Effect of Hot Rolling on Super plastic Properties of AIN Particulate Reinforced Aluminum Alloy Composites

(Received on December 13, 1994)

Tsunemichi IMAI, Sumito KOJIMA, Kazutaka SUZUKI and Shouichi KUME

AIN/7064 and AlN/6061 aluminium alloy composites fabricated by the P/M method are subjected to extrusion only or hot-rolling after extrusion and the superplastic characteristics are investigated. AlN/7064 and AIN/6061 Al Alloy composites subjected to extrusion only do not produce super- plasticity but the composites hot-rolled after extrusion show an m value of more than 0.3 and total elongation of more than 200% in the strain rate region from 0.1 to 1.5 s-' at 773- 873K. The composites are have fine grain size less than 3m.The fracture surfaces after superplastic deformation covered by a partially liquid matrix and have filaments. It is thought, therefore, that, primarily, deformation mechanisms of the composites include fine grain boundary sliding and liquid sliding at the interface between the matrix and AIN particle.

Keywords:composite material, superplasticity, extrusion, rolling, tensile test



Computational Simulation on the Shearing Process under Shock Pressure

(Received on June 28, 1995)

Masahiro FujITA, Minoru MOCHIHARA, Yasuhiro NAKIYAMA, Kazuyuki HOKAMOTO and Shigeru ITOH

In the present investigation, the shearing of rectangular plates with die edges at both sides by shock pressure is treated experimentally and analytically,and the shearing processes of an elastic -perfectly plastic metal plate and a strain-hardening one under shock pressure are numerically simulated by the finite-difference method. The calculated results are compared with the results of experiments in which two kinds of copper plates are sheared by an underwater shock pressure. These comparisons are made at a relatively low shock pressure which is not sufficient to cut through the plate. The computational results show good agreement with the experimental ones. Some aspects of the shearing process suggested by the results are discussed.

Keywords:shearing,punching,blanking,high-energy-rate forming,numerical analysis,shearing process,@elasto-perfectly plastic metal,FDM,explosively bonded multilayered material.



Prediction of Curvature of Extruded T-Shape Products

(Received on July 21, 1995)

Manabu KIUCHI, In-tai JIN and Ken SHINTANI

A kinematically admissible velocity field is developed for the analysis of curving of extruded products. The curving of a product during extrusion is caused by the linearly distributed longitudinal velocity on the crosssection of the workpiece at the die exit. In the analysis, the longitudinal velocity in the extrusion direction is divided into the uniform velocity and the deviated velocity. In order to satisfy the requirement of the kinematically admissible velocity field, the average value of the deviated velocity should be zero, the deviated velocity should change linearly with the distance from the center of gravity of the crosssection of the workpiece. The deviated velocity is determined through minimization of the total power of deformation. The results of the analysis show that the curvature of a product increases with increase in eccentricity of the center gravity the crosssection of the workpiece at the die entrance from that of the crosssection at the die exit. It also increases with aspect ratio of the crosssection of the product, die length and friction factor. It is also shown that the extrusion pressure increases with increase in curvature of product.

Keywords:extrusion, T-shape, kinematically admissible velocity field, numerical simulation,curving



Characteristics of Edge-Drop of Cold Rolled Strips in Single Pass Rolling
Development of Technology for Reducing Edge-Drop of Cold Rolled Strips by Pair-Cross Mill III

(Received on August 28, 1995)

Tetsuo KAJIHARA, Shoichi HASHIMOTO, Hideaki FURUMOTO, Atsushi TOMIZAWA, Ryuji HAMMED and Shoichi IMAM

To examine the performance of Pair-cross mill in terms of edge-drop reductions in cold-rolled strips, an experiment with model rolling mills and analysis using a 3-dimensional slab method have been carried out. It was found from the experiment that the strip edge profile changes from edge-drop to edge-rise when cross angle is increased, at the same time, the lateral deformation of the strip also changes from expanding to contracting. The shape of the strip acutually changed from edge-wave to center-buckle, but was not large enough to obstruct operation. These findings were also verified by the analysis. It is thus confirmed that Pair-cross mill is useful in reducing the edge-drop of cold-rolled strips.

Keywords:Cold strip rolling, cross rolling, edge-drop, flatness, frictional anisotropy, 3-dimensional slab method.



Enclosed-Die Forging with Axially Driven Container

(Received on September 11, 1995)

Kozo OSAKADA, Shinji HANAMI and Xin WANG

In order to reduce the pressure during enclosed-die forging, a method employing an axially moving container is proposed. In this method, the container is axially driven by an actuator while the billet is extruded into the die cavity by the punch. By moving the container, the billet material is induced to flow easily into the corner of the die cavity with the help of the friction over the container surface, and as a result, a product can be produced under a low forging pressure. Three patterns of container movement (one direction, one cycle and oscillation) and three coefficients of friction are examined. The effectiveness of the present method is investigated using a combination of physical model experiments and FEM simulation. It is shown that the forging pressure required for filling the corner of the die cavity is greatly reduced when the container movement is one cycle or oscillation.

Keywords:enclosed-die forging, forging pressure, die cavity filling, axially moving container, container movement, friction, FEM simulation.



Numerical Analysis of Hydraulic Forming by Rigid Plastic Finite Element Method

(Received on October 12, 1995)

Shinii TANAKA, Yuji YOSHITOMI and Shota IWAKURA

It is very difficult to analyze a hydraulic forming process using rigid plastic FEM, because this method is based on upper bound theory which can only be used if a velocity boundary condition is given. In this paper, a simple method is proposed for solving hydraulic forming problems using rigid plastic FEM. That is, one nodal point on the boundary surface under hydraulic pressure is selected, and one component of velocity at this point is given arbitrarily. Then, it is assumed that the nodal force corresponding to this forced velocity at vecter is equal to the force determined by hydraulic pressure. Consequently, hydraulic pressure " p" can be eliminated from simultaneous equations. This method can be easily applied to general hydraulic fanning with any material, such as work-hardening or strain-rate-dependent material. Some bulge-fanning problems involving a circular plate or cylindrical pipe are calculated. The results are in good agreement with theoretical and experimental results.

Keywords:hydraulic forming, rigid plastic finite element method, work-hardening material, strain-rate-dependent material



The Trial for Forming of a Spur Gear Made from the Drawn Cup

(Received on October 27, 1995)

Yoshinori NAGAI, Yukihiko UCHIDA Naoto SHOJI and Hiroyuki SHIINA

A new production method in which a spur gear is formed using a drawn cup is proposed. Blanks are thick circular metal plates. This forming method consists of four plastic forming processes, namely, drawing, restriking, ironing and compressing. In the compressing process, the cup is put into the die and is compressed in state of holding the top of the cup between the gear punch and the cushion punch. In this report, the forming of spur gears with modules of 1.5mm and 2.5mm is described. Then, relations between gear formability and forming conditions are examined by experiment. We obtained the following results. Once the forming stroke passes a boundary point at which the load becomes constant, the decrease in the face width without perfectly filling in the die at the end surface is little. The face width without perfectly filling is influenced by the material volume of tooth part in the point of stroke before compressing begins between the top and the end surface. Hardness near the tooth surface is 2.1-2.3 times greater than that of the base material annealed. Error in the tooth profile becomes large at the addendum and dedendum circles, but reduction of this error may be possible using a die which can compensate for elastic deformation during compressing.

Keywords:forging, drawing, restriking, ironing, compressing, formability, thick metal plate, spur gear.



High Accurate Bending by Controlling Bending Force

(Received on November 2, 1995)

Tetsuya ANZAI, jun-ichi ENDOH, Tsutomu MIZUNO and Hajime YAMADA

In sheet metal processing, high-accuracy bending is required for high-quality products. Generally, hydraulic press-brakes are used for such processing, and in order to obtain high-accuracy bending angle, accurate positioning of the table to which the metal molds are attached is necessary. However, this method is influenced by differences in material thickness or ambient temperature. In the method for controlling bending force developed by the authors, the maximum force in the bending process is measured, and the required force for high-accuracy bending angle is calculated. Using this bending force, the bending process is carried out. The following conclusions are obtained . 1) When the bending force is controlled, the dispersion of bending angles due to deviation of material thickness is less than 50% of that obtained with the conventional method. 2) Controlling the bending force can also reduce the bending angle drift due to changes in ambient temperature to less than 25% of that of the conventional method .

Keywords:bending, press-brake, sheet metal bending, bending angle, controlling bending force.



Effect of Precipitate State of Mg2Si on Surfacial Quality of Extruded Al-Mg2Si Alloys

(Received on November 6, 1995)

Toshihiro TAKE, Norio TAKATSUJI, Mitsugu TOKIZAWA, Kenji MATSUKI, Kazuo MUROTANI and Hiroyuki MORITA

The effect of precipitate state of Mg2Si as well as Si content in Al-Mg2Si alloys on the reduction of a die-line defect on the surface of extruded Products is investigated experimentally. A divided die is used in order to directly observe the correspondence of the bearing surface to the extruded sample surface. When Si content is low and a large amount of coarsened Mg2Si is present in the alloy, the extruded samples have bright smooth surface and nonbright rough surface. When a large amount of Mg2Si solute is present in the alloy, the extruded samples have high-quality surface with only nonbright and uniform surface roughness. When Si content is high, the extruded samples have high-quality surface with only nonbright and uniform surface roughness and are not influenced by the precipitate state of Mg2Si in the alloy. The bearing surface state which leads to high-quality surface for the extruded samples has uniform surface roughness and prior adhesion of the Al-Mg or Mg component.

Keywords:direct extrusion, tribology, divided die, non-ferrous metal (Al-Mg2Si), surface



Simulation of Chevron Cracks in Drawing

(Received on November 16, 1995)

Kazutake KOMORI

The objective of the present work is to clarify ductile fracture phenomena in bulk metal forming by means of FE analyses and experiments. We have developed a computer program based on a conventional FEM program by which crack propagation behavior after ductile fracture can be analyzed. The phenomenon that internal defects occur periodically in the axial direction in drawing has been simulated by the program. The following results are obtained. First, to analyze multipass drawing we have proposed a method of obtaining residual stress after drawing and a method of considering initial stress before drawing. Second, to perform accurate simulation we have developed a method of fracturing one element in each step and a method of separating nodes at fracture. Finally, we have proposed a method of evaluating ductile fracture in terms of void volume fraction and axial stress, and we have shown the validity of the method by comparing the analytical results with experimental ones.

Keywords:drawing, numerical analysis, rigid plastic FEM, ductile fracture, chevron crack.