Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(vol.42 no.486 July 2001)
A New Rolling and Fixation Method for Densification of Lumber
- Studies on the Rolling of Wood I -
Hiroyuki SHIOZAKI, Tadahiro KAWASE,
Motoyoshi IKEDA and Masao MIKAMI
(Received on June 15, 2000)
In the rolling of lumber, preventing the recovery of reduced thickness is an important issue. From the photoanalysis of rolling, it has been found that the recovery in the roll gap is less than half of that after the lumber leaves the roll gap. Using this phenomenon, a new rolling and fixation method has been proposed. In this method, the rolled lumber is inserted into the heated rectangular chamber located behind the rolling rolls and is held for the time necessary for fixation; e.g., for Sugi lumber (Japanese Cedar) under rolling conditions of entry thickness of 30mm, fixed thickness of 17.2mm and chamber temperature of 200 C, the time necessary for fixation is 30 min. However, the fixation at this stage is a temporary fixation. It needs an additional 5 hour of heat treatment to get the lumber fixed permanently. By separating the processes for temporary fixation and for permanent fixation, the productivity of this process is expected to increase tenfold.
Key words : rolling, wood, lumber, temporary fixation, permanent fixation, new fixation method
Deve1opment of Cross Roll Edge-Bend Method
for Electric Resistance Welded Pipe Forming
Daigo SUMIMOTO, Kenji HADA,
Takashi OHSAWA and Toshio KIKUMA
(Received on August 1, 2000)
A method was proposed and investigated for improving the commonality of rolls being used in a variety of outside diameters and wall thicknesses of Electric Resistance Welded pipes, together with improving their formed edge profile and quality, where pipes having a broad wall thickness range from thin-wall to thick-wall are manufactured. The cross roll edge-bend (CRE) method was therefore developed. The method can regulate the gap profile by crossing the vertical axes of the upper and lower rolls, to accommodate both the required bending curvature and the wall thickness. From the results of a testing using a stand fabricated on an experimental basis together with a numerical analysis, it has been demonstrated that the CRE method is advantageous for both improving the commonality of rolls to cope with varied dimensions and in the high precision formation of an edge profile with fewer impression defects.
Key words : material testing, roll forming, deformation-load property, ferrous metal, plasticity theory, finite element method
Property of Cross Roll Edge-Bend Method
for Electric Resistance Welded Pipe Forming
Daigo SUMIMOTO, Kenji HADA,
Takashi OHSAWA and Toshio KIKUMA
(Received on August 1, 2000)
The cross roll edge-bend method has been developed. This method can regulate the roll gap profile by rotating and crossing the vertical axes of the upper and lower rolls to accommodate both the required bending curvature and the wall thickness. From the results of testing using a cross roll stand fabricated on an experimental basis together with a numerical analysis, it has been demonstrated that:(1) The curvature of the edge can be predicted by numerical analysis, and this analysis reveals the effect of the inward cross roll edge-bend method. (2) In the inward cross roll edge-bend method, the compression stress in the width direction of the inner surface and the tensile stress in the width direction of the outside surface are forced near the edge part in the early stage of formation, and the edge formation is improved by the effective bending moment. (3) The precision of the outside diameter and the thickness of the pipe are improved by the cross roll edge-bend method. (4) The twist in the case of formation is converged to zero due to self-restrain for the thrust force between a top roll and a material.
Key words : material testing, roll forming, deformation-load property, ferrous metal, plasticity theory, finite element method
Effects of Guiding Conditions on Longitudinal Bowing
of Rolled Sections
Manabu SASAJIMA, Manabu KIUCHI and Yoshihiro NARITA
(Received on August 1, 2000)
In this paper, the effects of guiding conditions on longitudinal bowing of rolled sections in light reduction rolling are presented. A series of experiments was conducted using a specially designed test mill and employing various rolling and guiding parameters, such as inlet angle, thickness reduction, caliber gap and caliber angle. The resulting curvatures of the rolled sections were measured to discuss the effects of those parameters. A statistical data-handling method, that is, the GMDH (group method of data handling), was used to analyze the measured data, and a regression formula was derived which makes it possible to predict the bowing curvature of rolled sections. The predicted curvatures agree very well with the experimentally measured one.
Key words : rolling, roll forming, longitudinal bowing, statistical data handling, test mill, forming machine
Accuracy of an Ironed Flange in Stretch Flanging
- Accuracy of Formed Product in Axisymmetric
Stretch Flanging of Steel Sheet III -
Shigeo ICHIKAWA, Yasuhisa TOZAWA and Naoyuki KANETAKE
(Received on August 4, 2000)
The effect of ironing on the accuracy of a formed flange is investigated for the axisymmetric stretch flanging of a cold-rolled steel sheet. The thickness reduction of the flange becomes uniform with decreasing the clearance between a punch and a die. However, the difference between the clearance and the flange thickness increases with decreasing clearance due to the elastic deformation of tools. The accuracy of the diameter and the roundness of the flange is improved by ironing because of the decreases in a residual bent region and a flange angle. A small punch corner radius causes a shock line at the die shoulder, and it is difficult to make it disappear by ironing. Therefore, a large punch corner radius is desirable for stretch flanging with ironing, and the suitable clearance is smaller than the thickness calculated under the condition of circumferential uniaxial tension at the flange edge.
Key words : stretch flanging, axisymmetric flanging, ironing, accuracy, steel sheet
High Strain Rate Superplasticity of
Nitrided-Fiber-Reinforced A6061 Composites
Sumito KOJIMA, Tsunemichi IMAI,
Mao JIANFU and Takashi ISHIKAWA
(Received on August 7, 2000)
Nitrided mullite (48%Al2O3-52%SiO2)-short-fiber-reinforced 6061 aluminum alloy composites fabricated by the powder metallurgy method were hot-extruded and their superplastic behaviors were investigated. These composites exhibited an m value of about 0.4 and a total elongation of 220% in the strain rate range from 1.0~10|2 to 1.0~10|1s|1 at 853K. In these composites, subgrains of approximately 2¬m remained after high strain rate superplasticity. On the other hand, the non nitrided mullite (48%Al2O3-52%SiO2) short-fiber-reinforced 6061 aluminum alloy composites exhibited a total elongation of 100% only at 853K, because an interface reaction between mullite short fibers and the aluminum matrix occured at 845K and some cracks could be observed in the reaction phases after superplastic deformation. In the case of the nitrided mullite-fiber-reinforced 6061 aluminum composites, the reaction phases could be rarely be observed even after superplastic deformation with the total elongation of 220%. These results indicate that surface nitriding of short fibers enhances the superplastic characteristics of metal matrix composites.
Key words : material testing, superplasticity, nitriding, composite, mullite, aluminum alloy
Influence of Mechanical Properties of Metallic Material
on the Reducing Effect of Axial Residual Stress after Cold
Drawing Using a Double-Taper Die
Takashi KUBOKI, Yutaka NEISHI,
Kouichi KURODA and Masayoshi AKIYAMA
(Received on August 10, 2000)
Experimental and numerical investigations were carried out to determine the influence of mechanical properties of metallic materials on the reducing effect of residual stress after cold drawing by a double-taper die. Yield stress, Young's modulus, and work-hardening ratio were chosen as indices of mechanical properties, and their influence was examined quantitatively. The work-hardening ratio was found to be the most influential factor on the reduction effect of axial residual stress, and an optimum die design was proposed to most effectively reduce the axial residual stress regardless of the materials.
Key words : drawing, numerical analysis, residual stress, FEM, die design, bar, wire
Contact Problems with Friction in Static-Explicit Finite Element
Method Code and Application to Sheet-Metal Forming Simulation
Kiyoshi KAMITA and Akitake MAKINOUCHI
(Received on August 30, 2000)
In this paper we discuss contact problems with friction using a static-explicit finite-element method (FEM) and an application to sheet-metal forming. We previously reported the method of solving contact problems that arise during sheet-metal forming simulations using a static-explicit FEM code. This time, we have enhanced this method in order to treat friction problems. Furthermore, we discuss how to explicitly treat contact problems with friction. Finally we enhanced the static FEM code ITAS3D using this method and demonstrate it. The spring-back problem also currently is a very important issue and is related to the blank holder pressure, which means that friction significantly influences spring-back problems. Therefore we also demonstrate this method to solve the spring-back problem.
Key words : sheet-metal forming, numerical analysis, elasto plastic FEM, contact, friction, static-explicit FEM
Development of Texture by Compression
under Semi-Molten State
Tohru SHIROTA, Tasuku DENDO and Boem-Suck HAN
(Received on September 8, 2000)
In order to discuss features of the texture development by compression under a semi-molten state, experiments on semi-molten Al-Si alloys were performed and textures of worked pieces obtained were examined with respect to the process parameters such as reduction, solid fraction and initial morphology of the microstructure of the work piece. Development of o100porientation is observed under medium conditions of reduction and solid fraction. This orientation is more significant when the aspect of solid structure in semi- molten metal is columnar. Under the conditions of greater reduction and higher solid fraction, o110p orientation appears in addition to the o100porientation. The development of o100porientation is due to the rotation and breakage of the columnar solid phase with q100rdirection.
Key words : semi-molten processing, texture, semi-solid metal, compression, Al-Si alloy
Optimum Forming Conditions of Box-Shaped Cross Section Products
- Research on Box-Shaped Reinforced Bumper Made of High Strength Steel SheetT -
Motoo ASAKAWA, Takuma ABE, Satoshi NISHIKIORI, Takayuki HAMA,
Isao KUWAYAMA, Yoshio FUJISHIRO and Ikuhiko HAYASHI
(Received on November 20, 2000)
A high-strength 120kgf/mm2 steel sheet has been recently developed and is now expected to be used for lightening of machines and structures. However there occurs difficulty in sheet forming when using the high-strength steel. The aim of this study was to research the optimum shape of box-shaped cross section products by die bending. In the U-bending process, two types of die were used which have different values of punch radius. In the C-bending process, several types of die were used which have different values of side wall angle and side wall width. The results are as follows; first, the punch radius did not influence the final shape of the product, but in some cases cracks appeared at the bending part when the punch radius was changed in the U-bending process. Second, change of the side wall angle in the C-bending process was effective for minimizing deflection on the wall part and for altering the location of maximum deflection. Finally, it was clarified that appropriate side wall angle and side wall width are essential in the C-bending process.
Key words : sheet metal forming, high-strength steel plate, box-shaped cross section