Key Engineering Materials Vol. 516

Abstract: This study describes a novel process to drill small holes in brittle materials such as glass, silicon and ceramic using a self-elastic polycrystalline diamond (PCD) drilling tool. In order to improve the surface roughness and reduce crack of the small holes, a new type of self-elastic PCD drilling tool equipped with vibration absorbing materials inside the housing was developed to fabricate small holes in glass in this study. The self-elastic PCD drilling tools could absorb the mechanical force by the vibration absorbing materials while the PCD tool penetrates into the small holes. Compared to conventional PCD drilling tools, the experimental results show that high-quality small holes drilled in glass can be achieved with cracking as small as 0.02mm on the outlet surface using the self-elastic PCD drilling tool.

Abstract: We propose the application of open-air type numerically controlled plasma chemical vaporization machining (NC-PCVM) to fabricate a doubly curved crystal (DCC) substrate. Since PCVM utilizes only a chemical reaction to remove the work piece surface, there is no degradation of the crystallographical properties of the work piece material. In our previous study, we succeeded in fabricating a curved Si (111) crystal substrate with a curvature radius error of 0.08 %. Rocking curve measurement results revealed that there was no lattice strain on the processed surface. However, surface roughness degraded after PCVM figuring. To reduce the surface roughness, we modified the structure of the electrode unit, which generates plasma, to be able to supply a shielding gas. By supplying helium with a flow rate of 0.5 L/min as the shielding gas, rms surface roughness of the silicon was reduced from 0.73 nm to 0.42 nm. Excessive supply of helium (> 1 L/min) and/or supply of argon caused deterioration of the surface roughness. These results indicate that appropriate supply of the shielding gas is effective in reducing roughness in the open-air type PCVM process.

Abstract: Shot-peening is the process of repeatedly hitting the work piece surface with small balls, making overlapping indentations on the surface. This process is extensively used on shafts, gears, springs, and jet engine parts because it imparts compressive residual stresses on the surface, thus improving the fatigue life of components. Under-peening does not give a sufficient fatigue life while over-peening induces cracking and reduces fatigue performance. Hence, determining optimal peening conditions such as peening time is very important. In general, optimal peening conditions are experimentally determined by measuring arc-height using Almen-strip or calculating coverage using microscope images. Shot-peening coverage is defined as the proportion of the exposed surface that has been impacted in a given time of shot-peening. To save the time and effort spent in repeating experimental measurement needed whenever the geometry of a work piece and peening conditions change, this paper presents a computer simulation algorithm for the prediction of shot-peening coverage, which is based on the geometry of a work piece. An example is presented to validate the proposed method.

Abstract: A novel internal diameter measurement method based on a low-coherence tandem scheme is firstly demonstrated. From operational analysis, it is understood that a low-coherence tandem scheme can be served for internal diameter evaluation by using a combination of a transmission grating and a ring gauge instead of a classical Michelson interferometer to store and transmit the internal diameter information. As a result of the experiment, in the present experimental environment, diameter measurement of several millimetres with a relative standard uncertainty of several micrometres was performed. Taken together, these results suggest that the present measurement method is expected to be used as a powerful remote internal diameter calibration tool for next-generation calibration network systems.

Abstract: This paper describes Autonomous Decentralized FMS (AD-FMS) and its method to control automatic guided vehicles (AGVs) by using a memory. The aim is to increase the reasoning efficiency of a system the authors call reasoning to anticipate the future (RAF) which controls AGVs in AD-FMS. This RAF applies hypothetical reasoning to the number of next actions that can be considered for the AGV (competing hypotheses). However, if the number of agents included in the hypothetical reasoning process in the RAF is increased, the number of next actions that are considered as competing hypotheses also increases. As a result, the replacement of true and false hypotheses and number of repetitions of discrete production simulations produced by these replacements are increased, giving rise to the problem of decreased reasoning efficiency of the RAF. The present article reports a method to solve these problems. The reported method, the authors call ranking by oblivion and memory (ROM), is based on the idea that when a production situation occurs that is the same as one in the past, the same destination as in the past is more likely to be selected; that is, it has a high probability of being selected as the true hypothesis. By applying the ROM to AD-FMSs constructed on a computer, it was found that under all conditions the ROM reduced the number of hypothesis replacements to half that of a conventional system, demonstrating the validity of this system.

Abstract: Rotary drilling rigs, general construction equipment, are widely used for deep drilling of ground for the foundations of public works. A new 250kN.m-type rotary drilling rig, most widely used in this field, is under development, and this study focuses on the operational safety of the mast subassembly on the basis of structure analysis of the mast subassembly using a finite element method with ANSYS. When using a drilling rig, an electric rotary drive supplies power for drilling. Here, the elevation of the rotary drive along the mast needs to be changed according to the geological construction environment. Through the analysis, the allowable torques at various elevations of the rotary drive are evaluated, also the safety of the drilling tool called the kelly bar subassembly is examined. Finally, the suitability of the mast subassembly design is examined from the analysis results.

Abstract: In recent years, there have been many studies concerning the effect of cutting parameters and tool parameters on the ultra precision machining of electroless nickel. However, there is no known reported study on the relationship between the cutting force and tool rake angle in ultra precision machining of electroless nickel. The objective of this study is to compare and investigate the cutting force with various rake angles for micro machining electroless nickel work pieces by theoretical analysis and experiment. Diamond tools with rake angles of-10^o, 0^o and 10^o were used in the experiment. According to theoretical analysis, the tool with a 10^o rake angle induces the smallest cutting force. However, the experiment showed that the tool with zero rake angle always gave us the smallest cutting force for all cutting speeds, cutting depths and pattern pitches.

Abstract: Position and orientation adjustment is an important issue in the micromanipulation of cells. A non-contact method based on micro-fluid for cell position and orientation control was introduced in this paper. The cells were positional fixed by the pressure force of a pair of lined micro-fluids from two tiny tubes. The orientation adjustment was realized by rotating cells in swirls caused by a pair of parallel micro-fluids. By spraying fluctuant micro-fluid, cells orientation can be controlled more precisely. The experiments proved that this non-contact cell position and orientation adjustment method is feasible and secure.

Abstract: In this paper, we proposed an optical vibration and circulation technique of a microsphere using plural optical flat-top fibres, mounted horizontally on the bottom of a sample chamber, and verify that an optically trapped object can be circulated by controlling laser power emerging from optical fibres without moving the optical fibres. We theoretically analyzed the optical forces exerted on a microsphere, a 10μm diameter polystyrene particle (refractive index 1.59), by laser beams. From these theoretical results, we verify that our proposed optical manipulation technique is useful for the manipulation of biological cells.

Abstract: Micro structured glass lenses are highly required in new fields such as Micro channels, Fresnel lenses for solar panels and Wafer Level Cameras (WLC). The glass lenses are moulded bypress moulding with micro ceramics moulds made of tungsten carbides (WC). In this paper, a new Vibration Assisted Polishing (VAP) method is proposed and developed by using circular vibration of the magnetostrictive vibrating polisher. The polisher is composed of a magnetostrictive vibrator and a small polishing tool, and the small polishing tool is mounted on the head of the magnetostrictive vibrator. The concrete design of the magnetostrictive vibrating polisher is assisted by the finite element method (FEM) and through vibration mode analysis, the 4th mode is selected. It generates a circular vibration trace at a frequency of 9.2 kHz with a radius of 30 μm. The polisher is fixed in a 5-axis (X, Y, Z, B and C) controlled polishing system. Through some fundamental polishing experiments, the shapes of the removal function is acquired and surface roughness is reduced to 9 nm Rz (1 nm Ra).