Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.40 No.466 November 1999)
Optimum Parameter Design Using the Taguchi Method
for Finite-Element Analysis of 3D Forging Deformation
Shin-ichiro FUJIKAWA
(Received on June 2, 1998)
This study shows the effectiveness of using the Taguchi method for optimizing parameters for the finite element simulation of 3D forging deformations. The optimization process includes minimizing both the simulation error and the calculation time. Operation samples of forgings, termed knuckle spindles, are first obtained to compare actual deformations with simulation results. Both deformation processes are compared by evaluating the difference function (the simulation error). Following the selection of eight parameters which are expected to influence either the simulation error or the calculation time, the author applies the Taguchi method to obtain the SN ratios for each parameter. The analysis shows that the shear friction coefficient greatly affects the simulation error and that several other parameters, such as the number of elements, influence the calculation time. Lastly, the optimum parameter combination is obtained. It is demonstrated to improve the simulation error from 5% to 1.5% and the calculation time from 114hrs to 2.2hrs.
Key words : forging, finite-element method, rigid-plastic FEM, Taguchi method, optimization, friction
coefficient
Minimum Thickness in Cold Thin Strip Rolling
Shigeru SHIDA, Yoshifumi KOMATSU,
Ken-ichi YASUDA and Kenjiro NARITA
(Received on August 26, 1998)
The requirement for thin strips of hard materials is increasing. In this paper, the minimum thickness for cold rolling of a thin, hard strip is investigated experimentally and theoretically. Regarding the minimum thickness, the first study by Stone is widely known. After that, Ford et al. and Roberts also proposed theoretical formulas similar to that of Stone for predicting the minimum thickness. Considerable differences, however, are seen among the values obtained from these formulas. In this investigation, experiments with rolls of various diameters and materials and with stainless steel as the strip material were carried out in order to obtain the minimum thickness in thin and hard strip rolling. A new theoretical formula is also proposed for calculating the minimum thickness. Good agreement between theoretical and experimental results is shown and the reason for the differences among the new formula and the above three formulas is discussed.
Key words : rolling, cold strip rolling, minimum thickness, SUS430, rolling mill, ceramic rolls, steel rolls, roll flattening
Necking Formability of Aluminum D&I Cans
during Smooth Die Necking or Spinflow Necking
Yoshinari KIKUTA, Shin TSUCHIDA and James E. PRICHARD
(Received on September 2, 1998)
The material's behavior of aluminum D&I cans made from different types of body sheet has been investigated during the reduction of the neck diameter. In smooth die necking with multiple stages, the smaller neck diameters lead to thicker and softer thickwalls, and earing appears at the trimmed can edge. The earing occurs at 45, 135, 225 and 315 degrees to the rolling direction. The thickwalls at the 90 and 270 degree positions thicken and soften the most. In spinflow necking the thickwall thins and hardens, and earing appears. The earing occurs at various positions around the trimmed can edge in the material from the hot rolling-(intermediate annealing)-cold rolling processes. In spinflow flange reforming, the thickwall and earing variation around the circumference are reduced by the effect of a stop ring incorporated into the reformer.
Key words : Al DI can, die necking, spinflow necking, 3004 Al alloy sheet, earing
Effect of Roll-Groove Profile on Tube Deformation
in Single-Stand Mandrel Rolling
Shuji YAMAMOTO, Kenji YAMADA, Shuichi HAMAUZU,
Ichirou MASUDA and Tatsuo OZAKI
(Received on September 10, 1998)
The effect of the roll-groove profile on the cross-sectional shape of the tube at the exit of the roll-bite and on the distribution of pressure acting on the tube surface was investigated through rolling experiments with a single-stand model mill and calculations using the rigid-plastic FEM. The roll-groove profile was evaluated with the DR|theta diagram, where DR(R|RG)/RG and theta is the angle from the groove center, R is the distance from the pass center to the roll surface at theta and RG is the distance from the pass center to the groove center. The results are as follows. (1) When DR at the roll flange is small, the flange diameter and peripheral length along the inner surface of the tube decrease and thickness at the tube flange increases. (2) Elongation mainly depends on DR at the groove center. (3) When DR at the roll flange is small, the pressure acting on the tube surface contacting with the roll flange increases.
Key words : tube rolling, mandrel rolling, roll-groove design, FEM
Construction of Intelligent CAD System for Cold-Forging Process
Design Corresponding to Combination Forming
Tsutao KATAYAMA, Soji SAKAMOTO, Kei HARA,
Ryuichi YOKOGAWA, Ken-ichi AKAMATSU and Takahiro KIMURA
(Received on September 30, 1998)
Cold forging has been used in the construction of complicated figures in recent years. When forming complicated figures, it is probable that more than six processes are needed to complete a product when forming is executed using the rule of one forming per process. However, the reality is that more than 80 percent of forging machines are only five-process machines. Thus, combination forming for one process is needed for cold forging. Therefore, as an extension of the prior system, we developed a system that was capable of treatment using combination forming for one process. This system generates a process design based on a five-process database is constructed using a design that met our needs. As a result, even designers who are relatively inexperienced can quickly and easily carry out process designs for complex products under control using our system. This paper describes the inference method with respect to combination forming and the framework of the intelligent CAD system developed by this research.
Key words : forging, process design, expert system
Use of a Micromodel for the Simulation of Shearing
Kazutake KOMORI
(Received on November 4, 1998)
The objective of the present work is to clarify the mechanism of ductile fracture in bulk metal forming, by means of analysis and experiment. We have developed a computer program, based on a conventional FEM program, by means of which crack propagation after ductile fracture can be analyzed. In the present work, we have proposed a micromodel in which the ductile fracture is evaluated first. Next, the analysis of shearing is performed after the model is incorporated into the computer program. The following are the results of this work. First, we proposed a method of evaluating ductile fracture using a micromodel. We mainly proposed a method of analysis effective for incremental analysis which requires a large number of steps. Second, the shearing analysis and the shearing experiment were performed under various clearances (gaps between the punch and the die). The behavior of crack propagation, the deformation gradient which denotes shearing strain, the shapes of chips and holes and the relationship between the punch displacement and the punch force, which are calculated analytically, agree with those obtained from the experiment. Hence, the validity of the proposed model is clarified.
Key words : shearing, upper bound method, rigid plastic FEM, forming limit, ductile fracture.
Acceleration Effect of Vectorization for Rigid-Plastic
Deformation Simulator
Akira MATSUDA, Tooru KAWABE, Takashi KATO,
Yoshio MIYAKAWA and Makoto OONISHI
(Received on November 26, 1998)
In this paper, we investigate the effectiveness of a vector computer in acceleration of deformation simulations using rigid-plastic FEM. The acceleration effect of the simulator by vectorization increases in keeping with the number of elements for analysis. An approximately twelvefold increase in speed is achieved by vectorization of our simulator. Then, we select and improve the simulator's four modules whose CPU time occupation ratios are higher than that of other modules. We finally achieve an about thirtyfold acceleration compared with that of the nonvectorized original simulator. Most of this increased speed is obtained by vectorization and improvement of only four modules whose sizes are relatively small compared to the total size of the simulator. We conclude that the vector computer is an effective tool for large-scale deformation simulation by rigid-plastic FEM. For acceleration of deformation simulation by vectorization and improvement, it is important to acquire detail data about the CPU time occupation ratio of all constituent modules of the program under practical execution.
Key words : cold forging, numerical analysis, rigid-plastic FEM, vector computer
Geometry and Forming of Serrations
Applied for Shave-Joined Rings and Pipes
Yasuyoshi EGAMI, Zhiqiang LI and Terufumi MACHIDA
(Received on December 24, 1998)
In manufacturing shave-joined camshafts for automobiles it is of the most significance to fasten a tubular shaft with the cams completely, because the joining strength is considerably influenced by the geometry of the serrations on shaft, which is engraved with a rotary forming method. In the present research, the geometrical model of triangular serration, is built to be applied for the production of parts. Following this, and then relationships among the number of teeth, the height of teeth, the top angle, and the outer radius of the pipe or shaft are analyzed using computer simulation. Furthermore, a forming machine with three knurling tools is newly developed to manufacture such a combined camshaft with high productivity. The optimum combination of forming factors, such as the revolution rate of the shaft and number of knurls is confirmed through observation of the metal flow and the work hardening of metal.
Key words : shave-joining, rotary forming, knurling, serration, geometrical model, teeth design, metal flow
Resistance Sintering Characteristics of Iron Powder
under Low Pressure
Seijiro MAKI, Yasunori HARADA and Masao NAKAMURA
(Received on January 12, 1999)
Resistance sintering of iron powder was attempted under a low pressure of less than 80MPa. The sintering was performed without any difficulty. The sintering conditions were examined in tems of the density and strength of the product, and discussed from the viewpoint of applied pressure, electrifying voltage and sintering time. Applications of prepressing and postpressing were also attempted to control the pressure in the sintering process. Postpressing always induced an increase in the density of the product, while prepressing behaved as if there might be an optimum pressure depending on the electrifying condition. In addition to the above, the results obtained are as follows. (1) The application of low pressure leads to a high heating temperature through reductions in contact area between the powder and electrodes, and hence heat dissipation to the electrodes, and (2) a build-up behavior is observed in the amperage when the initial electric resistance of the powder is higher than the characteristic resistance defined as the maximum supply of electric power with nearly saturated amperage.
Key words : powder forming, sintering, resistance sintering, powder metallurgy, iron powder, sintering
machine
Lining of Aluminum Alloys with Hard-Metal Foils Using Shot Peening
Yasunori HARADA, Ken-ichiro MORI and Seijiro MAKI
(Received on January 27, 1999)
A method for lining aluminum alloys with hard-metal foils using shot peening is proposed. The foil is bonded to the surface of the aluminum alloy due to plastic deformation generated by the collision of the shots. The foil and base metal are heated to a temperature of 500Ž to improve the weldability. A test using a single shot is carried out to evaluate the possibility of bonding. In this test, aluminum alloy workpieces are A2017 and A5056, and the hard-metal foils are mild steel, nickel, titanium and stainless steel SUS304 of 0.1mm thickness. By inserting a pure aluminum foil, the hard-metal foil is successfully bonded to the aluminum alloys, even at room temperature. Finally, in actual shot peening using many shots, the hard-metal foils are bonded over the surface of the base metals.
Key words : joining, lining, shot peening, weldability, aluminum alloy, hard-metal foil, single shot, surface treatment, insert foil, plastic deformation
Graphitic Steel with High Machinability for Cold Forging
\\Development of Forging Steel Suited for Recycling ‡T\\
Takeshi MIKI, Makoto OKONOGI, Masahiro TODA,
Masayuki HASHIMURA, Hideo KANISAWA and Sakae KATAYAMA
(Received on April 26, 1999)
There is a possibility that free-cutting steel with lead will be prohibited in the near future due to environmental reasons. This paper proposes a recyclable graphitic steel which has high cold forgeability and high machinability. During annealing, the cementite in the steel transforms into graphite. The graphite in the steel exists as fine grains which have less resistance to deformation at room temperature, and this steel has higher machinability than free-cutting steel with lead. The flow stress level of this steel is as low as that of low carbon steel; as a result, good durability can be expected for the tools used in cutting the proposed steel after cold forging. In addition, the near net shaping of complex parts can be carried out easily using the steel. This steel can be quenched and hardened: and the high fatigue strength which is typical of carbon steels was observed.
Key words : forging, recycling, forging steel, machinability, graphitic steel, fatigue strength, near net shape