Characteristics of Coefficient of Friction under High Pressure
-- Tribology in Sheet Metal Forming I ---

July 17, 1995

Akira AZUSIIIMA, Taisuke UCHIDA, Kiyoshi IMAI and Hifumi YAMAGISHI

The coefficient of friction between the tool and the, workpiece in sheet metal forming is dependent upon a number of tribological factors. However, since the dependence has not yet been fu]ly explained quantitatively, it is still unclear which friction model should be used in the numerical simulations. In this work, the coefficients of friction are measured for various mean pressures and viscosities of lubricant using a flat s]iding test machine. The coefficient of friction is constant under low mean pressure, whilst it decreases with increasing mean pressure under high mean pressure, for a workpiece with a rough surface. From these results and photographs of the surface of the workpiece after testing, a qualitative friction mode] is proposed .

Keywords:coefficient of friction tribology hydrostatic pressure sheet metal forming, friction model, surface property.

Generation of Various Curves and Slitting of Aluminium Thin Sheet along the Curves
- Flexible Sheet Metal Processing with Rolls and Piano Wires I -

January 8, 1996

Norio TAKAKURA, Nobuhiko SIIIRAKAWA, Shoji IMATANI and Katsuhiko YAMAGUCHI

A new method is proposed for curvilinear slitting or cutting of thin sheet materials, in which a rolling mill and piano wires are used, as a versatile cutting device and tool. Various curves can be generated at the roll entrance using a computer-controlled guide which moves the piano wire across a sheet. The relationship between the movement of the guide at the roll entrance and the generated curve at the roll exit is derived geometrically. The effects of wire diameter d and roll gap G on the quality and dimensional accuracy of slitted products are also examined experimentally. The experimental results show that the slitting of an aluminium sheet 0.1 mm thick can be carried out using a wire with diameter equal to or slightly larger than the thickness of the sheet and by setting the roll gap G to be slightly larger than the wire diameter d. The quality of the edge of the slitted sheet depends on the shape of wire used, but it should be emphasized that there is no burr at the slitted edge. It is also shown that not only curvilinear slitting of sheet materials, but also other value-added processes, such as tapered slitting and in-plane bending of a sheet with curvilinear hems, can be easily achieved using this new method.

Keywords:shearing, curvilinear, slitting, thin sheet material, new forming process, FMS, inteligent machine.

Pseudo -3-Dimensional Analysis of Shape and Crown in Flat Rolling by the Rigid-Plastic Model
- Generalized 2-Dimensional Theory for Pseudo-3-Dimensional Analysis of Flat Rolling I -

January 26, 1996

Hiromi MATSUMOTO and Shuichi HAMAUZU

The purpose of the present generalized 2-dimensional rolling theory is to explain the "3-dimensional" phenomena observed in flat rolling, from the viewpoint of the well-known Orowan's 2-dimensional rolling theory. It is assumed that the Orowan's rolling theory holds at each position in the width direction, if the local rolling conditions including the boundary stresses for the position concerned are taken into account, The present model is based on the rigid plastic model; namely, the longitudinal speeds at the entry and exit boundaries must be compatible with the motions of the "rigid bodies" outside the entry and the exit, respectively. The conventional assumption that the tension distribution at the exit is determined according to the fractional difference in length after rolling is not made. The condition on exit speed imposed by Orowan's theory is introduced into the equation system. The tension distribution at the entry need not be the same as that at the exit . The only equation that must be new]y developed is the equation of lateral material flow, which is re]ated to the in-plane shear stress and the friction. The equations for the deformation of the material being rolled are coupled with that for the rolls. Thickness distributions obtained using the present theory agree well with the experimental results

Keywords:rolling theory, flat rolling, crown, shape, three-dimensional, two-dimensional, computer analysis, roll deformation, rigid plastic model

Lateral Material Flow Model for Use in the Pseudo-3-Dimensional Analysis of Flat Rolling
- Generalized 2-Dimensional Theory for Pseudo 3-Dimensional Analysis of Flat Rolling II -

January 26, 1996

Hiromi MATSUMOTO and Kenji YAMADA

The purpose of the present generalized 2-dimensional rolling theory is to explain the "3-dimensional" phenomena observed in flat rolling, from the viewpoint of the well-known Orowan's "2-dimensional rolling theory". The only equation that must be newly developed is that which governs the lateral material flow. The equation of lateral displacement is derived from the equilibrium equation in the width direction. The latter is integrated over the contact length in order to reduce it to an ordinary differential equation. The driving force of lateral material flow is the lateral gradient of a weighted average of the rolling pressure. It is found that the influence of the driving force on the lateral ow is large at the backward-slip zone and is small near the neutral position. The weight should be chosen so that it represents such lateral mobility. The resisting force to lateral flow consists of the in-plane shear stress and the frictional stress. Under typical rolling conditions, the effect of frictional force is several times larger than that of shear stress. The width spread in the rigid roll case Is derived using the present equation.

Keywords:rolling theory, flat rolling crown, shape three-dimensional two-dimensional lateral flow widths read

Forward-Backward Extrusion with Axially Driven Container

February 22, 1996

Kozo OSAKADA, Xin WANG and Shinji HANAMI

To attain cold combined forward-backward can-can extrusion to arbitrary extrusion lengths, a method employing an axially driven container is proposed. In this method, the container is moved using an actuator in he axial direction while the billet material is extruded in two directions by the punch. The material flow in the direction of the container movement is promoted and the flow in the opposite direction is constrained due to he effect of the friction over the container surface. Thus, the material flow in the two directions can be controlled by changing the container speed. The effectiveness of the proposed method is examined by experiment using a model material (plasticine) and by FEM simulation for various combinations of coefficients of friction and relative extrusion ratios Rf/Rb. The effect of this method on controlling the material low is evaluated and the method for determining container speed is established on the basis of FEM simulation. The upper bound approach (UBA) is shown to be feasible for the analysis of the proposed process.

Keywords:extrusion, forward-backward extrusion, container movement, friction, flow control, FEM, upper

Finishing of Metal Mould for Free-Form Surface Using Elastic Polishing Tool

March 5, 1996

Isamu AOKI, Kiyoshi SUZUKI and Tetsutaro UEMATSU

In this paper, wc describe a new polishing method which is effective for various die-mould geometrics, especially sharp comers and the bottom surfaces of deep holes. In this method, an elastic tool made of polymer plastic resin with abrasive particles contained in it is used. The operating principle and procedure are as follows. When the cylindrical elastic tool Is pressed onto the mould surface, Poisson strain occurs and the abrasive particles embedded in the tool surface move radially and polish the mould surface. Many repetitious of the compressive action result in a smooth mould surface. It is also possible to use the tool as a conventional polishing tool as well as a grinding wheel. Experimental results showed that the proposed method can be used to finish moulds with complex shape.

Keywords:tool, surface finishing, die mould, free form surface, polishing tool , elastic tool, grinding tool, abrasives.

Examination of Working Limitation for Change of Sectional Shape on Dieless Shearing of Section
-Research on Shearing of Extruded Section by Low-Cost Die II -

March 18, 1996

Hidetaka KIDA, Norio TAKATSUJI, Mitsugu TOKIZAWA, Kazuo MUROTANI and Kenji MATSUKI

The relationship between the buckling_ Iimitation and the change of sectional shape "„°" of a section during dieless shearing using a low-cost die has been investigated. It was found that the buckling limitation was influenced by the thickness ratio i=t2/t1 and the rectangle size ratio a/b. Either with decreasing the rectangle size ratio alb (a/b<1. O) when the shearing length, b, is kept constant, or with increasing a/b (a/b> 1.0)when the rectangle height, a, is kept constant the minimum upper bound in order that the change of sectional shape does not occur, tends to increase. Three patterns of the change of sectional shape during dieless shearing were identified, each of which corresponded to a working load curve. In order to determine the buckling limitation under all conditions, the correspondence of the numerically simulated result to the experiment result was examined. The results from numerical simulation model adopted in this research showed a good agreement with the change of sectional shape during the pratical dieless shearing.

Keywords:shearing, Iow-cost die, extruded aluminum alloy section, dieless shearing, buckling, working limitation, change of sectional shape, numerical simulation.

Influence of Surface Defects on Bulge-Forming Limit of Aluminum Thin-Walled Tube

March 26, 1996

Tetsumanro HIROI and Hisashi NISIIIMURA

The influence of a single surface defect (scratched using a conical diamond stylus) on the hydraulic bulging limit of aluminum thin-walled tubes was studied experimentally and theoretically. A tube with a surface defect, scratched after annealing, does not break at the defect when the depth of the defect is less than 14010 of the initial thickness of the tube. A tube' with a surface defect, annealed after scratching, also does not break at a defect depth of less than 11.50/0 of the thickness. Results of numerical calculation indicate that work hardening at the defect area affects the critical-defect-depth qualitatively. However, parameters such as defect length, defect position, and normal anisotoropy are not determinig factors at the critical-defect-depth of 14% and 11.5%.

Keywords:tube forming, surface defect, bulge-forming limit, aluminum tube, critical-defect-depth

Development of Three-Dimensional Microcomponent Forming Press Machine
- Trial Die Forming of Three-Dimensional Microcomponent from Round Wire and Development of Exclusive Press Machine -

April 1 , 1996

Isamu AOKI, Toshinori TAKAHASHI, Haruya UENO and Toshiro HIGUCHI

We describe the die forming of three-dimensional microcomponents. At present, most micromachincs or devices are re o m fabricated by chemical etching of silicon. From a practical point of view, fabrication using metals as the raw materials should be discussed. In this work, the die forming of medical forceps, as an example of a typical medical microtool was attempted. The forceps currently used are fabricated by a combination of precision machining and hand finishing, so that a very long period of time is required resulting in a high price. The problems of die forming for fabricating the micro-components are investigated first through fabrication using a single die. After that, a micropress system exclusively fit for the fabrication of three-dimensional microcomponents is designed and developed. This system is based on the turret-type punch press, and flexible functions for material processing, such as rotation of material are added. An other feature is that the system uses a round wire as a raw material for the components. The results of practical forming experiments confirmed that the developed micropress can be used to fabricate microcomponents.

Keywords:metal forming, die forming, three-dimensional microcomponent, micromachine, press machine .

Application of an On-Line Pass Schedule Calculation Based on Roll Force Ratio Distribution

April 8, 1996

Masashi TSUGENO, Kunio SEKlGUCHI aud Yoshiharu ANBE

A newly developed on-line pass schedule calculation method is implemented using a process computer and applied to the operation of the finishing train of a hot strip mill. The calculation procedure uses the Newton-Raphson method and is based on the specified roll force ratio distribution between the stands. Advantages of using this method are confirmed. Before application of the new method to the plant, the reliability of convergence was checked and the optimal initial thickness schedules derived. When applied to the plant, the method showed no failure of convergence for rolling of over 5,000 coils. Also, the calculation method proved effective in reducing the software maintenance workload and in achieving stable finishing mill operation.

Keywords:hot strip rolling, pass schedule calculation, roll force ratio distribution, numerical procedure, strip crown, optimal load distribution

A New Method to Measure Solid Fraction of Mushy/Semi-Solid Meta]s and Alloys

April 8, 1996

Manabu KIUCHI and Sumio SUGIYAMA

A new method for measuring solid fractions in mushy (and/or mashy) or semisolid metals and alloys is proposed. First, the relationship between electric resistance (or electric potential difference) and temperature from the solidus-line to the liquidus-line are measured for binary. alloys and multicomponent alloys. Then, the solid fraction quantity in a given binary alloys in the range where solid and liquid phases coexist, is determined from its respective equilibrium phase diagram Finally, by combining the two results, a general relationship between normalized electric potential difference and solid fraction is obtained for all of the binary alloys tested. This value is used t,o determine t,he solid fractions of multicomponent, alloys from their measured normalized electric potential differences The determined values are verified using the rapid solidification method

Keywords: measurement, solid fraction, mushy metal, semi-solid metal, electric potential difference, binary alloy, mu]ticomponent alloy

Mashy-State Forging of Cast-Iron

April 8 , 1996

Manabu KIUCHI , Sumio SUGIYAMA and Masao ARAI

Mashy-state forging of cast iron billets was carried out, and tho effect.s of some process parameters, such as the temperature and aspect ratio of the billet, on the flow and deformation charactoristics of the liquid and solid components, internal structure and hardness of the forged products were investigated Tho following results were obtained (1)Mashy-state forging can result in internally sound and acceptable shaped cast, iron products. (2)When the solid fraction of a workpiece is low, the solid and liquid components flow separately. (3) In that case, the internal structure of the forged product differs from that obtained by. hot forging. (4)A new type of functional gradient, material can be manufactured using this process.

Keywords: mashy-state forging, new material, functional gradient, material, cast iron. flake graphite cast iron, eutectie graphite cast iron, spherical graphite cast iron.