The grindability of fine-ceramics is most important information in order to determine the optimum grinding conditions. This study proposes the method of grindability evaluation of fine-ceramics by removal rate in constant pressure grinding. The processing model under the constant pressure grinding was composed, and the removal rate was formulated from this processing model. As a result, the removal rate calculated from the processing model is well correspondent with the removal rate obtained by the experiment. From this result, the possibility of evaluating the grindability from the mechanical properties of fine-ceramics was found.
New compositions of a Pt-Zr-Ni amorphous alloy as a mold material for glass lens production were searched using a new combinatorial synthesis called the combinatorial arc plasma deposition (CAPD). First, 3,267 thin film samples of 1 mm x 1 mm size were deposited by CAPD. The phase and composition of 883 samples of the thickness more than 500 nm were evaluated and 312 amorphous samples were found. Secondly, six amorphous samples expected to have a high crystallization temperature (Tx) and a high tensile strength (σB) were deposited using a sputtering system because CAPD samples were too small and thin to evaluate mechanical property such as σB,Young's modulus, elastic limits and anti-sticking with melted glass. Finally, Pt50Zr36Ni14 was found as a new mold material of a high Tx (985 K), a high σB (2.12 GPa) and anti-sticking. The new mold material was also expected to have a high resistance to oxidation at a high temperature range of glass molding.
A multi-polygon laser scanner system has been developed by using a shrink fitter, in order to produce a new laser direct imager having an ultra wide scanning width and high resolution. The shrink fitter is a new machine element which is cylindrical-shaped and made of plastic materials. This is developed to connect the two machine elements that have different thermal expansion coefficients with a shrinkage fit. In this joining method, the optical axes of the lenses coincide with the axis of the lens-barrel. The positioning accuracy of the lenses in the lens-barrel did not change at any temperature since the shrink fitter sufficiently expanded or contracted in the radial direction to compensate the change in interference. Therefore, the beam spot became very fine all over the wide scanning width at elevated temperature. In this study, we applied laser scanner units using the shrink fitter to the multi-polygon system, which arranged these units in a line. The performance of the new laser direct imaging system was confirmed experimentally.
This paper proposes a new micro electrical discharge machining (EDM) method which can machine micro rods and holes quickly and cheaply without special equipments. Since the rod electrode is formed using a hole which is self-drilled by the rod electrode in a plate electrode, this method does not need initial positioning of the rod electrode with respect to the plate electrode. Hence, the operation is easy and the processing time is short. However, the rod electrode is formed into tapered shape even when the self-drilled hole is not yet worn at the outlet. Thus the mechanism of generating tapered rod electrodes was clarified by simulation. Then some novel techniques were proposed to improve the straightness of the micro rods: spark out forming method and step forming method. In these methods, machining was conducted stepwise using all the periphery of the self-drilled hole.
A cylindrical-lensed optical fiber is used for single-mode fiber coupling for 980-nm pump lasers. This paper proposes a new machining method for the cylindrical-lensed end of an optical fiber. The method uses the bending force of the optical fiber which has homogeneous elasticity characteristics. An analysis of the cylindrical-lens machining process reveal the influence of fiber holding angles and slope angles of the polishing plane. Experiments indicate that cylindrical lenses with a curvature radius of 3 to 5 μm can be made with good precision.
In this study, “stealth dicing” (SD) was applied to ultra thin wafers 50 μm in thickness. A coupling problem composed of focused laser propagation in single crystal silicon, along with laser absorption, temperature rise and heat conduction was analysed by considering the temperature dependence of the absorption coefficient. When the depth of the focal plane is too shallow, the laser is also absorbed at the surface as the thermal shock wave reaches the surface. As a result, not only is an internal modified layer generated but ablation occurs at the surface as well. When the laser is focused at the surface, strong ablation occurs. Ablation at the surface is unfavorable because of the debris pollution and thermal effect on the device domain. It was concluded that there is a suitable depth for the focal plane so that the thermal shock wave propagates inside the wafer only. The optimum irradiating conditions such as pulse energy, pulse width, spot radius, and depth of focal plane can be estimated theoretically also for ultra thin wafer.
Scratching and indentation test on (0001) (Ga surface) of single-crystal gallium nitride (GaN) by spherically tipped (10μm radius) diamond is reported in this paper. GaN has attracted keen attention as a new material of electric and light emission devises. It can realize high power and high frequency electric devices and ultra violet∼blue high luminance light emitting device. High-precision processing, however, is difficult because of its hard and brittle properties. Thus basically processing properties of GaN is important for wafer processing. Radial crack initiation load is 0.75N and lateral crack initiates at 1.0N. And two indents under 25μm distance generate interference of cracks. In scratching test for , radial crack and lateral crack initiation loads are 0.97N and 1.17N. These are about 5% higher load than other direction scratches. Proximity scratch test by 0.4N constant load (under crack initiation load) on 100μm× 500μm area achieves flat surface, with 0.012μm Ra and 0.122μm Ry.
Nano-scale mechanical properties, such as hardness, yield load and Young's modulus of metals, are investigated by using nanoindentation test. However, the results of the test are considerably affected by sample surface condition, nose configuration of tip, and so on. In this study, 99.99% and 99.9999% purity aluminums are exposed in air, and the thicknesses of an oxide layer are measured using an X-ray photoelectron spectroscopy (XPS). To investigate the effect of oxide layer on the yield load and hardness on nano-scale, nanoindentation test is performed on the aluminums with the different oxide layer thickness. The oxide layer thickness increases with the period exposed in air, and the layer thickness of low purity aluminum is higher than that of high purity aluminum. In nanoindentation test, it is revealed that the yield load and hardness are considerably affected by the oxide layer.
We report the development of a piezoelectric actuator having a single stator with rotational and translational motion (TR motor). The stator has been fabricated as a rectangular metallic solid with a through-hole. The surface of the inner circle of the hole generates rotational and translational vibration modes, transferring the energy to a shaft, when the voltage at each resonant frequency is applied to the piezoelectric elements. In this paper, the driving principle of the TR motor was clarified using finite element methods (FEM). The characteristic analysis showed the mode shapes and the natural frequency, and then the figure of the stator was designed. The dynamic analysis of the inner surface generated elliptical motions and indicated the motions of the TR motor. Several stators of TR motor were made varying the figure of the length in direction to the axis. The impedance characteristics of the stators have accorded with the simulation.
For development of an adaptable assist device, it requires to quantify users' skillfulness. In this paper, we propose and verify a method to index skillfulness on arm reaching tasks for motor learning. Process analysis of motor learning gives us substantial information on functional adaptability of human motion activities. Hence, we define skillfulness as reproducibility and motion accuracy of motion patterns. In our experiment, a computer monitor displays a moving cursor (e.g., cyclical and random movements), and seven subjects track the cursor with a joystick. We measure electromyogram (EMG) and cursor trajectories on skill acquisition process of the subjects. Then, we evaluate their skillfulness with the internal conditions: the reproducibility is calculated from the variance value of EMG patterns and the motion accuracy is calculated from the trajectory error. Eventually, the results indicated variety of skill acquisition processes, and proved that the proposed method quantitatively-analyzed their skillfulness.
Distributed control systems (DCS) consist of many sensors/actuators and a network interconnecting them, and are being introduced in various automation areas. For assuring the control performance of a DCS under heavy communication traffic, the precise simulation of the DCS is strongly needed. For this purpose, we propose a uniform, efficient and systematic method based on object-oriented design patterns for modeling and simulating DCSs. In this paper, two design patterns are newly proposed; Time-Warp pattern and Protocol pattern. Time-Warp pattern describes classes and interaction for executing the DCS simulation by communicating events having send/receive times, using Time Warp mechanism. Protocol pattern describes classes and interaction for uniformly structuring various communication protocol models used in DCSs, which are composed of the interactions among several layers and the state transition of each layer in a communication protocol. Finally, the effectiveness of the DCS simulator which is developed using these patterns was proved by comparing simulation results with the experiment results using the real DCS consisting of four CAN-based control nodes.
In the hip replacing arthroplasty, to make the stem shape of an artificial hip joint fit to the morphology of proximal femoral canal is generally effective to the fixation in an initial stage. Furthermore, it contributes to reduce a stress shielding at the proximal femur. Therefore, this paper proposed the design method of the custom-made stem corresponding to each patient in order to improve the fill ratio of the stem to the proximal femoral canal. This modeling is mainly achieved by means of a Boolean operation (logical AND operation) of the cross sectional contours of the proximal femoral canal along the circular insert axis, which is decided by the bow of the femoral canal morphology with 3D X-ray CT images and a CAD system. As a result, the fill ratio of the stem to the proximal canal by the proposed method was higher than that by a method with the simple straight type as an insert axis. Also, the fill ratio and the spatial distributions of it in the femoral canals with this proposed method were so similar between the different femoral morphology. The result is important for a design of the custom-made model corresponding to variable femoral morphologies.