Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY

(vol.42 no.480 January 2001)

An Improved Punch Friction Test in Sheet Metal Forming

Mohsen Abdel-Naeim HASSAN MOHAMED, Mohamed Gad El-SEBAIE and Katsuhiko YAMAGUCHI

(Received on November 11, 1999)

The punch friction test Is considered to be the best simulator of sheet metal stretching over the punch corners during deep drawing and stretch forming processes. . In this study, an improved punch friction test, which enables direct force measurement and on-line evaluation of the friction coefficient values, has been conducted. This technique eliminates the error due to the strain-rate effect, which is observed in other punch friction tests proposed elsewhere. An improved boundary friction model has also been introduced to predict the friction coefficient and the real area of contact at the punch nose portion. This has been done by incorporating the effect of bending in the equilibrium equations of forces. The predicted values obtained from the model were compared with experimental results obtained using the newly developed test rig. A good agreement was obtained between the theoretical and experimental results : also these results are consistent with the work published by other investigators.
Key words : tribology, sheet metal forming, punch friction test, friction model

Effects of Tip Clearance and Blade Hardness on Cutting
Resistance and Tip Shape in Paperboard Die Cutting

Shigeru NAGASAWA, Hitoshi SATO, Daishiro YAMAGUCHI, Yasushi FUKUZAWA, Isamu KATAYAMA and Akinori YOSHIZAWA

(Received on February 3, 2000)

The relationships between cutting line force and several mechanical factors, such as cutting time, cutting speed and tip clearance. were investigated experimentally by varying blade hardness. The variation of blade tip shape with cutting time was observed by the replica method and was discussed in terms of crushing behaviour and blade hardness.
Key words : shearing, hardness, tip crushing, paperboard, die cutting, wedge indentation

Sinter-Forming of Ceramic-Particle-Dispersed Metal Matrix Composites Using Resistance Heating

Seijiro MAKI, Naoki AOYAMA, Yasunori HARADA and Ken-ichiro MORI

(Received on February 28, 2000)

The feasibility of a resistance sinter-forming method newly designed for parts production of ceramic-particle- dispersed metal matrix composites was investigated. SiC-particle-dispersed composites were taken up as an example, and basic resistance sintering and sinter-upsetting experiments were conducted using metal powders of copper, iron, nickel and aluminum mixed with abrasive SiC powders. The success or failure of resistalnce sintering depends on the magnitude of the electric resistance of mixed powders. The results of resistance sinter-upsetting experiment using a green compact billet strongly depended on electrifying conditions including the applied pres.'sure. Experimental resistance sinter-forging using shaped electrodes was succesfully performed for both copper and aluminum matrix composites, thereby demonstrating a high feasibility of the method.
Key words : powder forming, sintering, resistance sintering, resistance heating, sinter-forging, composite material, metal matrix composite, metal powder

Partial Shot-Lining Process of Metal Foil Using Masking

Yasunonri HARADA, Ken-ichiro MORI, Masaaki HARA and Seijiro MAKI

(Received on February 28, 2000)

A lining process that utilizes shot peening was carried out for partial lining application. The shot impact area on the surface of a workpiece was limited by a masking plate. The foil was slightly larger than the masking plate, and was fixed to the plate for impact. A centrifugal shot-peening machine with an electric heater was employed. The workpieces were aluminum and magnesium alloys, and the foils were commercially available pure nickel, commercially available pure titanium and stainless steel SUS304. To assist the bonding, a piece of pure aluminum foil was inserted between the foil and the workpiece. The accuracy of the geometric shape for the lining, i. e., the difference between the lined shape and the masking shape was investigated. Partial lining of a circle and a triangle on the surface of the workpiece was achieved. The bonding of the lined workpiece was confirmed to be satisfactory based on the results of a bending test of the lined workpieces.
Key words : joining, accuracy, partial lining, shot peening, bondability, aluminum alloy, magnesium alloy, masking, surface treatment, insert foil

Behaviour and Mechanism of Grain Coarsening in Hot Rolling of Steel Bars

Yutaka NEISHI, Shinji MURAKAMI, Haruhiro FURUTA and Masayoshi AKIYAMA

(Received on March 2, 2000)

An investigation was carried out on the grain coarsening behaviour in hot working of carbon and low-alloy steels. A hot deformation simulator was used to quantitatively determine whether the size of a coarse pearlite grain is identical to the size of an austenite grain. This assumption was made based on the criterion of the occurrence of pearlite grain coarsening in S45C, as presented by us in a previous study, and we investigated whether this assumption is applicable to all carbon and low-alloy steels. In order to confirm the validity of this assumption, additional experiments were carried out using SCr420, SCM435, and SUJ2, which represent major materials of hot-rolled steel bars. The results obtained using both the hot deformation simulator and a prototype mill show that the original criterion for S45C can be applied to other carbon steels, and it is suggested that the mechanism of grain coarsening is closely related to static recrystallization.
Key words : grain coarsening phenomenon, 3D FEM, S45C, SCr420, SCM435, SUJ2, hot deformation simulator, austenite grain size, equivalent plastic strain, temperature

Analysis of Superplastic Blowforming under Plane Strain with Consideration of Strain Hardening and Friction

Nobuyuki SUZUKI, Masahide KOHZU Shigenori TANABE and Kenji HIGASHI

(Received on March 10, 2000)

The process of bulging under plane strain, which simulates blowforming of a thin pan using superplastic 7475 aluminum alloy, is analyzed in order to optimize the loading schedule of forming pressure and to predict the thickness distribution. Constitutive equations used in the analysis take into consideration the stress-strain relationship with strain hardening, which characterizes this material. Friction with a die reduces the strain rate of the contacting portion, and this results in the thickness distribution of the formed pan. The calculation is repeated for each time increment until the maximum strain rate in the entire deformation area converges at the optimum strain rate for superplastic flow. This analysis gives the distribution of stress, strain rate, strain and thickness at any stage of the forming process, and determines the optimum loading schedule in the case of some friction coefficients.
Key words : sheet metal forming, superplastic blowforming, optimum loading schedule, distribution of thickness, frictional coefficient, work hardening, numerical analysis

Cyclic Plasticity Behavior at Large Strain for Mild Steel Sheet and Its Constitutive Modeling

Takeshi UEMORI, Kenji FUJIWARA, Tatsuo OKADA and Fusahito YOSHIDA

(Received on March 10, 2000)

In order to examine cyclic stress-strain responses under large strain for a mild steel sheet (SPCC), cyclic tension-compression tests were performed using adhesively laminated sheet specimens. By comparing the experimental results with the corresponding numerical simulation, it was found that a constitutive model of isotropic I kinematic hardening with the evolution of non hardening strain range has the capability to describe cyclic plasticity behavior such as the Bauschinger effect, the cyclic hardening characteristic and its cyclic strain range dependence. A method of identifying of material parameters in the constitutive model involving the use of experimental data on large-strain uniaxial tension (the stress-strain curve) followed by cyclic bending (bending moment versus curvature) is presented.
Key words : cyclic plasticity, large strain, constitutive model, SPCC, material parameter identification

Multivariable Control of Bar Rolling and Precision Rolling System

Yukio NOGUCHI, Kanji BABA, Harutoshi OGAI, Toshihiro OKA, Hitoshi ISHII and Makoto BABA

(Received on March 22, 2000)

The users' demand for a close dimensional tolerance in bar and wire rod products prompted the development of a sophisticated dimensional control technology in continuous rolling. As a result of basic research, a multivariable control system for interstand tension and exit height of each stand, with rolling speed and gap as control input, has been developed, using a continuous rolling model and an optimal regulator theory as the in-billet dimensional control method. The validity of the multivariable control system was verified by computer simulation and model mill experimentation. On the basis of the multivariable control system, the 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 profile meter signal processing and a free tension setup, and an in-billet dimensional control system of multivariable control consisting of tension control and automatic gauge control (AGC).
Key words : multivariable control, discrete-time optimal regulator theory, bar rolling, control system, precision rolling system