Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.39 No.444 January 1998)
Collapse Strength Formula for Commercial Casing
under Constant Axial Tensile Strain with Plastic Strain
Toshitaro MIMAKI, Susumu MIZUNUMA, Toshitaka TAMANO and Sa mon YANAGIMOTO
(Received on August 28, 1996)
In recent years, arctic oil and gas field wells, called permafrost wells, have been successfully developed. In
a well, the collapse of casings takes place under constant axial tensile strain with plastic strain when local
melting occurs in the underground permafrost stratum. However, the collapse strength of commercial casings
under the boundary condition has rarely been analyzed by experimental and/or statistical methods. We
conducted collapse tests and established empirical formulas for estimating the collapse strength. That is th
yield strength after work-hardening, the compressive axial stress caused by axial deformation constraint and the
reduced modulus of the plastic constitutive equation are formulated by regression analysis. It was found that
the formulas proposed yield a more accurate estimate of the collapse strength under constant axial tensile strain
with plastic strain than that of conventional formulas.
Key words : experimental analysis, defornration-load property, collapse strength, plastic strain, reduced modulus, work-hardening effect
Mechanical Alloying of Brass-Nickel Plating
on Steelwire in the Drawing Process
Shunji HACHISUKA
(Received on November 6, 1996)
Mechanical alloys are studied mainly in ball milling and their mechanisms are well established. The alloys
are produced by a grinding/sticking of powder particles. Another mechanism is assumed to play a part in a
compression field where plastic deformation is caused by shear force. The effect of kneading has been
confirmed by the cyclic rolling press. We suspect that the drawing process has potential in the field of
mechanical alloying (MA) due to severe plastic deformation. An experimental test was performed using a steel
cord as the reinforcing material for a tire. Brass (65%Cu-35%Zn) is usually plated onto steel for adhesion to
rubber. To improve adhesion degradation under high humidity conditions, the alloying of an additional element
to brass was studied. We plated nickel on a brass plated steel wire (dual plating) and the MA was determined
to have formed after drawing. The surface of this alloy showed a great improvement of aged adhesion. The
MA formed by different dies is shown in the X-ray diffraction, glow discharge spectroscope analysis, and a
gradient effect was determined by X-ray photoelectron spectroscope analysis. This surface MA, formed by
means of drawing has a great potential in the tire industry in the future.
Key words : drawing, wire drawing, material, composite material, non-ferrous material (Cu-Zn-Ni), ferrous
material (Fe), mechanical alloying, surface property
Simulation of Multistage Forging Sequence for Nut
Analysis of Multistage Warm Forging Sequence for Austenitic Stainless Steel ll
Sachihiro ISOGAWA, Isao MORI and Yasuhisa TOZAWA
(Received on December 24, 1996)
A three-stage warm forging sequence for a nut made of austenitic stainless steel is analyzed by the
thermomechanical finite element method. In order to simulate the temperature change in the tool during
repeated operations, a simplified method, in which heat generation due to the deformation of the workpiece is
not taken into account, is used. The temperature distribution of the tool reaches the steady state after a
certain number of cycles of operation, though it changes periodically. This temperature distribution is adopted
as the initial condition of tool temperature, and temperature transition of the workpiece during three-stage
forging is calculated using the input date determined in the first report. In the multistage forging calculation,
the heat conduction to the tool, coolant and air are taken into consideration. The forging load at each stage
is predicted satisfactorily by the present analysis. Deformation and stress distribution of the shrink fitting dies
under various conditions of heat and load are also calculated.
Key words : warm forging, multistage forging sequence, thermomechanical analysis, finite element method,
closed die forging, forward-backward extrusion, SUS304
The Smooth-Necking Die Design
Development of Die Smooth-Necked Can I
Hideki UTSUNOMIYA and Hisashi NISHIMURA
(Received on January 10, 1997)
The smooth-necking die technique for steel DI ( Drawn & Ironed) cans with a wall thickness of O . I 4 mm
was experimentally investigated. A smooth neck is advantageous because a large neck angle can be achieved,
and it is possible to shorten the neck length. Therefore, the thickness of the neck area is increased to facilitate
necking and flanging. The smooth shorter neck leads to a reduction in metal usage and lighter weight. An
experiment was performed using standard conical necking dies. The wrinkling mechanism was studied and it
was determined that in multidie smooth-necking, necking dies must have curvatures in the forming area, and
the die semi-angle must be larger than the can neck angle. Because the relation between the tangential angle,
the die semi-angle at a distance from the inner surface of the die and the distance is very important in
designing a necking die, the relation was calculated using several die profiles, and resulting in an improved die
design. The performance of the newly developed dies was confirmed by experimentation. Necking of I . O mm
diameter for each stage was obtained without wrinkling.
Key words : tube forming, nosing, die design, DI can, die smooth-necking, wrinkle
Analysis Model for Deformation of Coil of Thin Strip under Coiling Process
Flatness Change of Thin Strip during Coiling Process I
Shusuke YANAGI, Shigeo HATTORI and Yasushi MAEDA
(Received on February 9, 1997)
The flatness of a thin strip sometimes changes through the coiling process, but the mechanism for this has
not yet been clarified theoretically. Therefore, we developed a method to analyze the deformation of the coil
throughout the coiling process to investigate the change in flatness. We assume the coil is a thick cylinder and
strip is a thin cylinder. We replace the coiling process by successive coupling of the thin cylinder onto the
thick cylinder and the coiling tension by a circumferential stretching force within the thin cylinder. We
allocate the thin cylinder a thickness distribution determined from the strip crown in order to consider the
inhomogeneous deformation of the coil in the axial direction of the coil. The deformation of the thick cylinder
after each coupling of the thin cylinder is obtained using Love's stress function. Using this model, we
examined the effect of th t
e s rip crown and the coiling tension upon the deformation of the coil and obtained
the results that the axial inhomogeneity of the coil deformation is enhanced as the strip crown or the coiling
tension increases.
Key words : strip coiling, strip crown, coiling tension, flatness change, Love's stress function
Identification of a Yield Locus of Aluminum Alloy Sheet
A5182-O by Biaxial Tensile Tests Using Cruciform Specimens
Toshihiko KUWABARA, Ippei SUSUKI and Satoshi IKEDA
(Received on March 10, 1997)
The yield locus of as-received aluminum alloy sheet A5182-O ( 1mm thickness) is identified precisely using
newly designed cruciform specimens. Each arm of the specimen has slits to exclude geometric constraint
during the deformation of the central square region at which biaxial stress components are identified. The
specimens are subjected to linear loading paths in a servo-controlled biaxial tensile testing machine. The
deformation generated in the central square region is confirmed to develop uniformly, well beyond the yield
points of the aluminum alloy sheet. A yield locus is determined as a contour of equal plastic work 0.227MPa.
The measured yield locus is rather close to a Mises locus and is compared with those predicted by conventional
yield functions : Hill's quadratic and '79, '90, '93 yield functions, Logan and Hosford's yield function and
Gotoh's biquadratic yield function. The measured yield locus and measured incremental strain vectors have the
best agreement with those predicted by Gotoh's yield function, verifying a normality flow-rule. Other yield
functions cannot predict accurately the geometry of the yield locus and the in-plane r-value distribution
simultaneously.
Key words : biaxial tensile test, cruciform specimen, liner loading path, yield locus, A5182-O, Hill's quadratic,
'79, '90 and '93 yield functions, Logan and Hosford's yield function, Gotoh's biquadratic yield
f unction
Drawbead Restraining Force for Different Drawbead Shapes
Study on Drawbead Restraining Force in Sheet Metal Forming I
Hideyuki SUNAGA and Akitake MAKINOUCHI
(Received on March 25, 1997)
The quality of the final products is greatly influenced by the material flow control under the tools of the
sheet metal forming operation such that defects as tears and wrinkles are prevented. Drawbeads can be used
in the deep drawing process of automotive panels in order to control the flow of the blank during the forming
operation. This paper investigates the drawbead force for a variety of drawbead shape under the drawbead gap
constant. We found that the sheet angle in the drawbead cavity plays an important role in determining the
drawbead restraining force of a single bead. However, it is difficult to determine the restraining force of a
double bead, which can be estimated by the clearance. These results suggest that we do not need to examine
or simulate each case for different shapes of drawbeads in order to determine the drawbead restraining force.
The restraining force can be provided for the finite element code to simulate the forming process of automotive
panels.
Key words : sheet metal forming, experimental analysis,
drawbead, drawbead force, drawbead clearance, drawbead groove
Prediction of Drawbead Restraining Force by FEM
Study on Drawbead Restraining Force in Sheet Metal Forming H
Hideyuki SUNAGA and Akitake MAKINOUCHI
(Received on March 25, 1997)
In a finite element simulation of a three-dimensional industrial sheet forming process the drawbead is not
generally modeled by its actual shape. Since the sheet around the drawbead has a complex deformation, a very
fine mesh is required to simulate these drawbead forming phenomena, which increases the calculation time. It
is very important to develop a practical but accurate method to model the drawbead effect, and to establish a
method for estimating the restraining force as a function of drawbead geometry. In this paper it is shown that
two-dimensional elastoplastic finite element code, ITAS-2D, can provide a sufficiently accurate drawbead
restraining force for an arbitrary drawbead geometry without actual experiments. The results of this
simulation improve our understanding of the drawbead forming process, and provide us with a very efficient
method for obtaining the drawbead restraining force from the relation of the sheet angle in the drawbead cavity.
Key words : sheet metal forming, numerical analysis, drawbead, drawbead force, drawbead clearance,
drawbead groove, FEM
Influence of Deformation Conditions on Deformation-Induced
Martensitic Transformation in Austenitic Stainless Steel
Manabu SANGA, Nobuki YUKAWA and Takashi ISHIKAWA
(Received on March 21, 1997)
To explain the effect of stress on the deformation-induced martensitic transformation of austenitic stainless
steels, uniaxial tension, biaxial tension, uniaxial compression and biaxial compression tests were carried out, and
the amount of deformation-induced martensite was measured. To carry out the four tests, all test samples
were made from the same sheet metal with the same chemical composition and grain size. The compression
test samples had precompressed diffusion bonding. Sheets were piled up and slightly compressed before
diffusion bonding could occur. The following conclusions were obtained. The amount of deformation-induced
alpha' martensite increases in the following order: biaxial compression test, uniaxial compression test, uniaxial
tension test and biaxial tension test. Therefore, the amount of deformation-induced alpha' martensite in the biaxial
tension test is the highest of the four tests. The deformation-induced alpha' martensitic transformation was
assisted by an increase in tensile hydrostatic stress and hindered by an increase in compressive hydrostatic
stress. This phenomenon can be ascribed to assist of volume expansion due to the transformation from
austenite to alpha' martensite.
Key words : material testing, material, deformation-induced martensitic transformation, austenitic stainless
steel, diffusion bonding
Stretchability of a High-Strength Steel Sheet
with Transformation Induced Plasticity
Matsuo USUDA, Shunji HIWATASHI, Koji SAKUMA,
Tomohisa KATAYAMA and Manabu TAKAHASHI
(Received on March 31, 1997)
An investigation was carried out to determine the stretchability of high-strength steel sheets which had a
tensile strength of 590 MPa and exhibited transformation induced plasticity, which have been developed to aid
in the weight reduction of an automotive body and in the improvement in the crashworthiness of an
automobile. The steel exhibits increased strain hardening and an instantaneous n value at the strain from O to
20 pct when subjected to the tensile test. The increase is attributed to the recent change from austenite to
martensite. In punch-stretching, the forming strain is almost identical to the strain which makes the most of a
transformation effect and the limiting forming height of developed steel exceeds that of conventional steel with
a tensile strength of 440 MPa and has a comparable elongation. In hydraulic bulging, the effect of the
transformation is reduced due to a larger forming strain than that which accompanies the transformation. In
model door forming, a large formable range of blank holding force is obtained for the developed steel.
Increased n values result in a large strain at the center of the panel, and the desired shape can be obtained by
applying a large blank holding force without ruptures.
Key words : stretch forming, forming property, high-strength steel sheet, transformation induced plasticity
Elastic-Plastic FE Analysis of Tension-Levelling Process
Masaki URABE, Fusahito YOSHIDA, Keiji TANITA and Tetsuo KAJIHARA
(Received on May 28, 1997)
This paper presents a new algorithm for the elastic-plastic finite element analysis of the tension levelling
process. The final shape of steady stream line of a strip in the process is determined by the analysis of
step-by-step roll stretch-bending using the deformation theory of plasticity. An elastic-plastic constitutive model
with the linear and nonlinear kinematic hardening and the isotropic hardening is used for the analysis to
describe the Bauschinger effect and cyclic hardening characteristics of the strips. To verify the analytical
method, tension-levelling experiments with a three-roll unit and a four-roll unit were performed. The analytical
results of the work curvature of the strips agree with the corresponding experimental results.
Key words : shape correction, tension leveller, metal strip, elastic-plastic FEM, cyclic plasticity, maximum
curvature, experiments
Development of the Static-Explicit FEM
for Deformable Multi-Body Contact
Hisashi TAKIZAWA and Akitake MAKINOUCHI
(Received on July 2, 1997)
The most important problems in analysis of metal formmg processes using FEM is description of contact
phenomena between tools and deformed materials. In this report, we present a new formulation and associated
algorithm for solving the contact problems of elastic plastic deformable bodies within the framework of the
static-explicit and elasto-plastic FEM. Simulation examples show that the proposed algorithm can handle
contact problems in a stable and efficient way and is suitable for analyzing practical metal forming problems.
This algorithm is also expected to provide useful information such as tool deformation and stress concentration
in the area of tool design.
Key words : numerical analysis, elastic-plastic FEM, contact problem, forming process, tool design