Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY

(vol.42 no.481 February 2001)

Flange Thickness in Stretch Flanging
- Accuracy of Formed Product in Axisymmetric Stretch Flanging of Steel Sheet I -

Shigeo ICHIKA\VA, Yasuhisa TOZAWA and Naoyuki KANETAKE

(Received on April 6, 2000)

Based on experimental results of axisymmetric stretch flanging, the flange thickness does not always decrease monotonically from the die shoulder to the flange edge. Reducing the punch diameter and increasing the flange height significantly reduces the flange thickness, while web width does not affect it. In cases where the punch corner radius is small, the thickness reduction of the flange from the edge becomes greater than that of the flange edge, where as thickness reduction at the die shoulder depends on the die shoulder radius. The thickness reduction at the flange edge is estimated using the calculated values under conditions of circum- ferential uniaxial tension.
Key words : sheet metal forming, stretch flanging, axisymmetric flanging, accuracy, thickness, steel sheet

Effect of Thickness on Accuracy of Tube Spinning

Makoto MURATA and Reiko MUTA

(Received on April 10, 2000)

The circular tube has high flexural rigidity and high torsional rigidity as compared with its weight. Therefore, its applicability has increased in many products, and a metal-forming technology which can form the cross section of tubes to various shapes is required. Spinning is a very effective manufacturing technology because it can form the cross section of tubes to various shapes. The authors have developed a prototype CNC (Computer Numerical Control) spinning machine that can form the cross section of tubes to various shapes. Using this machine, the authors carry out various experiments under various spinning conditions, i. e., the shape and the locus of roller tools, and compressive forces in the axial direction. In this study, spinning of aluminum circular tubes is carried out. Then, the effects of conditions such as tube thickness and restraint condition in the axial direction on spinning accuracy, tube thickness after spinning, spinning force and spinning limit such as buckling and rupture are examined. The characteristics and the mechanism are clarified in this study.
Key words : rotary forming, tube forming, spinning, forming property

Addition of Pulling Force to Pipe Bending Method Using a Floating Expanding Plug

Seijiro MAKI, Takahiro TAKEDA, Yasunori HARADA, Ken-ichiro MORI and Masao NAKAMURA

(Received on April 28, 2000)

Addition of pulling force at the exit in circular pipe bending using a floating expanding plug method is investigated both experimentally and theoretically. In the experiment, rotary draw bending using an eccentrically fixed expanding plug, which bears resemblance to the floating expanding plug method, is performed by varying the pipe expansion ratio, eccentricity, bend radius and pulling force ratio, and bending performance is examined in relation to the pulling force ratio. Draw bending using an eccentric plug fixed protrusionly produces a smaller bend radius and smaller flattened cross sections in pipes than using a concentric plug fixed normally at any pulling force ratio. However, draw bending using only pulling force produces large flattened cross sections compared with those using one-third or two-thirds of the pulling force, indicating that there is. an optimum pulling force ratio. Based on the results, addition of pulling force is suggested for the floating expanding plug method. This suggestion is also supported by theoretical analysis using the slab method.
Key words : tube forming, bending, draw bending, pipe, expanding, eccentric plug, forming limit, slab method

Elongation-Control Effects in Rolling of Flat Wire from Round Wire
- Development of Elongation-Control Rolling II -

Masaki SHINKAWA, Hiroshi UTSUNOMIYA, Yoshihiro SAITO, Kagenori OKA and Fumihisa SHIMAYA

(Received on May 10, 2000)

We have developed an elongation-control mill. It is a five-stand tandem mill and is able to control the deformation of the workpiece by means of the interstand forces generated by the differences of roll speeds. In this study, flat wires of various widths were rolled from round wires. Aluminum, copper, medium carbon steel, and stainless steel wires were used as stock. Various rolling properties, such as deformation of the workpiece, load on the mill, and forward slip, were examined. The interstand force was precisely measured and its influence on rolling properties were elucidated. It was confirmed that the elongation in rolling or the lateral spread could be changed over a wide range with this mill.
Key words : rolling mill, tandem mill, elongation-control rolling, elongation, dimensional control

Bending of Pipe Having Nonuniform Distribution of Temperature by High-Frequency Induction Heating

Shinhou KURIYAMA and Tokuo AIDA

(Received on June 14, 2000)

Bending of a pipe with an axisymmetrical cross section by high-frequency induction heating is investigated theoretically. The area of the pipe heated to high temperature is localized to a narrow ring part of it, whose temperature is varied by heating and cooling. Analysis of nonuniform distribution of temperature is carried out. The heated material is assumed to be a rigid-plastic material which has plastic flow stress depending on temperature. By extending the beam bending theory to the plastic deformation region, two equations that can predict the position of a neutral plane, and the bending force are obtained in the case of a circular cross section.
Key words : bending, plasticity theory, high frequency induction heating, axial force, pipe, nonuniform distribution of temperature, neutral plane, reduction of wall thickness

Oil-Free Deep Drawing of AZ31 Magnesium Alloy Sheets Using Hard Thin-Film-Coated Tools

Nobuhiro KOGA and Ratchanee PAISARN

(Received on June 26, 2000)

Because of the current popularity of lightweight and recyclable metal components, the possibility of processing metal components composed of various magnesium alloys by press working, such ass deep drawing and forging, has already been examined in several research institutions and companies. Although AZ31 magnesium alloy is more ductile than other magnesium alloys, it is still inferior to other metal materials. Therefore, it is difficult to perform press working on an AZ31 magnesium alloy at room temperature, and warm working is currently applied. When press working, such as deep drawing and forging, is performed by warm working, the magnesium being processed adheres to the tools and thus, it becomes a problem, even when lubricant oil is used. This. may lead to the gradual deterioration of precision of the product shape and reduction of the tool life. The purpose of our study is to solve these problems and experimentally examine the possibility of oil-free deep drawing using hard thin-film-coated tools. The results indicate that the limiting drawing ratio can be improved to approximately 2 . 6 when tools coated with carbon films such as WC/C or Me-C : H are used in oil-free deep drawing, and stable production of flawless products becomes possible.
Key words : deep drawing, magnesium alloy, oil-free, hard thin film, coating, tool life