Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY

(vol.44 no.507 April 2003)

Effect of Tip Thickness of Center Bevel Cutter on Load Characteristic of Cutter Indentation to Aluminum Sheet

Mitsuhiro MURAYAMA, Shigeru NAGASAWA, Yasushi FUKUZAWA and Isamu KATAYAMA

(Received on April 30, 2002)

This paper reports on the fundamental relationship between the tip thickness of a crushed cutter and the thickness of a wedged sheet. Aluminum sheet was used for the specimen, while the cutter made of tool steel was modified by filing. By varying the tip thickness cutter, the resistance of cutter indentation and the shared profile were investigated experimentally. Frictional conditions between the wedged sheet and the counter plate beneath it were selected as lubricated and nonlubricated. For discussing the deformation mechanism, Hill's solution with slip line theory and finite element analysis with an elasto-plastic model were applied to the wedge indentation. The derived results were as follows. The initial contact with the crushed wedge can be approximated with a flat punch indentation into the elasto-plastic body, and also the first inflection point of the load indentation curve can be predicted by Hill's solution. The second inflection point is the marginal depth of the wedged sheet, where a half-infinite object cannot be assumed to be applicable. The maximum load point depends on the tip thickness of the cutter and also on the friction of the counter plate.
Key words: shearing, cutting edge, wedge indentation, rule die, crushing, dead zone, critical thickness

Hydraulic-Bending Process of Non-Circular Pipe

Takashi NAGANAWA, Shinji TANAKA, Yuuji YOSHITOMI, Syouta IWAKURA, Takamitsu NAKAZAKI and Toshimi SATOH

(Received on May 17, 2002）

We established a new hydraulic-bending process that enables us to form a complicated non-circular pipe directly from a blank tube. Using the process, we formed a pipe that had a circular cross section at both ends and a rectangular one in the middle. The process consists of two stages. In the first pre-forming stage, we transform the original circular tube into a bulge-shaped tube using a hydraulic-bulge process, while taking into account the shrinkage that will occur during the next stage, bending. Following pre-forming, we bend the bulge-shaped tube using upper and lower dies while applying internal pressure. Measurements showed that the shape of the products formed by the new process deviated by less than 0.8% from that of the designed figures. Also, the maximum compression strain measured in one end of the rectangular section and the thickness loss of the products were within 8%. We consider that these figures prove that the process is sufficiently applicable, and the pre-forming contributes to the high dimension accuracy of the final product.
Key words :tube forming, expanding, die bending, forming property, deformation-load property, accuracy, hydraulic-bending, non-circular pipe

Press-Forming Technique for Sliced Wood Sheets

Kazutoshi TAKEUCHI, Masaya NOGI, Hiroshi IMANISHI, Yuzo FURUTA and Kozo KANAYAMA

(Received on May 31, 2002)

Wood is a porous anisotropic material produced by woody plants. It is processed mainly by cutting and rarely by plastic forming. In this study, laminated sliced wood sheets were pressed into shapes and the possibility of plastic forming of sliced wood sheets was investigated. Wood cracks more easily in the direction parallel to the grain than in the direction perpendicular to the grain. It is necessary for wood to be processed under the condition that no crack parallel to the grain occurs in the case of plastic forming of wood. A cross section of the wood fiber of a molded part was directly observed under an optical microscope. It was found that the cells were deformed due to wall buckling of thin cell walls. It is considered that this deformation is caused by in-plane compression stress that occurred upon press forming and that cell compression restrains the increase in compression stress. These results indicate that sheet forming can be applied to sliced wood sheets by making use of cell compression.
Key words: sheet forming, sliced wood sheet, anisotropic material, porous material, cell shape

Measurements of Pressure on Die Surface and Deformation of Extrusion Die to Hot Extrusion of Plate and H-Shape
――Deformation of Extrusion Die in Aluminum Hot Extrusion V――

Tsutomu MORI, Norio TAKATSUJI, Kenji MATSUKI, Tetsuo AIDA, Kazuo MUROTANI and Kouichi UETOKO

(Received on June 17, 2002)

The pressure on the die surface and the deformation of extrusion dies to complicated shapes (plate, H-shape) of 1050 aluminum extrusion at 623K are measured. The pressure on the die surface and the deformation of extrusion die are measured by using the semiconductor-strain-gauge-type pressure sensor and laser displacement meter commercially available, respectively. For both the plate and H-shape extrusions, the extrusion pressure gradually decreases or remains constant at a certain pressure with increasing the ram stroke, while the pressure on the extrusion die surface gradually increases with increasing the ram stroke. The pressure on the extrusion die surface hardly changes with changing the bearing length. For both the plate and H-shape extrusions, the deformation angle (total deflection of die) increases with increasing the ram stroke. The deformation angle of extrusion die in H-shape extrusion is high at the tongue part of extrusion die compared with at the other parts.
Key words: aluminum extrusion, pressure distribution, deflection of extrusion die, measurement, 1050 aluminum

Shot Lining of Light Metals with Hard Powder

Yasunori HARADA, Hitoshi KOSUGI, Ken-ichiro MORI and Seijiro MAKI

(Received on July 16, 2002)

Lining light metals with hard powder by shot peening was carried out. The hard powder is bonded to the surface of the workpieces due to the collision of many shots. To fix the hard powder to the surface of the workpiece, the powder was set on an uneven surface. To facilitate easy fixing of powder, lining the workpiece with the powder sandwiched between two aluminum foil sheets was also attempted. In this experiment, a centrifugal shot peening machine with an electrical heater was employed. The workpieces were aluminum and magnesium alloys, and the hard powder was commercially pure chromium, cemented carbide or ceramic. The effects of collision speed and the processing temperature on the bondability were examined. The wear resistance was also evaluated by a wear test. It was found that the hard powder was successfully bonded to the surface of workpieces by the shot lining process.
Key words: shot peening, joining, lining, hard powder, bondability, aluminum alloy, magnesium alloy, ceramic, cemented carbide

Shaping of Spur Gear by Two-Step Extrusion Method through Reducing Outer Diameter of Workpiece

Yozo SAWAKI, Hajime YOSHIDA, Yoshihisa SAKAIDA and Tadashi SUZUKI

(Received on August 6, 2002)

The authors previously proposed a two-step cold extrusion method of forming internal spur gears and inner helical splines. This method was applied to form external gears using plain carbon steel, S15C. A specially designed die for forming an external spur gear in two steps was used to reduce the outer diameter of the cylindrical workpiece. The specifications of spur gears examined were as follows;module, 1.25;number of teeth, 18. It was shown that almost all the shaping conditions examined resulted in complete teethed spur gears with even only 33 precent area reduction under a low punch pressure. Analysis by Finite Element Method shows that 1) the flow of material towards the tooth tip (radial direction) is improved, because of the bigger tooth profile of the die in the first step of extrusion, and that 2) the flow of material in the circumferential direction is also induced by forming a thinner target tooth profile from the bigger tooth in the second step of extrusion.
Key words: cold extrusion, ferrous metal, spur gear, reduction in area, formability



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