Three-Dimensional Analysis of Mandrel Rolling Using Rigid-Plastic Finite Element Method

(Received on June 15, 1994)

Kenji YAMADA, Shigeru OGAWA, Shuichi HAMAUZU and Toshio KIKUMA

A three-dimensional finite element code for analysis of mandrel rolling of a seamless tube has been developed. The code is based on the rigid-plastic FEM which is fotuided on the theory of plasticity for slightly compressible solid. Introducing a method for correction of streamline profiles of material which is preceded by three-dimensional contact analysis, the code enables the precise analysis of material deformation occurring during rolling. The data necessary for the contact analysis, such as ffiction coefficients and peripheral velocity vectors of tool surfaces, are stored as values of mesh points of the tool surface, making it possible to apply this code to a variety of roll groove profiles. The results of analysis are given, which show the material geometry contacting with the tools, cross-sectional view of the material at exit of the roll-bite, distribution of pressure acting on the tube surfaces. Moreover, the relationship between these observations and rolling conditions, such as the roll groove profile, the ffiction coefficients and mandrel bar speed, is studied.

Keywords:tube rolling, mandrel rolling, iiwnerical analysis, rigid-plastic, finite element method, three dimensional analysis



Behavior of Charge Welding in Porthole Die Extrusion

(Received on June 17, 1994)

jian-Xin XIE, Tadasu MURAKAMI, Keisuke IKEDA and Hiroaki UKAJI

The welding resulted from the charge of a succeeding billet in hollow die extrusion, so-called charge welding, has important effect on both the quality and the yield of products. The behavior of charge welding in A1050 pipe extrusion is researched. 3- and 4-porthole die extrusions are carried out at 450'C with a container of 50 mm in diameter. The influences of the process van'ables (dividing rafio of billet (R,= 2.15 - 2.78), total extrusion ratio (R = 20.8,28.7) and depth of the welding chainber(h = 5, 10mm) ) on the state of charge welding in products are investigated. With a larger dividing ratio of billet and/or a shallower welding chamber, the distance between the front end of charge welding seam and the die mark is shorter, while the extrusion load is higher. For the dies used, the length of extrudate between the die mark and the axial position of the cross section on which the neighbon'ng charge welding seams begin to mutually contact corresponds with the extrusion length of a charge billet of (0.23-0.39)D, long (D, denotes the diameter of container). For commercially pure aluminum as working material, the extruded pipes have excellent expanding strength even at the part including front end of charge welding seams, except for the case with the shallower welding chamber (h = 5 mm) and the smaller extrusion ratio (R = 20.8).

Keywords: extrusion, hollow section, porthole die, charge welding, metal flow, die design.



Fabrication of Bi-Metallic Pipes by Hot Multi-Billet Extrusion Method

(Received on June 27, 1994)

Jian-Xin XIE, Tadasu MURAKAMI Keisuke IKEDA and Wataru YAMANASHI

An application of the multi-billet extrusion method to fabrication of the bimetallic pipe is attempted. By using a container block having four holes spaced symmetrically with the same interval and a special die set having dual welding chambers, A2014/AIO50 (inner/outer layer) or A1050/A2014 pipes are I tru extruded at 5000C. The variations of cross-sectional shapes and dimensions of ex dates and the welding state between the inner and outer layers are mainly investigated. Under all experimental conditions, excellent welding is attained between the inner and outer materials as well as between the same materials. The diffusion of copper from A2014 to A1050 across the inner/outer interface is confirmed by EPMA. Using either A1050 or A2014 as the outer material, the extrusion loads are almost constant. The dimensional accuracy on the cross-sections of the pipes is higher with the combination of A2014/AIO50 than A1050/A2014. Even for the case of A]050/A2014, the dimensional deviations are within the JIS standard for extruded pipes of conunon aluminum alloys. It is effecfive for improving the dimensional accuracy to employ a longer cover (h,=7mm) which is attached to reduce the radial pressure on the inner pipe resulted from the outer working material in the welding chamber.

Keywords:extrusion, multi-billet, bimetallic pipe, solid-state welding, aluminum alloy.



Effect of Multi-Axial Loading on Deep Drawing
Square Cup Deep Drawing of Thick Plate by Multi-Axial Loading I

(Received on July 6, 1994)

Eiji SATO, Toru SHImizu, Kiyoyuki OHUCHI, Toshio SANO and Sadakatsu FUCHIZAWA

Squiirc cup deep drawing of thick plates by multi-@ixial loading applied by a punch and four side-tools is studici. First of all, i finite clement an@ilysis is performed in order to verify the validity of this method. In this @inalysis, B-spline patches for the description of the tool geometry and a direct method of the contact algorithm are adopted. The results show that this deep drawing method provides more uniform thickness distribution than the conventional method, which means this method is effective to increase the Limiting Drawing R-,itio (LDR). In the experiment to investigate the LDR, a mechanism to prevent the tool interference during the deep drawing process is introduced. Using this mechanism, the LDR is measured under the two different constant velocity ratios: RV=O.O and Rv=0.5 (Rv=VvlVp, Vv: side-tool velocity, Vp: punch velocity). Octagonal shaped, commercially pure aluminum plates of 3.Omm in thickness are used as the blank. This method gives the LDR improving of about 20% comparing with the conventional method. Analytical and experimental results show that this deep drawing method is very effective especially for thick plates.

Keywords: square cup, deep dr@twing, multi-axial lo@iding, thick plate, FEM, LDR.