Research on Surface-Flattening Mechanism in Sheet Metal Forming and Its Application

(Received on January 11, 1994)

Kuniaki DOHDA, Masami SAITO, Zhrgang WANG and Nozomu KAWAI

The possibility of mirror surface fi,nishing by the ironing process has been investigated. The surface flattening is performed by replicating the smooth tool surface onto the workpiece under the conditions of the high pressure and the small relative slide between the workpiece and the tool. A strip-ironing type test and a pipe ironing test were conducted. It was found out that the plastic strain and the contact pressure are the most effective factors in surface flattening process. Through this principle, optical drums satisfying the specification were successfully produced directly from hot-extruded aluminum pipes.

Keywords:Plastic Forming, Tribology, Surface Roughness, Ironing, Replication,Surface Flattening, Mirror Surface, Extruded Aluminum Pipe, Optical Drum



Analytical Method for Reaction Force and Driving Torque in Leveling Process
Numerical Study of Roller Leveling Process II

(Received on September 20, 1993)

Koji KADOTA, Ryouichi MAEDA

A new analytical method is proposed for the estimation of reaction force and driving torque acting on a roll in a leveling process, which gives practical knowledge of design and operation of a roller leveler. The method consists of the following three steps. First, plate curvature and bending moment during a leveling process are analyzed by the procedure proposed in the previous paper. Then, the energy required to bend the plate elasto-plastically is calculated by integration along the analyzed bending moment-curvature path. Finally, the reaction force and driving torque are determined by equalizing the energy required for the plate bending with the energy by the externally applied force and moment in the leveling process. The analytical results for the torque and force acting on each roll agree well with the corresponding experimental results by model levelers under various intermesh conditions and for a variety of plate materials.

Keywords:leveling, roller-leveler, numerical analysis, leveling torque, bending energy, elastic perfect-plastic material



Finite Element Simulation of Deformation Features of Round Welded Steel Pipes Reshaped into Square Shape by Extroll-Forming

(Received on January 6, 1994)

Yoshitomi ONODA, Takuo NAGAMACHI and Tsutomu SUGIYAMA

Deformation features of round welded steel pipes being reshaped into a square shape by the extroll-fom-iing according to a high-reduction schedule (reduction for No.i fanning rolls ri = I in(2HT/Do) 1, 2HT = maximum height of groove of No.i fomiing rolls, Do = initial outer diameter of round pipe, ri =1 3. 1 %, r2=20.0%, r3=25.7%) are discussed referring to the experimental measurements and the results calculated by the rigid-plastic finite element method. The results are as follows. The maximum value of the increase in wall thickness of each pipe formed by each pair of fom-dng rolls is found at the center of the comer zone for the reducfion=l 3. 1 % and at the position adjacent to the comer zone for the reduction >=20.0%, respectively. These maximum values increase with the decrease in n-value of round pipe. Peripheral distribution of wall thickness along the comer zone of each pipe fanned by each pair of fanning rolls is found to be affected by both the bending and the peripheral reduction imposed on the comer zone by the forming rolls.

Keywords:roll fon-ning, tube forming, extroll-fortning, round welded steel pipe, square pipe, non-driven grooved rolls,n-value, rigid-plasfic FEM.



A New Method for Determining Deformation of the Punches
-Mechanism of Fine Shearing Processes I -

(Received on January 6, 1994)

Toshinori TAKAIJASHI, Isamu AOKI

In double-side shearing, imbalance is inevitably caused between tool clearances on both sides of a punch. Thus, a lateral force as well as an axial force acts on the punch. In the case of a punch with a high slendemess ratio, it is deformed into curved configuration. A new method for determining the punch deformation is presented in this paper. Specifically, surface strains ot' 4 portions of the punch are measured independently with each other. Using the strain values, an equation of deflection curve can be determined. To confirm the effectiveness of this method, displacement of the punch tip is measured. This experimental value has proved to be consistent with the one calculated from the shape of the punch.

Keywords:shearing, punch deformation, deflection curve, strain measurement



Shape Defects of Cold Roll Formed Products with Pre-Notches
-On Cold Roll Forming of Steel Sheet Plates with Pre-Notches I

(Received on January 26, 1994)

Hisaki WATARI, Hiroshi ONA, Takao UENO and Satoru IZAWA

Cold-rolled steel sheets, after being punched square holes (ermed as "pre-notches", were formed through a cold-roll forming process into V-section or Channel-section beams of a relatively short length. During the forming process of the pre-notched sheets, various shape defects such as edge wave, longitudinal bend in both vertical and horizontal planes, and twist appeared in the products.The mechanisms causing the defects are investigated in terms of the dimensions of the cross sections and pre-notches. The main results are as follows: 1) Experimental formula of the dimensions to limit the edge wave within an allowable mnge is given by a X d /b X t=10- 15, where a denotes hole length, b distance of hole from plate edge, d width of hole len2th and t viate thickness. 2) The longitudinal bend in vertical plane can be sufficiently reduced when I/I0 <=4.0 X 10-3(a/t)+O.77; where IP and Io denote the moment of inertia of the pre-notched cross section and that of the cross section without pre-notches, respectively. 3) A roll-pass schedule used for successfully fanning wide profile beams is also effective in manufacturing pre-notched products without causing the defects.

Keywords:cold roll forming, pre-notch, shape defect, edge wave, bend, twist, roll-pass schedule



Effects of Surface Finishing Condition and Annealing on Transformation Sensitivity of Zirconia Die Surface under Interaction of Lubricant
-Characteristics of Zirconia Die Surface Il -

(Received on February 3, 1994)

Tatsuo BESSI, Teisuke SATO, Yoshihiro TADA, and Fumie ABE

Transformation behavior of a toughened zirconia die surface is affected by not only stresses but also environmental conditions. In this paper, effects of surface finishing conditions such as grinding and lapping and annealing after them on transformation sensitivity of a zirconia die surface in hot oil are evaluated by tetragonal phase content calculated from X-ray diffraction patterns. The depth of transformed layer after held in oil at 473K is also measured by a microscopic exaaination of the cross section of specimens. The work-affected layer of the worked surface is evaluated by the value of IPT(002)/IPT(200) where IPT(002) and IPT(200) are the intensities of the tetragonal phase peaks T(002) and T(200) at 20 # 35' in a X-ray diffraction pattern respectively. When the value of IPT(002)/IPT(200) of worked surface is larger than that of the sintered one, as in the surfaces ground by #200 and #400 diamond wheels, following annealing at 1473K is effective to improve resistibility of surfaces against phase transformation in hot oil. The annealed specimen however, whose work-affected layer is removed by lapping prior to the annealing treatment shows the same transformation sensitivity of the sintered one. It is also shown that the compressive residual stress has a significant effect to increase the resistibility of surfaces against phase transformation.

Keywords:sheet metal forming, wire drawing, ceramics, zirconia die surface, grinding, lapping,transforzation sensitivity, annealing.



Development of the Mechanical Variable Crown Roll Equipment and Flatness Control Effects in Cold Rolling
-Development of the New Variable Crown (VC) Roll@1

(Received on February 14, 1994)

Atsushi TomIZAWA, Takeshi MASUI, Shigezou OKAMOTO Eiji HIROOKA, Toshiaki KITANO and Masanori SHINOHARA

A new type of Variable Crown Roll(New VC Roll) has been developed in order to meet requirements for higher flat- ness control ability. The new VC Roll consists of a sleeve, bearings and a curved arbor. Side and quarter bearings are inclined to the arbor center axis. Roll crown is changeable by adjusting phase angle of the arbor. Experimental research works were carried out in model mill. Based on these data, the new VC Roll was designed and introduced in the 80" cold reversing mill of WAKAYAMA Steel Works. Main results are as follows. (1) The new VC Roll has twice or third times larger crown control capability than the conventional VC Roll. The new VC Roll is an effective actuator to compensate work roll deflection. (2) Horizontal tilting arrangement of bearings has a little influence on its performance. (3) A simple calculate ng model to predict bearing temperature has been developed in practical rolling. (4) Mill modulus with the new VC Roll is smaller by Z5% than that of the conventional VC Mill.

Keywords:sheet rolling, experimental analysis, production system, flatness control, crown control