Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.40 No.458 March 1999)
Development of Repeat Bending Test Machine
\\Development of Computer-Aided Bending Test and Forming Machine T\\
Enxiang ZHANG, Hideo KOYAMAC
Masao NAKAMURA and Osamu HAGA
(Received on May 8, 1998)
A computer-aided bending test machine having forming ability was developed. The new machine is composed of three major parts:the control part, the measuring part and the forming part. The major structures of the forming part are two rotatable chucks. One chuck is mounted on a table fixed on the machine base, while the other chuck is mounted on a slide table that provides straight-line motion on a pair of rails. Specimens are bent cylindrically by rotation of the chucks, and the slide table movement is synchronized with the bend angle by a control program. Relationships between bending moment and curvature were obtained by repeated bending tests. The relationships gave good agreement with the calculated results. As a result of cylindrical forming, the measured values of curvature at the central portion of the specimen after springback tended to be slightly larger than the proposed values.
Key words : bending test, bending, cylindrical forming, CAE, CAM, CIM
Tensile Properties of Poly (Amide Imide) (PAI) and
Poly (Ether Ether Ketone) (PEEK) under Hydrostatic Pressure
Tetsuya AYA and Toshio NAKAYAMA
(Received on May 25, 1998)
Tensile properties of PAI and PEEK were studied at temperatures ranging from 20 to 165 and at strain rates ranging from 10|3 to ls|1 under various hydrostatic pressures up to 392MPa. As pressure increased, the elastic modulus and the yield stress increased;as temperature increased, the modulus and the stress decreased;¬and as strain rate increased, the modulus and the stress increased. At temperatures above the glass transition temperature, the elastic modulus of PEEK decreased while its yield stress did not. The yield stress could be expressed by a linear equation with pressure, temperature and natural logarithm of strain rate as parameters. Strain hardening after yielding could be expressed as an exponential equation including the yield stress.
Key words : tension test, high polymer materials, hydrostatic pressure, elastic modulus, yield behavior, plastic deformation, strain hardening
Gas Blowforming of Grooves on Superplastic Aluminum
Alloy Sheet to Increase the Surface Area
Ryuuta ONODERA, Sanae MAEHARA,
Tatsuo YOKOTE and Masatoshi ARAMAKI
(Received on May 29, 1998)
The purpose of this study is to investigate the application of superplasticity to blowforming. To form an efficient heat exchanger plate, blowforming is carried out to increase the surface area of the plate as much as possible. A plate made of 7475 aluminum alloy (t1.5mm) is placed over the hot die which results in the formation of concentric grooves on the plate. The formability of grooves was examined by using two types of die shapes with a constant gas pressure of 0.5MPa. One of the shapes has four grooves (depth:H8mm) and the other has three grooves (H10mm), both of which have a surface area 2.5 times larger than the original area. In the latter case, the ratio of the number of specimens blowformed without fractures to the total number of specimens blowformed was small (`30%). The distributions of the thickness strains were not symmetrical with respect to the center of grooves, and the value of the strain at the groove wall on the side of the die center was greater than that on the outer side of the die. Thus, it is necessary to consider the fluidity of the material which flows into the grooves. On the other hand, the radius of the die corner, R, may have little influence on the blowformability.
Key words : blowforming, superplasticity, 7475 aluminum alloy, formability test, die, strain distribution, cavity, fracture strain, surface area
Effects of Mg Content and Forming Speed
on Cup Test Formability of Al]Mg Alloy Sheets
Masakazu NIIKURA, Naotake YOSHIHARA, Shinji MITAO, Koichi OSAWA,
Kohei HASEGAWA, Takeshi FUJITA and Kenji ARAKI
(Received on June 2, 1998)
The effects of Mg content and forming speed on three types of cup test formability were studied using Al-Mg alloy sheets. Mg content dependence of limit forming depth in round head stretch forming critically depended on forming speed, and alloys with high Mg content showed high stretchability in a static test, while alloys with low Mg content showed high stretchability in a dynamic test. Limit forming depth in cylindrical deep drawing showed positive Mg content dependence regardless of drawing speed. Conical cup values varied in the same manner as round head stretch forming with the change in Mg content and forming speed.
Key words : formability test, deep drawing, stretch forming, non-ferrous metal, forming speed
Development of High-Strength Cladding Wire with
Extremely High Drawability
Takeshi MIKI, Masahiro TODA, Osamu KADA,
Eiichi TAKEUCHI and Ikuo OCHIAI
(Received on August 18, 1998)
In drawing of high-strength wire, cuppy breaks occasionally occur under unsuitable drawing conditions. The break has been analysed by the slip line method, the admissible velocity field analysis and the finite element method. The increase of one pass reduction, the decrease of die angle and the decrease of frictional coefficient are resultantly effective for preventing break. However, these processes are not useful in practical production, because of high heat generation and wire aging. This paper proposes a new cladding wire which has extremely high drawability. The outer layer of the wire is composed of high-carbon eutectic steel, and the wire core is made of low-carbon steel. The wire is manufactured by casting high-carbon steel around a low-carbon solid steel
bar and subsequent rolling. The drawing limit of this wire is twice that of conventional high-carbon steel wire.
Key words : drawing, torsion test, clad material, forming limit, iron and steel, slip line method, cuppy break