• Journal of the Korean Society for Precision Engineering
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• v.31 no.5
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• pp.395-401
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• 2014

Development of five axis tool grinding machine and CAD/CAM systems increase tool design flexibility. In this research, investigated are cutting characteristics of ball-end mill with different helix angle. Special WC ball-end mills with $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ helix angles are designed and used in various cutting tests. Machining performance according to helix angle variation is evaluated from cutting forces, surface roughness, tool wear, produced chip shape, and vibration characteristics. The ball-end mill with $10^{\circ}$ helix angle shows the best cutting performance due to appropriate chip load distribution and smooth chip flow. This research can be used for cutting edge geometry optimization and novel design of ball-end mill.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.292-300
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• 1995

According to the number of cold-rolled coils, the amount of roll wear and thermal expansion, and roll gap profile were calculated, by using the actual data from the finishing mill. Also, based on those data, the calculations of the deflection, the flattening, and the contact pressure of vwork rolls and backup rolls were made respectively. Specially, in the calculation of contact pressure, the numerical results were obtained not only during the normal rolling, but also during the abnormal rolling, by modeling mathematically the dynamic impact force which occurs when the head section of the strip is threading through rolls. With those results the growth of the fatigue region and the fatigue damage of rolls were predicted. Also the optimum roll-grinding depth was determined to maximize the roll life.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.109-115
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• 2001

This paper investigates the mechanical characteristics of angle-ply laminates with non-woven carbon tissue. The lami- nates were made by inserting non-woven carbon tissue at the interface. Specimens were rounded near the tabs by grinding and polishing to reduce the stress concentration. Cyclic loads were applied to the specimens and the stress and fatigue life curves were obtained. The matrix crack density was also evaluated to check the effects of non-woven carbon tissue on the fracture resistance of composite laminates. C-Sean technique was used to evaluate the delamination, and SEM was used to understand the fracture mechanisms of the laminates. Experimental results show that the fatigue strength and life of composite laminates were increased by inserting non- woven carbon tissues. The results also show that the matrix crack density and delamination area were reduced by inserting non-woven carbon tissues.

• Plant Journal
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• v.6 no.4
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• pp.63-71
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• 2010

The best way to prevent the corrosion of piston rod is a selection of quality of the material and method of construction which minimize the porosity. The high velocity oxy fuel(HVOF) method, which generates lower porosity than existing plasma spray, was applied to ceramic laminated bond layer. Porosity percentage fell to bellow 2%, lower than that of plasma spray at 7%. Coating material of ceramic-coated main layer was selected as the $Cr_2O_3$ affiliation material, which is more dense than $Al_2O_3$ affiliation. To fill up the pores formed after the coating process, we sealed the bond layer and main layer. Sealing process was performed twice, once after the coating and once after the grinding. Upon the anti-corrosion test on the sealed sample and on the non-sealed sample, it is confirmed that the sealed sample was not corroded for 1,000 hours while the non-sealed sample was corroded within 48 hours.

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.155-163
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• 2007

The control of the fuel to be introduced into the combustion chamber under idling and low-load conditions is known to be a problem in Diesel engines, owing to the relatively small fraction of the full-load fuel needed under light loads. Thus, particular attention should be paid to the behavior of the injector with reference to short injection events. This work presents the results of an experimental campaign carried out with two different types of common rail injectors, a standard injector and a modified one. The latter, coming from a simple modification realized in a standard injector, exhibits linear behavior between injected fuel and solenoid energizing time in the field of short injections. A direct comparison of the two injection behaviors suggests a possible way to better control short or pilot injections.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.1
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• pp.89-94
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• 2011

The swivel joint is an important part in hydraulic machine. The analysis on the material was made using the EDAX method to localize the swivel joint. Also, the modeling and design drawing were finalized with application of 3 dimensional measurement and structure analysis. The prototype product based on design drawing was made with cutting and grinding process. No abnormalities were found in the prototype product through the durability test and measurement. The localized swivel joint with light weight, price reduction and diversification was developed in this study.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.81-86
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• 2020

A ceramic vacuum chamber feedthrough ceramic insulator is made of Al2O3; the manufacturing process involves filling alumina powder into a urethane mold and pressing it with a rubber press to produce a molded body. Thereafter, manufacturing is completed through primary shape processing, sintering, and secondary shape processing in the green body, which is a pressurized molding body, This work is intended to prevent defects in the first shape processing by improving the ceramic insulator in the green body, and to improve the productivity of the ceramic insulator by determining the optimal processing conditions.

• Resources Recycling
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• v.31 no.2
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• pp.63-69
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• 2022

In this study, mechanical grinding using a planetary ball mill was performed under various conditions to evaluate its effect on the crystal structure of vanadium titanium magnetite (VTM) ore from the Kwain Mine in South Korea. The crystal structure of the activated product was also evaluated. Magnetite and ilmenite were identified as the main types of VTM ore used in the Kwain Mine, and the main types of gangue minerals were iron-based silicate minerals. According to the mechanical activation results, the crystallinity and crystal size decreased as the size of the grinding media (balls) decreased, and the amorphization of the sample/ball filling was significant as the amount of the sample was reduced. In addition, as the grinding speed and time increased, the crystal structure significantly changed, proving that these two parameters had a greater effect on the crystal structure than the ball size and sample/ball filling ratio.

• Journal of Mechanical Science and Technology
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• v.16 no.11
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• pp.1428-1434
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• 2002

The ball-on-disk type sliding tests with boundary lubricated steels were carried out to verify the effect of initial spacing in surface profiles on wear and scuffing. Three kinds of surface spacing, which are closely related with initial surface micro-cracks on sliding surfaces, were produced on AISI 1045 steel surfaces using different grinding and polishing processes. Frictional forces and time to scuffing were measured, and the shape and amount of wear particles were analyzed to compare the with original surface profiles. From the tests, it was confirmed that the size of wear particles are related closely to the original spacing of the surface profile. The time to failure and amount of wear were sensitive to the surface spacing. The wider surface spacing shows much longer sliding life and smaller amount of wear than the others. Time to scuffing was increased with increasing surface pro(lie spacing. The size of wear particles increased while the wear and wear rate K were decreased with an increase in surface spacing. After the sliding tests, surface cracks of inner parts of the wear track formed due to scuffing were observed and compared among the specimens having the different surface spacing.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.218-223
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• 2001

The chemical-mechanical polishing process was carried out for 2"-dia. sapphire wafer grown by horizontalBridgman method on the urethane lapping pad with the silica sol. The polished wafer shows the full-width at halfmaximum of 200~400 arcsec in double-crystal X-ray diffraction, indicating that the slicing, grinding and lapping processes before the polishing process affected the crystalline structural property of the wafer surface by the mechanical residual stress. For the inclusion of surface treatments after chemical-mechanical polishing such as the thermal annealing at the temperature of $1,200^{\circ}C$for 4 hrs. and chemical etching, the crystalline quality was sigdicantly enhanced with the reduced full-width at half maximum up to 8.3 arcsec.arcsec.