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101.
102.
《钢铁冶炼》2013,40(1):3-13
AbstractThe present paper develops a one-dimensional model of a novel coal based iron ore direct reduction process. In this process, a mixture of iron ore, coal fines and small amount of binder is made into pellets and these are placed in a bed. Air is forced upward through the pellet bed and provides oxygen for the volatiles and part of the coal in the pellets to be burnt. Initially the pellet bed is heated from the top. As the temperature of the top level of pellets increases, they start to evolve pyrolytic matter which is ignited and, as a consequence, the pellets at lower levels in the bed are heated. In this way, a flame propagates downward through the bed. The iron ore reacts with the gases evolved from the coal (including volatiles) and carbon in the coal and undergoes reduction. The model presented in the article simulates the processes occurring in the solid and gaseous phases. In the solid phase, it uses a novel porous medium model consisting of porous pellets in a porous bed with two associated porosities. The model includes equations for energy balance, reactions of iron oxide with carbon monoxide and hydrogen, coal pyrolysis and reactions between the gas components in the voids. The model shows that a rapidly increasing temperature front can travel downward through the bed if the air is supplied for long enough. The predictions of the modelling are discussed and compared with observations obtained from an experimental rig. 相似文献
103.
《钢铁冶炼》2013,40(2):147-153
AbstractThere are several motivations for minimising slag entrainment during the teeming of steelmaking ladles. Cleaner steel, improved yield, and higher productivity are all at stake. As one of several identifiable contributors to slag entrainment, vortexing has received considerable attention in the past decade and a half. What is commonly referred to as 'vortexing' in fact comprises two distinct phenomena, namely, vortexing funnels and non-vortexing funnels, each controlled by entirely different sets of variables. Dimensionless correlations describing the two phenomena were determined, and validated, using separate sets of dimensional analyses and appropriately designed scale model experiments. The importance of these findings to the teeming of steel is discussed. Performance results of a patented 'vortex buster' device, developed on the basis of the understanding gained from these studies, and validated in water models as well as in a 12 ton tundish, are also presented. 相似文献
104.
《Journal of Adhesion Science and Technology》2013,27(1):125-138
Colloidal forces outside the microscopic probe (particle)–substrate adhesion contact area were analyzed theoretically. Equations describing the van der Waals, electrical double layer, and hydrophobic forces were derived for the non-contact area of a probe–substrate system assuming a simple sphere–flat geometry. Two cases were considered: particles freely resting on the substrate surface and particles pulling off the substrate. The results of modeling presented in this communication suggest that the adhesion of fine particles (microscopic and sub-microscopic particles) to flat surfaces can be affected by the forces acting outside the contact area. However, due to increased distance between the particle and substrate during separation, both the van der Waals and electrostatic forces acting outside the contact area are negligibly small compared to the short-range adhesion forces and they do not contribute to the measured pull-off force to any great extent for most systems. On the contrary, our calculations suggest that the long-range hydrophobic forces can contribute to the strength of adhesion between hydrophobic fine particles and hydrophobic substrates. 相似文献
105.
《Journal of Adhesion Science and Technology》2013,27(9):959-979
In this work, a smart cure cycle with cooling, polymerization and reheating was devised to nearly completely eliminate thermal residual stresses in the bonding layer of the co-cure bonded hybrid structure. In situ dielectrometry cure monitoring, DSC experiments and rheometric measurements were performed to investigate the physical state and the cure kinetics of the neat epoxy resin in the carbon fiber/epoxy composite materials. From the experimental results, an optimal cooling point in the cure cycle was obtained. Also, process parameters such as cooling rate, polymerization temperature and polymerization time in the curing process were investigated. Then, the thermal residual stresses were estimated by measuring the curvatures of co-cure bonded steel/composite strips and their effects on the static lap-shear strengths of co-cure bonded steel/composite lap joints were measured. Also, the effects of thermal residual stresses on the tensile strength, the interlaminar shear strength and the interlaminar fracture toughness of the composite material itself were measured using tensile, short beam shear and double cantilever beam tests. From these results, it was found that the smart cure cycle with cooling, polymerization and reheating eliminated the thermal residual stresses completely and improved the interfacial strength of the co-cure bonded hybrid structures, as well as the tensile strength of the composite structures. 相似文献
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107.
《Materials Science & Technology》2013,29(11):1385-1390
AbstractThe effects of elements such as Ni, Mo, Cr, Cu, and V on the wear behaviour of high manganese steels have been reported extensively. Most researchers agree on the influence of many of the elements but disagree on the effect of Cr. A study has been conducted to evaluate the effect of 1.7 and 2.3 wt-Cr on high manganese steel when subjected to various wear conditions: impact loading, abrasion, combined impact-abrasion, and combined abrasion-corrosion. The study has revealed that adding Cr to high manganese steel resulted in an increase in hardness and hardenability, and a decrease in toughness. The effect on wear resistance was found to depend on the wear conditions. Chromium alloyed high manganese steels showed superior wear resistance compared with plain Hadfield steels where corrosion, abrasion, and combined impact-abrasion conditions prevailed. Such conditions required a high surface hardness. Plain Hadfield steel showed superior wear resistance in conditions where pure impact wear is encountered. Such conditions required an increase in toughness rather than surface hardness. 相似文献
108.
Finite Element Analysis of Axial Feed Bar Rolling 总被引:1,自引:0,他引:1
A flexible technique of hot working of bars by axial feed rolling was introduced . The process deformation, strain field, stress field, and temperature field of the parts are analyzed by finite element method (FEM)-simulation software DEFORM-3D. The material flow rule and tool load have been investigated. 相似文献
109.
《Advanced Robotics》2013,27(7):711-728
The design of the controller of a two-wheeled mobile robot is usually based on a kinematical model. The kinematical model is derived under the assumption that the wheels do not skid or float. However, in the real world, wheels may skid on the ground or float away from the ground due to the rotational motion of the body. This paper analyzes the effects of the skid and the float on the robot with a controller designed based on the kinematical model—by the use of the Lyapunov control method. Numerical simulations are carried out based on the dynamic model including the translational and rotational motion of the body, and then experiments are performed using a hardware model. 相似文献
110.
《Advanced Robotics》2013,27(1-2):159-177
This paper addresses the inverse dynamics of a 4-d.o.f. parallel robot, H4. Simplified inverse dynamics models have been proposed so far in which the inertia of a rod is neglected. Computation of the inertia of the rod was a heavy load for past computers and, hence, the simplified inverse dynamics were useful for online computation. However, owing to the recent great progress in computer hardware, online computation of the full dynamics is no longer a heavy load for modern computers. Therefore, a detailed inverse dynamics model of H4 is proposed in this paper. The Newton–Euler method is adopted for generating inverse dynamics solutions for H4 which have four (S–S)2 (two spherical–spherical) chains in each rod. In order to evaluate the proposed inverse dynamics model, three controllers are tested: (i) PD controller, (ii) PD controller with velocity feed-forward and (iii) dynamic compensation controller based on the proposed dynamics model. The experimental results are presented and analyzed. It is also shown that the simplified dynamics model can be used without clear deterioration of control quality. 相似文献