Study on Bending Work of Corrugated Fiberboard Sheet

(Received on April 4, 1994)

Hiroshi ISHIBUCIii, Shigeru NAGASAWA, Akinori YOSHIZAWA and Yutaka YOSHITANI

The reacting force required for the bending process of corrugated fiberboard sheet was measured continuously.There is a groove which is useful for specifying bending posifion of the sheet. The deformation and the stress of the sheet in the bending process was calculated using the three-dimensional finite element method serving for elasto-plastic large deformation. The influence of fiber orientation and groove depth on the reacting force, and the influence of material properfies and working condi6ons on the bending stress were exan-dned. In the beginning of bending process the reacting force is rapidly increased. But meanwhile it reaches maximum and then it decreases. We say the angle denofing maximum force peak angle. Both the maximum reacfing force and peak angle increase with increasing of fiber orientation angle and with decreasing of groove depth. With increasing of Young's modulus of intermediate core of the sheet, the stress concentrafion remaining after spring back is relaxed and the stress occurring at the end portion of surface liner in the bending process decreases.

Keywords: bending, folding, numerical analysis, finite element method, elasto-plastic FEM, paper, residual　stress, corrugated fiberboard sheet.



Prediction of Tension Breaking Properties for Corrugated Fiberboard Stencil

(Received on April 4, 1994)

Hiroshi ISHLBUCHI, Shigeru NAGASAWA, Akinori YOSHIZAWA and Yutaka YOSHITANI

A criterion is proposed predicting tensile breaking load and breaking angle of corrugated fiberboard stencil. The stencil shows orthotropic anisotropy, along whose principal axes it has orthotropic breaking strengths X, Y and shear breaking strength S where X is the strength along longitudinal direction of the stencil. These strengths influence tensile breaking stress and breaking angle depending upon tensile direction. This dependency is simulated and following results are obtained. (I)With increasing the ratio XIY, the cracking with the breaking mode along longitudinal direction tends to increase compared with the case XIY=I, and breaking stress increases where the angle between loading direction and fiber orientafion angle is smaller than ,rl4. (2)With decreasing S, the longitudinal cracking mode also increases, and breaking stress in all direcfions decreases.

Keywords: material tesfing, tension test, material, paper, breaking property, corrugated fiberboard stencil,　finer, medium.



Evaluation of Roller Leveling Effect on Thin Rolled Sheet by Shape Measuring Instrument
A Study of Shape Improvement Ability of a Roller Leveler 2

(Received on June 24, 1994)

Fumio HIBINO

Lack of flatness in sheet accompanies differences in elongation in width caused by rolling.The shape is evaluated by examining the distirbution of diff.in elongation derived from　longitudinal lengths measured along buckles on the surface.To examine various rolled sheets, the shape meter which is designed on this principle and reported on the previous paper has been applied-The results reveals the effect of rolling conditions in rolling mill on rolled sheet shape,the difference in roller leveling effect on each sheet shape,the effect of level- ing on internal strains,etc.:that is (1) the disrtibution of diff.in elongation is affected by changes of roll diameter, (2) center buckle in sheet is improved by leveling, (3) wavyedges grow worse in stead of being improved,(4) the cause of herringbone shape is different from others,(5) the effect of deflection of leveling roll by backup rolls is ambiguious,(6) in- ternal strains decreas after leveling although the shape is not improved,(7) the effect of temperature changes on shape is little for leveled sheet.These facts have been deduced anew through use of the shape meter developed for various rolled sheets.For getting the flatness of a sheet,the understanding and combination of characteristics of both rolling and leveling are important.

Keywords:measurement, profile measurement, rolling, strip rolling, finishing, shape correction, leveling, roller leveler, internal strain.



Powder Forming of Box Type Parts with Inner Ribs by Die CIP Method
Near Net Shape Powder Forming of Large Size Ceramic Parts with Complex Shapes I

(Received on June 29, 1994)

Susuiiiu MIZUNUMA, Toshimasa TOMOKIYO, Matsuo ATAKA, and Kazuo WATANABE

In order to eliminate the difficulties which occur when conventional die pressing and CIP (Cold Isostatic Pressing) are applied to forming large and complexy shaped parts, a new die CIP method is proposed, in which a vacuum- sealed die set is pressurized in a CIP machine. The potential of the method and the most suitable forming condition are investigated experimentally. Initially, copper powders are compacted using a die set for a columnar part. The die CIP is successfully performed and the relationship between pressure and density in the die CIP is found to be identical with that in die pressing, confirming the principle of the die CIP method. Next, sialon agglomerates are compacted by both die pressing and die CIP using a die set for a box type part with inner ribs, representative of complexy shaped parts, in order to find the optimum forming condition. Cracking during compaction can be prevented by increasing the powder flow into lower density portions near the bottom of the compact. Uniform density distribution in the compact can be attained by increasing the reduction in thickness at the bottom of the compact with increasing the total height reduction of the compact. When the density distribution in the compact is uniform, cracking is not occurred in sintering.

Keywords:die CIP, CIP, die pressing, powder fon-ning, ceramic parts, sialon



Influence of Addition of Liquid Paraffin on Powder Compaction and Sintering Characteristics of Complex Shape Ceramic Parts
-Near Net Shape Powder Forming of Large Size Ceramic Parts with Complex Shapes II -

(Received on June 29, 1994)

Toshimasa TOMOKIYO, Susumu MIZUNUMA, Matsuo ATAKA and Kazuo WATANABE

As a new process for near net shape powder forming technology of large size and complex shape parts, a metal- die CIP method has been presented in the previous paper. In this method, reduction in compacting pressure and improvement of density distribution of green compact are required as in the usual die compaction process. The addition of liquid paraffin to powders is known to be useful for the improvement of towability of them. So, before applying this technology to the metal-die CIP method, the influence of addition of liquid paraffin to ceramic granules on the compacting and sintering characteristics of complex shape parts are investigated in the usual die compaction. It is found that the addition of liquid paraffin to the granules remarkably reduces the compacting pressure; the compacting pressure can be reduced to one-third by adding 10 wt.% paraffin. The density distribution of the green compact is also improved significantly with the addition of the paraffin. The addition of paraffin leads to the increase in debinding time, but if the thickness of compact is less than 15 mm, the usual debinding condition can be applied without problems.

Keywords: powder fanning, metal-die CIP, die compaction, ceramic parts, binder, paraffin



Estimation of Friction Coefficient and Improvement of Rolling Force Prediction based on Forward Slip during Hot Strip Rolling
Advanced Technology for Schedule Free Rolling I

(Received on July 14, 1994)

Takeshi ODA, Syuichi HAMAUZU and Toshio KIKUMA

An irrprovement of the accuracy of head-end strip thicknesses in hot rolling is required strongly at present. Answering these requests , the improvement of the prediction accuracy of rolling forces on the finishing mill plays an important role. The basic idea is based on the estimation of the friction coefficient and the deformation resistance independently by means of measuring the forward slip during rolling. The results obtained were 1) the friction conditions in the roll bite can be known and predictable by measuring the forward slip and 2) as friction coefficient varies under the mixed-grades rolling such as mild steel and silicon steel , it is very important to take acount of the behavior of the .friction coefficient for the calculation of the deformtion resistance.

Keywords:strip rolling , control system , rolling mill , friction coefficient , forwarKI slip



Magnetic Field Powder Forming Analysis by Granular Modeling

(Received on September 7, 1994)

Shigeyuki TAMURA, Tatsuhiko AIZAWA and junji KIHARA

Magnetic field powder forming is a promising method for producing high-quality ferromagnetic materials. In this process, magnetic powder is net-shaped under a high magnetic flux density by the powder injection molding process. Since various parameters are related to this process in a complicated manner, it is difficult to determine the optimum forming conditions. Tlie granular model is a very effective tool for investigating the optimum forming clesign and the mecliaiiism of inagnetic powder flow under an applied magnetic field and pressing. A nenv coupling method was developed to simulate the powder flow subjected to pressing load and magnetic field witli consideration of magnetization in powder and its change. In the numerical example, the dependence of magnetic powder flow on the pressing schedule is discussed and compared with experimental results. The preferred orientation of magnetization of the magnetic powder is taken into account in the particle model.

Keywords:powder forming, magnetic field forming, ferromagnetic material, numerical analysis



Infiltrating and Joining Processes under Semi-Molten State for Making Metal-Ceramic Composite

(Received on September 9, 1994)

Tohru SHIROTA, Tasuku DENDO and Manabu KIUCHI

Pressure infiltration of molten metal into porous ceramic compact under semi-molten state was carried out to form a metal-ceramic-composite-layer near the surface of the compacts. Besides, joining of the ceramic compact with the solid component in semi -molten metal was performed. The infiltrating metals employed were Pb-Sn alloys which have wide region of semi-molten state, and the porous ceramic compacts were made of loosely -sintered alumina. Some experiments proved that a composite layer structure can be formed in the surface portion of the compact, and some joining pieces of metal and ceramic can be obtained. Infiltrating behavior, morphology of the composite layer and bonding quality were examined in relation to the processing conditions.

Keywords:mashy state processing, composite material, pressure infiltration, joining.



Characteristics of Web ExPansion and Rolling Load in Hot Rolling Model Experiments
-Development of Flexible H-Beam Rolling by Skew Roll Mill 2

(Received on September 12, 1994)

Kazushige IKUTA, Koushirou AOYAGI, Kenji BEKKI, Akira INAGAKI, Taneharu NISIIINO nd Takao KAWANAMI

Plasticine-model experiments have revealed that the new section rolling mill "Skew Roll Mill(SKM)" can efficiently expand the web outer width by simultaneously supplying the direct web-expanding force and the thickness reduction force using four cantilever-type rolls inclined against the rolling direction. The feasibility of SKM has been experimentally investigated by the use of a hot rolling model in this study. The experiments reveal that efficient web expansion without quality and operational problems is attained in the hot rolling. The main results of the experiments are as follows : (1) The web expansion can be controlled through the geometric relationship between the H-beam dimensions and the positions of the rolls . The web expansion capability is about five times greater than by the conventional method. (2) The thickness reduction 　force and the rolling　torque are much less than in the conventional rolling method. (3) The back and front tensions have little influence upon the rolling forces and the H-beam dimensions if each tension is the same level as in the conventional H-beam rolling.

Keywords:section rolling,universal rolling,hot rolling model,H-beam,web outer width,web expansion, rolling　load,back and front tensions, four cantilever-type rolls



Influence of Microstructure on Bendability of Ultrahigh-Strength Steel Sheet
-Formability of Ultrahigh-Strength Steel Sheet

(Received on September 22, 1994)

Kazumasa YAMAZAKI, Yaichirou MIZUYAMA, Masaru OKA and Yoshikuni TOKUNAGA

Bendability of an ultrahigh-strength steel sheet is investigated through V- type bending to clarify the influence of microstructure on formability. Homogeneity in the microstructure is quantified by the standard deviation of hardness, which is introduced as a homogeneity index. Bendability is closely related to the homogeneity index. Bendability is found to have no correlation with total elongation, but to be closely related to local elongation. Homogenizing the microstructure increases the local elongation, and improves the bendability. Bendability is affected more by homogeneity in a microscopic area which includes several thousands of grains than by the difference in phase of each grain in a microarea which containing only a few grains.

Keywords: Bending, Ferrous metal, Maten'al property, High-strength steel sheet



Measurement of Dimensional Change in Repeated Backward Cold Extrusion

(Received on October 5, 1994)

Tooru KAWABE, Takeshi KATO and Tomoyuki WADA

In previous reports, numerical analysis for backward cold extrusion has been performed under various process conditions, paying attention to the temperature rise of die and punch. In this study, dimensional accuracy of forged products during repeated backward cold extrusion is investigated experimentally under several typical conditions (pre-heating, forced cooling and high-speed working), with reference to previous analytical reports. Under simplified conditions such as pre-heating and forced cooling, good agreement between experimental results and previous analysis is observed in spite of some difference in the working conditions. However, in the case of high-speed working, the inner diameter of products becomes larger than the standard one, and bottom thickness is the same as that obtained under standard condition. This result differs somewhat from the numerical result obtained previously. Therefore, it is not easy to predict these behaviors only from numerical analysis or experimental result obtained on a laboratory scale without consideration of engineering-scale production data. Furthermore, in the case of complicated heat-transfer mechanism, each processing condition is found to largely affect the experimental result.

Keywords:cold forging, thermal influence, final shape, product accuracy, factory working.



Prediction of Forming Limit in Deep Drawing Using Finite Element Simulation and Ductile Fracture Criterion

(Received on October 21, 1994)

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

To predict forming limits in sheet metal forming, the criterion for ductile fracture is included in the finite-element simulation. From the histories of stress and strain in each element calculated by the finite- element simulation, the critical stroke and the fracture initiation site are predicted by means of the fractUTe criterion. Material constants in the criterion are determined from uniaxial and plane-strain tension tests of the sheets. Calculations are carried out for axisyrmnetric deep drawing of aluminium alloy and mild steel sheets. The predicted limiting drawing ratios are in good agreement ' with the experimental ones, even for alminium alloy sheets with low ductility. It is shown that the fracture initiation site is dependent on the degree of ductility, i.e., the punch corner for mild steel and aluminium alloy sheets with high ductility and the sidewall for aluminium alloy sheets with low ductility.

Keywords:sheet metal forming, forming limit, ductile fracture criterion, deep drawing, FEM, aluminium alloy sheet.



Numerical Simulation of Form Rolling Process of Polygonal Tube
-Forming of Polygonal Tube by Form Rolling IV -

(Received on November 8, 1994)

Masahide KOHzu, Kenji ASAKURA and Hiroyuki ICIIINOSE

The form rolling process to form a polygonal tube from a round tube is analyzed numeri- cally by an improved elastoplastic matrix method. Neglecting volume change due to elastic deformation and replacing normal force induced by contact with tools by shearing force on the boundary of major elements, this method leads to a very simple solution and drastically reduced calculation time. In this analysis, the model of a ring consisting of only the formed portion is used and plane strain is assumed. The ring is compressed by four rollers around it, and is then rotated by uniform circumferential force. The forming process of a triangular tube obtained under the widest range of forming conditions can be well simulated, and the decrease of deformation work during this process is supported theoretically. For the forming condition necessary to obtain a pentagonal or heptagonal tube, analysis using the ring model is difficult and the simulation is incomplete. Nevertheless, the tendency of the tube to approach these shapes can be observed.

Keywords:form rolling, numerical analysis, polygonal tube, elastoplastic matrix method, forming process, ring model



Experimental Investigation on Metal Flow Control in Hot Extrusion of Al-Alloy

(Received on November 28, 1994)

Kenji NAKANISHI, Hiroyuki KINOSHITA, Shunpei KAMITANI and Katuhisa HIRAYAMA

Dimensions, shape and grain structure of the extruded products from hot extrusion of aluminium alloy are closely related to metal flow characteristics in the process. Some investigations on the above subjects were carried out and the results were applied to die design and selection of extrusion conditions. The present experimental and analytical study proposes two types of metal flow control techniques. One involves the use of pins or beads attached to the container wall or die surface by which the configuration of a dead metal zone is changed and metal flow is controlled as a result. The other involves temperature control on the die surface by which metal flow characteristics are changed. Temperature control can be done by using a die in which one part of its surface is formed by PSZ ceramics having low thermal conductivity and other part is formed by SKD steel die material. Fundamental experiments and detailed analyses of the above techniques were carried out by plane-strain hot extrusion of 6063 aluminium alloy and useful results for engineering application were obtained.

Keywords: extrusion, aluminium alloy, metal flow control, die design, ceramic die.



Fabrication of Two-Layer Pipes Composed of ZrO, and Stainless Steel by Powder Multi-Billet Extrusion Method

(Received on December 9, 1994)

Zhongchun CHEN, jian-Xin XIE, Tadasu MURAKAMI and Keisuke IKEDA

A new forming method for ceramic/metal two-layer pipes by mulfli-billet extrusion is proposed. Three kinds of ZrO2 powders with different mean particle sizes (0.7, 2 and 32pm) and stainless steel powder (mean particle size 36 Wn) are chosen and water-soluble hydroxypropyl methylcellulose (HPMC) is used as binder. The forming possibility and soundness of ZrO2(inner)/SUS304L(outer) two-layer pipes as well as the factors controlling formability are mainly investigated. The results show that ZrO2/SUS304L two-laver pipes can be formed by multi-billet extrusion method. The change of forming load in the extrusion process of two-layer pipes is roughly divided into four stages. Load vs. stroke curves are characterized by serration. When binder composition is 15wt%HPMC-85wt%H20, the maximum extrudable contents of ZrO2 in the inner layer are 76%, 80% and 78% for powders with mean particle sizes 0.7, 2 and 32 Wn, respectively, while the formable range of SUS304L outer layer is 82-83.5%. The formability of pipes is also dependent on the binder content and HPMC/H20 ratio in the binder. It is necessary to possess adequate viscosity and fluidity in powder and binder mixtures. When extrusion speed is less than I mm/min, sound two-layer pipes can not be obtained, because powder compounds are easy to dewater.

Keywords:extrusion, multi-billet, ceramic/metal two-layer pipe, ZrO2, stainless steel, powder, binder.



Effect of Prestrain on Stress Aging in Mild Steel
Removal of the Bauschinger Effect by Stress Aging-

(Received on December 12, 1994)

Takenobu TAKEDA, Shin-ichi KIKUCHI and Masahiro HOSHI

Tubular specimens of mild steel are subjected to various amounts of torsional prestrain and then aged under stress states along the Bauschinger curve at 1500C for lhr. The shear stress imposed on the specimen during aging, called here the aging stress, is employed up to a maximum level of 90 percent of the prestress. Reloading tests in forward and reverse torsion are carried out at room temperature, and the critical aging stress at which the yield stresses in the two reloading directions become equal is examined as a function of the amount of prestrain. With increasing aging stress, the yield stress in forward torsion decreases while that in reverse torsion increases. At high aging stress, sharp yielding reappears on the reverse flow curve. The results show that the critical aging stress normalized by the prestress remains essentially constant independent of the amount of prestrain. Under such critical stress aging conditions, the aging index, i.e., the ratio of yield stress to prestress, decreases with increasing prestrain and approaches a saturation value of 0.85.

Keywords: material testing, torsion test, ferrous metal (Fe-C), deformation-load property, torsional　prestrain, stress aging, Bauschinger effect, yield stress.



Optimization of the Variable BHF Deep-Drawing Process by Fuzzy Model

(Received on December 12, 1994)

Ken-ichi MANABE, Syoichiro YOSHIHARA, Ming YANG and Hisashi NISHIMURA

A fuzzy control system is developed to optimize the circular cup deep-drawing process for an aluminum alloy sheet. An optimum closed-loop control based on a fuzzy model is applied to the variable blank holder force (BHF) control technique in order to obtain a drawn cup with uniform wall thickness and to improve the forming flexibility. Ideal punch stroke vs. blank reduction ratio curve and a wall thickness constancy are adopted as evaluation functions for the optimum control and the weighting factors are obtained using the fuzzy model. A multi-function computerized deep-drawing apparatus capable of in-process control of BHF was used for the fuzzy-controlled variable BHF process. Several experiments with different blank sizes and lubricants were carried out to optimize and evaluate the fuzzy model. The fuzzy model is evaluated and corrected off-line by measuring the drawn cup thickness distribution. It is confirmed that the fuzzy model is valid for the optimum process control and the fuzzy BHF control technique with the evaluation and Teaming of the model has great potential for improving dimensional accuracy, reliability and flexibility for various materials, blank sizes and lubricants.

Keywords:sheet fon-ning, deep drawing, optimum process control, fuzzy model, variable BHF control, on-line control　system, active control, fanning flexibility.



Deformation and Forming Limit of Clad Tubes in Conical Nosing and Flaring

(Received on January 25, 1995)

Shigeki MORI, Ken-ichi MANABE and Hisashi NISHIMURA

The forming property of metallurgically bonded two-layer clad tubes in conical nosing and flaring is investigated experimentally and numerically. An experiment was carried out to examine the forming limit of clad tubes consisting of titanium, nickel and copper. In order to clarify the influence of the configuration of constituent clad tubes on deformation behavior, the bending component in the meridional strain at the forming zone is analyzed by the finite-element method. In nosing, the thickness ratio of the clad metals affects the mode of wrinkles observed at the nosing zone. From numerical results of nosing and flaring, it is found that the configuration of clad tubes affects the meridional strain, thickness strain and bending strain.

Keywords:tube forming, clad material, nosing, f lari ng. forming limit, forming property material property, experimental analysis, finite element method



Estimation of Impact Stress by Piezofilm Stress Gauge

(Received on April 22, 1994)

Hiroki SEKIGUCHI, Shigeki MINEGISHI, Yasuhisa SATO, Toshiyuki ATOH, Kiyoto FUKUOKA and Yasuhiko SYONO

I mpact stresses up to I 0 G Pa in uniaxial strain state are comparatively easily estimated by a piezofilm stress gauge package with using a charge mode technique. H owever, it is difficult to estimate impact stresses above 10 GPa in conductive materials as metals and also to estimate impact stresses in materials where tensile strain in the lateral direction is imposed on the gauge.

Keywords:PVF2 or PVDF, high-energy-rate forming, stress measurement, experimental　analysis, high strain-rate, piezofilm stress gauge.



Wave Pattern at Wall of Cup Drawn by Hydraulic Counterpressure Deep Drawing and Its Control Method

(Received on December 9, 1994)

Masami NAKAMURA and Kazuhiko NAKAMURA

If the pulsation phenomenon of fluid pressure occurs during hydraulic counterpressure deep drawing, a wave pattern appears at the wall surface of the drawn cup and deteriorates its surface quality. This pulsation phenomenon occurs due to intermittent outflow of liqu ' id from the flange. Consequently, the stabilization of fluid pressure by maintaining continuous outflow of liquid becomes important for restraining the occurrence of the wave pattern and obtaining good surface quality. Die profile radius can be given as the important influential factor that affects the outflow of liquid from the flange. Making die profile radius larger is effective in obtaining continuous outflow of liquid. Furthermore, we can also restrain the occurrence of the wave pattern by eliminating the pulsation of fluid pressure using a relief valve.

Keywords:deep drawing, hydraulic counterpressure forming, forming property, surface quality,　wave pattern, pulsation phenomenon