Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.39 No.449 June 1998)
Development of an Intelligent V-bending Process Control
System with Database and Fuzzy Inference Model
Ming YANG, Naoki KOJIMA, Ken-ichi MANABE and Hisashi NISHIMURA
(Received on September 24, 1997)
An intelligent control system based on a new database concept and a fuzzy inference model is proposed and developed for an accurate V-bending process. The database contains information on the punch force-stroke curve (F-S curve), which includes all key parameters such as material properties, machinery conditions and ambient factors, and is retrieved during the V-bending process. The retrieved F-S curves are compared with the in-process measured curve, and discrepancies are evaluated using a fuzzy inference model to predict the control value for adaptive control. Furthermore, the intelligent control system is capable of learning from results obtained from experiments in order to cope with new materials. The intelligent V-bending operation is carried out on a distributed information processing system, which has a multiprocessor with different platforms on network so that the database retrieval and fuzzy inference run parallel to the process sensing and control. Experimental results show that the intelligent control system significantly improves the accuracy and reliability of the V-bending process. The concept of developed intelligent control system may be useful in a wide range of metal forming applications.
Key words : bending, database, F-S curve, fuzzy inference model, adaptive control, learning
Shape-Fixability of Various Kinds of Sheets in Model Forming Tests for Car Doors and Roofs
Tomohisa KATAYAMA, Matsuo USUDA, Yoshikuni TOKUNAGA, Yuuji ABE and Masakatsu YOSHIDA
(Received on May 12, 1997)
Shape-fixability in model forming tests for car doors and roofs is invetigated using various kinds of sheets, including high-strength steel sheets, aluminum alloy sheets and austenitic stainless steel sheets. The results obtained in this work are summarized as follows. (1) Aluminum alloy sheets demonstrated worse shape-fixability than steel sheets because of a difference in Young's modulus. (2) Materials possessing low yield strength showed good shape-fixability because the bending moment is easily reduced with low applied tension. (3) Materials possessing high n value showed good shape-fixability because plastic strain at the center of a panel can be increased by applied tension without failure. (4) Use of a dry lubricant improved shape-fixability. The reason for this improvement is thought to be the change of the strain state at the center of the panel, which causes yield strength along the curvature to be low and Young's modulus to be high.
Key words : sheet metal forming, shape-fixability, high strength steel sheet, aluminum alloy sheet, dry lubricant
Analysis of Surface Deflection of Sheet Metals in Press Forming
Takao SAWADA and Linsheng LIU
(Received on September 8, 1997)
Hill's criterion of uniqueness to analyze the deflection of sheet metals in press forming cannot be applied to most cases since it could contact the die. Therefore, the following method is proposed to characterize the deflection. Deflections of sheet metal are caused by shear stress in the out-of-plane direction, such that the development of surface deflections can be easily detected when shear stress is observed using deformation analysis during press forming. In this paper, the relationship between the results of deformation and bifurcation analyses is represented in numerical examples by using Mindlin's shell theory in terms of axial compression of sheet metal and embossing of circular sheet metal by punches. It is revealed that the proposed method can determine the approximate bifurcation limit and the mode of the deflection of sheet metal, where initial imperfection of the configuration with a reasonable value should be assigned to sheet metal. Criteria to evaluate the deflection caused by a lack of bifurcation must also be established.
Key words : sheet metal forming, embossing, elasto-plastic FEM, surface deflection, wrinkling, shear stress, bifurcation
Application of a Numerical Simulation Database to the Intelligent X-bending System
Ming YANG, Ken-ichi MANABE, Naoyuki AIKAWA and Hideo OGAWA
(Received on October 9, 1997)
A concept of an intelligent process control system with a numerical simulation database for the V-bending process is proposed and developed. FE analysis is employed to simulate the V-bending process and the results are stored in a database and then applied to a real-time process control developed by the authors. The control system depends significantly on the reliability of information in the database, which can not be only guaranteed by experimental data due to the partiality. Since it is difficult to take all of the influential factors into account in the FE simulation, discrepancies between the simulated and experimental results exist. To improve the accuracy of the control system with the simulation database, the authors proposed a filtering technique to compensate for the discrepancies. The proposed compensation filter is designed to modify the simulated punch force-stroke curve (F-S curve) of the V-bending process. The modified curves are stored in a database for the process control. The process control is carried out by comparing the inprocess measured F-S curve and ones in the database during the process, while the fuzzy inference model is used to evaluate the comparison results and to predict the control value of the punch stroke. The control results show that FE simulation results modified by the compensation filter is significantly effective for the precision process control, and the simulational database is found to have higher reliability than the experimental one.
Key words : bending, FEM, simulation database, compensation filter, F-S curve, bend angle
Density Unifying Technology in Hot Press Lamination of Ceramic Green Sheets
――Plastic Working of Ceramic Green Sheets III――
Ryoji IWAMURA, Masayuki KYOI, Hideaki TANAKA and Kazutoshi TAKAHASHI
(Received on October 17, 1997)
In the production of a multilayer ceramic circuit board, shearing, hole punching and hot press lamination are required for accurate plastic working. Hot press lamination is performed before sintering. Density distribution in a hot-press-laminated body causes shrinkage distribution during sintering. This results in the low accuracy of a sintered body. Therefore, a method to obtain a hot-press-laminated body with uniform density by unifying the pressure distribution was examined. By setting a die along the edges of stacked ceramic green sheets, their plastic flow can be restrained and a unifying effect in pressure distribution can be expected. As a result, a hot-press-laminated body with little density distribution can be obtained and sintering shrinkage distribution can be reduced to about 1/10. However, in the hot press lamination of stacked wired ceramic green sheets, considerable pressure distribution occurs due to the thickness of the printed circuits. This pressure distribution can be unified by using a frame shaped shim plastic sheet with a restraining die.
Key words : hot press lamination, ceramics, green sheet, pressure, density
Free Bulging of Square Tube under Internal Pressure
――Deformation of Square Tube in Hydrostatic Bulge Forming T――
Atsushi SHIRAYORI, Sadakatsu FUCHIZAWA, Michiharu NARAZAKI and Shinji TANAKA
(Received on October 24, 1997)
Deformation of an annealed A6063 aluminum alloy square tube in free bulge forming under internal pressure was investigated by experiment and rigid plastic FEM analysis. A cross section of the tube was a square, with sides 30mm long and 2mm thick. The deformation lengths of the tube were set at 40mm, 60mm or 80mm. The tube was deformed freely and burst at one of the four corners in all cases. The radial expansions of the tube corners were much smaller than those of the tube sides, and the cross section at the center of the burst tube became almost circular. This research clarifies that the forming limit of a square tube in free bulge forming depends on the deformation of its corners. Radial expansion differences between the sides and the corners cause circumferential bending at the corners, and this is responsible for the great circumferential elongation of the inner surface at the corners. The substantial local elongation at the corners makes it impossible for the tube to expand greatly.
Key words : tube forming, hydrostatic bulging, square tube, forming limit, experimental analysis, rigid plastic FEM