Key Engineering Materials Vols. 315-316

Abstract: Selective laser sintering (SLS) of a multi-component Cu-based alloy, which consisted of a mixture of Cu, CuSn, and CuP powder, was successfully processed. The XRD, SEM, and EDX analysis shows that the bonding mechanism of this process is liquid phase sintering with partial melting of the powder occurred. The CuSn powder with lower melting point acts as the binder, while the Cu powder with higher melting point acts as the structural metal. The element phosphorus acts as a fluxing agent to prevent the Cu particles form oxidation. The distribution of phosphorus shows higher concentration at grain boundaries due to low solubility of P in Cu. A case study on SLS of this powder system to fabricate a gear was carried out. The relative density of 82% and radial dimension error of 1.9% were achieved.

Abstract: In this paper, finite element method (FEM) was applied to analyze the natural characteristics of a diamond saw-blade for deep sawing of natural granite. The vibration mode and nature frequency of the saw-blade were theoretically studied by a commercial FEM software. The factors influencing the natural characteristics of the saw-blade were also discussed. It was found that the natural frequency of the saw-blade increases with its thickness, rotary speed and clamping ratio, but decreases with its diameter.

Abstract: This article first presents the performance of Electrorheological Fluid (ER fluid). Thus, a new-style machining technique based on ER effect to form a tiny grinding wheel is developed for superfine machining. By adding abrasive particles to ER, an array of stable chains of ER particles can be shaped when an electric field is applied and abrasive particles are fixed to these chains structure. When the tip of tool is rotated, the abrasive particles rotate with the flow and a superfine grinding process come into being. This process is expected to be applicable to the aspheric surface machining of micro miniature components made of optic glass or other hard-brittle materials.

Abstract: Balling process in selective laser sintering of 316 stainless steel powder was investigated. It showed that the balling phenomenon was ascribed to the higher liquid viscosity and surface tension effect during laser sintering. The effects of laser power and scan speed on the balling initiation was studied. It was found that increasing laser power and scan speed within a moderate range can reduce balling effect. However, care should be taken to control laser powers and scan speeds that can be used since their excessive increase may give rise to detrimental effects.

Abstract: Few existing systems can support the reuse of conceptual design knowledge due to the lack of satisfying modeling technologies. In the present study, we investigated the ontology-based modeling technologies and apply them to develop a framework of conceptual design knowledge management. The practicability and validity of our framework were then examined in a Construction Machinery Design Knowledge Management System.

Abstract: The contact rigidity and damping between joints of machine tools could vary greatly because of the difference of static and dynamic loading conditions. The pseudo-random gashing cutting is adopted in this paper, which makes the identification of structure transfer function of machine tools close to actual machining condition and improve the identification accuracy. The main idea of this method is to decouple the transfer function in two directions based on left edge and right edge cutting. Therefore, the structure transfer function identification of machine tools in actual cutting excitation is implemented. Finally, this method is compared with the traditional transfer function identification based on electromagnetism excitation and the qualified error is given.

Abstract: A three-dimensional model of molecular dynamics (MD) simulation was employed to study the generation process of nanometric machined surfaces of monocrystalline copper. The model included the utilization of the Morse potential function to simulate the interatomic force between Cu-C and Cu-Cu. By analyses of the MD simulation snapshots of the various stages of the nanometric cutting process and local radial distribution function (RDF), the structure of the bulk and the machined surface with no change and that of the chip with minimal change were observed. Potential energy had significant fluctuations due to generation and propagation of dislocations around the tool. The elastic recovery along the machined surface of the work material was observed after the tool passed. Because the state of machined surface was an important influence on the performance and the physical and chemical properties of product, the effects of surface relaxation on the machined surface state were investigated under the vacuum condition.

Abstract: The functional materials such as sapphire, silicon wafer etc. are processed efficiently with ultra-smooth surface for the demand of the rapid development of the IC industry. The precise double sided polishing process is one of the main methods of getting the ultra-smooth surface for these materials. This paper introduces the structure and characteristic of the precise double sided polishing machine with a precise pressure control system equipped a new type electro-pneumatic digital servo valve. The works, such as machine design, development of the control system and optimization of process parameters etc. are carried out to meet the requirement of the precise double sided polishing machining process. This equipment has the characteristic of high machining precision and precise control capability, so it can be applied to the ultra-precise machining of the ultra-thin sapphire, silicon wafers etc.

Abstract: DC-Plasma arc behavior is one of the key factors on growth of diamond film. The results show that keeping steady DC-Plasma arc can grow better quality diamond film. In a long-time growth of diamond film, there is sediment carbon on about 5mm border-entad anode annulus, which was proved to be graphite. It results in fluctuating and instability of DC-Plasma arc and in the DC-Plasma density, which causes graphite generation and much stress in the film. By means of adjusting anode annulus assembly, pausing the supply of carbon source and increasing H2, the problem of sediment carbon cab be effectively resolved. Finally, the mechanism of the effect of arc behavior on growth of diamond film is discussed.