Toshihiko Mori

Clarification of magnetic abrasive finishing mechanism

Abstract In order to clarify the mechanism of magnetic abrasive polishing, a planar type process for a non-magnetic material, stainless steel, was examined. A magnetic abrasive brush was formed between a magnetic pole and a workpiece material, in which the summation of three kinds of energy necessary for magnetization of abrasives, i.e. repulsion between bundles (Faraday effect) and line tension of outer curved bundle was considered to be minimum. A normal force that pushes the abrasives on the brush end to be indented into the material surface is generated by the magnetic field. The magnetic abrasive brush will then be an extension of the magnetic pole. In this process, the tangential force acts to be the returning force created when the abrasive deviates from the magnetic balance point. Thus, the magnetic abrasives are expected to polish the material surface softly.

Press-formability of stainless steel and aluminum clad sheet

Abstract This paper deals with a stainless steel and aluminum clad sheet produced by pressure welded hot rolled sheets. The tensile tests made on the clad sheet as well as the elements which compose it, stainless steel and aluminum sheets, were carried out in order to determine the fundamental mechanical properties. Basic press-forming tests, which include punch stretching and deep-drawing, were done. The characteristics of the joining process within the range of uniform elongation shows that the aluminum portion has higher ductility than that of stainless steel. However, the latter has higher local deformation and a larger Lankford, r, owing to the inherent characteristic of the two materials. The formability in the processes of both stretching and deep-drawing, are higher when the aluminum is set on the outer side of the cup. The factors related to deformation, such as wrinkling and cup height are controlled by the stainless steel portion due to its high strength. The fracture and deformation mechanisms are clarified by the detailed measurements of thickness strain.

Improvement of mechanical properties of Ti/TiN multilayer film deposited by sputtering

Abstract Advanced functional (multi-layer) coatings, were conducted by r.f. magnetron sputtering. Ti–TiN multi-layer coatings were deposited on a silicon (100) by using multi cathodes. The total thickness was kept at 150 nm and the number of layers was changed from 4 to 40. The relief of internal stress in a film, which causes breaking of the film, and formation of a preferred orientation of the film by increasing the number of layers, was confirmed by measurements of scratching, nano-indenting tests and XRD. These phenomena were explained by minimization of total energy composed of interface and strain energies. The preferred orientation was predicted to change from (111) to (100) with increasing layer number, and XRD produced the expected result.

Combined effects of strain hardening characteristics and tool geometry on the deep-drawability of square aluminum cups

Abstract The combined effects of the corner radii of square tools and the strain-hardening characteristics ( n -values) on the deep drawability of square aluminum cups were investigated. Several materials having different n -values were prepared under various annealing conditions and used in the experiments. Typical fractured cups were observed and classified into several types, according to the location and the propagation of the cracks induced in the drawn cups. The fracture types were strongly influenced by both the n -values and the corner radii of the square punches. The maximum limiting drawing ratio was obtained under the appropriate combination of n -values and the corner radii of the square punches. However, the limiting drawing ratio decreased considerably under the following two combinations: the first, when blanks having higher n -values were drawn with square punches of small corner radii; the second, when blanks having lower n -values were drawn with square punches of large corner radii. The variation in the limiting drawing ratio with n -values and punch corner radii corresponded well to the variation in drawing forces, fracture forces and fracture types of cups.

Ultra-fine piercing by SiC fiber punch

A new ultra-fine piercing in which SiC fiber was used for a punch was proposed. Many new techniques had to be developed in order to realize the process. Thus the ultra-fine punch which has a flat end and an acute edge was obtained and the center of the punch agreed with that of a die. Three kinds of metals which have various thickness and strengths were pierced. A 17 /spl mu/m thick aluminum foil is a specimen of high aspect ratio and low strength, a 15 /spl mu/m thick beryllium copper is a specimen of high strength and a 8 /spl mu/m stainless steel is hard-to-form material. It was shown by observations of a scanning electron microscopy that every hole is truly round and the sheared surface is smooth.

SiC solution growth on Si face with extremely low density of threading screw dislocations for suppression of polytype transformation

In order to achieve a high-quality SiC crystal in solution growth, one of the most difficult issues is to grow a thick layer on Si face avoiding polytype transformation. In this case, two-dimensional nucleation, which leads to the polytype transformation, is frequently induced because a density of threading screw dislocations acting as a source of spiral step decreases and wide terraces form by step bunching as growth proceeds. Therefore, it is very difficult to stabilize the polytype of crystals grown with extremely low density of threading screw dislocations. In this study, we tried to overcome these problems by using specially designed seed crystal and optimizing growth temperature and temperature distribution. We successfully grew thick low-threading-dislocation density SiC crystal without polytype transformation under the condition of high growth temperature and homogeneous temperature distribution.

Die making of ultra-fine piercing by electric discharge machining

The die-hole of the ultra-fine piercing was produced by electric-discharge-machining. A fiber which was used for the punch in the ultra-fine piercing was also used for the electrode in the electric-discharge-machining. Generally, a ceramic fiber is not fitted to the discharge electrode, so new discharge method should be developed. Presented techniques are coatings of gold on the electrode so as to increase electric conductivity and short time discharge so as to machine finely.

Newly developed ultra-fine piercing system

In order to pierce hole of about several micro-meter diameter on stainless steel and so on, a punching method in which a number of techniques were developed. A ceramic fiber cut, ground, polished and gripped by punch holder, and then it could be ceramic used for a punch. Worked material was fixed on a die by vacuum pressure. particularly, a die hole was made by electric-discharging where the fiber punch was used for a cathode electrode. Consequently, the axis of the punch and the die could be positioned with each other.

Improvement of ultra-fine piercing by vacuum system

A new ultra-fine piercing process utilizing SiC fiber as a punch was proposed and micro holes of 14 /spl mu/m diameter were successfully pierced for three kinds of metal foils 8 to 15 /spl mu/m in thickness. In this paper, process refinement to assure the stability of piercing action and good tool life are discussed. As a result of applying a vacuum system, it is confirmed that tool life is rather improved for aluminum and beryllium copper foils and also good quality is maintained after 1000 heats.

Thread Forming by PCR.

A new process for tube ironing, the planetary conical rolling (PCR) process, is proposed. A number of rollers rotate around the cone while revolving around their respective axes, preventing sliding friction which is the main cause of galling and breakage in the conventional ironing process. This process has a number of advantages. For example, high pressure can be applied to the deformed material because of the high rigidity of the axis support cone. For making use of these characteristics, products having surface feature were formed by flowing material into concavities on a die. A thread was chosen as the surface feature, given its practicality. The formed thread was of excellent quality. By this method, a thread can be formed on a thin tube. However, a thread cannot be formed on a thin tube by conventional roiling methods. It was found that a higher filling rate of a material into the concave is obtained with a higher radial pressure. The radial pressure can be controlled by control of the feed speed.