Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(vol.43 no.497 June 2002)
Size-Free Rolling of Rectangular Wire on Elongation-Control Mill
-- Development of Elongation-Control Rolling 3 --
Hiroshi UTSUNOMIYA, Yoshihiro SAITO,
Munetoshi UEYAMA and Masaki SHINKAWA
(Received on October 10, 2001)
The elongation-control mill is used to produce aluminum and copper rectangular wires from round wires
5mm in diameter. The mill used is a five-stand tandem mill in H-H-H-V-H arrangement and is able to control the deformation of the workpiece by the interstand forces generated by means of the differences in roll speeds. The vertical grooved rolls at the fourth stand are used to reduce the wire width. The resultant interstand force is measured precisely and its influence on the rolling characteristics is cralified. Wire width increases with interstand compressive force and decreases with interstand tensile force. In the case of a 2.3mm-thick aluminum wire, the width is varied from 4.8mm to 7.4mm. The corner radius increases with the tensile force and decreases with compressive force and edging draft. Arbitrary combination of width and corner radius is achieved by varying the roll speeds and the edging draft. The size-free rolling of rectangular wires is realized. The higher interstand tensile force makes the product hardness higher and its distribution more homogeneous.
Key words : wire rolling, rolling mill, elongation-control rolling, elongation, rectangular wire
Analysis of Fatigue Crack Initiation and Propagation in Cold
Forging Tools by Local Approach to Fracture
Kunio HAYAKAWA, Tamotsu NAKAMURA and Shigekazu TANAKA
(Received on October 24, 2001)
A local approach to fracture with damage mechanics was applied to establish a more precise method of estimation of service life of cold forging dies. First, modeling of elastic-plastic-damage behavior of the tool steel was conducted in the framework of thermodynamics. Then, the initiation and propagation of a fatigue crack in the cold forward extrusion die was analyzed by the local approach to fracture. The initiation and propagation of the fatigue crack in the vicinity of the die radius was found to occur as the extrusion number increased. Furthermore, the present approach was found to estimate the actual behavior of the fatigue crack growth in good agreement with the calculated rate of crack propagation to the extrusion number. The calculated crack propagation rate also tended to decrease due to the decrease of the major principal stress at the crack tip as the crack propagates.
Key words : fatigue crack, forging tool, finite element method, elastoplastic, damage mechanics, cold forward extrusion
Effects of Temperature and Forming Speed on Deep Drawability
of 5083 Aluminium Alloy Sheet
Tetsuo NAKA, Ryutaro HINO and Fusahito YOSHIDA
(Received on October 26, 2001)
The effects of temperature and forming speed on the deep drawability were investigated for a fine-grain Al-Mg alloy (5083-O) sheet by performing cylindrical deep drawing tests at die temperatures of 293 to 573 K at various forming speeds (0.2 to 500mm/min. The die was heated up, while the punch was water-cooled during the tests. The limiting drawing ratio (LDR) became higher with increasing die temperature and with decreasing forming speed. Such effects of temperature and forming speed are attributed to the temperature and strain-rate dependencies of flow stress and ductility of the material. The LDRs for various conditions of temperature and punch speed were analytically predicted using a constitutive model that accurately describes the rate and temperature dependencies of flow stress of the material. The predicted LDRs are in good agreement with the corresponding experimental results.
Key words : deep drawability, Al-Mg alloy sheet, forming speed, temperature, limiting drawing ratio, numerical analysis