Application of Finite Element Method to Shaping of Watch Back Case by Superplastic Forging
-Development of Watch Case Made of Titanium Alloy Ill

(Received on November 25, 1994)

Isao KUBOKI, Kazunari YOSHIDA, Tadashi ARIGA, Katsuhito OGURA, Keitaro KOROISHI and Hiroyuki HUNAMOTO

It is possible to shape thin disks of Ti-9.5V-2.5Mo-3Al alloy by superplastic forging with only one step. The original thicknesses of 1.24 to 1.93mm of the disks are reduced into a watch back case with a projection whose hight is hp=O.l7mm. As the results of the foging experiments are qualitatively consistent with those of the finite clement method (FEM) analyses of the forging, the FEM analysis is found to be able to apply to the watch back case forging of the thin disks. Although the forging load decrease with a increase in m-value and with a decrease in K-value in the FEM analyses, the state that the alloy is filled into dies is almost unaffected by the changes in those values. It was clarified in the experiments, however, that both the increase in the m-value and the decrease in the K-value are effective in the improvement of the accuracy of product sizes and in filling the dies with the alloy, since the degree of spring back decreases with the decrease in the forging load

Keywords:forging, superplasticity, Ti-alloy, finite clement method, spring-back, watch@back case, friction coefficient.



Double Strip Rolling of Stainless Steel Foil with Tension

(Received on January 30, 1995)

Ken-ichi YASUDA, Kenjirou NARITA and Shigeru SHIDA

Possible thickness reduction of a thin stainless steel strip without annealing is investigated experimentally under three rolling conditions: (a) conventional rolling of a single strip, (b) conventional rolling of double strips with the same thickness, (c) rolling of double strips having different thicknesses. Thickness reduction by (c) is maximum among the three, and is four to five times that by (a). Tension is also effective for achieving high thickness reduction in thin strip rolling. Effect of the difference in tension applied to the upper and the lower strip on the thickness reduction difference between the two strips is found to be small. In case (c), therefore, a high thickness reduction of the thinner strip can be attained without strip breakage by applying a large tension to the thicker strip during rolling. With this method, the minimum thickness obtained by (c) is one-sixth of that by (a).

Keywords:rolling, cold rolling, double strip rolling, stainless steel foil, deformation-load property, minimum@thickness.



Calculation Method of Loads on Skew Roll Mill for Web Expansion of H-Beam
Development of Flexible H-Beam Rolling by Skew Roll Mill Ill

(Received on February 21, 1995)

Koushirou AOYAGI, Kazushige IKUTA and Takao KAWANAMI

In order to select adequate rolling conditions for the web expansion of H-beams by the new beam rolling mill "Skew Roll Mill (SKM)" , a method of calculating loads on SKM is proposed in this study. First, the equation of the mean compression stress during the thickness reduction at both ends of the web is theoretically introduced using both the balance equation of lateral stresses and the yield criterion by assuming the plane strain state. Secondly, experimental equations of the boundary stresses are established on the basis of plasticine-model and hot-rolling-model experimental findings. Moreover, an equation of the mean roll pressure is given by proportionally combining the theoretical equation of the mean compression stress with the experimental equation of the boundary stress . As a result, equations of the radial force are introduced using the mean roll pressure. Then equations of the thrust force depending on the radial force, the strain stress and shear stresses are introduced. The rolling torque can be calculated using the radial force and the thrust force. Results calculated using this model under various rolling conditions, including the geometrical relationship between the roll and H-beam, and the rolling temperature, agree well with hot-rolling-model experimental data.

Keywords:section rolling , load property, numerical analysis , experimental analysis, H-beam , plane strain,@mean roll pressure



Verification of Efficiency of Theory Including Elasticity Effects of Punch and Plug
-Multishock Compaction of a Copper Powder Medium in a Die by Punch Impact IV -

(Received on May 9, 1995)

Koji TOKUSHIMA and Yukio SANO

A mean green density-initial powder length relation is obtained by analyzing numerically a set of governing equations taking into account the elasticity of the punch and the plug. Firstly, the influence of their elasticity on the relation is examined based on the relations computed for eight different types of compaction. Secondly, two critical lengths, which were deduced in an earlier paper, are confirmed to exist in the curve representing the relation. Finally, the efficacy of this theory Is verified by comparing the results with experimental data.

Keywords:dynamic powder compaction, compaction process, die wall friction, elasticity of punch and plug, shock wave, elastic wave, theoretical analysis, pseudo-viscosity method, green density, powder forging



Effects on Forming Load of Clad Tubes in Conical Nosing and Flaring

(Received on June 12, 1995)

Shigeki MORI, Ken-ichi MANABE and Hisashi NISHIMURA

The load property in conical nosing and flaring of adhesive-bonded two-layer clad tubes is investigated experimentally and analytically. An experiment was carried out in order to examine the influence of the combination and thickness ratio of the clad metals on the forming load of clad tubes consisting of soft aluminum, hard aluminum and copper. In order to clarify the influence of the bending deformation at the die inlet and the friction between material and die on the load property of clad tubes, the forming -is analyzed by the finite element method. In flaring of the clad tubes having material with large flow stress on the inside, the reduction in the wall thickness of the inside component is inhibited due to the bending deformation, and the increase in the wall thickness of the outside component is enhanced. Therefore. the additional load exerted by the bending deformation is larger than that of the clad tube having the reversed configuration. It is emphasized that the influence of the bending resulting from the differences in material properties and the friction should be taken into account in selecting the forming load and optimum die semi-angle in the nosing and flaring of clad tubes.

Keywords: tube forming, clad material, nosing, flaring. load property, friction. material property, experimental analysis, finite element method.