Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.38 No.436 May 1997)
Tribo-Characteristics of Zinc-Coated Steel
Sheets During Ironing
Kumaki DOHDA Satoshi KASHIWAYA, Zhrgang WANG and Hirotaka FUJIE
(Received on April 18, 1996)
The tribo-characteristics of some types of galvanized steels during ironing have been evaluated using a strip
ironing type tribometer. The results showed the destruction of the coated layer in GA, GAE and EL due to
the ironing, which squeezed out the lubricant. For this reason, the friction coefficient during ironing was
determined by the original friction coefficient of the coated layer in these materials, obtained using the ring on
disk type friction test. Thus, the order of the friction coefficient in GA, GAE, EL materials during ironing,
was the same as for the friction coefficient of the coated layer itself namely, ĘGA >ĘGAE >ĘEL. In the case
of use of a phosphoric type EP agent, the friction coefficient decreased in all materials. However, in the case
of use of a sulfuric type EP agent, the extent of the decrease in the friction coefficient was different for the
coated layer materials.
Key words : sheet metal forming, ironing, tribology, extreme pressure agent, friction, zinc-coated steel sheet
Dependence of Final Mean Density on Initial Medium Length
in Dynamic Powder Compaction with Elastic Punch and Plug
|Multishock Compaction of a Copper Powder Medium in a Die by Punch Impact V|
Koji TOKUSHIMA, Yukio SANO and Kiyohiro MIYAGI
(Received on June 20, 1996)
In the previous study, the analysis of the multishock compaction processes of a die-contained copper powder
medium, supported by an elastic plug at one end and impacted by an elastic punch at the other end, showed
a mean green density ( Īmean* )-initial medium length( S* ) curve with a complicated waveform, where the first
and second critical lenghts, Scr1* and Scr2* , were included. This analysis was performed for a constant sum
of the lengths of the medium and plug S1*. In this study, it is clarified in the same example as in the previous
study that the waveform is caused by shock waves and unloading waves transmitted in the medium from the
plug, whose number is increased with an increase in the medium length. In the second critical length the
shock waves, which are weakened by the unloading waves and die wall friction, cause a maximum increase in
density. Furthermore, approximate similarity conditions for compactions with various S1* values are presented.
They are given by two fixed parameters, punch mass M* and initial punch velocity vĄin the region S* < Scr1* ,
three fixed parameters, S* /S1* , M* and vĄin the region from Scr1* to small S* , where the wall friction effect
can be neglected, and three different fixed parameters, S* , M* and vĄin the region S* > ( 1/2)S1*. The
calculated Īmean*-S* and Īmean*-S*/S1* relations support these conditions.
Key words : dynamic compaction, powder, compaction process, shock wave, unloading wave, elastic wave
simulation, mean green density
Proposal of a New Simulation Method by Means of Triborneter
Controlled by Computer for Sheet Metal Forming and Evaluation
of Tribological Properties of Lubricant for Aluminium Alloy Sheet
\Tribology in Sheet Metal Forming II \
Akira AZUSHIMA, Ken IGARASHI and Kiyoshi IMAI
(Received on June 28, 1996)
We previously experimentally confirmed that the coefficient of friction was constant in the low pressure
range, while in the high pressure range, it decreased with increasing average pressure.
In the present work, a sheet metal forming simulator in which the average pressure can be controlled in a
wide range is newly developed in order to determine of the relationship between the coefficient of friction and
the average pressure for use in numerical simulation. The coefficient of friction is also found to decrease with
increasing average pressure in the high pressure range during simulator. The experiments are carried out using
aluminum alloy (Al-5%Mg) at constant speeds of 150 and 1500mm/min with several lubricants under average
pressure conditions controlled by the computer. It is found that the sheet metal forming simulator is effective
for investigation of the pressure dependence of the coefficient of friction.
Key words : sheet metal forming, coefficient of friction, tribometer, aluminum alloy.
Simulation of Rectangular Extruded Pipes by Porthole Die
\Study on Improvement in Quality of Hollow Extrusions W\
Satoshi MURAKAMI, Mitsuyuki ISOGAI, Toshiyuki INAGAKI,
Norio TAKATSUJI, Mitsugu TOKIZAWA and Kazuo MUROTANl
(Received on August 5, 1996)
It is known that the deviation from circularity of a rectangular extruded pipe can be predicted by
examination of the metal flow in a welding chamber. In this study, a simulation method was used in order
to elucidate metal flow behavior in a welding chamber. As a result, the analytical accuracy and practicality
of the simulation have been confirmed experimentally, and two results have been obtained by analyzing of the
simulation result for the continuous extrusion of aluminum alloy. One result is that the transformation
resistance of the metal is related to the extrusion temperature and strain rate; the other is that determination
of the slipping friction between the metal and the wall is very important for the simulation.
Key words : extrusion, porthole die, extrusion press, rectangular extruded pipes, welding chamber, shape of
porthole, simulation, finite element method
Determination of Basic Data for Numerical Simulation
\Analysis of Multi-stage Warm Forging Sequence for Austenitic Stainless Steel I \
Sachihiro ISOGAWA, Isao MORI and Yasuhisa TOZAWA
(Received on August 12, 1996)
This paper is intended to clarify basic data necessary for a numerical simulation of a warm forming process
of SUS304 stainless steel. The upsetting tests with concentric grooved platens are performed from room
temperature to 800 ), and at strain rates of 0.008 to 78 s-1,
using three kinds of presses. From the obtained
stress-strain curves, which include the effect of temperature rise during deformation, the constant temperature
and constant strain rate flow curves are determined by taking the heat generation into consideration. The
contact thermal conductance at the tool-material interface is estimated by comparing the analytical results of
the subsurface temperature transition of tool during upsetting with the measured results. The coefficient of
heat transfer from the material to air and coolant are also estimated by comparing the analytical results of the
temperature transition of material with measured results.
Key words : warm forging, upsetting, thermomechanical analysis, flow curve, contact thermal conductance,
heat transfer, SUS304