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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
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Volume & Issues
Volume 21, Issue 8 - Dec 2012
Volume 21, Issue 7 - Nov 2012
Volume 21, Issue 6 - Oct 2012
Volume 21, Issue 5 - Aug 2012
Volume 21, Issue 4 - Jul 2012
Volume 21, Issue 3 - Jun 2012
Volume 21, Issue 2 - Apr 2012
Volume 21, Issue 1 - Feb 2012
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Finite Element Analysis of Superplastic Forming Processes Considering Grain Growth (I)
Kim, Y.G. ; Song, J.S. ; Kim, Y.H. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 151~159
DOI : 10.5228/KSTP.2012.21.3.151
Finite element simulations were conducted to investigate the influence of grain growth in the superplastic blow forming process. A microstructure-based constitutive model considering grain growth effects is proposed and used in the simulations. Also, a grain growth rate equation accounting for both static and dynamic grain growth is implemented. The simulations were made using a 2D plane-strain model for constrained blow forming and an axisymmetric model for free bulging. These two models showed different features during the forming stages. However, the forming pressure-time curve and the thickness distribution obtained by both simulations explained well the deformation hardening induced by the grain growth during superplastic forming. This study shows that grain growth is an important factor in determining the material behavior during superplastic deformation.
Finite Element Analysis of Tube Swaging
Kim, M.C. ; Eom, J.G. ; Lim, S.J. ; Choi, H.J. ; Joun, M.S. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 160~163
DOI : 10.5228/KSTP.2012.21.3.160
In this paper, a new approach to finite element analysis for tube swaging is presented. An analysis model is developed with emphasis on the pusher that imposes back pressure in order to keep the workpiece from slipping along the die-workpiece interface especially when tapered dies are used. A rigid-plastic finite element method is employed. The approach is to simulate the tube swaging process and the results are compared quantitatively with predictions, showing close agreement with each other.
Finite Element Analysis of Half Channel Angular Extrusion (HCAE) as a New Severe Plastic Deformation Process
Kim, K.J. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 164~171
DOI : 10.5228/KSTP.2012.21.3.164
This paper focuses on the development of a new SPD (severe plastic deformation) process named HCAE (half channel angular extrusion). HCAE technology is based on principled similar to ECAE, but imposes a larger amount and more effective plastic deformation on materials. The amount of shear deformation can be altered by varying the process parameters. Finite element analyses of HCAE were conducted in order to investigate the characteristics of deformation during HCAE and the simulated results show that the predicted value of imposed plastic strain in a single pass reaches 2.5.
Verification of Finite Element Model Using the Almen Strip Test and Its Applications to Calculate Residual Stress Distribution
Yang, Z.R. ; Park, S.H. ; Lee, Y.S. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 172~178
DOI : 10.5228/KSTP.2012.21.3.172
We performed a shot peening test and used a 2-D finite element model which predicts the compressive residual stress distribution below the material's surface. In this study, the concept of 'impact cycle' is introduced to account for the irregularity in the shot's impact position during testing. The impact cycle was imbedded in the finite element model. In the shot peening test, shot bombarded a type-A Almen strip surface with different impact velocities. To verify the proposed finite element model, we compared the deformed cross sectional shape of the Almen strips with the shapes computed by the proposed finite element model. Good agreement was noted between measurements and the finite element model predictions. With the verified finite element model, a series of finite element simulations was conducted to compute the residual stress distribution below the material's surface and the characteristics of these distributions are discussed.
Numerical Analysis and Experimental Study of Thread Rolling Process for Micro-sized Screws(Part II: Application to a Micro-screw with Diameter of 800㎛)
Song, J.H. ; Lee, J. ; Lee, H.J. ; Lee, G.A. ; Park, K.D. ; Ra, S.W. ; Lee, H.W. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 179~185
DOI : 10.5228/KSTP.2012.21.3.179
In this paper, it is proposed to produce high precision screws with a diameter of
and a thread pitch of
) by means of a cold thread rolling process. In this part II of the study, the focus is on the production and reliability testing of the prototype
micro-screw. Designs for two flat dies were developed with the aid of the literature and previous studies. Process parameters during the cold thread rolling process were established through FE simulations. The simulation results showed that the threads of the micro-screw are completely formed through the rolling process. Prototype
micro-screw were fabricated with a high precision thread rolling machine. In order to verify the simulation results, the deformed shape and dimensions obtained from the experiment were compared with those from the simulations. Hardness and failure torque of the fabricated micro-screw were also measured. The values obtained indicate that the CAE based process design used in this paper is very appropriate for the thread rolling of micro-sized screws.
Blank Shape Design Process for a Hot Stamped Front Pillar and its Experimental Verification
Kim, J.T. ; Kim, B.M. ; Kang, C.G. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 186~194
DOI : 10.5228/KSTP.2012.21.3.186
Hot stamping is a forming method that offers various advantages such as superior mechanical properties, good formability, and very small springback. However, relatively large-sized parts, such as front pillars, exhibit poor formability when hot stamped due to the limited material flow and thickness reduction imparted by the process. This reduction in thickness can also lead to cracks. One of the reasons is the relatively high friction between the sheet and the die. In this study, in order to obtain the optimal conditions for hot stamping of front pillars, various process parameters were studied and analyzed using the sheet forming software, J-STAMP. The effects of various parameters such as the die structure, blank shape, blank holding force, punch speed, clearance(upper and lower dies) and distance block were analyzed and compared.
Development of a Housing Component for an Auto-compressor Using Vacuum Ladling Die Casting
Lee, H.S. ; Park, J.S. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 195~201
DOI : 10.5228/KSTP.2012.21.3.195
A vacuum ladling die casting system is suggested as a means to obtain a high vacuum level. A high vacuum of 17.8 mmHg is obtained by sealing the inner space of the mould. The sample product is a rear-head housing for an auto-compressor, and the die-casting with 6-cavities was conducted. The flow analysis shows that the filling speed during vacuum ladling is faster than for a non-vacuum system. The air holes in the sample product were too small to be seen with the naked eye in X-ray films. Density tests show that the high vacuum ladling system reduces the internal porosity as much as 57.8% when compared to the non-vacuum system. A defective rate of only 0.17% was found from leak testing. The results of this research prove that the high vacuum die-casting process is useful for manufacturing of aluminium components under high internal pressure.
Forming of Circular Protrusion by Half-Piercing and its Application to Marking of Sheet Metal
Jung, H.K. ; Kim, J.H. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 202~206
DOI : 10.5228/KSTP.2012.21.3.202
Marking is a process that engraves letters or a pattern onto the surface of sheet metal. During marking, it is important to set the proper working conditions for clarity of the letters. In this study a simple case for forming circular protrusions by half-piercing and embossing was initially attempted to determine the working conditions which gave good results with respect to shape accuracy. Corner-radius and flatness of circular protrusions made under several experimental conditions were measured and compared. It is shown that the precision of protrusions by half-piercing is superior to that of embossing, and the clearance between punch and die exerts a strong influence on the shape accuracy rather than the penetration percentage into the thickness of the sheet metal. The marking dies for "SNUT" letters, as an example, by applying the above results were manufactured with four different clearances. The working variables for the experiment were clearance and marking depth. For the very shallow depth of 0.1mm the letters were not clearly read. Letters marked under other conditions were easily distinguished with increasing marking depth. It was confirmed that the half-piercing technique with proper values of the working variables gives good quality for the marking of sheet metal.
Influence of High Temperature Deformation Process Variables on the Microstructure and Thermo-physical Properties of a Ni-Fe-Co Alloy
Yoon, D.H. ; Jung, J.E. ; Chang, Y.W. ; Lee, J.H. ; Lee, K.S. ;
Transactions of Materials Processing, volume 21, issue 3, 2012, Pages 207~214
DOI : 10.5228/KSTP.2012.21.3.207
High temperature deformation behavior of a
alloy, with its extraordinary low coefficient of thermal expansion less than
at temperatures ranging from room temperature to 673K, was investigated by conducting a series of compression tests. From an empirical processing map, the appropriate working temperature-strain rate combination for optimum forming was deduced to be in the ~1373K,
region. This region has a relatively high power dissipation efficiency, greater than 0.36. Furthermore, open die forging of a 100mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase in the average grain size.