Papers by Keyword: Viscosity

Abstract: This paper considers a deformation process of an incompressible elastoviscoplastic material placed between two coaxial rigid cylinders. The material is deformed when the internal cylinder rotates around its axis while the external one is fixed. The adhesion conditions are set on both boundary surfaces. The theory of large elastoviscoplastic deformations is used to solve the problem. The mathematical model is constructed in cylindrical coordinates.

Abstract: The equation σ=Kέ^m, where σ is the applied stress, έ is the strain rate, K and m are material constants that depend on stress / strain rate, temperature and grain size is often used to describe structural superplasticity. The general shape of the logσ-logέ curve is sigmoidal. Based on limited data, it was suggested by us earlier that a universal σ-έ curve could exist in a properly normalized space. έ and m are normalized with respect to έ_opt and m_max, the strain rate at which m is a maximum and the maximum m value respectively. Here a multi-dimensional relationship involving σ/σ_opt-έ/έ_opt-m/m_max-ΔF₀/kT-η/η_opt is developed; σ_opt corresponds to έ_opt, ΔF₀ is the free energy of activation for the rate controlling mechanism, k the Boltzmann constant, T the absolute test temperature, η the (apparent) viscosity of the superplastic alloy and η_opt is the viscosity of the same alloy for m=1 in a dimensionless σ-έ space. Using data concerning many systems, the phenomenology of structural superplasticity in all classes of materials is shown to be unique.

Abstract: In a global context of saving energy and the desire to improve heat exchangers, the use of nanofluids today seems like a craze growing. Are nanofluids a solution What are the limitations of the use of such fluids This article proposes a review of thermo physicals coefficients of carbon nanotube-water nanofluids. This article reports on an experimental study completed to observe the impacts of the concentration, temperature, aspect ratio, and surfactant on the thermal conductivity and viscosity. Finally this article advocates a field for using nanofluid in heat exchangers.

Abstract: Development of binder system based on natural resources is one the main interest among researchers in ceramic injection moulding (CIM) with the main aim of processibility of complex biomedical implant. In this paper, the influence of single binder comprised of palm stearin mixed with HAP powder was investigated. The powder and binder mixture, generally known as feedstock was analyzed for its flowability in order to get some insight for injection moulding purposes. Two different mixing temperatures were investigated for preparing the feedstock; 160°C and 70°C. The feedstocks viscosity was then evaluated using a capillary rheometer at temperature range from 70°C to 90°C. The results clearly showed that the use of 100% palm stearin was promising in providing required pseudoplastic flow for injection molding. The injection molding process can be carried out at relatively low temperature in comparison with the conventional binder systems used.

Abstract: Day by day depletion of liquid fossil fuels creates necessity to find out an alternative liquid fuel like biodiesel. Rapid growth in transportation, industrialization and civilization from time to time causes increase in requirement of fuel and energy. This paper deals with the production of biodiesel from Simarouba Glauca, Dairy scum and Karanja oil by transesterification process using calcium oxide as a heterogeneous catalyst and methanol as the alcohol. Biodiesels are blended with diesel in different proportions and tested the physicochemical properties such as viscosity, flash point and density for each blended biodiesel. The important properties of biodiesel such as cloud point, pour point, ash content and carbon residue are tested and compared with other biodiesels.

Abstract: The paper features the mathematical model of analytical calculation of thermodynamic properties like viscosity, speed of sound and thermal conductivity for fluids in one and two-phase region (fluid-solid, fluid-gas) on the basis of statistical mechanics. For the calculation of thermal conductivity and viscosity for fluids will be presented Chung-Lee-Starling model Equations for the thermal conductivity are developed based on kinetic gas theories and correlated with the experimental data. The low-pressure transport properties are extended to fluids at high densities by introducing empirically correlated density dependent functions. These correlations use acentric factor, dimensionless dipole moment and an empirically determined association parameters to characterize molecular structure effect of polyatomic molecules. The calculation of thermodynamic properties for fluids was developed under the theory of statistical thermodynamics and statistical associated fluid theory. For the calculation of thermal conductivity of solids are the most important two contributions: the heat transport by electrons (el) and by phonons (ph). In our model we have made the assumption that heat transport by electrons and by phonons is independent and the thermal conductivity is than a sum of both terms.

Abstract: An brief overview of the selected thermo-physical measurements realized in the VILA laboratories for the glass industry and for the fundamental research of glass is presented. Among the routine measurements realized for the glass industry the thermodilatometry for measuring the glass transition temperature, and linear thermal expansion coefficients of glass and metastable glassforming melt are described in detail. The fact that the glass transition temperature is not a single valued physical quantity is stressed in connection with the measurement time temperature schedule. The probably most important quantity related to the glass production technology is the viscosity. Its measurement in the range extending ten orders of magnitude is described. The combination of the falling ball method, the rotation viscosimetry and the thermomechanical analysis is needed to cover the above viscosity range. Among the methods used in the fundamental research of glass structure and properties the study of structural relaxation is overviewed. Here the own method of combined viscous flow and structure relaxation TMA measurement is described in detail.

Abstract: Environmental problems caused by high temperature during the production of asphalt and road paving prompted research on alternative material that is more environmental friendly. Recent advances in asphalt technology have allowed the reduction of construction temperature using the warm mix asphalt additives. This paper presents the laboratory results on the effects of a wax warm mix additive on the asphalt binder rheological properties. The additive were blended with conventional binder using laboratory mechanical mixer at 0, 1, 2, 3, 4 and 5% by the mass of binder. Then, the binders were tested for flow properties, stiffness and its resistance to rutting and fatigue. Tests were performed using rotational viscometer and dynamic shear rheometer on unaged and aged samples. The results show that the addition of wax warm mix additive improves the flow properties by reducing the viscosity and leads to lower construction temperature. Characterization of modified binders’ rheological properties at intermediate and high temperature indicates that the amount of wax warm mix additive addition slightly affects the binder stiffness and its resistance to rutting and fatigue. Based on the rheological test results, the 3% wax warm mix additive produce comparable rheological properties with the conventional binder. Therefore 3% wax warm mix additive is suggested to be the optimum amount for the road construction application.

Abstract: In sustainable asphalt pavement construction, the proper selection of materials can be a challenging task. This paper focuses on a newly developed asphalt modifier named calcium carbonate (CaCO₃) combined with Treated Palm Oil Fly Ash (TPOFA) to improve the properties of asphalt mastic. The rheological properties of mastic in terms of penetration, softening point, rotational viscosity and Superpave rutting factor using 60/70 asphalt binder blended with 5, 10, 15, 20 % of CaCO₃+TPOFA were calculated to evaluate asphalt binder properties subjected to different aging conditions. The rotational viscometer (RV) was used to evaluate the properties of mastic at test temperatures from 120°C to 170°C. The dynamic shear rheometer (DSR) was used in temperature sweep test from 46°C to 82°C at 6°C increments at 10 rad/sec frequency to measure the G*, δ and Superpave rutting factor G*/sinδ. A one-way ANOVA statistical analysis was used to analyze the results .The test results showed that all asphalt mastic exhibited higher viscosity compared to the base binder. The addition of CaCO₃ +TPOFA increased the G* but reduced the phase angle which indicated improved stiffness of asphalt mastic. Hence, incorporating CaCO₃+TPOFA can potentially improve the rutting resistance of asphalt mastic.

Abstract: Methods of chromatography-mass spectrometry, IR spectroscopy, viscometry were used to study structural and mechanical properties of highly paraffinic crude oil processed in high-frequency acoustic field. It was shown that ultrasonic treatment leads to an increase in viscosity, yield stress, viscous flow activation energy and internal fracture energy of dispersion system with an increase in processing time. Proportion of n-alkanes С₁₅Н₃₂–С₁₆Н₃₄ and concentration of aromatic hydrocarbons increase in the composition of dispersed phase of processed crude oil according to chromatography-mass spectrometry.