Papers in JOURNAL OF THE JAPAN SOCIETY
FOR TECHNOLOGY OF PLASTICITY
(Vol.41 No.473 June 2000)
Twisting Effects of Wires during Coiling
and their Application
Ken YAMAYA, Takahiko KUNOH and Kazunori TSUSHIMA
(Received on April 19, 1999)
It is clarified that the wire torsion caused by curved wires and the inclination of a reel plane influences the torsion of formed coils. Then, the effects of wire twisting in coiling on the pitch or on the initial tension of formed coils are elucidated. It is also clarified whether processing of the pitch or adjusting the initial tension of formed coils is possible without using coiling tools. It is also shown that the largest initial tension can be achieved by the wire twisting in coiling. Furthermore, it is clarified theoretically and experimentally that nonlinear helical extension springs can be obtained by changing the torsion of wires monotonically during coiling.
Key words : wire forming, coiling, process design, coil spring, pitch, initial tension, nonlinear characteristics
Elastoplastic FE Analysis on the Combined Bending and
Torsion of Square Cross-section Bar
Naozumi HATADA, Keii UENO, Shinobu WATANABE,
Keiichi NAKAMURA, Hiroya MURAKAMI and Taylan ALTAN
(Received on July 21, 1999)
3D elastoplastic FE analysis is carried out for solving the problems in the case of combined bending and torsion of square section bars. Using the ABAQUS program, the combined effects of bending moments and torsion moments, and spring back processes under various loading paths are examined. The analysis is treated as a large deformation problem, and the material is considered to be a perfectly rigid elastoplastic material. As a result, it is confirmed that despite the loading paths, spring back curvatures and spring back torsion angles coincide with the numerical results obtained from theories of pure bending and pure torsion.
Key words : bending, torsion, finite element method, spring back
Theoretical Analysis of Die-less U-Bending Process
- Development of Die-less Bending Process for Precision Bent Tube T -
Takashi KUBOKI, Munekatsu FURUGEN,
Shin-ichiro OHSAKA and Toshihide ONO
(Received on August 2, 1999)
A new precision tube bending process without bending die, i.e. a die-less bending process, has been developed. The bending facility consists of feeding rolls, a bending roller and a rotating arm with a clamp for fastening the tube. The bending radius after springback is controlled by two bending conditions, the position of the bending roller LR and the velocity ratio of tube-feeding to the rotating arm . The influences of these bending conditions on the bending radius were studied by theoretical analysis. The simulated moment distribution during bending and the bending shape after springback were in good agreement with the experimental measurements. The die-less bending process has successfully been developed and can be applied to produce precision U-bent tubes.
Key words : bending, numerical analysis, tube, curvature, moment, die-less, springback, U-bent tube
Improvement of Surface Roughness on Sheared Edge
during Cold Multistage Forging
Isao KUBOKICToshio KUSANO and Kazunari YOSHIDA
(Received on August 16, 1999)
Wristwatch crowns have been shaped from ferritic stainless steel and nickel silver wires using continuous cold multistage forging. It is necessary for the crown to be in the mirror-finished condition without large defects on the surface. Shearing of the wire results in roughness of the sheared edge. When the end of the punch used in the middle of the multistage forging process is convex shaped (the tip angle:160), the roughness which was present at the head of the crown decreases in the final forging stage and becomes less than that when using a flat-ended punch (180). Because frictional resistance between the punch and the crown decreases when using a convex punch, the material flow on the surface is promoted, thus improving the contact between the punch and the crown. When the end of the punch is concave shaped (radius of curvature:
R2.5mm), punch failure is bound to occur during the forging.
Key words : forging, shearing, heading, ferrous metal (Fe-20Cr), nonferrous metal (Cu-18Ni-18Zn), surface roughness, finite element method