• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.69-74
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• 1998

In order to monitor the tool wear in milling operation, cutting force is measured as the tool wear increased. The digital signal processing methods are used to detect the tool wear . As AR parameter extract the feature of tool wear , it can be used as input parameter of pattern classifier. The FFT monitor the tool wear exactly , but it can not do real time signal processing. The band energy method can be used to real time monitoring of tool wear ,but int can degrade the exact monitoring.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.101-103
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• 2000

In the present work, we have investigated the combined effect of high-energy milling and Agb addition on microstructure and superconducting properties for Bi-2223/Ag. tape. The addition of siver plays an important role in enhancing liquid phase formation, Resulting in densification and cracking during solidification. Further study is needed for the optimization of Ag content and heat-treatment which can reduce the cracking.

• Journal of the Korean Ceramic Society
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• v.30 no.8
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• pp.623-628
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• 1993

Lead monoxide has two phases at room temperature. One is a yellow orthorhombic phase, the other is a redtetragonal phase. Sometimes two phases are hybrided. The specificity of phase transitions of lead oxide is found during the milling of the batch including lead oxide. The pure orthorhombic phase of PbO can be transformed to the tetragonal phase perfectly by wet ball milling (milling liquid is distilled water) without thermal energy. However, when ethyl alcohol, isopropyl alcohol and aceton are used as milling liquid, respectively, the hybrid form of orthorhombic andtetragonal phases is obtained by wet ball milling. From the hybrid form heat-treated at $600^{\circ}C$ for 3hrs, this work results that mechanical phase transition of orthorhombic phase make a new form as distorted type orthorhombic phase of PbO.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.464-467
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• 1996

The microstructural evolution during mechanical alloying of Nb and Sn powders, of average composition Nb3Sn, has been investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). Observations by SEM showed a progressive change of milling time. From the XRD studies, the structural development with milling time depends on the ball size for a given powder/ball ratio. Using a larger ball of 9.5mm diameter, the elemental powders initially alloy mechanically to form an A15 structure phase, and then amorphised with continued milling. However, in case of milling with a smaller ball of 3.968mm diameter, an amorphous phase is first formed. These results can be understood by considering the dependence of the milling energy on the ball size. The homogeneous stoichiometric $Nb_3Sn$ phase could be easily obtained by heat treatment of a supersaturated solid solution produced by MA. Heat treatment of an amorphous phase formed by MA resulted in the mixture of the $Nb_3Sn$ and $Nb_6Sn_5$ phases.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.1
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• pp.49-57
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• 1999

In order to study the effect of high energy ball milling on the $Mg_2Ni+Ni$, $Mg_2Ni+0.5Ni+0.5Al$ powders, we have investigated on the discharge properties, microstructures. The powder size of samples decreased as ball milling time. From the XRD results, the crystal structure of $Mg_2Ni+Ni$ mixed powders were changed to amorphous or nano-structure after 60hr ball milling. The discharge capacities of both $Mg_2Ni+Ni$ and $Mg_2Ni+0.5Ni+0.5Al$ powders increased, with increasing ballmilling time, the maximum capacity(342mAh/g) was shown for the 60 hrs ballmilled $Mg_2Ni+Ni$ sample. The capacity decreased drastically after a few charge-discharge cycles.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.4
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• pp.353-358
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• 2015

Energy consumption reduction has become an important key word in manufacturing that can be achieved through the efficient and optimal use of raw materials and natural resources, and minimization of the harmful effects on nature or human society. The successful implementation of this concept can only be possible by considering a product's entire life cycle and even its disposal from the early design stage. To accomplish this idea with milling, minimum quantity lubrication (MQL) strategies and cutting conditions are analyzed through process modeling and experiments. In this study, a model to predict the cutting energy in the milling process is used to find the cutting conditions, which minimize the cutting energy through a Kriging meta-modeling process. The MQL scheme is developed first to reduce the amount of cutting oil and costs used in the cutting process, which is then employed for the entire modeling and experiments.

• Journal of Powder Materials
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• v.16 no.1
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• pp.9-15
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• 2009

Amorphization and crystallization behaviors of $Ti_{50}Cu_{50}Ni_{20}Al_{10}$ powders during high-energy ball milling and subsequent heat treatment were studied. Full amorphization obtained after milling for 30 h was confirmed by X-ray diffraction and transmission electron microscope. The morphology of powders prepared using different milling times was observed by field-emission scanning electron microscope. The powders developed a fine, layered, homogeneous structure with prolonged milling. The crystallization behavior showed that the glass transition, $T_g$, onset crystallization, $T_x$, and super cooled liquid range ${\Delta}T=T_x-T_g$ were 691,771 and 80 K, respectively. The isothermal transformation kinetics was analyzed by the John-Mehn-Avrami equation. The Avrami exponent was close to 2.5, which corresponds to the transformation process with a diffusion-controlled type at nearly constant nucleation rate. The activation energy of crystallization for the alloy in the isothermal annealing process calculated using an Arrhenius plot was 345 kJ/mol.

• Journal of Powder Materials
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• v.24 no.5
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• pp.406-413
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• 2017

A Nanosized $WO_3$ and CuO powder mixture is prepared using novel high-energy ball milling in a bead mill to obtain a W-Cu nanocomposite powder, and the effect of milling time on the structural characteristics of $WO_3-CuO$ powder mixtures is investigated. The results show that the ball-milled $WO_3-CuO$ powder mixture reaches at steady state after 10 h milling, characterized by the uniform and narrow particle size distribution with primary crystalline sizes below 50 nm, a specific surface area of $37m^2/g$, and powder mean particle size ($D_{50}$) of $0.57{\mu}m$. The $WO_3-CuO$ powder mixtures milled for 10 h are heat-treated at different temperatures in $H_2$ atmosphere to produce W-Cu powder. The XRD results shows that both the $WO_3$ and CuO phases can be reduced to W and Cu phases at temperatures over $700^{\circ}C$. The reduced W-Cu nanocomposite powder exhibits excellent sinterability, and the ultrafine W-Cu composite can be obtained by the Cu liquid phase sintering process.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.418-425
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• 2011

In this study, a high energy ball milling process was introduced in order to improve the densification of direct nitrided AlN powder. The sintering behavior and thermal conductivity of the AlN milled powder was investigated. The mixture of AlN powder and 5 wt% $Y_2O_3$ as a sintering additive was pulverized and dispersed by a bead mill with very small $ZrO_2$ bead media. The milled powders were sintered at $1700^{\circ}C-1800^{\circ}C$ for 4 h under $N_2$ atmosphere. The results showed that the sintered density was enhanced with increasing milling time due to the particle refinement as well as the increase in oxygen contents. Appropriate milling time was effective for the improvement of thermal conductivity, but the extensive millied powder formed more fractions of secondary phase during sintering, resulted in the decrease in thermal conductivity. The AlN powder milled for 10min after sintering at $1800^{\circ}C$ revealed the highest thermal conductivity, of 164W/$m{\cdot}K$ in tne densified AlN sintered at $1800^{\circ}C$.

• Journal of Powder Materials
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• v.17 no.6
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• pp.443-448
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• 2010

The $\beta$ phase Ti-Nb-Sn-HA bio materials were successfully fabricated by high energy mechanical milling and pulse current activated sintering (PCAS). Ti-6Al-4V ELI alloy has been widely used as biomaterial. But the Al has been inducing Alzheimer disease and V is classified as toxic element. In this study, ultra fine sized Ti-Nb-Sn-HA powder was produced by high energy mechanical milling machine. The $\beta$ phase Ti-Nb-Sn-HA powders were obtained after 12hr milling from $\alpha$ phase. And ultra fine grain sized Ti-Nb-Sn-HA composites could be fabricated using PCAS without grain growth. After sintering, the microstructures and phase-transformation of Ti-Nb-Sn-HA biomaterials were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The relative density was obtained by Archimedes principle and the hardness was measured by Vickers hardness tester. The $\beta$-Ti phase was obtained after 12h milling. As result of hardness and relative density, 12h milled Ti-Nb-Sn-HA composite has the highest values.