• 한국분말재료학회지
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• 제21권4호
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• pp.307-312
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• 2014

This study is focused on investigating the relation between the particle size of silver flake powder and mechanical milling parameters. Mechanical milling parameters such as ball size, impeller rotation speed and milling time of the attrition ball-mill were controlled to produce silver flake powder. The particle size of the silver flake powder increased with increasing ball size and impeller rotation speed. The change of the particle size of the silver flake powder with mechanical milling parameters was analyzed based on balls motion in the mill container of the attrition ball-mill. The silver flake particles were formed at the elastic deformation area of the ball due to the collision between balls. The change of the particle size of the silver flake powder with mechanical milling parameters well consists with the change of the collision energy of ball with parameters mentioned above.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1789-1794
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• 2003

As a new approach to analyze shear behaviors in the shear plane and chip-tool friction behaviors in the chip-tool contact region during an end milling process, this paper introduces a method to transform an end milling process to an equivalent oblique cutting process. In this approach, varying undeformed chip thicknesses and cutting forces in the up-and down-end milling process are replaced with the equivalent ones of oblique cutting. Accordingly, in the current paper, the shear and friction characteristics of end milling operations, up- and down-end milling, have been analyzed based on the equivalent oblique cutting models. Two series of cutting tests, up- and down-end milling tests and the equivalent oblique cutting tests to that, have been carried out to verify the validity of the analyses. And using the results of cutting tests the cutting characteristics of the up- and down-end milling processes have been thoroughly investigated.

• 대한금속재료학회지
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• 제49권6호
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• pp.454-461
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• 2011

In this study, the relationship between corrosion resistance and microstructural characteristics such as grain size reduction, preferred orientation, and homogenous distribution of elements and impurity by mechanical milling of magnesium powder was investigated. Mechanical milling of pure magnesium powder exhibited a complex path to grain refinement and growth together with preferred orientation reversal with milling time. It was also found that anisotropic formation of dislocation on the basal plane of magnesium was initially the dominant mechanism for grain size reduction. After 60 hrs of milling, grain coarsening was observed and interpreted as a result of the strain relaxation process through recrystallization. In spite of the finer grain size and strong (002) texture developed in the sample prepared by spark plasma sintering at $500^{\circ}C$ for 5 min after mechanical milling for 2hrs, the sample showed a higher corrosion rate. The results from this study will be helpful for better understanding of the controlling factor for corrosion resistance and behaviors of mechanical milled magnesium powders.

• 한국분말재료학회지
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• 제18권6호
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• pp.496-501
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• 2011

In this study, the effect of milling time on the microstructure and phase transformation behaviors of Ni-12 wt.%B powders was investigated using vibratory ball milling process. X-ray diffraction patterns showed that the phase transformation of mixed Ni-B elemental powder occurred after 50 hours of milling, with a formation of nickel boride phases. Through the study of microstructures in mechanical alloying process, it was considered that ball milling strongly accelerates solid-state diffusions of the Ni and B atoms during mechanical alloying process. The results of X-ray photoelectron spectroscopy showed that most of B atoms in the powder were linked to Ni with a formation of nickel boride phases after 200 hours of milling. It was finally concluded that mechanical alloying using ball milling process is feasible to synthesize fine and uniform nickel boride powders.

• 한국기계가공학회지
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• 제12권3호
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• pp.76-80
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• 2013

This paper reports some experimental results on the machining performance of ground & non-ground milling inserts. Five kinds of milling inserts were manufactured without grinding process and one milling insert was manufactured with grinding process. Machining experiments were carried out to compare the performance of ground & non-ground inserts. This experimental result indicate that tool wear, cutting force and surface roughness of the each tool. From the result five milling inserts that have non-grinding process and one milling insret that have grinding process compared appear.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1520-1527
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• 2001

In end milling process the undeformed chip thickness and the cutting force components vary periodically with phase change of the tool. In this study, up end milling process is transformed to the equivalent oblique cutting. The varying undeformed chip thickness and the cutting force components in end milling process are replaced with the equivalent average ones. Then it can be possible to analyze the chip-tool friction and shear process in the shear plane of the end milling process by the equivalent oblique cutting model. According to this analysis, when cutting SM45C steel, 72% of the total energy is consumed in the shear process and the balance is consumed in the friction process.

• 대한기계학회논문집A
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• 제29권7호
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• pp.1022-1027
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• 2005

In this study, ball milling process was applied to reduce the particle size of bio-material down to submicron size. The material used was Ibuprofen. The ball milling was performed at low temperature of about $-180^{\circ}C$. The effect of processing conditions (milling time, milling speed) on the particle size was determined. The results showed that the degree of crystallite of Ibuprofen was slightly reduced by the ball milling process. The results also showed that the size of Ibuprofen was significantly reduced by the ball milling process. The effect of milling time was significant within the milling time of six hours while it was small thereafter.

• 한국분말재료학회지
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• 제23권1호
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• pp.54-60
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• 2016

This study focuses on fabricating silver flake powder by a mechanical milling process and investigating the formation of flake-shaped particles during milling. The silver flake powder is fabricated by varying the mechanical milling parameters such as the amount of powder, ball size, impeller rotation speed, and milling time of the attrition ballmill. The particle size of the silver flake powder decreases with increasing amount of powder; however, it increases with increasing impeller rotation speed. The change in the particle size of the silver flake powder is analyzed based on elastic collision between the balls, taking energy loss of the balls due to the powder into consideration. The change in the particle size of the silver flake powder with mechanical milling parameters is consistent with the change in the diameter of the elastic deformation contact area of the ball, due to the collision between the balls, with milling parameters. The flake-shaped silver particles are formed at the elastic deformation contact area of the ball due to the collision.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.223-228
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• 2003

In end milling processes, characterized by use of rotating tools, the underformed chip thickness varies periodically with the phase change of tool. In current study, as a new approach to analyse shear behaviors In the shear plane and chip-tool friction behavior chip-tool contact region during an end milling process. In this approach, an up-end milling process is transformed into an equivalent oblique cutting process. Experimental investigations for two sets of cutting tests i.e.. up-end milling and the equivalent oblique cutting test were performed to verify the presented model.

• 한국정밀공학회지
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• 제27권7호
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• pp.49-54
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• 2010

The cryogenic ball milling was performed on carbon nanotubes (CNTs) at an extremely low temperature to increase the dispersion of CNTs. The effects of milling speed and time on the deagglomeration and structural changes of CNTs were studied. FESEM was used to analyze the dispersion and the change of particle size before and after milling process. Transmission electron microscopic (TEM) analysis was also investigated the effect of cryogenic ball milling on the morphological characteristics of CNTs. The structural changes by the cryogenic ball milling process were further confirmed by x-ray diffraction (XRD) and Raman spectroscopic analysis. The results showed that the agglomeration of CNTs was significantly reduced and amorphous structure was observed at high milling speed. However, the milling time has no great effect on the dispersion property and structural change of CNTs compared with milling speed.