Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.40 No.465 October 1999)
Appropriate Interpolation Function and Mesh System for Stabilizing Calculated Temperature Distribution -Three-Dimensional Finite Element Thermal Analysis of Hot Rolling I-
Manabu KIUCHI, Jun YANAGIMOTO and Eiji WAKAMATSU
(Received on September 30, 1998)
Recently, significant progress has been made with respect to the numerical simulation of manufacturing technology. This depends mainly upon the development of the finite element method and advancement in computer technology. Simulations of metal-forming processes are now feasible by utilizing various computer codes. However, in order to obtain correct insight into various phenomena, more investigations into simulation methods are required. Regarding hot rolling processes, effective analysis of both the deformation features and the thermal behavior of workpieces are indispensable for controlling the internal structures and mechanical properties of rolled products. In this paper, a strategy for solving thermal problems in hot rolling processes is described. The analysis is based on Eulerian description which includes the convective term, heat conduction term and heat radiation term at the boundaries of both the workpiece and the roll. Through the study, the numberical stability of the solution is discussed, and an appropriate interpolation function and mesh system are proposed.
Key words : rolling, numerical analysis, thermal analysis, finite element method, Galerkin method, Eulerian description
Development of the Elongation-Control Mill and Its Application to
Flat-Wire Rolling
―Development of Elongation-Control Rolling I―
Yoshihiro SAITO, Hiroshi UTSUNOMIYA,
Masaki SHINKAWA and Kagenori OKA
(Received on October 9, 1998)
A novel continuous tandem rolling technique, elongation-control rolling, is proposed. The aim is to control the elongation or the lateral spread of a workpiece during rolling to achieve size-free rolling, a rolling technique usable with a workpiece of any size. The elongation is controlled by interstand force, which varies widely from tensile to compressive. A prototype five-stand mill was constructed. Flat-wire rolling experiments were conducted using commercially pure round aluminum bars. Interstand forces were generated by changing the roll speed ratio of the stands. The limits of interstand force to achieve stable rolling operation were clarified. The tension limit is due to the slipping of rolls on the workpiece, while the compression limit is due to the buckling of the workpiece between stands. It has been clarified that elongation of the workpiece can be controlled to be a great degree. Compressive interstand force decreases the elongation and increases the lateral spread.
Key words : rolling mill, tandem mill, elongation-control rolling, elongation, dimensional control
Mechanism of Controlling Edge Drop by Tapered-Crown Work Roll
Shifting and Work Roll Crossing in Cold Strip Rolling
Jun-ichi TATENO, Kazuhito KENMOCHI, Ikuo YARITA,
Tomohiro KANEKO, Teruhiro SAITO and Yasuhiro YAMADA
(Received on November 20, 1998)
For the purpose of controlling the edge drop in cold strip rolling, a tapered-crown work roll shifting method was developed and applied to numerous commercial cold rolling mills. A pair crossing mill is also introduced to control the thickness profile in cold strip rolling. In this paper, the mechanism of controlling the edge drop by work roll shifting and work roll crossing are investigated to advance the technology of controlling the edge drop in cold strip rolling. The experiment is carried out on a laboratory mill, in which the work roll shifting and work roll crossing devices are installed. Rectangles are scribed on the strip surface before rolling, and the three-dimensional metal flow in the strip edge is measured after rolling. In the work roll shifting mill, predeformation near the strip edge in both the rolling direction and width direction is observed. Thus, the metal flow occurs from the prerolled area at the entrance of the roll bite, and the edge drop is reduced according to the contour of the work roll taper at the roll bite.
Key words : cold rolling, rolling mill, edge drop, roll shifting, roll crossing, predeformation, metal flow
Metal Flow Control by Flow Guide of Spreading Extrusion
―Study of Spreading Extrusion Process V―
Yoshinobu IMAMURA, Norio TAKATSUJI, Kenji MATSUKI,
Tetsuo AIDA, Hideshi YASUDA and Hikaru SASATANI
(Received on December 4, 1998)
In order to extrude aluminum profiles wider than the container diameter, the authors are conducting research on spreading extrusion utilizing spread rings. In this study, metal flow is controlled by installing a flow guide between the spread ring and the die to ensure uniform metal flow velocity distribution at the bearing exit with the goal of eliminating profile deformation. The shape of the flow guide, which ensures uniform metal flow velocity distribution at the bearing exit, has been determined through extrusion tests, and the relationship between the flow guide entrance width and profile exit speed has been using take into consideration. Furthermore, phenomena which occur during the extrusion process are analyzed using a flow analysis finite-element method (FEM) program, and the metal flow conduct in the flow guide is discussed.
Key words : extrusion, wide shape, spread ring, flow guide, metal flow, simulation, finite-element method
Welding Defect Vanishing Criteria in Ceramic Injection Molding
Yongho CHUNG, Kazunori KATO and Naoto OTAKE
(Received on December 18, 1998)
Welding defects in the joining of flow fronts is a typical molding defect in ceramic injection molding. In this paper, the welding defects tendency to appear and disappear have been examined and the following results have been obtained. First, from the welding experiments of counterflow joined using a two-gate mold cavity, it was found that both a weld line at the surface and voids in the cross section occur at the welded part. Then, criteria needed for these two types of welding defects to vanish are obtained on the plane of the material temperature TM and the welding pressure PW. Both criteria approximately coincide with each other in this standard condition. Second, the welding defect vanishing criterion is applied for the evaluation of welding defect generation under various injection conditions, such as flow length and cavity thickness, and it was found that the welding defect vanishing condition does not greatly depend on the asperity of a flow front. Third, the welding defect vanishing criterion is also effective for estimating the degree of welding defects in injection molding by use of a mold cavity with inserts. Finally, it was confirmed that the above criterion approximately coincides with that in a previous paper, which was obtained by the use of a simple void-reducing condition in the joining of green ceramic blocks with artificially grooved surfaces.
Key words : ceramic injection molding, forming limit, welding defect, front surface asperity, counter flow joining, welding defect vanishing criteria
Three-Dimensional Analysis of Helical Rolling of Tube
Using Rigid-Plastic Finite Element Method
Hideo TAKIZAWA and Toshio KIMURA
(Received on December 24, 1998)
A three-dimensional finite element analysis code for helical rolling of tube has been developed. The code is based on the rigid-plastic finite element method which uses a penalty function for the incompressibility of material. To simulate a complicated deformation, while regarding the circumferential direction of the tube as the rolling direction, a steady-state analysis method is used. Only 1/3 of the tube is analyzed with the periodic boundary condition. The calculated shape and forming loads are in good agreement with the experimental results. The analysis results clarify that the energy is consumed mainly for redundant deformations (circumferential bending, shear deformation and increase of thickness at both sides of contact area). The objective deformations in this process are achieved as follows. In the contact area, the material that is reduced in the thickness direction between the roll and the mandrel flows mainly in the circumferential direction. The redundant circumferential length is reduced by a constraint of three rolls on the free surface. Longitudinal elongation occurs mainly in the contact area and also occurs around the tube at the contact point of the roll corner.
Key words : rotary forming, helical rolling, tube rolling, finite element method, rigid-plastic FEM, steady-state analysis, three-dimensional analysis
Numerical Prediction of Ferrite and Pearlite
Microstructure and Hardness
―Material Property Predictions in Hot Forging of
Vanadium Microalloyed Steels U―
Zhe WANG, Akira KONO,
Nobuki YUKAWA and Takashi ISHIKAWA
(Received on January 14, 1999)
Empirical models combined with FEM simulation were developed to predict the microstructure of hot-forged vanadium miroalloyed steel products. Experiments were conducted performed to investigate the influence of austenite grain, strain, compression temperature, and cooling rate on transformation. An experimental formula for predicting ferrite volume fraction and hardness was developed. These empirical models were incorporated into the FEM and ferrite grain size, volume fraction of ferrite and hardness for practical multiple-stage hot-forging were calculated. The experimental results agree well with the predicted results.
Key words : hot forging, microalloyed steel, FEM simulation, austenite grain size, ferrite grain size, pearlite block size, ferrite volume fraction, hardness
Development of Online Adaptive Filter for Intelligent V-bending Process
Control System with Numerical Simulation Database
Ming YANG, Ken-ich MANABE, Naoyuki AIKAWA and Atsushi KATAYAMA
(Received on February 10, 1999)
An online adaptive filter was proposed and applied to the intelligent V-bending process control system with a numerical simulation database developed by the authors in order to improve the accuracy and flexibility. The adaptive filter was designed during the V-bending process by comparing the measured punch force and stroke curve (F-S curve) with the curves in the simulation database in order that the F-S curves in the simulation database can be optimally modified to cope with any kind of material. Furthermore, a multiregional filtering algorithm was proposed in order to deal with variation in the F-S curve, according to the trasition of deformation of the workpiece. The evaluation results demonstrate that the modified F-S curve has higher accuracy and reliability using the multiregional filter than by using the singular filter. The adaptive filter with the multiregional filtering algorithm was introduced to the V-bending process control system and evaluated by using experimental data of four kinds of materials. The results show that the process cntrol with the online adaptive filter can flexibly deal with the various materials and give a highly accurate bend angle without any trial bending test.
Key words : bending, database, process control, online adaptive filter, multiregional filtering, FEM simulation, F-S curve, bend angle accuracy