Papers in JOURNAL OF THE JAPAN SOCIETY
FOR TECHNOLOGY OF PLASTICITY

(Vol.40 No.470 March 2000)

Analytical Study on the Hereditary Characteristic of Crown-Ratio by
Hot Rolling of Strip Using Three Dimensional Rigid Plastic FEM

Yuuji MITAI, Yuichi HONGO and Yukinobu OHSHIMA

(Received on November 30, 1998)

A three-dimensional rigid-plastic finite element method is applied to calculate the profile of a hot strip. Lateral metal flow takes place in a rolled material of located some distance from the edge of the material, which means that the crown-raito hereditary coefficients in the lateral direction are not uniform, but have a hill-type distribution. In this study the effects of hot strip width and roll diameter on crown-ratio hereditary coefficients are calculated. Hot strip width affects only the value of the crown-ratio hereditary coefficient at the edge of the hot strip width. The remaining part of hot strip width is uniform. The crown-ratio hereditary coefficients in the lateral direction are not effected by hot strip width. When a roll diameter is smaller crown-ratio hereditary coefficients are smaller.
Key words : rolling mill, strip rolling, profile, hot strip mill, crown-ratio heredity

Deformation Resistance of Regularly Perforated Plates

Shinji TANAKA and Toshitsugu MIYAWAKI

(Received on March 19, 1999)

To calculate the mechanical strength of perforated plates such as the shadow masks of color picture tubes, an algorithm was developed for the analysis of uniaxial tension in a thin plate with regularly spaced holes. An elastoplastic finite element simulation based on this algorithm was carried out. The calculated strains in the directions of OKand 90K were compared with those measured by a photoelastic coating method. The simulation results show that maximum and minimum flow stresses are induced at the angles of I 5Kand 30K from the X-direction, respectively. In addition to the plate with circular holes, a similar analysis was conducted of a plate with square holes, and it is shown that the simulation results are consistent with the experimental ones.
Key words : numerical analysis, finite element method, perforated plate, circular hole, square hole, tension test

Relation Between Drawing Tool Shape and Product Precision
- Drawing Process of High-Precision Thin-Wall Tube Using
Ultrasonically Vibrated Dies and Plugs I -

Pongpan KAEWTATIP, Masahiko JIN, Tadashi TAKANISHI and Masao MURAKAWA

(Received on April 1, 1999)

In an effort to manufacture high-precision drawn tubes, we employed radial ultrasonic-vibration tools which can improve the cylindricity and surface roughness of drawn tubes. First, we utilized an aluminum tube as a workpiece to determine the effects of drawing tools of different configurations and their combinations when conducting a conventional drawing operation. Next, we applied ultrasonic vibration in the radial direction to the plugs and/or dies to examine the effects of vibration on various working parameters such as drawing force, precision and surface integrity. The results revealed that the effects of vibration applied to the tools with a tapered approach and a short parallel tool portion were significant in improving the precision of drawn tubes.
Key words : tube drawing, radial ultrasonic vibration, high-precision tube

Evaluation of Formability of Light Metal Sheets at High Temperatures
by Conical Cup and Erichsen Tests

Makoto SUGAMATA, Jun-ichi KANEKO and Masahiro NUMA

(Received on April 2, 1999)

Experimental methods to evaluate the formability of sheet metals at a high, uniform temperature have not been established. Conical cupping and Erichsen tests were carried out using a self-constructed apparatus in which a blank sheet, die and punch were heated uniformly at temperatures between 293 and 573K. Five kinds of fully annealed light metal sheets of 0.8mm thickness were used as the test materials :1100, 3004, 5052 aluminum alloys, AZ31 magnesium alloy and commercial pure titanium. Tensile strength, total elongation, strain hardening exponent and Lankford value were obtained by tensile tests at various testing temperatures. The conical cup values of aluminum alloy sheets were not markedly affected by test temperature, while the Erichsen values of aluminum alloy sheets increased with increasing temperature. Thus, stretch formability of aluminum alloy sheets is more dependent on the testing temperature than is the deep drawability. The AZ3 l magnesium sheet showed poor conical cup and Erichsen values at room temperature, but appreciable improve- ment of both values was observed with increasing test temperature. The formability of a pure titanium sheet was relatively high at room temperature and the temperature dependence of formability was essentially the same as that of the magnesium alloy sheet. The correlation between Erichsen values and total elongation was stronger than that between conical cup values and total elongation.
Key words : metal sheet formability, conical cup test, Erichsen test, high-temperature test, aluminum alloy sheet, magnesium alloy sheet, pure titanium sheet

Factors Influencing Torsional Strength of Shave-Joined Ring/Pipe Parts

Terufumi MACHIDA, Yasuyoshi EGAMI
Zhiqiang LI and Nozomi SAKAMOTO

(Received on April 5, 1999)

Aluminum alloy and mild steel rings were experimentally shave-joined with triangularly knurled steel pipes to study the torsional strength of shave-joined parts such as automotive camshafts. The investigation was conducted under various influencing factors: material combination of ring on pipe, joining temperature, induction heating and shaving depth. Such a ring/pipe shave-joint can be obtained by a lower pressure of press. Joining strength or torsional strength increases uniformly with increasing shaving depth and heating temperature, as the engagement between the inner wall of the ring and the triangular serration of the pipe becomes tighter. Softening of the ring by changing the material and/or heating is observed to be useful for penetrating the knurled serrated teeth of the ring into the inner wall and for increasing lateral stress at the interface. The torsional failure was caused by shearing of the ring material at the interface. Vickers microhardness in the joining parts suddenly changed at the interface of both materials.
Key words : shave-joining, ring on pipe, combined cylinder, camshaft, torsional strength, hardness distribution, mild steel, aluminum alloy, induction heating

Evaluation of Antiseizure Properties and Seizure Mechanism
of Surface-Treated Tool

Akria AZUSHIMA, Kohichiro TAZIMA and Tohru HAYAKAWA

(Received on April 8, 1999)

Akria AZUSHIMA, Kohichiro TAZIMA and Tohru HAYAKAWA In order to evaluate the antiseizure property of surface-treated tools, simulation tests were carried out using the tribo-simulation testing machine. VC coated TRD (thermo reactive deposition) rolls and TiN-coated PVD (physical vapor deposition) rolls with different surface roughnesses were used as surface-treated tools and low-carbon steel was used as the workpiece material. In order to evaluate the antiseizure property, the occurrence of friction pickup is observed as roll speed and reduction change. The results are as follows. (1) The antiseizure property of the surface-treated tool depends on the surface roughness, and the friction pickup of the surface-treated tool with a greater degree of surface roughness occurs at lower reduction. (2) The limitation reduction when friction pickup occurs coincides with the reduction at which the calculated value of oil film thickness approaches the surface roughness value of the surface-treated tool.
Key words : surface-treated tool, seizure, friction pickup, surface roughness

Frequency Characteristics Analysis of Ultrasonic Blanking Die Using FEM
- Optimal Design for a Stepped Solid Horn -

Jun TONG, Kenji SHINODA and Shun-ichi KAWANO

(Received on April 19, 1999)

In this paper, we describe a design method for stepped solid horns using the FEM (Finite Element Method) and the experimental evaluation of an ultrasonic blanking die. A simulation method for an ultrasonic vibration system by FEM is proposed to determine the optimal size of a stepped solid horn. In this simulation method, the forced vibration and the damping are considered, and the calculation model is not only applicable to a horn but also to an ultrasonic vibration system comprising a cone, a tool horn, a flange and a vibrator. An ultrasonic tie-bar cutting die has been developed based on the FEM optimal design. The effects of ultrasonic vibration on blanking were experimentally investigated using this die. By comparing the FEM simulation results with experimental results on the amplitude of the tool horn and the frequency characteristics of the ultrasonic vibration system, it is clarified that the proposed simulation method is valid for the design of an ultrasonic vibration system. It is also found that the shearing force is decreased and the clearance is increasedby ultrasonic vibration.
Key words : ultrasonic tie-bar cutting die, ultrasonic effect, frequency characteristic analysis, ultrasonic vibration system, optimal design, natural frequency, resonant frequency, stepped solid horn, cone

Caulking Technique for Paper Rotor of Total Heat Exchanger Fan Unit

Toshiyuki AMIMOTO, Masaru KUNIKATA, Hiromichi TAKEDA,
Tatsuya NIINOMI and Hiroya MURAKAMI

(Received on April 21, 1999)

A technique for manufacturing rotors made of noninflammable paper has been developed. This rotor is one of the most important components of a total heat exchanger fan unit. In the mass production of these rotors, a process used in corrugated board manufacturing has been adopted, and its practicality has been confirmed. A caulking technique of attaching the corrugated paper to the flat paper has been proposed. This technique uses the friction of cut-offs processed at the contact points of the attaching materials. A prototype rotor made by this new paper caulking technique has been manufactured, and an intermittent caulking shape which has the least air-blocking rate has been suggested to meet the product specifications. The caulked rotor has similar joining strength, pressure loss, and heat exchange efficiency compared to the previous bond-attached rotor. This paper material caulking technique can improve the processing environment due to reduction of volatile organic solution usage, and can simplify the skills needed for proper machine maintenance. A machine for mass production using this process has been designed and adopted to an actual production line of total heat exchanger fan units.
Key words : joining, structural joining, caulking, material, paper, forming machine

Effect of Processing Temperature on Warm Shot Peening of Spring Steel

Yasunori HARADA, Ken-ichiro MORI, Yoshiteru FUKUOKA and Seijiro MAKI

(Received on June 18, 1999)

Effects of processing temperature on the residual stress and hardness in the warm shot peening process of springs were investigated to determine the optimum shot peening conditions. Springs made of hard spring steel were heated to facilitate a shot peening operation by the decrease in flow stress. In a model experiment using shots of a large size, the shot peening apparatus was covered to keep the processing temperature constant, and the distributions of residual stress and hardness in the peened workpieces were measured. Although the flow stress of the workpiece is decreased by the increase in the processing temperature, the decrease of hardness and residual stress in the workpiece increases. The compressive residual stress and the hardness in the peened workpiece were the highest at a temperature of 200 'C. The optimum temperature was also evaluated in an experiment using an actual shot peening apparatus with shots of an average size.
Key words : shot peening, spring steel, warm processing, residual stress, hardness,plastic deformation recovery, surface treatment,

Magnetic Pressure Seam Welding of Thin Aluminium Pieces

Tomokatsu AIZAWA

(Received on September 2, 1999)

This paper describes a novel seam welding technique and its experimental results. When an impulse current from a capacitor bank passes through a one-turn flat coil, eddy currents are induced within two thin (0.3mm) aluminium pieces placed in the coil. The pieces can be welded by either Joule heat generated in them or under magnetic pressure applied onto them. The bank energy required for seam welding an area of 5 x 50mm2 is less than 2kJ.
Key words : aluminium joining, pressure welding, seam welding, high-energy rate forming, sheet-metal forming, electromagnetic forming, magnetic pressure