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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Transactions of Materials Processing
Journal Basic Information
Journal DOI :
The Korean Society for Technology of Plasticity
Editor in Chief :
Volume & Issues
Volume 11, Issue 8 - Dec 2002
Volume 11, Issue 7 - Nov 2002
Volume 11, Issue 6 - Oct 2002
Volume 11, Issue 5 - Sep 2002
Volume 11, Issue 4 - Aug 2002
Volume 11, Issue 3 - Apr 2002
Volume 11, Issue 2 - Apr 2002
Volume 11, Issue 1 - Feb 2002
Selecting the target year
A Study on the Friction Characteristics in Tube Hydroforming Process
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 475~481
DOI : 10.5228/KSPP.2002.11.6.475
Tube hydroforming is a relatively new technology in comparison with conventional stamping process. Thus, there is no large knowledge base to assist the product and process designers, especially from the friction point of view. This paper covers the topic of friction and lubrication with regard to tube hydroforming. It presents the fact that frictional characteristic can have an effect on the formability of specific components. The presented concept describes the equipment which is required to determine the friction coefficient. Some example results of the friction and bulge test are shown.
The Effect of friction between Roll and STS the Roll Cladding Behavior of STS/Al/STS Sandwich Sheet
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 482~486
DOI : 10.5228/KSPP.2002.11.6.482
Sandwich sheets composed of stainless steel/aluminum/stainless steel were produced by roll cladding. In order to investigate the effect of the friction between roll and cladding sample, the lubrication condition of the roll surface was varied. Clad rolling without lubrication gave rise to a small increment of the normal strain of aluminum in the rolling direction. This experimental result was confirmed by FEM modeling. Through-thickness hardness gradients in the mid aluminum layer was successfully explained by variations of the strain state through thickness layers. FEM modeling implied that cladding without lubrication led to a large shear strain variation at the surface of aluminum layer.
Development of Optimal Blank Shape Design Program Using the Initial Velocity of Boundary Nodes
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 487~494
DOI : 10.5228/KSPP.2002.11.6.487
A new method of optimal blank shape design using the initial nodal velocity (INOV) has been proposed for the drawings of arbitrary shaped cups. With the given information of tool shape and the final product shape, corresponding initial blank shape has been found from the motion of boundary nodes. Although the sensitivity method, the past work of the present authors, has been proved to be excellent method to find optimal blank shapes, the method has a problem that a couple of deformation analysis is required at each design step and it also exhibits an abnormal behaviors in the rigid body rotation prevailing region. In the present method INOV, only a single deformation analysis per each design stage is required. Drawings of practical products as well as oil-pan, have been chosen as the examples. At every case the optimal blank shapes have been obtained only after a few times of modification without predetermined deformation path. The deformed shape with predicted optimal blank almost coincides with the target shape at every case. Through the investigation the INOV is found to be very effective in the arbitrary shaped drawing process design.
A Study on the Welding Pressure of Billets in the Extru-Bending Process of Hollow Tube
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 495~502
DOI : 10.5228/KSPP.2002.11.6.495
The welding pressure in extru bending process is affected by the shape of welding chamber of porthole die. It is very important to increase the welding pressure when the tube should be extruded particulary from four billets of the materials. The high circumferential stress of the tube can make the welding pressure increase during the extru-bending. In order to increase the circumferential stress, it is necessary to make the billets pass through the narrow gap between the conical die and the conical plug. This paper describes the welding pressure by the experiments and the analysis with the two types of the chamber. One of them is the chamber between the flat die and straight mandrel, and the other one is the chamber between the conical die and conical plug. The results of the experiments and the analysis shows that the conical chamber makes the welding pressure increase by the effect of the reducing diameter of tube and the welding pressure by the conical dic and plug is stronger than the welding pressure by the flat die and straight mandrel.
Elastic-plastic Finite Element Analysis of Drawbead Forming for Evaluation of Equivalent Boundary Conditions in Sheet Metal Forming - Part I : Evaluation
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 503~512
DOI : 10.5228/KSPP.2002.11.6.503
The drawbead is used to control material flow into the die during the binder wrap process and the stamping process in the sheet metal forming process. Since the dimension of drawbead is relatively small in comparison with the typical dimensions, it is difficult to include drawbeads in finite element analysis of the sheet metal forming process. It is because the mesh system has to be fine enough to describe the drawbead and the computation time is drastically increased. In this paper, simulation of drawbead forming has been carried out to obtain the equivalent boundary conditions in the binder wrap process and the stamping process. In order to investigate the effect of various die geometries, parameter studies are performed with the variation of parameters such as the blank length, the drawbead depth, the drawbead radius, the inclination of die and the friction coefficient.
Elastic-plastic Finite Element Analysis of Drawbead Forming for Evaluation of Equivalent Boundary Conditions in Sheet Metal Forming - Part II : Application to the front Door Panel Forming Process
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 513~518
DOI : 10.5228/KSPP.2002.11.6.513
The equivalent boundary conditions have been applied to the front door panel forming process, in order to demonstrate its reliability and validity. The elongation in the bead forming process is applied to the binder wrap process as the equivalent displacement boundary condition and the restraining force in the drawing process is applied to stamping process as the equivalent force boundary condition. The result calculated with the equivalent boundary conditions shows closer coincidence with the experimental result than simulation with different boundary conditions. The numerical result fully demonstrates that drawbead forming simulation for calculation of equivalent boundary conditions is necessary and effective.
Microstructural Evolution during the Equal Channel Angular Pressing of Ti-6Al-4V Alloy
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 519~528
DOI : 10.5228/KSPP.2002.11.6.519
The microstructural evolution during the equal channel angular pressing of Ti-6Al-4V alloy was investigated using the transmission electron microscopy (TEM). ECA pressing was carried out isothermally with route C at
for two types of initial microstructure, i.e., equiaxed and Widmanstatten microstructures. At an initial stage of ECA pressing, the equiaxed microstructure showed more uniform flow than the Widmanstatten microstructure. However, both microstructures were significantly refined revealing nearly equiaxed grains of 0.3
in diameter with high angle grain boundaries after 4 passes of ECA pressing. These ultrafine gains were found to be stable with little grain growth, when annealed up to
High Temperature Deformation Behavior of Gamma TiAl Alloy - Microstructural Evolution and Mechanisms
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 529~537
DOI : 10.5228/KSPP.2002.11.6.529
A series of load-relaxation tests and tensile tests were conducted to study the high temperature deformation mechanism of fine duplex gamma TiAl alloy at temperatures ranging from 800 to 105
. Results of load relaxation test showed that deformation behavior at a small imposed strain (
≒0.05) was dominated by dislocation glide and dislocation climb. To investigate the deformation behavior at a large amount of strain, the processing map was constructed using a dynamic materials model. Two domains were characterized in the processing map obtained at a strain level of 0.6. One domain was found at the region of 98
with a peak efficiency of 48%, which was identified as a domain of dynamic recrystallization from the microstructural observation. The order was observed at the region of 125
with a peak efficiency of 64%. The strain rate sensitivity measured indicates that the material was deformed by the superplasticity in the region.
Assessment of Hot Deformation and Grain Size Distribution in a Udimet 720Li Pancake
Transactions of Materials Processing, volume 11, issue 6, 2002, Pages 538~546
DOI : 10.5228/KSPP.2002.11.6.538
Hot deformation behavior of Udiment720Li was characterized by compression tests in the temperature range of 10
and the strain rate range of
. The combination of dynamic material model (DMM) and Ziegler's instability criterion was applied to predict an optimum condition and unstable regions for hot forming. A dynamic recrystallization model coupled with FEM results was used to interpret the evolution of microstructures. In order to verify the reliability of the present coupled model, isothermal forging was performed in the temperature range 1050~115
at strain rates of
. The present model was successfully applied to the hot forming process of Udimet720Li.