Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(vol.42 no.483 April 2001)
Forming Characteristics in Hole Flanging
with Ironing on Thick Metal Plate
Ryosuke IMASEKI, Yukihiko UCHIDA and Michihiko HOSHINO
(Received on February 9, 2000)
Flanging of a hole on a thick metal plate has special advantages in improving the precision of the inner and
outer diameters and in increasing the forming height under a constant thickness condition. In this process, the
outer surface of the boss is accompanied with ironing. In this study, forming characteristics of hole flanging on thick metal plates are investigated experimentally and by FEM. The test material is pure aluminum A1050.
Blank thickness, pre-hole diameter, punch diameter and inner diameter of the die are varied, and the effect of
shaping the boss by hole flanging is examined under the above conditions. There are three ways of shaping
bosses by hole flanging on thick metal plates, that is, shaping by ironing the outside of the boss, shaping
without ironing and shaping with fracturing. The results of this study are shown that these three types can
be classified by the relationship between the sizes of the tools and the blank. It is clear that the desired
forming height in hole flanging can be obtained by the relationship between the clearance and the diameter of
the pre-hole. In addition, the deformation mechanism during the hole flanging operation and the prediction of
fracture are analyzed by FEM simulation.
Key words : sheet metal forming, hole flanging, ironing, thick plate, forming property, FEM
Improvement of Pure Stretchability by Overlapping Sheet Metals
Masanori KOBAYASHI, Nobukazu HAYASHI and Yasushi KUROSAKI
(Received on April 7, 2000)
This study showed the increase in critical forming depth, H.., in a pure-stretching test using overlapping
sheet metals. In this study, two soft metal sheets were investigated. Two sheets were overlapped with each
other without lubricant. The H.. of the two overlapping sheets was larger than that of the original single sheet. Radial (meridian) distribution of thickness strain after stretching was measured and it was observed that the
two overlapping sheets had the same large fracture strain. To confirm these results, the contact plane between
the overlapping sheets was lubricated. In spite of the overlapping using the same sheet, the necking position of the inner (punch-side) sheet was located near the punch top compared with that of the outer sheet. Thus, it
was confirmed that the discrepancy of the necking position brought about the improvement in pure
stretchability.
Key words : sheet metal forming, stretch forming, pure stretchability, overlapping sheet, critical forming depth, necking, lubrication
Free-Tension Setup System for Bar Rolling Based on Fuzzy Inference
Harutoshi OGAI, Yukio NOGUCHI, Akira FUJII,
Kanji BABA, Makoto BABA and Hitoshi ISHII
(Received on April 19, 2000)
Precision rolling of a bar with a nominal diameter tolerance of +-0.1 mm has been put into practical
operation. The precision bar rolling system comprises two parts : an interbillet dimensional control system
consisting of a finishing size setup based on influence coefficients and a profile meter signal processing and a free-tension setup based on fuzzy inference, and an inbillet dimensional control system with multivariable
control consisting of tension control and automatic gauge control (AGC). This paper deals with the interbillet
dimensional control system. A free-tension setup was developed as follows. The difference in the rate of
change in the rolling torque-load ( =load parameter) of the No. i + I stand between before and after the tail
of the rolled material leaves the No. i stand is proportional to the interstand tension and is controlled to zero.
Since large fluctuation of the rolled material temperature weakens the correlation between the rate of change
of the load parameter and that of the interstand tension, the roll speed correction to be made for the next
billet was determined based on fuzzy rules.
Key words : bar rolling, precision rolling system, free-tension setup, fuzzy inference, intelligent control, multivariable control, automatic gauge control
Development on Bending and Torsion Combined Forming Machine
for Rectangular Cross-Section Conductor
Naozumi HATADA, Keii UENO, Makoto TATEMURA, Shinobu WATANABE,
Keiichi NAKAMURA, Michio TAKAHASHI, Shinsaku IMAGAWA and Osamu MOTOJIMA
(Received on June 21, 2000)
A superconducting helical coil is a main part of fusion devices. Because the helical coil is wound on the
donut shaped winding core, the superconductors must be bent and twisted into a helical shape. The helical
shape is changed along the length of the conductor and in a cross-section of the coil. Then, the super-
conductor must be continuously formed into different 3D-shapes. Then, a new forming method that combines
bending and torsion is investigated for a conductor with a rectangular cross section. The forming machine
consists of 3 sets of 4 rolls whose sides touch the sides of the conductor. Combined in-plane and out-of-plane
bending and torsion forming is controlled by the 3 axes of the NC controller. In the case of short conductors,
the shape errors are within 10% of the maximum shape of in-plane and out-of-plane bending curvature and the
torsion angle of the coil. In the present study, a 3D measuring machine was developed to measure the bending
and torsion combined shapes continuously near the forming machine.
Key words : bending, forming machine, torsion, spring back, 3D-shape, superconductor, helical coil, fusion device
Characteristics of Burr-free Blanking Method
Utilizing Large Negative Clearance
Kenji HIROTA and Kazuyoshi KONDO
(Received on August 21, 2000)
Push-back blanking is one of the burr-free shearing processes in which a partially sheared product is pressed
between platens and separated with no burr. Some advantages of applying a large negative clearance to this
process were confirmed using semihard aluminum by the authors. In this study, further investigation of this
clearance range was carried out. Through the experiments with ductile aluminum and brittle aluminum alloys,
it was clarified that burr prevention in both materials could be achieved under large negative clearance
condition, while it was difficult under conventional small negative clearance condition. Influences of working
parameters such as die edge radius, stock length and inclination of the punch face on the successful range as
well as the dimensional accuracy were studied in detail. Consequently, although the successful range was not
expanded further, dimensional accuracy could be rather improved by the optimum selection of parameters. In
particular, upon using a hollow punch, a fine sheared edge was obtained because of less necking deformation
required for separation.
Key words : shearing, reciprocating blanking, forming property, accuracy, burr, negative clearance, necking, fracture
Determination of Forming Conditions and Optimization of Wall
Thickness Distribution of Ring in Rotary Forging of Large Wheel
Disks for Trucks and Buses by Finite Element Simulation
Osamu EBIHARA, Ken-ichiro MORI, Kenji YOSHII, Hiroshi TAKAHASHI and Masahiro ABE
(Received on August 30, 2000)
Osamu EBIHARA, Ken-ichiro MORI, Kenji YOSHII, Hiroshi TAKAHASHI and Masahiro ABE
A forming process for large wheel disks by rotary forging was developed to reduce material losses. Since
several defects occur during the two-stage rotary forging, this forging method was designed by finite element
simulation in order to avoid occurrences of defects. To attain a realistic computing time for the simulation,
an axi-symmetric approximation was used in the simulation. The calculated shape was in good agreement with
that obtained by a rotary forging experiment. Disks without defects were successfully formed using the
designed process by finite element simulation. The distribution of the wall thickness of the ring supplied for
the rotary forging process was optimized to reduce the amount of deformation caused by shear spinning during
finishing. The optimum distribution of the wall thickness was determined by iterative calculation in order to
minimize the difference between the calculated and desired shapes after rotary forging.
Key words : rotary forging, large wheel disk, defects, finite element method, axi-symmetric approximation, forming conditions , process design, shape optimization