Eiki Okuyama

Concurrent measurement method of spindle radial, axial and angular motions using concentric circle grating and phase modulation interferometers

This paper describes a concurrent measurement of spindle radial, axial and angular motions using concentric circle grating and phase modulation interferometers. In the measurement, a concentric circle grating with fine pitch is the reference artifact. A frequency modulated laser diode is used for the light source of the phase modulation interferometers. The phase modulation interferometers, which consist of three Michelson and three grating interferometers, measure three radial and three axial displacements of the grating. From these six measured displacements, radial, axial and angular motions of a spindle can be determined concurrently. In the paper, a measurement principle, a measurement instrument and experimental results are discussed. Concurrent measurements of spindle radial, axial and angular motions were successfully attained.

New analytical method for V-block three-point method

The V-block method is a widely accepted method for measuring the roundness of a cylindrical workpiece. However, the complexity of conventional analysis schemes, based on Fourier transformation, makes it difficult to develop specific software programs for analyzing the measured data. Here, a new algorithm developed for the three-point method using inverse matrix calculations is extended to the analysis of the V-block method. The results are compared with the conventional analytical algorithm and the validity of the new method is confirmed.

Prediction of central bursting in extrusion

Abstract Central burst defects which are also called chevron cracks, in extruded products are analyzed. The criterion based on plastic instability was used in order to predict central bursting. It satisfies sufficient condition s ˙ i ɛ ˙ i = 0 for the multiplicity of the solution, which is derived from the necessary condition, Δ s ˙ i Δ ɛ ˙ i = 0 where s ˙ i denotes the nominal stress rate, and Δ the difference of any two multiple solutions. The criterion gives the limit strain identical to that derived from Swifts criterion (diffuse necking) under plane stress condition, but conceptually it is entirely different from Swifts. Stress and strain on the specimen were evaluated using the finite element method (FEM). We proposed a measure y M which represents the risk probability of cracking and calculated it using the stress and strain on the central axis of the product. When y M ≤0, bursting occurs. The value of y M is shown in the range of combinations of the die half angle and the reduction area. Boundary curve that separates the defect zone from the non-defect zone in the relationship with respect to the above combinations takes a nose-like shape, which is quite different from that based on Avitzurs prediction.

A two-dimensional atom encoder using one lateral-dithered scanning tunneling microscope (STM) tip and a regular crystalline lattice

In this paper, we propose a new 2D displacement atom encoder using only one lateral-dithered scanning tunneling microscope (STM) tip and one mono-crystalline area of the highly oriented pyrolytic graphite (HOPG) crystal. A high-speed lateral circular dither modulation with proper amplitude is applied to a tip scanner to position the STM tip on six specific points on the HOPG crystalline surface. Multi-tunneling-current signals obtained from the six specific points are utilized to determine the lateral 2D displacement based on the two unit lattice vectors on the HOPG crystalline surface. In addition, the interpolation method can be used in the newly proposed method to measure displacement less than the lattice spacing. In the paper, instrumentation and experiments of the new 2D displacement measurement technique are discussed. The experimental results show that the proposed technique has the capability to measure 2D displacement with a resolution of 10 pm order.

Proposal of concurrent measurement method for spindle radial, axial and angular motions using concentric grating interferometers

In this paper, we propose a measurement method for spindle radial, axial and angular motions using concentric circle grating interferometers. In this method, the grating is installed on top of the spindle. Three optical sensors, which consist of two interferometers, are fixed over the grating. One interferometer detects an interference signal between reflection lights from a fixed mirror and the grating for vertical displacement measurement. The other interferometer detects an interference signal between ±first diffraction lights from the grating for lateral displacement measurement. Using three optical sensors, radial, axial and angular motions of the spindle, can be measured concurrently.

Spindle error motion measurement using concentric circle grating and phase modulation interferometers

In the conventional methods to measure radial, axial and angular motions of spindles, complicated artifacts with relative large volume (such as two balls linked with a cylinder) are required. Small volume artifact is favorable from the viewpoint of the accurate and practical measurement of the spindle motion. This paper describes a concurrent measurement of spindle radial, axial and angular motions using concentric circle grating and phase modulation interferometers. In the measurement, the concentric circle grating with fine pitch is installed on top of the spindle of interest. The grating is a reference artifact in the method. Three optical sensors are fixed over the concentric circle grating, and observe the proper positions of the grating. The optical sensor consists of a frequency modulated laser diode as a light source, and two interferometers. One interferometer observes an interference fringe between reflected light form a fixed mirror and 0-th order diffraction light from the grating to measure the axial motion. Another interferometer observes an interference fringe between ±2nd diffraction lights from the grating to measure the radial motion. Using three optical sensors, three radial displacements and three axial displacements of the proper observed position of the grating can be measured. From these measured displacements, radial, axial and angular motions of the spindle can be calculated concurrently. In the paper, a measurement instrument, a novel fringe interpolation technique by sinusoidal phase modulation and experimental results are discussed.

A Circular Profile Measurement Method Using Software Techniques

In industry, disk type products with a highly accurate surface such as silicon wafer and hard disk, are important elements. To measure these surfaces, an interferometer is used. However, this method generally needs a highly accurate reference surface. Another method to obtain the disk surface profile is by a scanning displacement sensor. However, the output of this sensor is influenced by the parasitic motions of the scanning along the reference guide. This article presents novel measurement procedures, a reversal method, an improved reversal method and a multi-prove method, to measure the circular profile on a disk without any references but with high accuracy.

Surface Roughness Measurements of a Narrow Borehole — Development of Stylus with Cylindrical Mirror and Lensed Fiber

In various industrial fields, it is frequently necessary to measure surface roughness in confined spaces such as boreholes and grooves. However, using a small stylus, the surface roughness of a narrow borehole can be directly measured only a few millimeters from its end; alternatively, destructive measurements must be performed. This major disadvantage of conventional stylus-based surface profilometers is mainly due to an inductive pick-up that is connected to the stylus used to detect the surface roughness. In this paper, we propose a novel surface roughness measurement sensor. To make the surface roughness sensor small, we used a stylus with a cylindrical mirror and a lensed fiber instead of a conventional inductive pick-up. The proposed sensor converts the signal obtained by measuring the surface roughness of a borehole into an optical signal, which is transferred outside the borehole by an optical fiber. Experimental results demonstrate that this system has a measurement range of 8 μm and a sensitivity of 19 nm. Surface profiles were measured by the proposed sensor and by a conventional surface profiler and the results were found to be very similar.

Intrinsic criterion of plastic instability

Abstract Hitherto the approaches on plastic instability have been carried out mainly in evaluating sheet formability. The necking in press forming is a phenomenon relating to plastic instability. It is classified into diffuse and localized neckings. Swift [1] proposed the criterion of diffuse necking, and for localized necking Storen and Rice [3] presented the modified criterion of Hills [2] in order to make it possible to predict the formability in biaxial stretching. Since there is some imperfections in these criteria and they do not provide sufficient conditions for the emergence of necking phenomena, they must be improved. This paper presents comprehensive criteria based on the multiplicity of solution.

Criterion of plastic instability and its application for predicting ductility in metal forming

Abstract General criteria for ductility based on plastic instability are presented, and unreasonable treatments in the criteria proposed by Swift [1] and by Storen and Rice [2] are pointed out. It is shown that the correction of these imperfections makes their criterion consistent with general criteria proposed here. Then, the applications of the criteria to the prediction of cracking in several metal formings are demonstrated: the formability under linear strain paths in sheet metal forming, the free surface ductility and cracking mode in upsetting, and the central bursting (chevron crack) in drawing and extrusion. The analytical prediction in a wide range of processes are found to be in very good agreement with experimental results.