Advanced Materials Research Vols. 821-822

Abstract: CoFe₂O₄ (CFO) nanoparticles was synthesized by a simple hydrothermal method using NaOH solution as a mineralizer at 200 °C for 4 h. It was found that CFO particle sizes decreased firstly and then increased with the increasing of NaOH concentration, and had a minumum value about 10-20 nm when selected 4 mol/L NaOH solution, indicating the NaOH concentration played an important role in controlling the particle size of CFO powders. The room temperature magnetic measurements showed that the saturation magnetization value was 48 emu/g, which is less than the bulk value. The synthesis method is possible to be a general approach for the preparation of other spinel ferrite nanoparticles.

Abstract: The impact tensile behaviors of four parachute cloths have been studied experimentally by using Split Hopkinson Tensile Bars (SHTB). The force/strain curves at different loading velocities as well as the fracture mode are obtained for each material. Obvious loading rate effect was observed for both the strengths and the failure strains. The three Nylon silks are fractured mostly at the root of specimen/clamps connections and the Aramid silk is inclined to fracture in the middle of the specimen and in the shear direction.

Abstract: When there are existing flexible deformations in a mechanism, its motion reliability analysis will become more difficult. In this paper, we took a PUMA560 series mechanism as an example to analyze the flexible motion reliability. Firstly, considering the existence of its flexible characteristic we built a 3-D virtual model of this mechanism in ADAMS. Secondly, we inserted a pseudo random function that was programmed in VC++ software and used Monte Carlo method to simulate the distributions of different mechanism random errors, and then we calculated the motion reliability of this PUMA560, and this can evaluate the influence of different stochastic error on mechanism dynamic characteristics. This new method is convenient and accurate, and owns some application values for this mechanism design.

Abstract: In this study, finite element method is used to analyze the stress and strain distributions in various regions of a channel steel during the roll forming process, and reveal the deformation pattern of the channel steel. The results indicate that the deformation and thickness reduction of sheet metal mainly concentrates in the corner and the ends of web section, while it is insignificant in the channel edges and the central portion of the web. During the stable stage of roll forming process, the rolling force fluctuation in each pass is related to the change of forming angle in that pass. For the pass with the largest change of forming angle, the most significant fluctuation in rolling force is observed. It is also the pass that most probably causes quality issues to the final product. Finally, it is found that changing the forming angle distribution among all the passes cannot reduce the stress fluctuation among the passes. As such, the process optimization needs to be realized by other approaches.

Abstract: The research of the flow simulation in the inner stirring tank with the single pipe and dual pipe was studied by CFD, which has demonstrated the fluid simulation effect of the single pipe and dual pipe. It has found that the effect is better in the single pipe stirring tank than the dual pipe one. Basing on this result, the flow simulation effect of dual pipe is better than the single one, and the result has a certain practical significance effect on industry.

Abstract: In this paper, physical and mechanical properties of stitch-bonded fabrics were investigated. Ten fabrics with different fibers and structures were selected, and their basic parameters, physical and mechanical properties were examined and tested. The results show that the fabric thickness and weight, material as well as lapping movement of guide-bars have influences on fabric medical properties.

Abstract: The complex number method is employed to analyze the planar motion problems of mechanism. The angular velocities and accelerations of connecting rod and rocker are formulated, and the linear velocities and accelerations of key points are also given. The analyzing process and the numerical computation results of the example show the simplicity in comparation with that of the vector method introduced in theoretical mechanics.

Abstract: The effects of rotation and revolution speed ratio on the grinding kinetics of cement clinker were studied in a horizontal planetary ball mill. The grinding media and material were used in the tests: 20mm diameter steel balls, cement clinker of-2.36+2.00mm. The rotation and revolution speed ratio is 1, 1.5, 2, 2.5, 3 and 3.5. The results show that cement clinker obeys first-order grinding kinetics at different rotation and revolution ratio. The specific rate of breakage reaches the highest when the ratio equals to 2. γ achieves minimal value at ratio q=2 and 2.5. At the same time, φ and β values reach the lowest value.

Abstract: During baking, rectangular pans often overcook the product and round pans can't make full use of the space of the oven. In this paper, two models are build to discuss the heat distribution and uniformity of different shapes pans. Initially build the heat uniformity Model. Through the analysis of the heat distribution and geometrical property, a formula is given to calculate the uniformity of regular polygon. In order to describe the heat uniformity of all kind of shape, the thermal distribution model is build to discuss the heat distribution of the bottom of different pans. By computer simulation, the temperature at the corners of the rectangular pan is the highest and the temperature across the outer edge of the round pan is even, which is consistent with reality.

Abstract: Delayed expandable foam (DEF) is a new material that can significantly extend the range of foam curtain in electromagnetic waves interference, fire extinguishing and pollution washdown, etc. This paper studied the expansion of insoluble gas nucleus (IGN) in supersaturated solution of DEF. The radius and volume of IGN as well as DEF was calculated using double membrane model of mass transfer. Results show that the size of IGN raises steadily over time meanwhile the bulk volume of DEF is nearly invariable when both initial radius r₀ and number density ψ of IGN are small enough. This is called the volume sensitivity effect. At this stage, the time delay reduces linearly with r₀ and the square root of ψ. Accordingly, the time delay of DEF expansion can be adjusted by setting initial radius and number density of IGN. This research can provide theoretical basis for DEF development.