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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of Materials Processing
Journal Basic Information
Journal DOI :
The Korean Society for Technology of Plasticity
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Volume & Issues
Volume 23, Issue 8 - Dec 2014
Volume 23, Issue 7 - Nov 2014
Volume 23, Issue 6 - Oct 2014
Volume 23, Issue 5 - Aug 2014
Volume 23, Issue 4 - Jul 2014
Volume 23, Issue 3 - Jun 2014
Volume 23, Issue 2 - Apr 2014
Volume 23, Issue 1 - Feb 2014
Selecting the target year
The Effect of Temperature on Springback of AZ31, Ti-GR2 during V-bending with Focused Heating using Near-infrared Radiation
Lee, E.H. ; Hwang, J.S. ; Lee, C.W. ; Yang, D.Y. ;
Transactions of Materials Processing, volume 23, issue 8, 2014, Pages 469~474
DOI : 10.5228/KSTP.2014.23.8.469
With the increased concerns of environmental issues, industries are paying more attention to lightweight metals. Because the high degree of springback is an obstacle to the widespread use of lightweight metals, many investigations have been conducted to reduce springback by increasing temperature. However, increasing the temperature of the whole die or the material is energy inefficient, since generally only a limited area of the material is deformed during sheet metal forming. As a solution to this problem, focused heating that only heats the area where plastic deformation occurs may be an alternative approach. In the current study, V-bending tests were conducted at various temperatures after the AZ31, Ti-GR2 sheets were locally heated using near-infrared (NIR) radiation in order to evaluate the effect of temperature on springback. The results of the experiment confirm that the NIR focused heating reduces the springback of AZ31, Ti-GR2 alloys with increasing temperature.
Thermo-mechanical Simulation of Boron Steel Cylinders during Heating and Rapid Cooling
Suh, C.H. ; Kwon, T.H. ; Kang, K.P. ; Choi, H.Y. ; Kim, Y.S. ; Kim, Y.S. ;
Transactions of Materials Processing, volume 23, issue 8, 2014, Pages 475~481
DOI : 10.5228/KSTP.2014.23.8.475
Water quenching is one method of cooling after hot forming, which is presently being used for the manufacturing of automobile parts. The formed parts at room temperature are heated and then cooled rapidly in a water bath to produce high strength. The formed parts may undergo excessive thermal distortion during the water quench. In order to predict the distortion during water quenching, a coupled thermo-mechanical simulation is needed. In the current study, the simulation of heating and cooling of boron steel cylinders was performed. The material properties for the simulation were calculated from JMatPro, and the convective heat transfer coefficient was obtained from experimental tests. The results show that the thermal distortion and the residual stresses are well predicted by the coupled simulation.
Numerical Study of Aircraft Winglet Mold Manufacturing using Flexible Forming
Park, J.W. ; Ku, T.W. ; Kim, J. ; Kang, B.S. ;
Transactions of Materials Processing, volume 23, issue 8, 2014, Pages 482~488
DOI : 10.5228/KSTP.2014.23.8.482
Flexible forming technology has advantages in sheet metal forming, because it can be implemented to produce various shaped molds using a single apparatus. Due to this advantage, it is possible to apply it to the manufacture of an aircraft winglet mold. Presently, most aircraft winglets are manufactured from composite materials. Therefore, the mold for the curing process is an essential element in the fabrication of such composite materials. Compared to conventional mold forming, flexible forming has some advantages such as reduced manufacturing cost and uniformity of mold thickness. If the thickness of the mold is consistent, then the heat transfer will occur uniformly during the curing process leading to improved formability of the composite material. In the current study, numerical simulations were performed to investigate the possibility of flexible forming for manufacturing of the winglet mold. In order to match the size of the actual product, the shape of objective surface was divided to fit the dimensions of the apparatus. The results from the numerical simulations are compared with the objective surface to verify the accuracy. In conclusion, the current study confirms the feasibility and the potential to manufacture winglet molds by flexible forming.
Influence of Blankholding Force and Blank Diameter on the Drawability and Quality of Very Small Cylindrical Cups
Lee, K.S. ; Kim, J.B. ; Jung, W.J. ; Kim, J.H. ;
Transactions of Materials Processing, volume 23, issue 8, 2014, Pages 489~494
DOI : 10.5228/KSTP.2014.23.8.489
Micro forming is an appropriate process to manufacture very small metal parts which can be employed in the field of electronic devices or electrically controlled mechanical systems. The purpose of the current study was to investigate the influences of both blankholding force and blank diameter for the deep drawing of very small cups. It is essential to control the blankholding force because improper force can result in defects such as wrinkles in the flange or cracks in the corner of the drawn cups. In the current study blankholding force was controlled by springs connected to the blankholder of a press die. Exchangeable bushing dies with various die-corner radii were also used. To obtain the limit drawing ratio for each working condition several sizes of circular specimens were prepared using blanking tools. Beryllium copper(C1720) alloy sheet of
thickness was chosen for the experiments. The maximum limit drawing ratio of 2.1 was achieved experimentally for the conditions of the blankholder force(BHF)=5.3kgf and Rd=0.3mm. Both thickness and hardness along the central section of drawn cups were measured and compared for different drawing conditions. It was found that the deviation of measured data in the thickness and hardness distribution increases with increasing blankholder force and blank diameter.
A Study on the Mechanical Properties and Formability of Mg AZ31B Sheet
Lee, G.H. ; Yoon, T.W. ; Kang, C.Y. ;
Transactions of Materials Processing, volume 23, issue 8, 2014, Pages 495~500
DOI : 10.5228/KSTP.2014.23.8.495
Magnesium alloys are currently expected to be widely used for weight reduction of cars and as high efficient materials in the automotive and electronics industries. Although the specific strength of magnesium is excellent, it cannot be easily formed at room temperature due to its HCP structure. However in order to improve the formability of magnesium, it is necessary to investigate its formability in the warm temperature range. In the current study, the aim was to add to the magnesium property database so that the mass production of a magnesium car body can be accomplished. Warm tensile tests were conducted and the forming limit diagram was determined to confirm formability characteristics of magnesium AZ31B alloy sheet. In addition the bending formability and the magnesium damping capacity were evaluated for AZ31B and compared to SPRC440E which is a sheet steel used for car bodies.
Optimization of Spring Layout for Minimizing Twist of Sheet Metal Pins in Progressive Shearing
Song, H.K. ; Shim, J.K. ; Keum, Y.T. ;
Transactions of Materials Processing, volume 23, issue 8, 2014, Pages 501~506
DOI : 10.5228/KSTP.2014.23.8.501
Progressive shearing with blanking dies is commonly employed to produce large quantities of tiny sheet metal electronic parts. Sheet metal pins, which are narrow and long, that are sheared with a progressive die set are often twisted. The twist in the sheet metal pins, which usually occurs in the final shearing operation, generally decreases with increasing blank holding force. The blank holding forces in all shearing operations are not the same because of different shearing positions and areas. In the current study, the optimal layout of the springs in a progressive die set to minimize the twist of the sheet metal pin is proposed. In order to find the holding force acting on the tiny narrow blanks produced with the proposed springs during the shearing process, the equivalent area method is used in the structural analysis. The shearing of the sheet-metal pin was simulated to compute the twist angle associated with the blank holding force. The constraint condition satisfying the pre-set blank holding force from the previous shearing operations was imposed. A design of experiments (DOE) was numerically implemented by analyzing the progressive die structure and by simulating the shearing process. From the meta-model created from the experimental results and by using a quadratic response surface method (PQRSM), the optimal layout of the springs was determined. The twist of sheet metal pin associated with the optimal layout of the springs found in the current study was compared with that of an existing progressive die to obtain a minimal amount of twist.
Micro Pattern Forming on Polymeric Circular Tubes by Hydrostatic Pressing
Rhim, S.H. ;
Transactions of Materials Processing, volume 23, issue 8, 2014, Pages 507~512
DOI : 10.5228/KSTP.2014.23.8.507
The objective of the current investigation is to establish techniques in micro pattern forming operations of polymeric circular tubes by using hydrostatic pressing. This method was developed and successfully applied to the micro pattern forming on polymeric plates. The key idea of the new technique is to pressurize multiple vacuum-packed substrate-mold stacks above the glass transition temperature of the polymeric substrates. The new process is thought to be a promising micro-pattern fabrication technique for two reasons; first, (hydro-) isostatic pressing ensures a uniform micro-pattern replicating condition regardless of the substrate area and thickness. Second, multiple curved substrates can be patterned at the same time. With the prototype forming machine for the new process, micro prismatic array patterns, 25um in height and 90 degrees in apex angle, were successfully made on the PMMA circular tubes with diameters of 5~40mm. These results show that this process can be also used in the micro pattern forming process on curved plates such as circular tube.