Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY

(vol.42 no.491 December 2001)

Improvement of the Tooth Trace Accuracy of Spline
――Spline Rolling of Deep-Drawn Cups IV――

Ryoichi MATSUNAGA, Tatsuo OZAKI, Teruie TAKEMASU and Hiroshi MIYAHARA

(Received on August 4, 2000)

In our previous paper, it was shown that deep-drawn cups with splines are successfully formed by a rolling method of two-dies-plunge-feed type, but the tooth traces of the products are not accurate enough to use for clutch hubs in the automatic transmission of automobiles. In this paper, a proposal to divide the spline rolling process into two stages is made. The first stage is carried out using the optimized tools discussed in our previous paper. In the second stage, only the tooth bottoms of the spline are pressed by the outer tool whose tooth thickness is less than that in the first stage. It is proved that the spline tooth profile with the required tooth trace accuracy can be obtained by 3D FEM and this proposed experiment.
Key words : rotary forming, form rolling, forming property, accuracy of tooth trace, spline, two-dies-plunge-feed type, clutch hubs, automatic transmission

Consolidation of Surface Layer and Improvement of Surface Durability
of Sintered Fe Alloy Rollers by Finish Rolling

Teruie TAKEMASU, Tatsuo OZAKI, Hiroshi MIYAHARA, Shigeru HOYASHITA, Michiharu YOKOI and Hiroshi INADA

(Received on December 18, 2000)

If gear-shaped preforms of sintered Fe alloy can be finished by a cold forming process and enough load-carrying capacity can be secured, the production process of automotive transmission gears will be shortened and their total production costs greatly reduced. The purpose of this study is to examine the practical application of a finish rolling process using a screw-shaped tool to consolidate the surface layer of sintered Fe alloy gear teeth and improve the surface fatigue durability and the bending fatigue durability. In this study, preliminary rolling experiments using sintered Fe alloy rollers are carried out. A roller is installed on a work holder whose axis is set at a right angle to the rolling tool axis. The target consolidation level of the surface layer of the roller can be achieved by setting the amount of rolling stock to more than 250μm. A two-roller fatigue test proves that the surface fatigue durability is greatly improved by finish rolling.
Key words : form rolling, burnishing, surface finishing, sintered Fe alloy, rollers, gear, consolidation, void rate, surface fatigue durability

Limitation of Dieless Forming Technique and
Application to Triple-Layered Heat Exchangers
――Dieless Forming Technique for Double-Layered Heat Exchangers III――

Toshiyuki AMIMOTO, Satoru KIMOTO, Masaru KUNIKATA and Hiroya MURAKAMI

(Received on January 22, 2001)

A uniform moment bending method has been used in manufacturing a heat exchanger for packaged air conditioning units. This is because this method offers flexibility during the manufacturing process in terms of the bending radii and forming angles. It has already been adopted for double-layered heat exchangers, but to cope with the design changes on a number of layers or bending radii, limitations of the processing conditions had to be considered. Both sides of the portion of the workpiece to be bent have to be gripped to proceed with this method. The relationship between the grip length and the bending radius has been estimated through both experiments and calculations. As a result, for example, the minimum length of the gripper to form a 107.8mm radius is considered to be 125mm. As for triple-layered workpiece forming, a machine for practical use has been adopted in an actual manufacturing line. This can be accomplished using a four-axis controller as has been used previously for bending a double-layered workpiece. In this case, by controlling only the inner and outer layer positions, the middle layer position will be maintained by both controlled layers, which results in a simultaneous bending without workpiece damage.
Key words : bending，dieless bending, tube forming, experimental analysis, forming machine

In Situ Measurement of Interface between Tool and Workpiece under MPH Lubrication
by Means of Direct Fluorescence Observation Technique

Akira AZUSHIMA and Toshiyuki IDEUE

(Received on January 29, 2001)

In order to understand quantitatively and in detail the micro-plasto-hydrodynamic lubrication mechanism, the in situ measurement of 3D oil film thickness and topography at the interface between the tool and the workpiece in sheet drawing is carried out by means of the newly developed direct fluorescence observation technique. The new technique consists of a direct observation method and a conventional fluorescence method. The specimen sheets of aluminum are given uniformly distributed pyramidal indentations and drawn at a speed of 0.2mm/s. Reductions of approximately 10% with oil having a viscosity of 1611mm2/s at 20℃ are also carried out. The results obtained are as follows: (1) The sequential deformation of the pyramidal pocket trapped with lubricant can be measured by means of the direct fluorescence observation method. In the sheet drawing at a drawing speed of 0.2mm/s and a reduction of 10%, the volume reduction of the pyramidal pocket is 8% in the reductions ranged from 3 to 8%. (2) The oil film thickness distributions of the lubricant permeated from the pyramidal pocket into the contact area can be measured by means of the direct fluorescence observation method. The value of the lubricant volume estimated from the oil film thickness distribution is in good agreement with the value of the volume reduction of the pyramidal pocket.
Key words : micro-PHL, topography, in situ measurement, oil film thickness, florescence method

Analysis of Forming Process for Foam Products
Made from Waste Glass Powder

Kazunari SHINAGAWA, Takayoshi KANEKO, Mikio NAKASHIMA and Yasushi HIRASHIMA

(Received on March 7, 2001)

The methodology of forming by the firing process for glass foam products, with a goal to recycle waste glass powder, is investigated. Firing of the glass powder compacts for large planters, as an example of the products, is performed and the factors responsible for the change in shape of the compacts during firing are clarified by experimental and numerical methods. To formulate foaming and expansion behavior during firing, gas generation due to a foaming agent is examined by thermal analysis, and deformation of the compacts is described by a constitutive equation for sintering and a rate equation of the chemical reaction. Based on the formulation, the firing process for the planters is analyzed by a three-dimensional coupled finite-element method of viscoplastic deformation and heat transfer. It is found that nonuniform deformation of the compacts due to gas generation and gravity is significantly affected by the temperature distribution in the furnace as well as the distortion of the compacts in the drying process performed before firing.
Key words : powder forming, sintering, numerical analysis, FEM, glass

Effect of Blank Shape and Hydraulic Counterpressure on
Deep Drawing Limit of Rectangular Shells

Kazuhiko NAKAMURA and Haruhiko SUGATA

(Received on March 9, 2001)

In the deep drawing of rectangular shells with various side length ratios lP1/lP2, the effects of rectangular blank shape and hydraulic counterpressure on the height limit of deep drawing are examined. In the deep drawing of rectangular shells by both conventional drawing and hydraulic counterpressure drawing, when a rectangular blank with an increased length L1 parallel to the minor side of the shell is used, the height limit of deep drawing increases. That is because the increased L1 decreases the difference between the material flow speeds at the straight side flange and the corner, and mitigates the inflow hindrance at the corner flange by increasing the inflow at the straight side flange. The smaller the lP1/lP2 of the shell shape is, the larger the forming limit hmax/lP1 of the rectangular shell is. When an appropriate blank shape with the increased L1 is used, hydraulic counterpressure deep drawing yields a height limit 1.2〜1.8 times greater than conventional deep drawing. In deep drawing using a rectangular blank with an appropriate length of L1, hmax/lP1＝1.80 is obtained by conventional drawing, and hmax/lP1＝2.20 by hydraulic counterpressure drawing.
Key words : sheet metal forming, deep drawing, rectanglar shell, blank shape, hydraulic counterpressure, forming limit, material flow

A Scheme for Volume Loss Recovery and Incremental Volume Control in Non-Steady State Metal Forming Analyses by
Rigid-Plastic Finite Element Method

Shiro TOYOSHIMA, Jian SHANG and Manabu GOTOH

(Received on March 9, 2001)

One of the major advantages of rigid-plastic FEM is that it can use a relatively large increment and thus the computation efficiency is high. But, when a large time increment is used, a large volume change is induced and thus the volume constancy is disturbed. This causes a serious problem in the prediction of the proper filling of metal in a die cavity and produces some defects in the process design, though it is the main purpose of the numerical simulation. Therefore it is strongly desired to suppress such volume changes to be the allowable limit. In this paper, we propose a simple computational scheme recovering the volume change. It includes both the volume change accumulated over all the incremental calculation steps and that caused during a single step. Simple cylindrical billets in upsetting and extrusion are considered. From these it is confirmed that the volume change is significantly reduced and the accuracy of the calculated processing load is also improved. It should be noted that the proposed scheme is quite simple and can be easily implemented into any existing code.
Key words : numerical simulation, rigid-plastic FEM, volume loss recovery, upsetting, extrusion

Theoretical Analysis of Roll Profile by a Two-Roll Straightening Technique
――Greater Straightening and Lower Residual Stress Technology of Bar Products II――

Yousuke NISHIKORI, Motoo ASAKAWA, Tokukatsu SUZUKI, Taku YANAGIHASHI and Takayuki HAMA

(Received on March 13, 2001)

Two-roll straightening of bar products has become popular because greater straightness and lower residual stress are obtainable, and the polishing effect occurs, which are frequently demanded by customers in the automobile, precision machine and office automation industries. However, the technology is not yet advanced, and the method still relies on the experience and perception of artisans. The goal of this study is to develop a method to obtaining an optimal roll profile, considering the deformation features of the bars based on elastoplastic theory. A simulation program has been developed, which evaluates roll profiles with respect to straightening effects and the effect of residual stress reduction. Through a series of simulations, it is found that traditional rolls have essential faults. Moreover, the residual stress is calculated using the simulation program, and it is shown that residual stress is seriously influenced by the roll profile. In addition, some roll profiles are analyzed and evaluated, and the optimal roll profile is proposed.
Key words : simulation, bending, straightening, drawing, roll, elastoplastic theory

Optimization of Bending Condition for Dieless U-Bending Process ――Development of Dieless Bending Process for Precision-Bent Tube II――

Takashi KUBOKI and Munekatsu FURUGEN

(Received on March 23, 2001)

The present paper follows a previous paper by the same authors, in which the dieless bending process was proposed. In this process, compared to the conventional draw-bending process, the bending die is not necessary and high productivity can be realized. Although in the previous study the bending radius was well simulated by theoretical analysis under various bending conditions, a constant bending radius within the whole bending region had still not been realized. In the present study, the effects of bending condition control during bending on the bending radius distribution were clarified by numerical analyses and experiments. Moreover, the optimum conditions for realizing a constant bending radius distribution were calculated by inverse analysis. Finally, the calculated results were verified by experiments for various bending radii in the range of 300‐1700mm. As a result, the dieless bending process was successfully applied to the production of stainless steel tubes and nickel-based alloy tubes installed in nuclear and thermal power plants.
Key words : bending, numerical analysis, curvature, dieless bending, U-bent tube, optimization, effect of conditions