Effect of Sizing Process on Residual Stress of ERW Pipes
-Improvement of Pipe End Roundness for Thin Wall Pipes I

(Received on June 28, 1994)

Yoshiaki ITAMI, Matsuo ATAKA and jyuzou SHIBATA

The residual stress of electric resistance welded (ERW) pipes caused in roll forming process was investigated in detail by use of the basic elastic-plastic calculation and experimental measurement. The purpose was to clarify the effect of sizing reduction, roll radius, ratio of thickness to diameter (t/D) and initial stress on the resultant residual stress of ERW pipes. It was found that previous strain histories were eliminated by sizing process and the residual stress in the longitudinal direction caused by sizing mills was greater than that in the circumferential direction. The large longitudinal residual stress on the surface of pipe was attributed to bending and rebending deformation in the sizing roll bite. It was also confirmed and revealed by axisymmetrical two dimensional elestic-plastic finite element analysis.

Keywords:forming property, residual stress, finite clement method, finishing, sizing, roll forming, electric@resistance welded pipes.



Mechanism of Pipe End Deformation and Improvement of Pipe End Roundness
-Improvement of Pipe End Roundness for Thin Wall Pipes -

(Received on June 28,1994)

Yoshiaki ITAMI, Matsuo ATAKA and jyuzou SHIBATA@

The deformation beheavior and the resultant residual stress on electric resistance welded (ERW) pipes during a sizing process is investigated in detail by both the three dimensional elastic-plastic finite element analysis and experiments. The purpose was to clarify the cause of pipe end deformation after the pipe was cut which deteriorated the pipe end roundness. It was found that the non-uniform disturibution in the circumferential direction of longitudinal membranous component stress controlled the pipe end deformation. The influence of the residual bending stress was not so significant as that of membranous stress. It was also confirmed by calculation and experiments that the use of 4-roll sizer resulted in more uniform distribution of plastic strain and residual stress than those by 2-roll sizer and therefore the improvement of pipe end roundness as a result decreased amount of pipe@end deformation.

Keywords:forming property, residual stress, finite element method, finishing, sizing, roll foming, electricresistance welded pipes.



Development and Application of Die Design Algorithm for Optimization of Crankshaft Twisting Process
-Development of Quantitative Die Design Method for Crankshaft Forging Process -

(Received on-October 21, 1994)

Kenji TAMURA, Yasuo HIDA, Tomihiko FUKUYASU, Masaru NISIIIGUCHI and Masayoshi AKIYAMA

A new algorithm has been developed to evaluate quantitatively the validity of die design for crankshaft forging, which has led to successful adoption of a thorough]), new die design method to the production line. The new method can be used regardless of the designer's experience. The core numerical method is the three-dimensional rigid-plastic finite-element method and the new algorithm was used to analyze the deformation throughout crankshaft twisting to verify that the thinning phenomenon on the arm portion of a crankshaft could be well simulated. Based on this new algorithm, a new scheme was then developed to determine the optimum die design to forge the mother geometry on which the thinning phenomenon is highly dependent. In order to realize the shortest convergence time, the simplest boundary condition was carefully chosen. Another algorithm was developed by which to reach the solution in the quickest manner. Two different matrix solvers were installed in the scheme and the shortest convergence time was achievable by adopting the better solver of the two, depending on the convergence rate. An arrangement was then given to standardize the new method, and it was successfully applied to the production line to obtain the most reliable die design.

Keywords:forging, crankshaft, twisting, numerical analysis, experimental analysis, die design,@rigid-plastic FEM, CAE



Application of Numerical Analysis Method to Design of Roller Levelers
Numerical Study of Roller Leveling Process

(Received on March 27,1995)

Koji KADOTA and Ryouichi MAEDA

We have developed a method of numerically analyzing the roller leveling process. Using this method, we can estimate the plate curvature, the reaction force and the driving torque acting on the rolls in a leveling process. A series of numerical analyses have been performed with various roller leveler specifications (roll pitches and roll diameter) and material properties (yield stress, plate thickness and Young's modulus). Based on the results of these analyses, the relationship between the initial conditions (roller leveler specifications and material properties) and the effects of leveling (the maximum and residual curvature of plate, the reaction force and the driving torque) has been clarified. Approximate equations were derived from results of these analyses. The optimum maximum curvatures to minimize the residual curvature were determined. Using this method of numerically analyzing the roller leveling process, we also confirmed the effectiveness of recently developed leveling processes, including a curved distribution of the intermesh, roll bending and an application of tension.

Keywords:leveling, roller leveler, numerical analysis, elastic perfect-plastic material, plate bending, curvature, local wave, steepness



Measurement of the Contact Pressure in Aluminum Hot Extrusion

(Received on April 5,1995)

Takeshi YONEYAMA, Kazuhiko TAKATSUKA, Masayoshi KITAGAWA and Yotaro HATAMURA

Pressure acting on the container surface in the aluminum hot extrusion process has been measured by a pressure sensor using an optical fiber displacement meter which has been devised for use at high temperatures of about 400'C. In order to prevent deterioration of the output performance of the pressure sensor at high temperature, the reflection surface for the light beam from the fiber probe has been plated with nickel and the sensing hole space has been filled with nitrogen gas and sealed. Pressure increases from the die exit to the pressure pad along the container surface due to the friction between the billet and the container surface in aluminum hot extrusion. High pressure is produced in the clearance between the pressure pad and the container surface. The relation between the pressure distribution and the friction on the container surface has been investigated.

Keywords:extrusion, measurement, sensor, aluminum, tool, pressure



Rolling Characteristics of Cold Strips on Cross Rolling
Development of Technology for Reducing Edge-drop of Cold Rolled Strips by Pair-cross Mill

(Received on April 28,1995)

Tetsuo KAJIHARA, Shoichi HASHIMOTO, Yutaka MATSUDA, Atsushi TOMIZAWA, Masahiro MATSUURA and Shoichi IYAMA

In recent years demand has increased for new technology that reduces the edge drop of cold-rolled strips. As the first step in applying Pair-cross mill with large crown control capability to cold strip rolling, cold cross rolling characteristics were studied by means of experiment and numerical analysis. The results showed that the rolling force and forward slip were constant and nearly completely unaffected by the cross angle. In addition, the coefficient of friction between the strip and roII in the roIIing direction was found to be different from that in the strip' s IateraI direction; in other words, frictional anisotropy was observed in the experiment. Roll thrust force was shown to depend on the coefficient of friction associated with slipping in the strip's lateral direction. However, the maximum thrust force predicted is 6% to 7% of the rolling force. It was thus concluded that Pair-cross mill can be used for cold strip rolling.

Keywords:coId strip roIIing, cross roIIing, frictionaI anisotropy, roII thrust force, sIab method.



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

(Received on May 9,1995)

Koji TOKUSHIMA, Yukio SANO

Mean green densities predicted by an earlier theoretical analysis, where the punch and the plug were assumed to be rigid bodies, differ markedly from experimental densities when the plug length is sufficiently large compared with the powder length. In this study, the reason for this difference will be clarified. In addition, a qualitative mean green density-initial powder length relation Is derived from a theory including the effects of elasticity of the punch and the plug. The efficacy of the theory for a compaction with a long plug is discussed by comparing the qualitative relation with experimental data.

Keywords: dynamic powder compaction, compaction process, die wall friction, elasticity of punch and plug, shock wave, elasticity wave, theoretical analysis, dynamic similarity, green density, powder forging