Presentation of 3D Deformation Model for Free Helical Rolling with Zero Angle of Inclination of Roll Axis

(Received on May 13, 1995)

Masayuki YOUKAI and Kichitaro SHINOZAKI

To simulate the metal f low in a billet for helical rolling, a three- dimensional deformation model is proposed which is comprised of pyramidal velocity regions of a rigid perfectly plastic material. The roll pressure acting on the roll contact surface of the billet in the rolling process is estimated on the basis of the energy method using the proposed deformation model. Widths of the contact surface of the roll on the billet are also calculated . The flow stress of a lead billet during rolling is estimated from the values of roll pressure, roll contact area, and flow stress of lead obtained by a compression test and the measured value of roll separating force. Calculated and estimated values of the forces are proven to be in good agreement with the results of previous experiments on lead. The proposed deformation model was found to be reasonable and is expected to be applicable to forging problems.

Keywords:Helical rolling, deformation model, roll pressure, energy method, pre-form, presision forging



Prediction of Forming Limit in Axisymmetric Deep Drawing of Steel/ Aluminium Alloy Laminated Sheets Using a Simple Criterion for Ductile Fracture

(Received on June 19, 1995)

Hirohiko TAKUDA, Ken-ichiro MORI, Tomoyuki HIROSE and Natsuo HATTA

Deep drawing processes of laminated sheets composed of mild steel and various aluminium alloy sheets are simulated by the rigid-plastic finite-element method. From the stress and strain histories of elements in each layer calculated by the finite-element simulation, the fracture initiation site and the forming limit are predicted using the ductile fracture criterion. The predictions so obtained are compared with experimental observations. The results show that the ductile fracture criterion is useful to predict fracture initiation in forming of laminated composite sheets. Furthermore it is found that the drawability is improved by setting the mild steel sheet on the punch side for the case of aluminium alloy sheet with comparatively high ductility, and by sandwiching the aluminium alloy sheet with the mild steel sheets for the case of low ductility.

Keywords:sheet metal forming, forming limit, ductile fracture criterion, deep drawing, FEM, laminated composite sheet, aluminum alloy sheet.



Experimental Study of Square Tube Bending by MOS Bending Method

(Received on June 22, 1995)

Makoto MURATA

The bending of square tubes is experimentally examined using the CNC bending machine which is based on the penetration method (called the MOS bending method). The bending radius is controlled by the relative distance between the die and the tube using the MOS the bending method. The relationship between the relative distance and the bending radius is clarified. The distortion of the tube cross section, occurrence of wrinkles, bending forces and bending limit are clarified under various bending conditions. It is possible in the bending of square tubes to prevent the occurrence of wrinkles, to suppress the bending forces and to extend the bending limit by controlling the inclining angle of the die. Using inclining angle 25‹, the bending limit becomes maximum and R/H o (R:bending vadius, H o : length of square side) becomes about 8. The characteristics are clearly explained, using the MOS bending method./FONT>

Keywords:tube forming, MOS bending, square tube, CNN bending maichine, wrinkle, bending force,@bending limit, inclining angle of die, experimental analysis.



Influence of Dispersion of Workpiece Thickness on Change of Bent Part Angle
Study on Three-Point Air Bending I

(Received on July 3, 1995)

Hideo OGAWA and Akitake MAKINOUCHI

In the air bending method, if workpieces have thickness dispersion, the bend part angle change due to the difference in thickness. The three-point air bending method is one means of preventing this phenomenon. The prevention of change in bent part angle in the three-point air bending method is investigated in the present work. The investigation is carried out by means of experiments and the elastoplastic finite element method using the simulation program ITAS-2D. 'Me bent part angle becomes smaller with increasing workpiece thickness in both the conventional and the three-point air bending methods. However, the change of bent part angle in the three-point air bending method is about one-half of that in conventional method. The appropriate bending die dimensions for three-point air bending are also investigated. The change of bent part angle decreases as die opening increases, as die comer radius increases and as punch radius decreases.

Keywords:bending, die bending, air bending, three point air bending, accuracy, bend angle, elastoplastic FEM



Spline Rolling of Deep Drawn Cups

(Received on July 10, 1995)

Ryoichi MATSUNAGA, Tatsuo OZAKI, Teruie TAKEMASU, Ryuzo KAMASHITA and Hidehiko TSUKAMOTO

At present deep drawn cups with splines are used for automatic transmissions in order to reduce the weight of cars. In this paper, a new spline rolling method is proposed to replace the Grob method which is currently employed to form splines. This method is of the two-dies-plunge-feed type and is simple, economical and compact compared with the Grob method. It is experimentally confirmed that a spline is successfully formed by this method.

Keywords:rotary forming, form rolling, sheet metal forming, stretch forming, new forming process, spline, automatic transmission



Analysis of 3-Dimensional Deformation of Cold Rolled Strips Considered Frictional Anisotropy and Elastic Deformation of Strip at Exit
Development of Technology for Reducing Edge-Drop of Cold Rolled Strips by Pair-Cross Mill 11

(Received on August 28, 1995)

Tetsuo KAJIHARA, Shoichi HASHIMOTO, Kanji HAYASHI, Masahiro MATSUURA, Ryuji HAMADA and Atsushi TOMIZAWA

A new numerical calculation model of 3-dimensional deformation of a cold-rolled strip by the slab method is presented. In this model, effects of elastic deformation of the strip at the exit and frictional anisotropy between the roll and strip have been integrated into the previous model. The results calculated using the present model agreed with those obtained by elasto-plastic FEM and with experimental data obtained using a model cross mill. Furthermore, it was found that the elastic deformation of a strip at the exit has an important effect on strip flatness, but not on thickness profile, and edge-drop of the strip becomes short when the frictional anisotropy becomes large. It is thus concluded that the present model is very useful for 3-dimensional deformation analysis of a strip not only in cross rolling but also in general parallel rolling.

Keywords:cold strip rolling, cross rolling, 3-dimensional analysis, frictional anisotropy, elastic deformation of strip, edge-drop, flatness.



Pipe Bending Method Using Floating Expanding Plug

(Received on August 31, 1995)

Masao NAKAMURA, Seijiro MAKI, Yasunori HARADA, Kiyotaka HAYASHI and Masanori NAKAJIMA

A new pipe bending method employing a floating expanding plug is developed. Characteristics of this bending method are investigated by comparison with those of other methods using an expanding plug. The following characteristics of the new method are observed : (1) Both expanding pipe and plug movement effectively function to enable the bending of a pipe with good shape and small bending radius. (2) Bending moment, wall thickness difference, flattening and spring-back become small with an increase of the expansion ratio. (3) Three-dimensional bending of a pipe is feasible by control of the direction and magnitude of bending moment.

Keywords:tube forming, bending, expanding, new forming process, forming property



Extrusion Characteristics of Zirconia and Stainless Steel Powder-Binder Compounds

(Received on October 27, 1995)

Zhongchun CHEN, Jian-Xin XIE, Keiou NISHIMURA, Tadasu MURAKAMI and Keisuke IKEDA

The extrusion characteristics of ZrO2 powders and stainless steel powders (SUS304L) containing binder are investigated using a rod extrusion method. The mean particle sizes of the powders are 0.7 and 32ƒÊm (ZrO2), and 5 and 36ƒÊm (SUS304L). The binder used in this experiment is water-soluble hydroxypropyl methylcellulose (HPMC). It Is shown that there is a peak in the extrusion load vs. stroke curve for ZrO2 powders, and the smaller the particle size or the lower the binder content, the higher the peak load is. On the other hand, there is no peak or a much smaller peak for stainless steel powders. It is necessary to have a higher HPMC content in the binder for stainless steel powders, because they are easy to dewater. The extrusion load vs. stroke curves are characterized by serration, and the extent of serration is greater when powder compounds with smaller particle size or lower binder content are used. The length of the die land is an important factor in forming sound extrudates. When it is less than IOmm, the extrusion load is almost the same for samples with the same composition, but the appearance of the extrudates is quite different. With regard to a powder compound, there is a minimum length of die land for each extrusion ratio. It is necessary to extrude with a larger extrusion ratio or a longer die land if less binder is added.

Keywords:extrusion, forming, ZrO2, stainless steel, powder, binder.