Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(vol.42 no.489 October 2001)
Deformation Mechanism of Sheet Metal in Stretch Forming
with Computer Numerical Control Machine Tools
Takao SAWADA, Gunpei FUKUHARA and Makoto SAKAMOTO
(Received on January 29, 2001)
It is well known that the sheet metal can be stretched by incremental forming with Computer Numerical Control machiue tools. The deformation mechanism is studied by 3D-FE analysis. It is numerically presented that the thickness of the sheet metal is decreased under "the Sine rule", the deformation of which is subjected to bending and unbending with stretching along the meridian line aud shear in the circumferential direction. In addition, necking is induced on the part of the sheet metal in contact with the punch and it is stops after the punch passes through the necking point. This deformation process is repeated as the punch travels along the sheet metal, and significantly stretches the sheet metal.
Key words : incremental forming, stretch forming, 3D-FEM, necking, bending, sheet metal
Proposal and Fundamental Experiments of a Wire Drawing Method
Using Bisected Dies Vibrated Ultrasonically and Transversally
――Study on Drawing Using Bisected Dies Vibrated Ultrasonically and Transversally I――
Masahiro HAYASHI, Masahiko JIN, Pongpan KAEWTATIP, Hiroyuki NOGUCHI and Masao MURAKAWA
(Received on November 8, 2000)
In this study, we have proposed a new ultrasonic drawing method in which bisected dies, vibrated ultrasonically and transversally, are used for drawing difficult-to-draw materials such as titanium or difficult-to-draw shapes such as square so as to respectively obtain a good drawability. More specifically, although the conventional axial-symmetric and radial ultrasonic vibration drawing method has proven to be effective for drawing difficult materials with good results, the method is subjected to some drawbacks particularly decreased available amplitude for relatively smaller diameter wires. In an effort to solve the problem, we have developed the above new ultrasonic drawing method. This paper shows the experimental results in which round wires without any oxide coating surface layer were drawn by this method into round or square wires with good surface integrity and/or shape precision, which has been very difficult with the conventional methods with or without ultrasonic vibration.
Key words : drawing. wire drawing, ultrasonic drawing. titanium wire, manufacturing system
Shear Band Bifurcation Analysis and Results for a Single Crystal
――Ductile Fracture of FCC Crystals by Shear Band Formation I――
Shokichi KANNO, Jun NITTA, Koichi ITO, Yoshihiro KAMADA and Taketoshi SAGAWA
(Received on November 20, 2000)
The numerical analysis, based on crystal plasticity, of the formation of a localized shear band in a ductile single crystal is carried out. The critical state of shear band formation is predicted by the bifurcation theory. For a three-dimensional face-centered cubic single crystal which posesses 12 slip systems, we perform eigenvalue analysis of the acoustic tensor obtained from an equilibrium equation in which a shear band mode is assumed. Some ideas are proposed to overcome difficulties which occur in analyzing shear band bifurcation of a rate-independent crystal. The numerical results for an fcc single crystal under uniaxial tension are presented. The critical strain varies with initial tensile direction in the crystal coordinate system, aud its numerical value decreases as the initial tensile direction approaches [211] in the basic triangle.
Key words : crystal plasticity, numerical analysis, shear band, fcc single crystal, sheet metal forming, acoustic tensor
Measurement of Pressure Distribution on Die Surface
in Hot Extrusion of Pure Aluminum Rod
――A Study of Deformation of Extrusion Die in Aluminum Hot Extrusion I――
Tsutomu MORI, Norio TAKATSUJI, Kenji MATSUKI, Tetsuo AIDA, Kazuo MUROTANI and Kouichi UETOKO
(Received on December 14, 2000)
In this study, the pressure on the die surface in a rod (diameter=32 mm and extrusion ratio=10) of A1050 extrusion is measured at a position 27-45mm from the die center using the semiconductor-strain-gauge-type pressure sensor available on the market. As a result, it is found that the pressure on the die surface decreases or becomes constant at a central region at a position about 30mm from the die center where the pressure is highest. On the other hand, it is found that the pressure on the die surface decreases as a measurement position approaches the container wall. The temperature of the metal under extrusion decreases as a measurement position approaches the container wall, and it is found that the distribution of temperature hardly influences the distribution of pressure. The distribution of flow velocity and the equivalent strain rate are measured by visio-plasticity analysis; these parameters quantitatively determine the metal flow during plasticity processing. It is assumed that the change in the metal flow near the position about 30mm from the die center influences the distribution of pressure.
Key words : aluminum extrusion, pressure distribution, temperature distribution, visio-plasticity analysis