• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.26-30
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• 2003

Since the dimension of cold forged part is larger than the cavity size of forging die, the difference results from the various features, such as, the elastic characteristics of die and workpiece, thermal influences, and machine-elasticity. All of these factors should be considered to get more accurate prediction of the dimension of forged part. In this paper, severe FE techniques are proposed to improve the prediction accuracy of dimension for cold forged part. To validate the importance of the above mentioned factors, and the estimated results are compared with the experimental results. The used model is a closed die upsetting of cylindrical billet. The calculated dimensions are well coincided with .the measured values based on the proposed techniques. The proposed techniques have put two simple but important points into Fe simulation. One is the separation of forging stages into 3 steps, from a loading through punch retraction to ejecting stage. The other is the dimensional change, according to the temperature changes due to the deformation. The FE analysis could predict the dimension of cold forged part within the $10{\mu}m$, based on the more realistic consideration.

• Transactions of Materials Processing
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• v.28 no.6
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• pp.361-367
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• 2019

Microstructure evolution and tensile properties of Al-8mass%Mg alloy casting billet by biaxial alternative forging were investigated in this study. An alternative forging system tailored in this study was used to allow continuous strain accumulations on the alloy workpiece. A finite element (FE) simulation results revealed that the strain was mainly concentrated in the core and that the shear bands developed into a form with an X shape in the cross-section of workpiece after the alternative forging using octangular rod shaped dies. With increasing the forging passes, it was observed that the Al-8mass%Mg alloy workpieces were significantly deformed, and cracks began to form and propagate on the both ends of the forged workpieces after five passes at room temperature. In as-forged microstructures taken by microscopes, twins, clustering of dislocations, and fine subgrains were found. Tensile strengths of the forged specimens showed significant increases depending on the number of forging passes, and a trade-off relationship was observed between the elongation and strength. At room temperature and 100℃ the workpieces showed similar behaviors in microstructural evolution and tensile properties depending on forging passes, while the increase range in strength was reduced at 200℃.

• Journal of Technologic Dentistry
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• v.41 no.4
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• pp.255-262
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• 2019

Purpose: Recently, the production technology of dental prosthesis using 3D Printer workpeices has been developed. However, the lack of information on the work processes and casting techniques of materials for 3D printing casting is expected to require research. Therefore, in this study, we intend to cast a Dental DLP 3D Printer workpiece, which is being commercialized, to identify its appearance and internal clearance, and to observe its castability. Methods: Castability of the 3D Printer workpiece was evaluated. The specimen is prepared in a cylindrical shape and in a 1 mm thick coping shape. The control specimen is made of wax and the experimental specimen is made of resin using two types of 3D printers. After casting, the appearance of the casting body was observed and the internal clearance of the coping was measured. Results: RP1 and RP2, cylindrical specimens, were partially cast or fin. When coping-type specimens were measured before casting, the internal clearance of PE2 was more accurate than that of PC and PE1. When coping-type specimens were measured after casting, CE1 was the most accurate in occlusal clearance and CE2n was the most accurate in axial clearance. Conclusion: 1. Exterior observations of the casting body indicated casting defects and fins. 2. Internal clearance observations show that the occlusal clearance of the castings is larger after casting, and the axial clearance of the castings is smaller after casting. 3. It is judged that the RP2 specimen is more likely to be applied for casting than the RP1 specimen.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.51-57
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• 2001

A light beam reflected from a machined surface generally containes information concerning about its surface roughness. This study examines and proposes a surface roughness measurement technique for on-machine measurement of machined surfaces. The technique is based on the measurement of a reflected laser beam pattern and the statistical analysis of its light intensity distribution. The surface roughness was found to be closely related to the standard deviation of the light intensity on the primary axis of the reflected pattern. An image acquisition device is made up of a laser diode, a half mirror, a screen, and a CCD camera. The exact image with the primary and secondary axes of a reflected laser beam pattern is calculated through such image processing algorithm as thresholding, edge detection, image rotation, segmentation, etc. A median filter and a surrounding light correction algorithm are improve the image quality and reduce the measuring error. Using the developed measuring device the effect of screen materials and workpiece and workpiece materials was investigated. Experimental results regarding to relatively high-quality surfaces machined by grinding, polishing, lapping processes have shown the measurement error is within 10% in the range of $0.1{mu}m~0.8{\mu}m R_q.$Therefore, the proposed method is thought to be effectively used when quick measurements is needed with workpieces fixed on the machine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.22-28
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• 2022

In the semiconductor and display component industries, the use of ceramic materials, which are high-strength materials, is increasing for ensuring durability and wear resistance. Among them, alumina materials are used increasingly. Alumina materials are extremely difficult to process because of their high strength; as such, research and development in the area of mineral material processing is being promoted actively to improve their processing. In this study, the processability of an electrodeposition tool is investigated using the electrodeposition method to smoothly process alumina materials. Furthermore, processing is conducted under various processing conditions, such as spindle speed, feed speed, and depth of cut. In addition, the processing characteristics of the workpiece are analyzed based on the tooling.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.197-198
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• 2002

In order to produce micromachined parts with a great dimensional accuracy, it is important to clarify the influence of heterogeneity and/or discontinuity of workpiece materials on the micromachining process, because almost all structural materials are composed of heterogeneous and/or homogeneous crystal grains at the micro scale. Experiments where JIS S25C steel had been scratched with a diamond triangular pyramid indenter were conducted under a field emission scanning electron microscope (FE-SEM). The difference of plastic deformation at a groove scratched between a pearlite zone and a proeutectoid ferrite zone was investigated through comparison with the groove scratched of a pearlite zone and a proeutectoid ferrite zone.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.785-792
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• 1994

Ferrite is widely used in the material of magnetic head, but is difficult of grinding because of their brittleness and hardness. Therefore, diamond wheel with superabrasive is required for surface grinding of this brittle material. But the conventional dressing method can not apply to the diamond wheel with superabrasive. In this study describes a newly proposed method for carrying out effective inprocess dressing of diamond wheel with superabrasive. Using the IEDD the surface roughness of workpiece was improved and grinding force was very low. Resently IEDD is good method to obtain the efficiency grinding and surface grinding of brittle materials.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.4 no.3
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• pp.12-24
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• 1995

Various surface grinding experiments using resin bonded diamond abrasive wheels are carried out for tungsten carbide materials in order to minimize the damage on the ground surface and to purse the precise dimension compared to conventional grinding machine. When grinding quality is constant, theoretical grinding effect is changed according to the speed of workpiece. Accordingly, grinding forces, which are Fn, Ft, were analyzed for the machining processes of tungsten-carbide material to obtain optimum grinding conditions. Brief investigation is carried out to decrease the dressing efficiency of resinoid bonded diamond grinding wheel to grind tungsten-carbide. Truing is also carried out to provide a desired shape on a wheel or to correct a dulled profile. High quality in dimensional accuracy and surface are often required as a structural components, therefore 3-points bending test is carried out to check machining damage on the ground surface layer, which in one of sintered brittle material. From this experimental study, some useful machining data and information to determine proper machining condition for grinding of tungsten-carbide materials are obtained.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.190-195
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• 1997

The requirement of precision products about difficult-to-cut materials such as Cu and Aluminum alloy is becoming more and more. Because of soft materials, the exist narrow groves on surface are difficult to gotten off even on the polishing stage. It has been proved that Magnetic-Electrolytic-Abrasive Polishing (MEAP) is a efficient method to resolve this problem by using the nonwoven-abrasive pads together [1, 2]. In this study, through the experiments, their machining properties of newly developer polishing material of SiC, Al2O3 and diamond nonwoven abrasive pads have been proved. Through the experiments, the optimal machining conditions on larger cylinder shape workpiece of Cu and Aluminium alloy have been found, through the Taguchi[3] method the optimal machining conditions can be selected.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.5
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• pp.461-466
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• 2013

In this paper, main mechanism and measurement method of energy consumption for machine tools are investigated by experiment and simulation. To evaluate total energy consumption of the machine tools, standard test workpiece and measuring method and test procedures are suggested. And, improvement of energy consumption evaluation by the motion kinematics theory is used. In addition, to estimate energy consumption of machine tools in design process, mass distribution of the structure and 5 axis motions are investigated and simulated by numerical analysis.