Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.39 No.448 May 1998)
The Influence of Guide Structures on the Die Rigidity
Fumitaro SEKINE and Nobuo ENOMOTO
(Received on March 26, 1997)
The dynamic accuracy of a die has a great influence on the accuracy of the precision pressworking of electronic machine parts. This accuracy is mainly determined by the guide of the die and the press machine. Here, the influence of an eccentric load on the edge of a punch is discussed and dynamic accuracy is analyzed taking into consideration the dynamic deformation of a die-guide such as a guide post and rolling objects. The calculated results show that the lateral displacement of the edge of the punch of the die with a roller-guide is smaller than that with a ball-guide. Experimental results were seen to agree with the calculated ones because the rigidity of a die with a roller-guide is larger than that with a ball-guide. As a result, the press accuracy could be increased by considering these influences.
Key words : shearing, blanking, rigidity of die, eccentric load, ball-guide, roller-guide, dynamic accuracy
Influence of Oils and Die Materials on Lubrication
in Ball Penetration Test
Kazuhiko KITAMURA and Toshihide OHMORI
(Received on May 27, 1997)
Various oils were investigated in the ball penetration test in order to estimate their performance in terms of reducing friction and preventing galling using different die materials. Workpieces were constructed of 0.1%C carbon steel. For a high chromium bearing steel ball and a ball of tungsten carbide bound with cobalt, more active oils showed improved performance. This was closely related to the amount of chemically reactive products on the workpiece surface, and the products on the ball surface were also effective lubricants. For a partially stabilized zirconia ball and a vanadium carbide coated ball, no galling occurred with any oil. The sulphurized oil and the oil containing oleyl acid phosphate showed fairly low friction. It was suggested that the physical adsorption films retained the effect of reducing friction with the assistance of the high antigalling property of the die material. The most active oil, containing oleyl acid phosphate and phosphoric acid, showed excellent performance with each die material due to the strong films formed by chemical reaction and physical adsorption.
Key words : cold forging, tribology, lubricant additives, die material, galling, friction
Lubrication in Multicrown Roll (MC Roll)
Shoichi HASHIMOTO, Tetsuo KAJIHARA, Etsuro HIRAI,
Yutaka MATSUDA, Masashi YOSHIKAWA and Yukio SATO
(Received on July 7, 1997)
Due to the recent strong demand for improving the shape of a rolled thin strip, the shape controllability of a multicrown roll, also called a MC Roll, which consists of an arbor, roller bearings and a sleeve, has been investigated. When the inner structure of the MC roll has several roller bearings that are fixed around an eccentric arbor, a multicrown mode is arbitrarily created by the tangential phase shift of the arbor. Lubricant oil is introduced into the gap between the sleeve and the surface of the roller bearings. When the sleeve is driven by the work roll, an oil film is created in this gap by the wedge effect of fluid lubricant. In order to design the MC Roll, it is necessary to obtain the basic characteristics of the lubrication. The crown profile of the roller bearing is determined by calculating the contact pressure between the sleeve and the roller bearings. An optimal method for supplying oil is detemined by experiments using a single bearing model and a multi bearing model.
Key words : cold rolling, shape, arbor, roller bearing, sleeve, back up roll, fluid lubrication
Pushing Load Acting on Ram and Forming Load Acting on Idler Rolls
for the Reshaping of Circular Steel Pipes into Square Shapes Using an Extroll-Forming Mill with Expandable Inner Idler Rolls
Fujun LIU, Yoshitomi ONODA, Takuo NAGAMACHI, Sadao KIMURA and Takeo KITAWAKI
(Received on July 9, 1997)
The characteristics of the pushing load acting on the ram of a hydraulic cylinder and the forming load acting on each pair of idler rolls in reshaping the circular pipes (t0/D0＝2.4〜6.3%, where t0＝wall thickness and D0＝external diameter) into three different-sized square shapes (150.0, 152.0, 154.0mm wide) using an extroll-forming mill with expandable inner idler rolls inserted into the groove of No. 1 outer idler rolls are discussed with respect to both, the experimental results and the results calculated using the rigid-plastic finite-element method. The pushing load acting on the ram is found to be considerably affected by the expansion rate (=ln ((Sp+D0/2-t0)/(D0/2-t0)), where Sp=stroke of the inner idler roll in the direction of expansion), the reduction (=|ln (2HiT/D0)|, where HiT＝maximum height of the groove of No. i outer idler rolls) and the cross-sectional size ratio t0/D0 of the circular pipe. The forming load acting on each pair of idler rolls is also found to be considerably affected by both the expansion rate and the pushing load acting on each corresponding pair of idler rolls. From these results, the equations for estimating the pushing load acting on the ram and the forming load acting on each pair of idler rolls are formulated. The pushing and forming loads calculated using these equations are in good agreement with both, the experimental results and the results calculated using the rigid-plastic finite-element method.
Key words : roll forming, tube forming, extroll-forming, expanding, circular welded steel pipe, square pipe,
pushing load, forming load, non-driven grooved rolls
Effect of Partial Welding on Plane View of a Rolled Flat Bar
Hiroyuki HINO and Hiroyuki KOTANI
(Received on July 22, 1997)
In hot strip rolling, the head and tail ends of a single transfer bar undergo deformations such as overlap, flare, tongue or fishtail, and resulting in numerous problems in terms of quality, yield and threading stability. Endless hot strip rolling, namely joining of the head and tail end of each bar is performed to obtain a steady-state condition so as to prevent the occurrence of these problems. A miniaturized model test using plasticine slabs has been carried out in order to investigate the effect of partial welding on the plane view of the rolled flat bar. Partial welding involves 1 thickness partial weld, 2 width-center weld and 3 width-edges weld, moreover the welding ratio is defined as the ratio of area of the welded part to the cross section of the bar. As a result of the investigation, it is concluded that welding of the width edges with a 10％ welding ratio is highly effective for improving the plane view as well as crop loss or yield.
Key words : hot strip rolling, transfer bar, partial welding, overlap, plane view, crop loss, yield, plasticine, model mill
Drawbead Restraining Force When the Sliding Direction of
the Sheet is not Normal to the Drawbead Line
――Study on Drawbead Restraining Force in Sheet Metal Forming III――
Hideyuki SUNAGA and Akitake MAKINOUCHI
(Received on July 28, 1997)
The quality of final product depends on how well the sheet material under the tools in the forming process is controlled to prevent tears and wrinkles. Drawbeads are used to control the material flow in the automotive panel forming. However, simulating the drawbead forming process is time consuming. The method of reducing the calculation time has been proposed. But it doesn't include the drawbead effect on the material flow direction inclined against the drawbead. We need to develop a practical but accurate method of modeling the drawbead effect as well as a method of estimating the restraining force as a function of the direction of drawbead line and geometry. We therefore developed a specific apparatus to measure the drawbead force under a different clearance and different sheet sliding directions against the drawbead line. We also simulated the drawbead forming process to obtain a general understanding of the drawbead effect.
Key words : drawbead, sheet metal forming, numerical analysis, experimental analysis, drawbead force, FEM, bead clearance, bead groove
In-Plane Bending of Aluminum Plate by Flattening
Toshio YOKOYAMA and Hajime NAGASHIMA
(Received on July 30, 1997)
The present paper is concerned with bending working by incremental forming. The cross section of the specimen is T-shaped with an offset height corresponding to the compressibility ratio. Approximate formulas for calculating the curvature radius, which were derived on the basis of a simple assumption concerning the elongation distribution of a compressed specimen, are proposed. Next, bending of aluminum specimens is carried out. The curvature radius of a bent specimen is compared with the one derived using the approximate formula. It is shown that the agreement between the calculated and the experimental values is good. The influence of specimen dimensions, working condition, and compression ratio on the curvature radius was clarified. Moreover, the similarity condition of the present working method was considered.
Key words : bending, cold forging, incremental forming, in-plane bending, aluminum plate
Development of Three Dimensional Finite Element Method
――Adaptive to Wire-Rope Design and Forming――
Guilan WANG, Tatsuhiko AIZAWA, Junji KIHARA,
Takuya MURAKAMI and Shinji KURASHIGE
(Received on )
A new elasto-plastic finite element method is developed to discribe three dimensional behavior of a wire in forming. Use of a corotational finite element enables us to construct beam elements for accurate and reliable description of large rotation and deformation of wire elements from a straight wire. Rational linearization of a variational equation in the incremental displacements leads to tangential finite element equations, to be iteratively solved for each increment. Two elastica problems were employed to demonstrate the validity and effectiveness of the present method.
Key words : elasto-plastic analysis, wire rope forming, FEM analysis, three dimensional large rotation, structure design
Effect of Particle Diameters on Compaction Behavior of
Alumina Powder
Saiji MASAKI, Toshio HAGA and Susumu SHIMA
(Received on August 6, 1997)
Granulated alumina powders with three particle diameter sizes are compacted under a plane strain condition to determine the densification of ceramic powders. Biaxial compaction with various stress paths and at various speeds is performed by utilizing a specially designed device. The effects of stress paths and compacting speeds on the compaction behavior of the ceramic powders are discussed. The compressibility curve obtained by plotting the relative density in the various stress paths is expressed similar to Tresca's yield curve, which increases with increasing relative density and decreasing particle diameter. A proposed compressibility equation is expressed in terms of the relative density, the strength of the powder, the particle diameter and a few material constants.
Key words : ceramic, Al2O3, particle diameter, biaxial compacting, stress ratio stress path, compacting speed, compressibility curve
Consolidation Conditions for Hard Powders Using
a Hot Dynamic Compaction Technique Compressed by a Converging Underwater Shock Wave
Sei-ichiro TANAKA, Kazuyuki HOKAMOTO, Masahiro FUJITA,
Shigeru ITOH and Akira CHIBA
(Received on August 11, 1997)
The advantages of hot dynamic compaction in consolidating hard-to-consolidate powders were examined through a series of experiments. We attempted the compaction of high-speed steel, TiB2, c-BN and diamond powders at high temperatures using a converging underwater shock wave assembly that generates a shock wave with a relatively long duration. The pressure required for consolidating powders was determined to be strongly related to the hardness of the powders. The effect of high temperature on consolidation was discussed. High-speed steel, TiB2 and c-BN powders were well consolidated under conditions of moderate shock pressure, but diamond powders required a higher temperature or shock pressure.
Key words : high-energy rate forming, powder metallurgy, dynamic compaction of powders, underwater shock wave, hot dynamic compaction, high-speed steel, TiB2, c-BN, diamond
Pseudo-Viscosity Analysis of Compaction Processes of
Multilayer Powder Medium
――Multishock Compaction of a Copper Powder
Medium in a Die by Punch Impact VI――
Yukio SANO and Koji TOKUSHIMA
(Received on August 15, 1997)
In this paper, the compaction of a four-layer copper powder medium by punch impact is analyzed, where low (L) and high (H) initial densities are arranged alternately. In the early stage of compaction, reflection and transmission of induced shock as well as elastic waves occur along interfaces between two layers of L and H initial densities. As a result, the L layers are selectively compressed until the interfaces disappear. Compaction then continues due to the shock waves propagating through the whole medium. Separation of the punch from the medium and subsequent reimpingement was discovered in the H-L compaction.
Key words : dynamic compaction, powder, compaction process, shock wave, elastic wave, multiple layer, theoretical analysis, pseudo-viscosity method, powder forging
Draw-Ironing on Thin Cylindrical Parts of Austenitic Stainless Steel
Kouichi MINE and Isao IWASAKI
(Received on September 8，1997)
Although high-precision thin cylindrical parts made of austenitic stainless steel have been used for electronic parts, most of them are produced by machining because of the difficulty in plastic working. Since further reduction of the size and thickness of the parts will become necessary in the future in order to improve performance, the feasibility of plastic working has been studied as the technology necessary to meet this requirement. The draw-ironing process of forming cup shaped parts was selected to analyze specific phenomena, especially the ironing process of this material. Factors obstructing greater precision were found. Also, in order to solve any problems found, the draw-ironing process has been divided into two steps. As a result, target precision and properties, including a ±0.02mm outside diameter, a ±0.009mm inside diameter, Rz 3 surface roughness and 1.013 permeability, have been achieved, confirming the feasibility of plastic working in the future.
Key words : draw-ironing, thin cylindrical parts, plastic working of stainless steel