Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(vol.43 no.494 March 2002)
Cross Buckle in Temper Rolling of Ultrathin Annealed Strips
Hideo KIJIMA, Kazuhito KENMOCHI and Masanori KITAHAMA
(Received on May 18, 2001)
It is well known that gcross bucklesh occur in temper rolling of ultrathin annealed strips with large-diameter work rolls. Although this phenomenon was experimented in the case of cold rolling of thin strips with small-diameter work rolls, there have not been any reports on the phenomenon in the case of temper rolling. The mechanism of the phenomenon has not yet been clearly explained. In this paper, the effect of several rolling conditions on the buckling phenomenon is investigated in laboratory rolling. Results show that delivery tension predominantly affects the phenomenon. The buckling form changes from an edge buckle, to a cross buckle to flat depending on delivery tension. This tendency is the same for other rolling conditions in which the roll crown or roll roughness is changed. In addition, a hypothetical mechanism is discussed. It is hypothesized that not only compressive stress in the width direction but also a relative difference in elongation in the rolling direction affect the cross buckling phenomenon.
Key words : strip rolling, temper rolling, experimental analysis, model simulation, flatness, buckling, undulation, cross buckle
Development of Chemical-Reaction Coating Lubrication
Method for Hot Rolling Work Roll of Stainless-Steel H-Beams
Masaru IZAWA, Kunio GOTO,
Kenji TSUBOUCHI and Yoshiaki KUSABA
(Received on May 23, 2001)
A duplex lubricating method has been developed in order to prevent from causing seizure of stainless H-beams in a universal hot rolling mill. The method consists of two processes:1 iron oxalate is formed by oxalic acid on the steel roll surface, and 2 fine particles are formed by reaction with calcium chloride and oxalic acid. Experimental friction tests were conducted in order to evaluated anti-seizure performance. As a result, it has become clear that the iron oxalate film is easily formed on the steel base roll and that the grain size of fine particles is 5-10 micro meters. Furthermore, the lubrication mechanism has been examined, and it has been confirmed that this duplex lubricating method provides a superior effect in an actual mill.
Key words : hot rolling, tribology, seizure, stainless-steel H-beams, oxalic acid, iron oxalate
Investigation of Relationship between Blanking Conditions and Characteristics of
Edges of Products Blanked by Two-Step Counter Blanking Processes
-- Study on Burr-Free Blanking 1 --
Naozumi HATADA, Keii UENO, Makoto TATEMURA,
Shinobu WATANABE,
Sutasn THIPPRAKMAS, Masahiko JIN and Masao MURAKAWA
(Received on May 24, 2001)
Finite element method (FEM) simulation has been performed for burr-free blanking processes such as conventional two-step counter-blanking and so-called push-back blanking, and the relationship between the blanking conditions and the characteristics of product edges has been investigated. In the conventional two-step counter-blanking process, there are many process parameters such as the first step punch penetration, the first step blanking clearance and the dimensions of the punch and die. The present study aims at determining the successful conditions in which time and cost can be reduced for burr-free blanking by experimental trial and error. In order to achieve this, FEM simulations are performed to clarify the deformation modes of material under various blanking conditions and to identify the successful blanking conditions for burr-free blanking. It is shown that the results of FEM simulations are qualitatively in good agreement with those of experiments using a stainless-steel sheet of 1mm thickness.
Key words : blanking, counter-blanking, push-back blanking, burr-free blanking, FEM
Ductile Fracture Conditions of Bonding Layers under Combined Stresses
Hiroki URYU, Shigeru SHIDA and Hiroshi MIYATA
(Received on May 31, 2001)
For electronics parts that are represented by semiconductor devices, solder and adhesive joints are usually used considering their electric characteristics and productivity. The design of joints requires an accurate knowledge of the mechanical properties of their constituent materials. Their bonding layers receive combined normal and shearing stresses in practical use. In this report, the ductile fracture conditions of bonding layers under combined stress are examined experimentally using lap joints and the zig that is designed in order to increase the flexural rigidity of their base metals. It is found that the distortion energy theory can be applied to ductile fracture conditions of solder bonding layers but not to those of epoxy resin bonding layers.
Key words : joining, tension test, material property, combined stress, ductile fracture
Experiments and Static Implicit FEM analysis of Spring-back
in Bend Forming of Bumper Model
Tetsuro OHWUE, Tohru YOSHIDA,
Yasuyoshi SHIRAI and Toshio KIKUMA
(Received on July 4, 2001)
Experiments of bend forming of a bumper model with a 10 MN oil-hydraulic press and FEM analysis with the static code MARC were carried out in order to investigate spring-back behavior. The materials used were 3 types of high-strength steel (HSS) sheets of the 440~780MPa class. Experimental spring-back shapes were investigated using a 3-D measuring machine. Spring-back of a formed bumper increases with an increase in yield stress of the material. This spring-back behavior coincides with the results of 2-D FEM simulation.
Key words : FEM analysis, bend forming, bumper model, spring-back, 2-D simulation
Elastic-Plastic Behavior of High-Strength Steel Sheet
under In-Plane Stress Reversal and Its Modeling
Takeshi UEMORI, Kenji FUJIWARA and Fusahito YOSHIDA
(Received on July 25, 2001)
The elastic-plastic behavior of high-strength steel sheets of 590MPa ultimate strength under in-plane forward-reverse deformation at large strain has been investigated. From the experiments, it was found that the Young's modulus decreases rapidly with increasing prestrain, and approaches its asymptotic value when the prestrain becomes large. During reverse deformation, the transient Bauschinger effect, which is characterized by early re-yielding and the smooth elastic-plastic transition with rapid change of the work-hardening rate, is followed by plastic deformation with apparent permanent softening. In order to describe the above mentioned stress-strain responses under reverse deformation, mathematical models (an empirical equation for prestrain-dependent Young's modulus and a new backstress evolution equation) are presented.
Key words : reverse deformation, Young's modulus, Bauschinger effect, high-strength steel sheets, constitutive modeling
Isothermal Ring Compression Test of TiAl Intermetallics
Shin KAGUCHI, Kei ECHIZEN,
Masayuki SUGAWARA and Kiyoyuki OHUCHI
(Received on August 29, 2001)
TiAl intermetallics have excellent characteristics, such as low density, high strength and high heat resistance, but they also have some weak points, such as low ductility and poor workability. Isothermal forging has is prospecting for forming materials from a simply shaped preform to a near-net-shaped product in a single process. However, selection of appropriate die materials and lubricants becomes an important problem in the application of isothermal forging. In order to investigate optimum combinations of die materials and lubricants for the process, isothermal ring compression tests with two kinds of die materials and various lubricants are carried out in a vacuum and in air. As a result of the evaluation of damage on the dies, the characteristics of the lubricants and frictional shear factors by ring compression tests, it has become clear that a molybdenum alloy TZM die and a BN type lubricant are suitable for the isothermal forging in a vacuum, and a ceramic SiAlON die and a BN-type lubricant applied to the die surfaces and a glass type lubricant applied to the specimen are suitable for isothermal forging in air.
Key words : forging, intermetallics, TiAl, isothermal forging, friction, lubricants, ring compression test.