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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 13, Issue 8 - Dec 2004
Volume 13, Issue 7 - Nov 2004
Volume 13, Issue 6 - Oct 2004
Volume 13, Issue 5 - Aug 2004
Volume 13, Issue 4 - Jul 2004
Volume 13, Issue 3 - Jun 2004
Volume 13, Issue 2 - Apr 2004
Volume 13, Issue 1 - Feb 2004
Selecting the target year
FE Techniques for the Accurate Prediction of Part Dimension in Cold Forging
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 3~8
DOI : 10.5228/KSPP.2004.13.1.003
The improvement of dimensional accuracy for forged part is one of major goals in cold forging industry. There are many problems in controlling the dimension by the trial-and-error, especially for a precision forged gear. A FEM analysis has been used in developing the forging technology. However, FE techniques have to be reconfirmed for predicting accurately the dimension of forged part. In this study, the effects of elastic characteristics and temperature changes are investigated by the comparisons between experimental and FEA in cold forging. When FE models related with elastic characteristics are considered practically, FE results could predict the part dimension within the range of
. And if thermal effects also are considered additionally, the predicted dimensions are well coincided with the experimental down to about
Micro Forming of Bulk Metallic Glass using the Deformation Behavior in the Supercooled Liquid Region
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 9~14
DOI : 10.5228/KSPP.2004.13.1.009
Recently, various bulk metallic glasses (BMG's) having good mechanical and chemical properties were developed. BMG's can easily be deformed in the supercooled liquid region, via viscous flow mechanism. By using the viscous flow, the very low pressure is needed to deform the materials. In this study, we investigated the structural transition and deformation behavior of Vitreloy 1 (Zr/sub 41.2/Ti/sub 13.8/Cu/sub 12.5/Ni/sub 10/Be/sub 22.5/) using TMA and DSC. We applied the results to the micro forming process. The forming condition was chosen based on the viscosity data from TMA, and Si wafer with micro patterns on the surface was used as a forming die. The deformed surface was analyzed by SEM and 3D Surface Profiling System. The alloy showed good replication of the patterns. Quantitative measurement of roughness was useful to evaluate the replication. Surface condition of the deformed surface was determined by the initial surface condition.
Spring-back Evaluation of Automotive Sheets Based on Combined Isotropic-Kinematic Hardening Rule
;;;Chongmin kim;Michael L. Wenner;
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 15~20
DOI : 10.5228/KSPP.2004.13.1.015
In order to evaluate spring-back behavior in automotive sheet forming processes, a panel shape idealized as a double S-rail has been investigated. After spring-back has been predicted for double S-rails using the finite element analysis, results has been compared with experimental measurements for three automotive sheets. To account for hardening behavior such as the Bauschinger and transient effects in addition to anisotropic behavior, the combined isotropic-kinematic hardening law based on the Chaboche type model and a recently developed non-quadratic anisotropic yield function have been utilized, respectively.
A Study on the Unloading Stiffness of Instrumented Indentation Tests
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 21~26
DOI : 10.5228/KSPP.2004.13.1.021
Instrumented indentation tests have been used for estimating material properties. In order to analyze deformation characteristics with various factors, the unloading stiffness should be properly determined from the elastic behavior. The unloading stiffness is generally obtained from the shifted power functions fitting with the experimental unloading data. However, the functions often give rise to a poor representation of actual data, and also the unloading stiffness is governed by unloading condition. In this study, both numerical and experimental conditions to obtain proper unloading stiffness were investigated. The result showed that the amount of unloading ratio and hold time played an important role in fitting the unloading curves. The current efforts can successfully provide the unloading stiffness for indentation material properties.
Plastic Deformation Behavior of Al-Mg-Si Alloys at the Elevated Temperatures
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 27~32
DOI : 10.5228/KSPP.2004.13.1.027
Thermomechanical behavior of Al-Mg-Si alloys was studied to investigate the effect of microstructural features such as pre-existing substructure and distribution of particles on the deformation characteristics. The controlled compression tests were carried out to get the information on how the alloy responds to temperature, strain amount and strain rate. Then hot forging of Al-Mg-Si alloys carried out and analyzed by the comparison with the compression tests. Microstructural features after forging were discussed in terms of the thermomechanical response of Al-Mg-Si alloys. As already well mentioned, we found that the deformation of Al-Mg-Si at the elevated temperature brought the recovered structure on most conditions. In a certain time, however, abnormally large grains were found as a result of deformation assisted grain growth, which means that hot forging of Al-Mg-Si alloys could lead to a undesirable microstructural variation and the consequent mechanical properties such as fatigue strength.
Automatic Surface Generation for Extrusion Die of Arbitrarily Shaped Section using B-spline Surfaces and Scalar Field Theory
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 33~38
DOI : 10.5228/KSPP.2004.13.1.033
A new approach for the design of extrusion die surface of arbitrarily shaped section is presented. In order to generate the extrusion die surface. an automatic surface construction method based on B-spline surface and scalar field theory is proposed. The isothermal lines and stream lines designed in the scalar field are introduced to find the control points which are used in constructing B-spline surfaces. Intersected points between the isothermal lines and stream lines are used to construct B-spline surfaces. The inlet and outlet profiles are precisely described with B-spline curves by using the centripetal method for uniform parameterization. The extrusion die surface is generated by using the cubic curve interpolation in the u- and v-directions. A quantitative measure for the control of surface is suggested by introducing the tangential vectors at the inlet and outlet sections. To verify the validity and effectiveness of the proposed method, automatic surface generation is carried out for extrusion dies of arbitrarily shaped sections.
Modeling of Passive Heating for Replicating Sub-micron Patterns in Optical Disk Substrates
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 39~44
DOI : 10.5228/KSPP.2004.13.1.039
Transcribability of pit or land groove structures in replicating an optical disk substrate greatly affects the performance of a high-density optical disk. However, a solidified layer, generated during the polymer filling, deteriorates transcribability because the solidified layer prevents the polymer melt from filling the sub-micro patterns. Therefore, the development of the solidified layer during filling stage of injection molding must be delayed. For this delay, passive heating by insulation layer has been used. In the present study, to examine the development of the solidified layer delayed by passive heating, the flow of polymer melt with passive heating was analyzed. Passive heating markedly delayed the development of the solidified layer, reduced the viscosity of the polymer melt, and increased the fluidity of the polymer melt in the vicinity of the stamper surface with the sub-micro patterns. As a result, we predict that passive heating can improve transcribability of an optical disk substrate. To verify our prediction, we fabricated an optical disk substrate by using passive heating of a mold and measured the transcribability of an optical disk substrate.
Effect of Ball End Mill Cutting Environments on Machinability of Hardened Tool Steel
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 45~52
DOI : 10.5228/KSPP.2004.13.1.045
This research conducted milling tests to study effects of cutting environment conditions of ball end mills on the characteristics of hard milling process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAlN coated were utilized in the cutting tests. Dry cutting without coolant and semi-dry cutting using botanical oil coolant were conducted and MQL(Minimum Quantity Lubricant) device was used to spray coolant. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that dry cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than MQL spray cutting did.
Microstructural Characterization of Hot Extruded Al-Zn-Mg-Cu Alloys Containing Sc
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 53~58
DOI : 10.5228/KSPP.2004.13.1.053
The microstructural changes of Al-Zn-Mg-Cu alloy containing Sc during hot extrusion and post heat treatment were investigated. Two kinds of Al-Sc alloys with different alloying elements (B1, B2) were hot extruded to make T-shape bars at extrusion temperature of
, then the bars were solution treated at
for 2hrs followed by artificial aging at
for 24hrs. The interior microstructure of as extruded bar consisted of elongated grains, however, fine equiaxed grains were also observed around surface. The microstructural gradient suggested that different restoration process could proceed during the hot extrusion. For B1 and B2, different grain growth behaviors were found around the surface during the post heat treatment. Rapid grain growth behavior was observed for B1 around the surface, however, it was not observed for B2. Orientation pinning, which was related with the evolution of preferred orientation, and precipitation were thought to be responsible for the rapid grain growth.
Nanotribology of PMMA Thin Films Using an AFM
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 59~64
DOI : 10.5228/KSPP.2004.13.1.059
Nano-scratch tests were performed on PMMA thin films spin-coated on a Si substrate using an atomic force microscopy (AFM) with loads ranging form 10nN to 100nN. At low loads, a ridge pattern was formed on the PMMA thin film surface. No wear particles were observed during the pattern-forming mild wear. At high loads, severe wear by plowing occurred, accompanied by wear particles. The film with the highest hardness showed the highest wear resistance. Friction force generated during the scratching was measured, which was closely related with surface deformation of the film. A simple empirical equation to deduce scratch hardness of the film from a linear fixed-distance scratch test was proposed, and scratching-speed dependency of the scratch hardness was displayed.
Thickness Effect of Double Layered Sheet on Burr Formation during Micro-Via Hole Punching Process
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 65~71
DOI : 10.5228/KSPP.2004.13.1.065
Recent electronic equipment becomes smaller, more functional, and more complex. According to these trends, LTCC(low temperature co-fired ceramic) has been emerged as a promising technology in packaging industry. It consists of multi-layer ceramic sheet, and the circuit has 3D structure. In this technology via hole formation plays an important role because it provides an electric path for the packaging interconnection network. Therefore via hole qualify is very important for ensuring performance of LTCC product. Via holes are formed on the green sheet that consists of ceramic(before sintering) layer and PET(polyethylene terephthalate) one. In this paper we found the correlation between hole quality and process condition such as PET thickness and ceramic thickness. The shear behavior of double layer sheet by micro hole punching which is different from that of single layer one was also discussed.
Fracture Behavior of Oxide Scales and Influence of Oxide Scales on the Strength of Materials
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 72~77
DOI : 10.5228/KSPP.2004.13.1.072
An Fe-25Cr steel was oxidized in Ar atmosphere at 973K with and without applying external stress of 30∼35 MPa. A 0.1
scales formed during pre-treatment in Ar atmosphere. Initiation of cracking on the oxide scales took place at grain boundaries during the end of second creep stage, in which cracks were found nearly perpendicular to the tensile directions. On the contrary, a scale developed in
displaced a poor adherence on the metal substrate. In this sample, a fast grown of scales was observed during creep deformation, and the strength of materials was much lower than in Ar. The creep strain rate of
was determined in Ar and in
under 30MPa, respectively.
A Study on Multi-Filament Drawing of Bi2223 High-Temperature Superconductivity Wire by FE Method
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 78~83
DOI : 10.5228/KSPP.2004.13.1.078
High-temperature superconduction materials(Bi2223) possess electrical/electronic and magnetic properties. Because high-temperature superconduction materials is a ceramic powder, that cannot be produced singlehandedly. So Ag sheathed Bi-2223 wire was produced by drawing process using powder-in-tube(PIT) method. This superconductor has many difficulties to produce. The main difficulty is that the mechanical properties of the ceramic powder are very different from those of the Ag sheath. And by these properties, Bi2223 high-temperature superconductor, which has a single filament drawing process and multi-filament drawing process, has a defect like sausaging and bursting at a center. This study analyzed multi-filament drawing process by FEM, and a defect generated during multi-filament drawing was studied by FEH. Specially, in order to prevent a bursting at a center, this study presented a method that inserts a pure Ag at a center of multi-filament wire
A Study on the Cold Formability of Drawn Dual-Phase Steels
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 84~89
DOI : 10.5228/KSPP.2004.13.1.084
There is a growing interest to replace the commercial steels with non-heat treated steels, which does not involve the spheroidization and quenching-tempering treatment. However, Non-heat treated steels should satisfy high strength and good formability without performing heat treatment. Therefore, it is important to investigate optimum materials showing a good combination of strength and formability after the drawing process. In this study, Dual-Phase Steels were studied as candidate materials for non-heat treated steels, which have different martensite morphologies and volume fractions obtained through heat-treatment of intercritical quenching (IcQ), intermediate quenching (ImQ) and step quenching (SQ). The mechanical properties of DP steels were measured by tension and compression tests. Also, the cold formability of three DP steels which have similar tensile strength value was investigated by estimating the deformation resistance and the forming limit. The deformation resistance which is important factor in determining die life was estimated by calculating the deformation energy. And the forming limit was estimated by measuring the critical strain revealing crack initiation at the notch tip of the specimens.
A Study on the Generation of Initial Shape for the Initiation of Optimal Blank Design Sequence
Transactions of Materials Processing, volume 13, issue 1, 2004, Pages 90~101
DOI : 10.5228/KSPP.2004.13.1.090
An inverse mosaic method has been proposed to generate an initial blank shape from the final product shape. Differently from the geometric mapping method, the method can handle triangular patches. However, the generated blank shape is strongly dependent on the order of determination of nodes. In order to compensate the dependency error smoothing technique has been also developed. Although the accuracy has been improved greatly compared with the geometrical mapping method, the method has limitation, due to the no incorporation of plasticity theory. Even though the accuracy of the radius vector method is already proved. the method requires initial guess to start the method. In order to compromise the limitation of the present method and the radius vector method, the method has been connected to the radius vector method. The efficiency of the present optimal blank design method has been verified with some chosen examples.