• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.67-71
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• 2003

A hot press method was used to create the optimal fabrication condition for a Shape Memory Alloy(SMA) composite. The bonding strength between the matrix and the reinforcement within the SMA composite by the hot press method was more increased by cold rolling. In this study, the objective was to develop an on-line monitoring system in order to prevent the crack initiation and propagation by shape memory effect in SMA composite. Shape memory effect was used to prevent the SMA composite from crack propagation. For this system an optimal AE parameter should be determined according to the degree of damage and crack initiation. When the SMA composite was heated by the plate heater attached at the composite, the propagating cracks could be controlled by the compressive force of SMA.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.453-459
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• 2004

TiNi/ Al6061 shape memory alloy (SMA) composite was fabricated by hot press method to investigate the microstructure and mechanical properties. Interface bonding between TiNi reinforcement and A1 matrix was observed by using SEM and EDS. Pre-strain was imposed to generate compressive residual stress inside composite. A tensile test for specimen, which under-went pre-strain, was performed at high temperature to evaluate the variation of strength and the effect of pre-strain. It was shown that interfacial reactions occurred at the bonding between matrix and fiber, creating two inter-metallic layers. And yield stress increased with the amount of pre-strain. Acoustic Emission technique was also used to nondestructively clarify the microscopic damage behavior at high temperature and the effect of pre-strain of TiNi/ Al6061 SMA composite.

• 한국분말재료학회지
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• 제9권2호
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• pp.103-109
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• 2002

To investigate the fabrication possibility of a polymer particle dispersed metal matrix composite, polytetrafluorothylene (PTFE) particles were incorporated into the Al by the powder metallurgy process. The characteristics of a PTFE/Al composite were evaluated by measuring the density and hardness, and analysis of XRD, FT-Raman and microstructure. And wear properties of these composites were evaluated under the dry wear condition. It was possible to obtain the PTFE particles stably dispersed Al matrix composites by the hot press process at the sintering temperature of $500^{\circ}C$. The wear coefficient of a PTFE/Al compoite decreased with increasing of the volume fraction of PTFE. The wear weight of a PTFE/Al composite increased with increasing of the volume fractionof PTFE in the range of 0~10 vol.%PTFE, and showed maximum value at 10 vol.%PTFE, and then decreased at 20vol.%PTFE.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.277-280
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• 2008

Recently, a demand of nano/micro patterned polymer for display or biochip has been rising. Then many studies have been carried out. Nano/micro-embossing is a deformation process where the workpiece materials is heated to permit easier material flow and then forced over a planar patterned tool. In this work, the hot-emboss process is performed with different forming conditions; forming temperature, load, press hold time, to get the proper condition for linear pattern fabrication on plated-type polymers (PC). Replicated pattern depth increases in proportion to the forming temperature, load and time. Reduction of the workpiece thickness increases according to press hold time. In process of time, reduction ratio of workpiece thickness decreases because of surface area increment of the workpiece and pressure decline on it.

• 대한금속재료학회지
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• 제50권6호
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• pp.433-438
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• 2012

Strength change in ultra low carbon steel carburized at $880^{\circ}C$ and $930^{\circ}C$ for 10, 30, 60 and 120 minutes was investigated. The results were analyzed by a tensile test, chemical composition analysis, optical microscopy and scanning electron microscopy. Stress in the 0.5% strain specimen in the tensile test increased as the time treated at $880^{\circ}C$ and $930^{\circ}C$ increased, because the carbon diffusion layer and the martensite of the specimen increased with increasing treatment time. Martensite was found in the ferrite region in the specimen treated at $880^{\circ}C$, which is attributed to grain boundary diffusion.

• 대한금속재료학회지
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• 제50권12호
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• pp.883-889
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• 2012

Carbon diffusion of ultra low carbon steel treated at $880^{\circ}C$ and $930^{\circ}C$ for 10, 30, 60 and 120 minutes was investigated using optical microscopy, SAM, EPMA, and Micro Vickers. The martensite patterns of the specimens treated at $880^{\circ}C$ and $930^{\circ}C$ were different. Martensite in the ferrite region was found in the specimen treated at $880^{\circ}C$ because of grain boundary diffusion. Such phenomena is explained by a carbon diffusion model.

• 한국가구학회지
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• 제12권2호
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• pp.29-38
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• 2001

This study was carried out to develope a new process of flattening bamboo pieces(3 months old) by two steps of utilizing microwave oven and hot press. Internode bamboo pieces were impregnated with low molecular weight phenol formaldehyde resin (PF) under vacuum of 76 cmHg, heated in a household microwave oven in 1 minute, pressed on the temperature of $145^{\circ}C$ by the hot press for 10 minute, and then cooled by the cold press in their flattened form. The physical and mechanical . Properties of compressed flattened bamboo were as follows: 1) PF1(Mw:427) and PF2(Mw:246) sol. met the success of flattening of internode bamboo pieces in both of P. bambusoides and P. nigra var. PF2 showed the more plasticity to flatten the bamboo than PFI. The PF2 sol. with low molecular weight(Mw:246) gave the more weight gain than that of PF1 in the equal concentration. PF1 of 5% (NVC) and PF2 of 10% (NVC) sol. gave the best result for physical and mechanical properties and from a economical view point. 2) The PFI of 5% (NVC) sol. with low molecular weight decreased the water absorption of 62-63% and increased the bending strength (MaR) of 80-90%, compression strength of 43-54%. 3) The PF2 of 10% (NVC) sol. with low molecular weight decreased the water absorption of 56-57% and increased the bending strength (MaR) of 64-86%, compression strength of 39-63%.

• Advances in concrete construction
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• 제6권3호
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• pp.285-296
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• 2018

In the present paper, the results of an experimental study of the bond between repair materials and mortar substrate subjected to hot climate is presented. Half-prisms of size $40{\times}40{\times}80mm$, serving as a substrate mortar samples (SUBM) were manufactured in the laboratory and then stored at an ambient temperature for 6 months. Five self compacting mortar mixes (SCMs) incorporating 0%, 10%, 20%, 30%, and 40% of natural pozzolana as white cement replacement were used as repair materials. Repaired composite samples (SCMs/SUBM) were cured at hot climate for different lengths of time (28 and 56-days). During the first week of curing, the composite samples were watered twice a day. The test carried out to assess the bond between SCMs and SUBM was based on three-point bending (3 PB) test. The obtained results have proved that it was feasible to produce compatible repair materals in this curing environment by using up to 30% natural pozzolana as white cement replacement.

• 소성∙가공
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• 제10권1호
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• pp.30-34
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• 2001

The magnetic and metallurgical characteristics of Mischmetal(MM) -Ferroboron (FeB) Permanent magnets have been investigated by X-ray diffractometer, scanning and transmission electron microscope and vibrating sample magnetometer under hot-pressing and die-upsetting process. The best magnetic properties obtained in these studies were $H_c$=5.8 kOe, $B_r$=5.0 kG with $(BH)_{max}=7.6 MGOe for melt-spun ribbons, $H_c$=3.0 kOe, $B_r$=4.6 kG with $(BH)_{max}$=2.9 MGOe for hot-pressed magnets and $H_c$=1.8 kOe, $B_r$=5.5 kG with $(BH)_{max}$=4.1 MGOe for die-upset magnets. The higher magnetic properties in die-upset magnets were resulted from alignment of the c-axis along the die-upsetting direction.

• 한국정밀공학회지
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• 제11권2호
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• pp.104-109
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• 1994

This research describes some developments of computer-aided process planning and die design for hot forging products of H-shaped plane strain produced by the press. The system is composed of three main modules(process planning module, die design module and simulation module) which are used independently or in all. Systm capabilities include as follows: 1. In die design module, using the results of process planning module, the shape and size of bolcker and finish die in each operation are determined and the ouput id generated in graphic form for manufacturing drawing. 3. In simulation module, the flow pattern of workpiece and the load/stroke curve are approximately predicted. Design rules for process planning and die design are extracted from plasticity theories, handbooks, relevant references and empirical know-how of field experts in hot forging companies. The developed system provides poweful capabilities for process planning and die design of hot forging products.