Papers by Keyword: Elastic Constant

Abstract: The main transportation pipelines are subjected to complex stresses resulting from the nature and state of the transported material, the operating conditions, and the environmental factors and so on. Thus, the stress in the pipe wall is generated and influenced by the pressure, the temperature and the mass of the transported fluid, by the weight of the pipe, the ambient temperature and in certain periods of time by the wind speed. In this paper are presented dynamic phenomena generated by wind flow and their effect on the magistrate transportation pipelines. The content of the paper presents an detailed analysis regarding the regimes in which is developing the force generated by Karman vortex and the situation when resonance phenomena are developed. The study presents a mathematical model that describes the dynamic phenomena generated by the wind action, determining the mathematical expression of the aerodynamic force that act on the normal direction to the wind speed. This force is having a periodic variation, its size and the frequency variation is dependent on the wind speed. Some methods are proposed in order to decrease the wind influence on the lifetime of transportation pipelines. The main results of the study are: determination of the speed range for which the dynamic phenomena have a high influence on the pipeline lifetime; determination of the real conditions that can lead to sharp rises of the pipe deformations; determination of the pipeline lifetime reduction under development of dynamic loads.

Abstract: India is veritable emporium of medicinal and aromatic trees. It has been estimated those trees occurring in India are commonly useful. Adansonia Digitata AnD is useful for different purpose like in bio- medical, chemical industries etc. The study of elastic behaviour of a solid is very important in fundamental and technical research. Strength and stiffness assessment of Adansonia Digitata AnD fruit shell and dried fruit pulp was a crucial task in the rehabilitation of Adansonia Digitata And fruit structure and its mechanical property Unsatisfactory results given by traditional procedures, therefore we applied non-destructive technique NDT. Solid bodies are not absolutely rigid by the application of suitable forces. We used the composite piezoelectric oscillator technique to calculate elastic behaviour of Adansonia Digitata AnD fruit part (fruit shell and dried fruit pulp) by the frequency 123.4 KHz of quartz crystal. In the present study Ultrasonic Inspection is a very useful and versatile NDT method to calculate the Ultrasonic Longitudinal Velocity and elastic constant of Adansonia Digitata AnD fruit shell and dried fruit pulp in the longitudinal direction with ultrasonic frequency at room temperature 308 K. We have measured the resonant frequencies of the specimen’s fs. The specimen’s were collected from Mandu, Dhar Dist. (M.P.) India known as mandav ki imali. Characterization of the samples was made by scanning electron microscope (SEM) Model JEOL JSM5400.The resonant frequencies of the specimens were measured by Ultrasonic Interferometer (for solids) dual frequency Mittal Enterprises, New Delhi.

Abstract: ndia is veritable emporium of medicinal and aromatic trees. It has been estimated those trees occurring in India are commonly useful. Neera natural liquid is useful for different purpose like in bio-medical, chemical industries etc. The study of elastic behaviour of a solid is very important in fundamental and technical research. Solid bodies are not absolutely rigid by the application of suitable forces. We used the composite piezoelectric oscillator technique to calculate elastic behaviour of Borassus Flabellifier wood part from where the natural liquid NEERA collected overnight. Non-destructive testing (NDT) is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage. Ultrasonic Inspection is a very useful and versatile NDT method to calculate the ultrasonic longitudinal velocity and elastic constant of male and female tree (Borassus Flabellifier) wood part in the longitudinal and perpendicular direction of fibres with frequency at room temperature of 311 K. We have measured the resonant frequencies of the specimens f_s. The specimens were collected from Dhar Dist. (M.P.) India. Characterization of the samples was made by scanning electron microscope (SEM) Model JEOL JSM5400. The resonant frequencies of the specimens were measured by Ultrasonic Interferometer (for solids) dual frequency Mittal Enterprises, New Delhi.

Abstract: The electronic band structure, density of state and elastic properties of lead-free perovskite oxide SnTiO3 (ST) were investigated by employing first principles calculation using the Density Functional Theory (DFT) within local density approximation (LDA). The energy band gap was calculated from the separation between the Ti 3d (conduction band) and the maximum of O 2p (valence band). This gives an indirect band gap of 2.36 eV. The elastic constants and their pressure dependence were calculated up to 30 GPa and the independent elastic constants (C11, C12, and C44), bulk modules, B were obtained and analyzed. The results showed that SnTiO3 have a mechanical stability in cubic phase (Pm3m).

Abstract: In-depth study of compressible material constitutive equation, using incompressible condition, the nonlinear incompressible elastic solid’s complete irreducible constitutive equation and strain energy function expressed in invariants are derived in this essay. The elastic constants of rubber material are given by fitting the experiment data that was carried out by Treloar with the equation. Then we got evelen exact value of the elastic constants.

Abstract: The electronic structure and elastic constants of arsenic doped β-SiC have been studied by first principles density functional theory (DFT) calculations. The band structure, bulk modulus, and density of states were calculated. We have demonstrated that both the top of the valence and the bottom of the conduction band shift to lower energy levels. However, arsenic doped β-SiC exhibits a non-monotonic variation of the band gap and bulk modulus with the concentration of As. Keywords: arsenic doped β-SiC, electronic structure, elastic constant, first principles

Abstract: The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

Abstract: The equilibrium crystal structure, band structure, density of states, bulk modulus and its first pressure derivate of CdTe are systemically calculated by first-principles plane-wave pseudo-potential method, and then compared with experimental results. Applying the vibrational Debye-like model, complete sets of isochoric heat capacities can be obtained up to 1000K at pressure or not. With the temperature increasing from 0 to 1000K, a sharp increase in the heat capacity is observed. Moreover, the dependences between cell volume and pressure are also successfully obtained. Our calculated results are in agreement with available results.

Abstract: Elastic constants and some thermodynamic properties of Cu and copper oxides were studied by first-principles total energy calculations. The elastic constants of Cu and copper oxides were calculated on pressure. It was shown that the calculated elastic constants of Cu, Cu₂O and CuO at zero pressure were well consistent with previous experimental data. The specific heat capacities and thermal expansion coefficient of Cu and copper oxides were successfully obtained. The calculated specific heat capacities of Cu were well consistent with the previous experimental data.

Abstract: The ternary carbide Ti3SiC2 is the archetype of MAX phases. To date, MAX phases have proven difficult to synthesize as sufficiently large single crystals from which single crystal elastic constants might be obtained. Therefore, the elastic properties not only of Ti3SiC2 but other MAX phases are extensively studied by ab initio methods. Recently single crystal elastic constants were experimentally determined for the first time using neutron diffraction. The experiment revealed extreme shear stiffness which is not only quite rare in hexagonal materials but also strongly contradicts the predictions of all published MAX phase elastic constants from ab initio calculations. In the present paper we would like to show that such shear stiffness can possibly be supported by ab initio calculations and the calculated phonon dispersion along high symmetry directions.