Materials Science Forum Vols. 471-472

Abstract: Nanodiamond prepared by detonation synthesis using explosives as the precursor exhibits serious agglomeration characteristics in non-polar medium such as clean oil. Mechanochemical measures were introduced to modify nanodiamond (ND) surface, improve its dispersion behavior and actualize suspension stability. Hyperdispersants’s adsorption can be intensified with the participations of mechanical forces, and the main mechanism of hyperdispersant may lie in the steric stabilization of its adsorption layer founded on ND surface. After the eagglomeration and dispersion treatments, a suspension containing ND particles with the average diameter of around 55 nm can be prepared and it can be reserved for over 6 months without any sedimentation.

Abstract: In electric discharge manufacturing, especially to the complex part finishing machining, electrode wear effects the electrode’s life-span and the work pieces precision in both dimension and geometry. Although it is more difficult to explain the exact mechanism of metal erosion in sparking, the basic phenomenon that the work materials near the channels melted, vaporized, and then flushed off in the dielectric liquid has suggested that the mechanism of electrode wear is based on a thermal conduction process governed by heat generating from arc channels and dissipating into the tool and the work. On the basis of a review of the other researchers’ work and analysis to the thermal conduction phenomenon, this paper presents an electrode wear model based on heat conduction. Finite element is employed to solve the heat conduction model of wear, and in addition, a theoretic planar sunken function at electrode surface impacted by plasma flow is established. Some experiments and simulations are made to verify the hypothetic model, and the conclusions that the simulation result of erosion figure and erosion trend of the material are correspond to the hypothetic model are confirmed.

Abstract: This paper presents an investigation on the surface roughness of burnished hypereutectic Al-Si alloy ¾ a widely used light-weight and wear resistant material in automobile, electric and aircraft industries. Based on the techniques of Taguchi, an orthogonal experiment plan with the analysis of variance (ANOVA) is performed and a second-order regressive mathematical model is established. Meanwhile, the influence of process parameters on surface roughness and its mechanism are discussed. From the experiments, it is found that burnishing process is effective to decrease surface roughness of hypereutectic Al-Si alloy components, in which, all input parameters have a significant effect on the surface roughness. To achieve a small surface roughness, the optimum process parameters are recommended.

Abstract: Projection welding is a variation of electric resistance welding with the dynamic changes of the flow paths for heat and electrical properties with changing temperature caused by the large plastic deformation with collapse of projection. The common standards of projection welding are AWS, IIW and Harris& Riley which have been established and in use for some time. All these standards have the slots located under the projection. However, the standard proposed in this paper researches on is a special one with the slots designed on the two sides of the projection. A comprehensive thermal-electrical-mechanical analysis was performed to quantitatively simulate the projection welding of the special standard by a coupled finite element method. The electrical, thermal and mechanical aspects of the projection welding processes such as the projection collapse mechanism, the nugget formation process and the effects of different electrode forces were discussed in this paper.

Abstract: The investigation of the performance of the Particle Swarm Optimization (PSO) method for Vehicle Routing Problem with Time Windows is the main theme of the paper. “Exchange minus operator” is constructed to compute particle’s velocity. We use Saving algorithm, Nearest Neighbor algorithm, and Solomon insertion heuristics for parameter initialization and apply the “Routing first and Cluster second” strategy for solution generation. By PSO, customers are sorted in an ordered sequence for vehicle assignment and Nearest Neighbor algorithm is used to optimize every vehicle route. In our experiments, two different PSO algorithms (global and local), and three construct algorithms are investigated for omparison. Computational results show that global PSO algorithm with Solomon insertion heuristics is more efficiency than the others.

Abstract: According to the structure characteristic of the existing equipment for working special-shaped stones, the function partition sketch map of equipment is established in the paper by means of function analysis on the basis of various module partition methods. The theory of function analysis is used to discuss the procedure and method of module partition. Qualitative analysis method based on function is put forward in the paper to divide the main parts with explicit function and structure, while quantitative analysis method is for those whose ascription is ambiguous. The module partition of equipment for working special-shaped stones is completed according to the principle of module partition, establishing the foundation for modularization design and manufacture of equipment.

Abstract: In this paper, it has been studied that the thickness of the free confinement medium in the Laser Shock Processing. Then the relationships are analyzed between the peak pressure induced by laser shock and the properties of the free confinement medium. On the basis, the optimum thickness of the free confinement medium is obtained, which ensure not only the optimum LSP effect but also the elimination of the remains of free confinement medium at a time. In the experiments, a kind of materials of free confinement medium was invented successfully, which is applicable to laser shock processing. The estimation of the free confinement medium theoretical thickness is accorded with the result of the experimental.

Abstract: This study aimed to gain an in-depth understanding of the features of AFM micro probe nanomachining. With the aid of the orthogonal test analysis and synthesis method of point rating, factors of influencing the cutting process: the perpendicular load, the feed amount and the cutting speed, were analyzed. The study revealed that the feed amount and the perpendicular load had greater effect on the surface quality and machining efficiency than the cutting speed. The results were also compared with the conventional ultra-precision machining. The optimal machining parameters suitable for two application fields were achieved. This method is a novel and feasible method to perform the nanomachining.

Abstract: With the virtue of high Young's modulus, fine thermal stability, low density, low price, resourceful and easy to be industrialized, alumina matrix ceramics are widely applied in the environments of high temperature, high pressure, radiation, impact, abrasion and corrosion, etc. The sintering process of large-scale alumina matrix ceramic products is researched in this paper. The conception of temperature gradient is introduced to the sintering process, and corresponding mathematics model is established to get the cellular girder made of alumina, in which the microstructure is distributed evenly. Meanwhile, the material structure and the mechanics performance of the products are discussed. All the study will theoretically guide the development of large-scale fine alumina products.

Abstract: Reversible cutting method is a research thesis proposed to shorten processing route, decrease tool number and handling time, increase machining efficiency. There are three movement ways, i.e. reversible feed motion, reversible primary motion and reversible composite motion. Primary motion is done by workpiece, conventional or reversible feed motion is done by cutting tool in the way of reversible feed motion, e.g. turning. Cutting velocity is passed to cutting tool, clockwise or anti-clockwise cutting movement is done by cutting tool in the way of reversible primary motion, e.g. milling, shaping, drilling (spade drill), reaming. Primary and feed motions are all reversible in composite motion, e.g. turn-milling. Chip deformation and machined surface with reversible finishing is discussed. A mechanical analysis is carried out to the workpiece deformation of slender shaft turning in normal direction and reversible direction. The result has been verified by experiments. Experimental data for the range of cutting parameters tested showed that the reversible fine machining produce the compressive residual stresses at the surface, which are critical in the performance of the machined components. Experimental research indicted that the results of micro-hardness of reversible fine machining technique are smaller than that of general fine machining show that decreased plastic deformation of the surface layer and work-hardening. It can be adopted such planning which rough machining during advance stroke and fine machining during return stroke in machining process.