Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY

(Vol.38 No.437 July 1997)

Magnetic－ Pressure Metal Punching with One － Turn Flat Coils

Tomokatsu AIZAWA

(Received on April 9, 1996)

This paper clarifies an advantage of a new type of one-turn flat coil for magnetic-pressure metal punching. Two models of this coil have been designed, particularly for small hole punching. When an impulse current from a capacitor bank passes through the coil, eddy currents are induced in a 0.1-mm-thick aluminum or copper sheet fixed between the coil and a die. Magnetic pressure acts on the sheet and punches it with the die hole To obtain 0.4～10 mm diameter holes, the bank energy is required to be below I kJ.
Key words : high-energy-rate forming, electromagnetic forming, punching, magnetic pressure, electromagnetic force

Influence of Dynamic Parallelism of Hot Press on Discrepancy of Multilayer Printed Wiring Boards　　

―Study on Precise Adhesion Technology of Multilayer Printed Wiring Boards Ⅳ―

Hideyasu MUROOKA, Masayuki KYOOI, Hiroya MURAKAMI,
Nobuaki OHKI and Akimi MIYASHITA

(Received on May 16, 1996)

Investigation of the influence of the mechanical accuracy of a hot press on discrepancies at the through-hole-pad of Multilayer Printed Wiring Boards (MPWBs) clarified that higher mechanical accuracy of the hot press realizes fewer discrepancies. As a result, precise adhesion of MPWBS is facilitated by developing a precise hot press which has two new functions. One is a mechanism for maintaining parallelism below 0.05mm with a highly rigid frame. The other is a mechanism for controlling the profile of a heating plate surface with 3 annular oil cylinders to produce board thickness devitation of less than 0.035mm.
Key words : multilayer printed wiring boards, adhesion, lamination, hot press, discrepancy, registration, parallelism maintaining mechanism

Influence of Orientation of Surface Defects on Breaking Elongation of Aluminum Sheet Metal －Role of Carbide in Suppression of Galling Ⅱ－

Tetsumaro HIROI and Hisashi NISHIMURA

(Received on September 19, 1996)

The influence of the initial orientation of a single surface defect on breaking elongation was experimentally studied using an aluminum sheet. Breaking elongation does not decrease in the region where the defect is shallower than a critical defect depth,αe, when the initial orientation of the defect, φ, is inclined from O degrees to 35 degrees in the tensile direction.αe shows the minimum value, which is greater than zero, at the initial orientation, φmin, The value of φmin is different from the theoretical value calculated under Hill's anisotropic local-necking condition. Furthermore, we showed a method of predicting φmin, and that ae is greater than zero because the increase of such factors as strain inclination and surface roughness restricts the fracture portion more than the initial single surface defect for defect depths less than αe .
Key words : tensile test. aluminum sheet surfase defect, orientatin of defect, formability

Development of Control Rolling Process for Suppressing Grain Coarsening of Rod and Bar

Yutaka NEISHI Masayoshi AKIYAMA,
Yoshihiro INOUE and Kouichirou KAWAKAMI

(Received on December 11, 1996)

An experimental investigation was carried out using a hot deformation simulator on the grain coarsening phenomenon in hot metal working for a typical medium-carbon steel for cold forging of S45C. The occurrence criterion regarding the grain coarsening phenomenon is expressed by a narrow band in the temperature-equivalent plastic strain domain. A prediction of grain size after sizing rolling by a single stand was given using the criterion and 3D FEM, and its validity was checked experimentally on a production line. A further experiment was carried out to confirm that the accumulation effect of equivalent plastic strain throughout sizing rolling by tandem stands is valid as far as the grain coarsening phenomenon is concerned in normal speed sizing. The grain coarsening criterion obtained in a laboratory test was found to be valid and crucial also for tandem sizing. A new draft schedule for tandem sizing of a rod and bar was then proposed to prevent the grain coarsening phenomenon from occurring.
Key words : grain coarsening phenomenon, 3D FEM, S45C, hot deformation simulator, prediction of grain size, narrow band, equivalent plastic strain, temperature, accumulated equivalent plastic strain

Mechanical Consideration of Alligatoring Fracture of Rolled Plate

YANG Xi Qiang, Masatoshi ARAMAKI, Ryuuta ONODERA,
Tooru OKUI, Tatsuo YOKOTE and Kenji HIGASHIDA

(Received on January 16, 1997)

Alligatoring fracture is one of the most common types of fracture occurring during rolling. In this work the separation stress that acts in the thickness direction at the edge of a rolled plate and causes the alligatoring fracture is estimated. It is assumed that the stress has two origins: the stress generated at the plate edge by the compressive force of the roll, immediately after the plate passes through the roll gap, and the residual stress in the plate. For the estimation of the former, a photoelastic experiment and FEM computer simulation were performed. Both gave the result that the absolute value of the separation stress due to the roll force was 20% of the rolling pressure (nearly equal to 0.2 times the yield stress). For evaluation of the effect of the residual stress, parallel to the rolling direction, the measurements were made with a strain gauge. By thinning of the plate, the stress distribution in the thickness direction was determined. The results of stress analysis led us to the conclusion that the separation stress due to the residual stress was roughly equal to 50% Of the yield stress. It is suggested that estimation of fracture toughness is necessary for understanding the alligatoring phenomenon using the separation stress.
Key words : rolling, compression test, FEM, alligatoring fracture, photoelastic test, isochromatic line, residual stress, compressive stress

Material FLOW in Injection Upsetting

Toshihiro MIZUNO and Yukio KOJIMA

(Received on February 3, 1997)

Based on a material flow calculated by the rigid-plastic finite element method (FEM), a modified upper bound velocity field is proposed. The material in the flange region is compressed axially during radial expansion. The punch pressure is lower than that determined by other researchers. In addition, the flange profile can be calculated. For a specific flange thickness, b/a, of less than 1.8, the results calculated based on the modified velocity agree well with those calculated by the FEM. Both the punch pressure and the flange profile could be estimated by the upper bound method. The usefulness of the modification was confirmed However, in a case in which the flange thickness and the flange radius were large (b/a >1.8, r｡/a >1.25), barrel deformation occurred, so the upper bound method could not be used to estimate the flange profile. Also, the punch pressure was higher than that calculated by the FEM.
Key words : extrusion, injection upsetting, upper bound method, FEM, material flow profile , punch pressure, flange