Advanced Materials Research Vols. 154-155

Abstract: In order to reduce the internal cracks and control the quality of the steel strand in continuous casting, a thermal-mechanical model considering the movement of the strand, real roll arrangement and caster structure, has been established with the elasto-viscoplastic constitution to predict the three dimensional temperature distribution and bulging deformation of the strand. Using the sequentially coupled finite element method the model is solved numerically, and is validated by the comparisons of the simulation results and measured data. The model is suitable for future research on the whole strand bulging deformation to help improve the strand quality in continuous casting.

Abstract: Nickel(Ni) layer was applied to the surface of pure aluminum(Al) by electrodeposition for 15 minutes using a direct current (DC) condition at 0.13 Acm-2. Heat treatment was employed subsequently for 1, 2.25 and 4 hours at the temperatures of 600 and 650oC, which are below and above the eutectic temperature of Al-NiAl3, respectively. All samples were characterized by OM, SEM, EDS and GIXD. DTA was also performed to study heat release in the reactions. After heat treatment at 600oC, the specimens exhibit the non-uniform formation of Ni2Al3 and NiAl3, even after 4 hours of heat treatment where local melting possibly occurs due to the exothermic heat of formation. In contrast, owing to fast interdiffusion of Al and Ni as assisted by a liquid phase formation, multi-layer of Ni2Al3 and NiAl3 was uniformly formed along the interface of the specimens heat treated at 650oC.

Abstract: In this paper, a three-dimensional finite element model is developed to compute thermal phenomena of 0.5 mm thick Hastelloy C-276 alloy sheets during pulsed laser beam welding (PLBW). Temperature-dependent thermal properties of Hastelloy C-276 alloy, effect of latent heat of fusion, and the convective and radiative boundary conditions are taken into account in the model. The space-time temperature distributions in a butt-joint weld produced by the PLBW process are predicted from the beginning of welding to the final cooling. The heat input to the model is assumed to be a double ellipsoid heat source. The finite element calculations are performed by using ANSYS code with the parametric design capabilities. Experiments were carried out to determine the temperature evolution during welding and to measure the cross section profile of the weld bead. By comparing the simulation results with the corresponding experimental findings, it is found that they are in a good agreement. The validity and applicability of the numerical simulation model are confirmed.

Abstract: The rules of the distribution of magnetic field were carried out by numerical simulation. The distribution of magnetic field was got, and the effects of current intensity and frequency on the distribution of magnetic field were analyzed by constructing three-dimensional finite element model and using ANSYS software which is a kind of commercial FEM analysis software. The results show that the intensity of magnetic field is proportional to current intensity, magnetic field is mainly localized in the surface region of liquid melt and there is a notable edge effect in the corner.

Abstract: CrNx films were synthesized under graded/constant bias by DC magnetron sputtering. In the present work, the graded bias deposited CrNx films have both (111) and (200) orientations while only (111) orientation in low bias (-20 V) and (200) orientation in high bias (-200 V). Both the magnitude of bias and preferred orientation result in the variation in their surface morphology from pyramidal (loosen) to cellular (dense) structure. The hardness of the graded films is between the low and high constant bias ones. The relationship between the hardness and bias gradient is similar with the relationship of hardness and the content of (200) preferred crystallites, which implies the fine (200) preferred crystallites is an important factor for hardness of graded bias films.

Abstract: The on-off pressure mechanism has an important function to the printing press, the quality of which concerns the working performance of the printing machine and the quality of printed products directly. In this paper, the pneumatic on-off pressure mechanism is discussed; the work demand of order on-off pressure is analyzed. In addition, the three-dimensional digital model and the kinematic analysis process can be achieved on the basis of ADAMS software. What’s more, the on pressure value in the process of on pressure is derived from the kinematic analysis. Lastly, the relation between the motion of on-off pressure mechanism and cylinder’s angular displacement is analyzed, an important basis to the on-off pressure mechanism’s optimal design will be provided.

Abstract: In this work, properties and spot welding performance of copper matrix composite electrode reinforced with 15 vol% tungsten carbide particulate from inexpensive raw material were investigated. Mixture of copper and recycled tungsten carbide was milled, compacted, sintered and powder forged at different pressures. Higher forging pressure resulted in higher density and electrical conductivity as it accelerates the flow of copper matrix leading to porosity elimination and improves metal-metal contact within the copper matrix by reducing porosity and oxide film. Welding operation showed that composite electrodes with higher density, electrical conductivity and hardness forms larger and stronger spot weld.

Abstract: Investigating the changing quality of galvanized parts when pure zinc plated with other alloying additions. In the procedure of hot dip galvanizing, when pure zinc plated without other alloying additions, the corrosion resistance of zinc coating is poor, meanwhile the bath surface will produce a number of zinc dross, zinc ash, and this phenomenon will cause a waste of zinc, resulting in an increase in product costs, and the surface of product is relatively dark, the brightness is not enough, whilst sometimes even form a phenomenon of the formation of the Pan-color on the surface of the galvanized parts. However, when a proportion of aluminum or rare earth elements is added into melting zinc, the corrosion resistance of coating will be improved and much better than pure zinc galvanized parts;as the decrease of zinc ash, the cost will be reduced;synchronously the limititation of superficial quality above-mentioned will be improved. Via evaluating the superficial quality of galvanized parts and the corrosion resistance, the whole performance will be significantly improved when 0.5% aluminum and 1.5% rare earth elements is added into melting zinc.

Abstract: The concept of concurrent engineering is that designers, manufacturing engineers and all other members of the new product development team can work simultaneously or co-operate closely to avoid redesign and other problems at a later stage. The finite element method/FEM is the kernel of the approach. It enables the designed outputs to be optimal, robust and efficient so that high quality products could be achieved at a low cost in the shortest delivery time. The scroll components work in a high pressure and high temperature environment, which results in the deformation of the scroll wall. If the deformation was too great the vacuum pump would fail and would have to be redesigned and remanufactured. The designer can seek optimization under the limitations imposed by the displacement or stress of the scroll wall. The FEM and optimization can evaluate the deformation due to the cutting force and compensate accordingly.

Abstract: This paper was concerned with theoretical analysis and the static characteristics of the journal bearing lubricated with magnetic fluid. A general Reynolds equation based on magnetic fluid model is obtained, which can be easily extended to other non-Newtonian fluids and this equation can provide theoretical basis for hydrodynamic analysis of magnetic fluid journal bearings. For the case of static loaded magnetic journal bearings, the influence of magnetic fluid effects on the lubrication performance is studied under various eccentricity ratios, magnetic intensity and concentration. The numerical results show that: with the increasing of concentration, the bearing capacity is obviously increased; the increase magnitude is larger when the eccentricity ratio is large. Under the effect of magnetic field, the bearing capacity increasing with the increasing of magnetic field intensity. When the eccentricity is small, the side leakage is highly decreased. It can be completely eliminate by appropriately designing the bearing geometry and the magnetic field which can’t be existed in normal journal bearings.