Papers in JOURNAL OF THE JAPAN SOCIETY
FOR TECHNOLOGY OF
PLASTICITY
(Vol.41 No.478 November 2000)
Fractal Characteristics of Free Surface Profile
of Sheet Metals under Biaxial Tension
Masahito MATSUI, Yasushi KUROSAKI and Kensuke OHASHI
(Received on September 16, 1999)
The uniaxial and biaxial tension tests that cause four kinds of strain ratios are conducted on aluminum and killed steel sheets, and their free surface profiles are examined by employing fractal analysis. With an increase in plastic strain, long-wavelength components of the surface profiles become dominant, and their fractal structure tends to be constant beyond a certain strain. It is confirmed that the fractal dimension of surfaces is uniquely determined from the equivalent strain independently of the strain ratios, which was pointed out earlier by the authors. The fractal dimensions of newly generated surfaces of aluminum and killed steel sheets are found to be nearly equal.
Key words : sheet metal forming, stretch forming, profile measurement, surface roughness, fractal, self-affinity, free surface, biaxial tension
Analysis of Lead Error in Odd Teeth Pinion Rolling
- Development of Cold Form Rolling for Steering PinionsII -
Masaru AIZAKI and Masana KATO
(Received on November 1, 1999)
Rack and pinion steering gears for passenger cars have consisted mainly of hobcut helical pinions. Rolled pinions have recently emerged because of their merits of high productivity and strength. However, rolled pinion profile errors arise due to a complicated plastic deformation mechanism between a rolling pinion and dies. The rolled pinion tooth face undulates cyclically. In the case of even teeth pinions the adoption of an integer overlap ratio of the pinion was found to have a good effect on the undulation. However, such a strategy is not sufficient for odd teeth pinions. In this report, it is shown that undulation arises due to the elastic deflection of the pinion shaft under rolling, and a new method of rolling with jagged dies to prevent the undulation is proposed.
Key words : form rolling, gears, pinions, profile error
Fatigue Strength of Pressure-Welded Joint of Aluminum Alloys
Seijiro MAKI, Nobuhiko TSUJI,
Yasunori HARADA and Masao NAKAMURA
(Received on November 24, 1999)
In order to clarify the influence of joining surface treatment by scratch-brushing on the fatigue property of a pressure-welded joint, a fatigue test was carried out for joints of aluminum alloys A1050, A2017 and A6063, pressure welded in a container, and their weld interfaces were observed with an ultrasonic microscope. The results are summarized as follows. (1) Even when the bond strength is greater than the fracture strength of the base metal in a static test, the joint does not necessarily have a fatigue strength equal to that of the base metal. (2) The fatigue life of a joint subjected to scratch-brushing is short as compared with that of the joint without scratch-brushing. (3) An inhomogeneous bond shortens the joint's fatigue life, which well accounts for the inferior fatigue property of the joints formed with scratch-brushing treatment.
Key words : joining, pressure welding, nonferrous metal, aluminum alloy, fatigue strength, ultrasonic microscope inspection, joint performance
Effects of Hydrostatic Forming Conditions
on Shape Accuracy of Large Bellows
Toshiya TERAMAE, Kei-ichi NAKAMURA, Keii UENO,
Osamu TAKAHASHI and Satoru SHIRATA
(Received on January 17, 2000)
A large bellows is commonly used for the joint part of pressure vessels at the substation. High shape accuracy is required for the bellows in order to ensure high reliability. It is also necessary to reduce the cost and shorten the time for production, because the large bellows is low production product in many ways. Therefore, some conditions for forming bellows are investigated by numerical analysis, and are verified experimentally. In the conventional method for forming bellows, only applied pressure is used for forming. This study takes into account that the bellows height is determined by the bulge height and the die pitch. It is important to measure the bulge height during the bulging process. In order to reduce the press capacity of the equipment, the minimum applied pressure that causes no buckling during the upsetting process is chosen. Large bellows with the same shape, but different diameters and thicknesses, are manufactured by considering the relationship between the bellows height and the bulge height. Conventionally, bellows heights vary widely. However, by means of constraining drawing at the workpiece edge, this variation is reduced.
Key words : hydrostatic forming, bulge forming, numerical analysis, large bellows
Fabrication of SUS316L Stainless Steel/Fe-47Ni Permalloy Alloy
Composite by Combined Sinter Joining
Kunio OKIMOTO, Katsuhisa IZUMI, Sachio TOYOTA,
Seiichi HOSOKAWA, Yoshiyuki KATO and Susumu SHIMA
(Received on February 4, 2000)
A powder forming process is utilized to fabricate a composite part consisting of SUS316L stainless steel and Fe-47Ni permalloy. Green compacts of disk and ring shapes are separately produced and they are assembled into a unit. The unit is sintered at 1300C for 1h in vacuum. A coarse powder of -100 mesh size and a fine powder of 8um particles for the MIM process are used. The use of the fine powder increases the joint strength. The joint strength is discussed in terms of the materials of the inner disk and outer ring, and the clearance between them. The joint strength of the composite prepared with a combination of an inner disk of Fe-47Ni and outer ring of SUS316L is superior to that of the composite fabricated with the opposite combination, while it is negligibly influenced by the clearance. The thickness of the diffusion layer, measured by EPMA, ranges from 100um to 200um.
Key words : composite material, powder forming, stainless steel, permalloy, sinter joining, diffusion bonding, joint strength
Electric Resistance Sintering of Copper-Graphite Mixed
Powders under Pressure
Seijiro MAKI, Yasunori KYOSO,
Yasunori HARADA and Ken-ichiro MORI
(Received on February 8, 2000)
Resistance sintering characteristics of electrolytic and atomized copper powders mixed with graphite powder in steps of 10vol% up to 50vol% were investigated. The results obtained are as follows. It was possible to resistance-sinter the atomized copper powder mixtures, to which ordinary sintering is not applicable due to their poor compact formability. The dendritic electrolytic copper powder mixtures were easy to resistance-sinter as compared with the spherical atomized copper powder mixtures. Applying a high pressure just after the completion of electrification increased the sintered density for both powder mixtures; insertion of SUS304 stainless steel disks of low thermal conductivity between the sintering powder and electrodes increased it further.
Key words : powder forming, sintering, resistance sintering, powder metallurgy, copper powder, graphite powder, composite material