Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.40 No.462 July 1999)
Controlling Edge Drop by Tapered-Crown Work Roll Shifting Mill
and Work Roll Crossing Mill in Cold Strip Rolling
Jun-ichi TATENO, Kazuhito KENMOCHI, Ikuo YARITA,
Tomohiro KANEKO and Yasuhiro YAMADA
(Received on June 8, 1998)
For the purpose of controlling edge drop in cold strip rolling, a tapered-crown work roll shifting method was developed and applied to many commercial cold rolling mills, and a pair crossing mill was also developed to control the thickness profile in cold strip rolling. In this paper, the capabilities to control edge drop by work roll shifting and work roll crossing are investigated to advance the technologies needed to control edge drop in cold strip rolling. Experiments are carried out on a laboratory scale and in actual mills, in which the work roll shifting and work roll crossing devices are installed. In rolling that uses straight work rolls, edge drop is formed. In the work roll shifting mill, edge drop becomes smaller with increasing work roll taper position, EL. The flatness of the rolled strip is quarter buckles and the maximum elongation increases with increasing EL. In the work roll crossing mill, edge drop is reduced slightly and the strip flatness of the center buckles increases with increasing crossing angle. As the strip flatness is constrained to enable stable rolling, the capability of work roll shifting to control edge drop is greater than that by work roll crossing.
Key words : cold rolling, rolling mill, thickness, edge drop, work roll shifting, work roll crossing, strip flatness
Application and Improvement of Forming Precision
to a Forming Machine
――Development of Computer-Aided Bending Test and Forming Machine U――
(Received on June 18, 1998)
A computer-aided repeat bending test machine has been developed previously, and its performance was presented in a previous paper. It was shown that the machine can be used as both a bending machine and a bending test machine. However, this machine did not uniformly bent the specimens. In order to solve this problem, the increment of table transfer was changed to the proper rate (named “offset”), and more precise formings were realised. In addition to cylindrical forming by this machine, S-shape and 〓-shape forming were carried out successfully. Bending in two directions as also carried out by using arc-shaped chucks. In convex and concave shape formings, the curvature distribution of the second bending direction was not uniform. In order to reduce nonuniformity, the effectiveness of tensile force were examined experimentally.
Key words : bending test, bending, cylindrical forming, CAE, CAM, CIM
Effect of Forming Tool Conditions on the Warping and
the Spring Back in Flanging of Sheet Metals
Liwei GU, Koe NAKAJIMA, Yuzou HOSOI
Munenori ONO and Yasuhisa TOZAWA
(Received on July 15, 1998)
In this report, the model experimental results concerning the warp deformation property of web and spring back property of flange in flanging of sheet metals have been described. Four kinds of basic models, straight-type, stretch-type, shrink-type and reverse-type flanging (i.e., stretch-shrink mixed-type flanging) with various profile curvatures were used as forming tools. Moreover, steel sheets and an Al alloy sheet were used as the test materials. The effects of flange profile curvature, blank dimension, forming height and materials on the web warp and the flange spring back，were clarified in the flanging of sheet metals. The experimental results show that the web warp and the flange spring back are greatly influenced by profile curvatures. The stress induced in the direction of the flange profile was estimated based on the measured strain of the flange edge and the relation between stress and strain in the total strain theory. It was clarified that the web warp and the flange spring back were influenced by the stress induced in flanging.
Key words : straight flanging, stretch flanging, shrink flanging, reverse flanging, web warp, flange spring back, stress analysis, steel sheet, Al alloy sheet
Circularity Improvement of Cylindrical Parts
for U-O Process by Peripheral Axial Grooves
Satoshi SUGIYAMA and Takashi ISHIKAWA
(Received on August 21, 1998)
Most cylindrical parts for electronic appliances are produced by the U-O process or drawing. Although U-O process products have higher material yield than drawing products, the dimensional accuracy is inferior to those of other processes. In this paper, we performed studies to improve the circularity of U-O process products, by forming peripheral axial grooves equally a round the circumference using by means of a tool with a projection. We assessed of the stress distribution and the springback obtained by the elastoplastic finite-element method. By performing experiments based on this assessment, we verified that the method was more efficient compared to the conventional one.
Key words : bending, elastoplastic FEM, U-O process, groove, circularity, springback
Theoretical Approach to the Measuring Method for Grain Size
Distribution of Metal Microstructure
Masahiko YOSHINO and Takahiro SHIRAKASHI
(Received on February 18, 1998)
A basic theory for the estimation of grain size distribution from a microstructure image of metals is discussed in this paper. In the theory it is assumed that grains are spherical, and that many grains of various diameters are randomly distributed in a 3-dimensional material model. A relationship based on geometric theory between the true grain size distribution and the frequency of the scanline intercept length divided by grain boundaries, which is measured on a cut plane of a specimen, is derived. A relationship between the true grain size distribution and frequency of the grain cross section is also derived. Then, relationships between the average values; i.e., true average grain size, the average scanline intercept length and the average diameter of a grain cross section, are discussed. Volume fractions are also discussed, and it is proven that the area ratio of a texture measured from a microstructure image corresponds with the true volume fraction, independent of grain size distribution.
Key words : material testing, measurement, microstructure, grain size distribution, average grain size, volume fraction
Measuring System for Grain Size Distribution of Metal Microstructure
Masahiko YOSHINO, Shinya SAWADA and Takahiro SHIRAKASHI
(Received on October 7，1998)
In this paper, a new measuring system for grain size distribution that measures the true distribution from microscopic images of metals is indroduced. The system consists of an optical microscope with a CCD camera and a computer. The microstructure image observed by the microscope is digitalized by the CCD camera, and transferred to the computer. The computer scans the digitized image to measure the scanline intercept length, and makes a histogram of the intercept length. A method for estimating the true grain size distribution from a distribution chart is also developed, where quadratic programming is applied to the constrained least-squares method. By applying the method to several grain models (namely, the uniform model, JIS model and microstructure of pure copper), we prove the efficiency of the measuring system.
Key words : material testing, measurement, microstructure, grain size distribution, measuring system
Flexible Extrusion with Inclined Dies
to Control Metal Flow
Mitsunobu SHIRAISHI, Makoto NIKAWA
and Masafumi YAMAGUCHI
(Received on February 18, 1998)
manufacturing products whose cross sections vary along their length, we propose an extrusion process that uses dies inclined at varying angles to the center line of the container, in which the bending of products is effectively suppressed by continuously controlling the metal flow during extrusion. In order to understand the fundamental characteristics of this process, the bending of the extruded product is investigated by carrying out extrusion tests on the product with a trapezoidal cross section under several fixed inclination angles of the dies. It is confirmed that the bending of the product is suppressed by selecting the appropriate inclination angle of the die for each cross section and extrusion ratio.
Key words : extrusion, production system, FMS, experimental analysis, plasticine, metal flow control, bending,
inclined die