Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY

(Vol.40 No.464 September 1999)

Deformation Behavior in High-Aspect Hole Punching into Ceramic Green Sheets ――Plastic Working of Ceramic Green Sheets Ⅳ――

Ryoji IWAMURA, Hideaki TANAKA， Mitsuhiro TAKASAKI and Kazutoshi TAKAHASHI

(Received on June 8, 1998)

In the production of a mutilayer ceramic circuit board, shearing, hole punching and hot-press lamination of ceramic green sheets are needed as the accurate plastic working. Hundreds of thousands of high-aspect holes have to be punched into ceramic green sheets. Minor deformations around the holes due to punching cause low-accuracy hole positions and undesired deformations in the ceramic green sheets. To determine the deformation mechanism involved in punching high-aspect holes in ceramic green sheets, a large-scale model was examined and confirmed to be satisfactory for studying the deformation mechanism in high-aspect hole punching. It is clarified that deformation in high-aspect hole punching occurs during punch insertion. The deformation value is about twice that for pure copper. This deformation can be reduced by increasing the clearance between the punch and die to more than 6% and by increasing the punching speed.
Key words : shearing, punching, ceramics, green sheet, composite material

Numerical Simulation of Metal Flow in Spreading Extrusion of Wide Flat Bar ――Study of Spreading Extrusion Process Ⅱ――

Yoshinobu IMAMURA, Norio TAKATSUJI, Kenji MATSUKI, Tetsuo AIDA, Kazuo MUROTANI and Hideshi YASUDA

(Received on August 17, 1998)

A rigid-plastic finite-element method using a diagonal matrix is proposed to perform large-scale three-dimensional simulations of metal forming processes in a realistic computing time. Uncoupled equilibrium equations of forces at one nodal point are repeatedly calculated sequentially without solving the large global matrix. In the equilibrium equations, three corrective velocities at the nodal point are determined in order to eliminate imbalanced forces for trial velocities. This formulation leads to reduction in the increase rate of the computing time with the number of nodal points. In addition, the program for the developed simulator is much simpler than that of the conventional method, and the computer memory capacity is very small because the global simultaneous equations are not solved at a time. To examine the convergence of solutions in the present method, the three-dimensional deformation by upsetting a rectangular block with flat dies is simulated under non-sliding contact over the die surface. The effects of the initial nodal velocities, the order of nodal points for solving the equilibrium equations and a modification factor for the corrective velocities on the convergence are evaluated.
Key words : finite element method, plasticity, numerical analysis, rigid-plastic analysis, large-scale simulation, three-dimensional deformation, diagonal matrix, iterative solution

3-D Rigid-Plastic Finite-Element Method Using Diagonal Matrix

Hideori YOSHIMURA, Ken-ichiro MORI and Kozo OSAKADA

(Received on October 9, 1998)

Finite-Element Simulation of Deformation Features of Sheet Metal Welded through Squeeze Rolls in ERW Pipe Mill

Yoshitomi ONODA, Takuo NAGAMACHI, Tomotaka HAYASHI, Masayuki YAMADA and Tateo YAMADA

(Received on October 13, 1998)

Deformation features of sheet metal (0.23% carbon steel) that the seam is welded using a high-frequency electric resistance welding machine and a pair of squeeze rolls in a mill to produce a circular welded pipe (51.3mm in external diameter, 5.0mm wall thickness) are discussed with reference to experimental measurements and results calculated using the rigid-plastic finite-element method. The results are as follows. Both the V-convergence angle, that is, the apex angle of the V-shaped seam formed at the entry of a pair of squeeze rolls and the inclination angles of the metal flow lines directed outward or inward in the heat-affected zone adjacent to the welded seam increase with an increase in both the upset imposed by a pair of squeeze rolls and the flange diameter of the rolls. The maximum value of the inclination angle is found on the metal flow line close to the outer surface of the heat-affected zone. This maximum inclination angle can be reduced significantly by making the welding temperature uniform in the wall thickness direction.
Key words : roll forming, ERW pipe mill, high-frequency electric resistance welding, squeeze rolls, seam guide rolls, upset, welding temperature distribution, rigid-plastic FEM

Lining of Metal Surface with Metal Foil Using Shot Peening

Yasunori HARADA, Ken-ichiro MORI and Seijiro MAKI

(Received on October 15, 1998)

A method for lining metal surface with metal foil using shot peening is proposed. The foil is bonded to the surface of the base metal due to plastic deformation induced by the shot collisions. To heighten the weldability, the foil and base metal are heated up to 500℃. An experiment using a single shot is carried out under vacuum and air atmospheres, and the bond strength is evaluated by tearing the foil from the base metal. In this experiment, the base metals are mild steel and commercially pure copper and aluminum; the foils are commercially pure aluminum and mild steel with a thickness of 0.1 mm. The combination of the carbon steel base and the aluminum foil exhibited good weldability, whereas the lining of the copper base was difficult to bond. By performing actual peening operations with many shots, the aluminum foil is successfully bonded over the surface of the carbon steel base.
Key words : joining, lining, shot peening, weldability, aluminum foil, single shot, plastic forming, bond strength, surface treatment, plastic deformation

Incremental Forming for Automobile Body Panel by Supporter Method

Fuminori MATSUDA, Katsutoshi UENO, Tatsuya NAGATA, Nobuya KURITA, Atsunobu MURATA and Masao MATSUI

(Received on February 19, 1999)

Recently, the demand for the development of technologies which can realize short delivery time and low trial costs for parts produce for automobile body panels is increasingly growing. In this study, we attempted to develop the incremental backward-stretching process, which is dieless (simple) and makes effective use of Computer Aided Design / Computer Aided Manufacturing. The development of a (resin) supporter enables the production of high-precision panels with high-stretching rates, complicated free-form shapes and large sizes, which were not possible with conventional press-forming methods. Furthermore, using a grooved stylus, the accuracy of the panel form could be greatly improved.
Key words : sheet-metal forming, incremental forming, backward-streching forming, CAD/CAM/CAE, NC machine, supporter, stylus, production system, design, forming property