depth curves were plotted. Results showed a better mechanical behavior of Duplex treated.

Abstract: To work out effective damping materials it is necessary to perfect analytical dependences linking dynamic properties of a composite with its structure-forming parameters. The analytical model of the particulate-filled polymers, based on the method of strain energy, convenient for engineering use and allowing to predict damping properties of a composite more reliable is given in this article. The detailed leading-out of formulas for scaling of a bulk modulus and loss factor of both two-phase and three-phase model of a composite is presented. Comparison of numerical values of damping characteristics under the derived formulas with experimental researches show that the offered model allows not only to show a qualitative pattern of dependence of dynamic behavior of a composite from degree of admission, but also to receive comprehensible quantitative results.

Abstract: This paper describes a methodology based on “Bidirectional Evolutionary Structural Optimization” (BESO) for topological design of microstructures of materials with more than two constituent phases. The composite material is made by repeating microstructures known as periodic base cells. The aim is to achieve appropriate topology of microstructure phases that enhances the material’s bulk or thermal conductivity performance in macro-scale. Constituent phases are divided into some groups and by performing finite element analyses on microstructure, sensitivity numbers are calculated with the application of Homogenization theory. Properties of elements are gradually changed in the finite element model based on their sensitivity numbers and controlling volume of each constituent phase in the model. Some sample microstructures are generated and presented to show the capability of the approach. The results indicate that the proposed approach is very cost efficient. Moreover, there are distinctive boundaries between the constituent phases in the generated microstructures; which is an inherent advantage of application of BESO approach.

Abstract: Intermetallic compounds are innovative materials and are far superior to conventional metals and alloys. These intermetallic compounds have a great potential in industrial and technological fields because most of the intermetallic compounds are stronger as well asstiffer at elevated temperature and provide far better corrosion resistance than conventional metals and alloys.Over the past few years the scientific interest in the study of these intermetallic compounds emanates greatly because of their high-tech applications. Our motivation of the present studyMgTl mainly consernedon the physical data generation in context with its possible vast applications .We used a theoretical approach within the local density approximation method to study the structural and electronic properties of MgTl by calculating total energy. As far as our calculations are concerned, the band structure shows the overlapping of conduction and valence band thus itis clear that MgTl in its pure form is a good conductor of heat and electricity and falls in the category of metals. We have also calculated lattice parameters, bulkmodules, first order derivative electronic and lattice heat coefficient and Debye temperature.

Abstract: In the present work, we have investigated total energy, bulk modulus, elastic constants, pressure derivatives of elastic constants and pressure derivative of bulk modulus of HgX (X=S, Se and Te) semiconducting compounds using higher-order perturbation scheme with the application of our own proposed model potential. To consider exchange and correlation effect to the dielectric function, the local-field correction function proposed by Farid et al is employed in the present study. In most of the cases the experimental and other theoretical results of the aforesaid physical properties of the HgX are not available in the literature and hence this study provides a better set of theoretical results of the physical properties of the materials for future comparison either with theoretical or experimental results.

Abstract: The electronic structures, densities of states and Fermi surfaces of ErX (X = Cu, Ag and Au) intermetallic compounds are studied using full potential linear augmented plane wave (FP-LAPW) method within generalized gradient approximation (GGA) for the exchange-correlation functional. The total energies are computed as a function of volume and fitted to the Birch equation of state. The ground state properties such as equilibrium lattice constants (a₀), bulk modulus (B) and pressure derivative of bulk modulus (B') and density of states at the Fermi level N (E_F) are calculated. The states at the Fermi level (E_F) are dominated by Er ‘d’ states with significant contribution of ‘p’ and ‘d’ states of X. We have also plotted charge density and Fermi surface to study the bonding properties of ErX compounds.

Abstract: A series of Tm-doped zinc borotellurite glass have been extracted by conventional melt-quenching method. The density was measured and it had been found that the value is increased by the increment of Tm³⁺ ion. The elastic properties of the sample were determined by measuring longitudinal and shear velocities using an ultrasound technique. Then the values inserted into equations that calculate the elastic moduli of the glass samples. These include longitudinal, shear, bulk, Young’s modulus and also the Poisson’s ratio. The longitudinal and shear velocities show an increment as Tm³⁺ increases from 0.01 to 0.03 mol content. The trend then changes as Tm³⁺ increases from 0.03 to 0.05 mol content. In terms of elastic moduli, it produces a rapid increment with Tm³⁺ until 0.03 mol content. But after that, the increment becomes slow until 0.05 mol of Tm³⁺. The value of Poisson’s ratio decreases with the addition of Tm³⁺ concentration.

Abstract: This paper obtains the formula for calculating fuel dynamic viscosity based on the Barus formula and Eying formula from both macroscopic and microscopic perspectives, studies the mathematical model of fuel bulk modulus changing with temperature and pressure based on equation of state for gases and solids, and computes the fitting formula and correlation coefficients of dynamic viscosity and bulk modulus based on IFO 180 test data. The result indicates that the calculation models for fuel dynamic viscosity and bulk modulus are effective.

Abstract: High pressure (HP) fuel pipeline is one of the vital components of Combination Electronic Unit Pump (CEUP) fuel injection system besides pump and injector. Effect of four key fuel properties including density, viscosity, acoustic wave speed and bulk modulus on pressure wave profile has been investigated using a 1D viscous damped mathematical model. Wave equation (WE) based mathematical model has been developed in MATLAB using finite difference method. Dynamic variations of these fuel properties during fuel injection cycles have also been incorporated in mathematical model by utilizing empirical formulas. The results show that these four key fuel properties not only vary with the pressure during fuel injection process but also define the trend of pressure wave propagation inside HP fuel pipeline.