Key Engineering Materials Vols. 480-481

Abstract: The aluminium alloy bar is mainly obtained by hot extrusion in the past. In order to increase the production efficiency and reduce the cost, a new mold is designed, and horizontal continuous casting is used to produce the aluminium alloy bar in this work. The results show that aluminium alloy bar can be cast by horizontal continuous casting. The asymmetry of the sump is overcome by optimizing the design of the mold. When the temperature of the melt was 730°C, casting speed is 650 mm/min, cooling water is 15 L/min, the quality of lubricating oil is 0.5 ml/min, and the ingot with good surface quality can be cast.

Abstract: Ti50Fe45Sn5 amorphous alloys powder was prepared by mechanical alloying (MA) in a high-energy planetary ball mill. The non-crystallization degree was tested by X-ray diffraction (XRD). It was shown from the XRD results that a higher ball to powder weight ratio (BPR) is advantageous in preparing amorphous alloys powder. The microstructure and shape of the powder was observed by scanning electron microscope (SEM). It was shown from the SEM results that the as-milled amorphous alloys powder is flake shape and assembles together to be agglomeration structure, which is a typical morphology of amorphous powders prepared by MA. Thermodynamic properties and crystallization kinetics behavior of the as-milled amorphous alloys powder were measured by differential scanning calorimeter (DSC). The supercooled liquid region △Tx is broad (up to 119K) and the reduction glass transforming temperature Trg (0.78) is great, which shows that the as-milled amorphous alloys powder has a strong glass-forming ability and the thermal stability of the powder is excellent.

Abstract: The parameters that influence the dielectric properties of soil mainly include moisture content, density and temperature, in which moisture content is the most important. One subgrade under construction is selected as engineering example, the dielectric constants are tested with the special instrument, and the moisture content are tested with sand filling method, and then the tested data are analyzed, and the results reveal that: there are better relationship between dielectric constants and the tested moisture contents and compaction degree, and so the dielectric constants are to be tested and then the moisture contents and compaction degree would be calculated according to the relationship, which would be a rapid testing and evaluation method.

Abstract: Based failure criteria of composite materials structural damage and simulation of finite element dynamic impact, the drop process and damage failure of composite cylinder are calculated and analysed. For composite cylinders with different wind angles falling from a height, the stresses of internal points during the impact process are obtained. Based on the value of the process stress, the failure of the cylinder is analysed. The results show that at the moment when the cylinder bounces back after impacted with the ground, the stress and strain reaches to the maximum. The maximum hoop stresses are at cylinder mouth and cylinder bottom which collide with ground. Maximum axial tensile stresses are at the central body of cylinder. The stress distribution of 13 degrees fiber angle of cylinder is slightly less than that of 25 degree. By Tsai-Wu composite failure criterion, there is no failure of the composite cylinder.

Abstract: Foamed aluminum has been applied in many fields due mainly to its excellent properties. The tensile deformation process and characteristics of foamed aluminum with closed-cell were studied in this paper and the deformation mechanisms were discussed. The results show that foamed aluminum fractured without necking. The tensile stress-strain curves have similar characteristics, the linear elasticity at a low stresses followed by plastic yielding, strain hardening and rupture, which has obvious difference with compression stress-strain curve. The fracture mechanism is neither brittle fracture nor plastic fracture. The defects existed in foamed aluminum interior have important influence on tensile property.

Abstract: The PTC materials, as a kind of positive temperature coefficient materials, are used to heat diesel fuel in the high-pressure fuel pipe near the injector in Diesel engine, which have a lot of advantages, such as simple structure, safe and rapid heating, and fixed heating temperature around its Curie point. In order to study its heating effect on diesel fuel of the high pressure fuel pipe, the dynamical models for both the controlled object and PTC heater are presented by the way of lumped parameter, and the heating effects are also simulated and analyzed. The calculation results show that the diesel temperature is heated by the PTC materials effectively. Meanwhile, the heating law by PTC materials heating diesel fuel in the high pressure fuel pipe of engine is also summarized.

Abstract: This paper gives a way which utilizes the intelligent heating materials to preheat diesel fuel in the high-pressure tube in order to improve the cold starting and emissions of engine. A heating model of high-pressure tube was brought forward, and the pressure of tube was measured at a Diesel engine as the computational boundary condition. The unsteady heat transfer was simulated using the computational fluid dynamics by the temperature field and heating effect. Simulation results show that the diesel fuel temperature could improve by the right heating size and temperature in the high-pressure tube.

Abstract: In this paper, we have investigated the geometries and electronic structures of B-N co-doped carbon nanotube with inside adsorption of water molecules. The charge distributions, band structures and local density of states are calculated by using the first-principles theory in detail. The results show that the water molecules can adsorb stably on the inside surface of the doped nanotube with slight deformation. The π and π* subbands shift upward depending on the sites of the adoptions. The investigations will be beneficial to the biological application of B-N co-doped nanotube.

Abstract: The nonlinear electrical behavior and dielectric properties of WO3-based ceramics with various La2O3 contents have been investigated. Breakdown voltages Eb of WO3 doped with La2O3 are lower than that of undoped WO3, indicating that the dopant can reduce the breakdown voltage. The dielectric constant of doped samples is higher than that of undoped samples, and the high dielectric constant makes them suitable as capacitor-varistor materials. The theory defects in the crystal lattice was introduced to explain the nonlinear electricial behavior of the La2O3-doped WO3 ceramics. In view of these electrical characteristics, the WO3 ceramic doped with La2O3 is a viable candidate for capacitor-varistor functional devices.

Abstract: Heavy oil pyrolysis reaction was studied with formic acid as a body for hydrogen donor and homemade of oil-soluble organic nickel salt as a catalyst, by high-temperature and high-pressure Reactor simulating Thermal Recovery conditions. Explore the influence of the addition of hydrogen donor on heavy oil viscosity, group composition and sulfur contents before and after the catalytic aquathermolysis reaction. The results show that catalytic aquathermolysis of heavy oil leads to a percentage viscosity reduction of 64.69%, to an increase in saturates and aromatics contents from 24.32% and 36.89% to 26.12% and 38.08%, and to a decrease in resins, asphaltenes, and sulfur contents from 30.27%, 8.52%, and 0.5650% to 28.27%, 7.53%, and 0.3365%,respectively; when formic acid is introduced at dosage of 1-7% heavy oil mass, the percentage viscosity reductio is continuously raised to 69.16-87.02%, the saturates and aromatics contents-increased to 27.73-31.12% and 39.68-41.26% and the resins, asphaltenes, and sulfur contents-decreased to 26.29-24.12%, 6.66-3.50%, and 0.3095-0.0742%, respectively. The role of hydrogen donor formic acid and the functioning mechanisms involved in catalytic aquathermolysis of heavy oil are discussed.