Papers by Keyword: Saturation

Abstract: In this work, the preparation and processing of aluminum-copper alloys, which added amounts of copper to aluminum in different parentages (2, 4, 5%) so that it does not exceed the saturation limit for aluminum (6% Copper). After adding these specific amounts of copper to aluminum, have been melting each alloy to thaw copper in aluminum fully and diffusion copper atoms in it, and after that the specimens were prepared and quenched at 8-30 hours and rapid cooling in the water, and then were studied parameters of heat treatment and different percentages of copper. It is clear from the schemes and experimental results that each weight ratio of copper in aluminum has a different approach to reach the best mechanical properties. After performing mechanical tests and tests, it was found that the highest hardness of the (aluminum-copper) alloy in the case of (2% Cu) amounted to (120 HB) and in the case of (4% Cu) the amount (211 HB) and in the case of (5% Cu) the amount (188 HB).

Abstract: The purpose of the study is to study the possibility of using secondary resources of metallurgical production, namely: steel-making slag and carbon dioxide in the production of vibropress products for construction purposes. The tests were carried out with the complete replacement of the coarse aggregate in the concrete mixture with steelmaking slag and varying the hardening processes. The optimal condition for strength gain is hardening in carbon dioxide at an increased pressure of 0,2 MPa.

Abstract: Thermal conductivity is one of the most important properties of construction materials due to change the structure and the chemical composition of these materials particularly in hot weathers. Thermal conductivity testing of building materials in situ provides useful database about of temperature, moisture and conditions of storage. In this paper, thermal conductivity of Huston sand has been investigated for dry and saturation status by transient technique. TP02 Hukseflux probe used to calculate thermal conductivity of Huston sand. TP02 Hukseflux probe has been calibrated by Glycerol and compare with results from art-of-literature. The results showed that the value of thermal conductivity during the saturation is more than the dry state. This is identical to reality as the parameter is strongly influenced by presence of water. Comsol Multiphysics® simulation has been used to validate the experimental test. Slightly difference is marked between the experimental and theoretical results

Abstract: Based on the first-principles, using CCSD(T) ab initio calculation method, many-body potential energy of solid argon are accurately calculated with the atomic distance R from 2.0Å to 3.6Å at T=300K, and firstly establish and discuss the face-centered cubic (fcc) atomic crystal configurations of two-, three-, and four-body terms by geometry optimization. The results shows that the total number of (Ar)₂ clusters is 903, which belongs to 12 different geometric configurations, the total number of (Ar)₃ clusters is 861, which belongs to 25 different geometric configurations, and the total number of (Ar)₄ clusters of is 816 which belongs to 27 different geometric configurations. We find that the CCSD(T) with the aug-cc-pVQZ basis set is most accurate and practical by comprehensive consideration. The total potential energy U_n reachs saturation at R>2.0Å when the only two-and three-body interaction energy are considered. When R≤2.0Å, the total potential energy U_n must consider four-and higher-body interaction energy to achieve saturation. Many-body expansion potential of fcc solid argon is an exchange convergent series.

Abstract: Powder metallurgy was mainly used to produce automobile parts such as beds self-lubricating bearings, and gear wheels. In order to investigate the effect of porosity on the mechanical and tribological properties of sintered steel, specimens with 10%, 20%, and 30% porosity were produced on samples of parallelepipedic form, with technical of iron powders that has been used in a large industrial area. Sintering was carried out at 1100 ° C for 2 hours in an argon atmosphere. Metallographic studies such as pore formation, saturated area, and the nitrided layer analyses were performed by microscopy and optical microscopy. It was found that the irregular pore formation tendencies increase with an increase in porosity (%). Furthermore, an increase in porosity has proven to decrease the mechanical properties and increase the wear trace area and the friction coefficient of sintered steel.

Abstract: The saturation of primary tensile twins in heavily textured Mg-alloy AZ31 is investigated, and their strain accommodation limit is evaluated. EBSD results suggest that the mean number of twins per grain saturate rapidly, followed by the stop of twin growth. Twinning saturation is included in a physical model of twin evolution.

Abstract: The conditions of development of Delayed Ettringite Formation (DEF) in concrete when submitted to excessive heating during hydration and setting have deserved recent research efforts and tend to be better understood. However, quantitative evidence of DEF risk for concrete submitted to similar heating when mature is still scarce. The experimental program described in this paper confirms the risk of DEF-induced expansion for concrete normally cured, then heated after 90 days of age, when further kept in saturated environment, both for a DEF-prone mix and for a concrete made with a low C₃A, low SO₃ and low-alkali content-cement.

Abstract: Geological CO₂ sequestration is a promising method to reduce atmospheric CO₂. Deep saline aquifers are one of the most important sites due to their capacity for CO₂ storage. Thus, a better understanding of immiscible brine-CO₂ mobility and their saturations including invading patterns in deep saline aquifers as CO₂ storage sites is required. Microfluidic model provides the opportunity to discover unrecognized processes and to explore existing theories in fluid flow through porous media. In this study, the microfluidic model is used to explore the effects of both the supercritical carbon dioxide (scCO₂) injecting velocity and ionic strength in saline aquifers on scCO₂ invading patterns in geological CO₂ sequestration. The results show that scCO₂-brine displacement ratio increases with (1) increased scCO₂ injecting velocity up to 40 μL/min, and (2) decreased ionic strength in the range of 1M~5M NaCl.

Abstract: An accurate mathematic model of permanent magnet synchronous motor (PMSM) is necessary for precise torque control and/or high efficiency drive control. This paper discusses the development model of PMSM by taking all losses and saturation into account. In the proposed model, all losses composing of the copper loss, core loss, mechanical loss and stray loss were analyzed to improve the torque equation. In addition, considering the influence of saturation level, the variations of the core loss resistance, direct-quadrature axis magnetic inductance and permanent magnet flux were discussed on support of the data analyzed by Ansoft. In order to verify the developed model, a start up simulation is performed in the mode of open-loop and the results confirm the validity of the model.

Abstract: The conventional PD controller could cause the saturation problem of ballistic missile actuators. A design method of anti-windup variable parameter PD controller was proposed. The proportional coefficient and derivative coefficient were designed to be Gauss functions of system tracking error. Both were small when tracking error was big; whereas both increased as the tracking error decreased. This method not only restrained effectively the saturation problem, but also produced enough control force to drive system outputs to track their commands speedily. The control effect of anti-windup variable parameter PD controller was compared with that of the conventional PD controller in the numerical simulation. The simulation results show that the anti-windup variable parameter PD controller has better control effect.