• 한국안전학회지
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• 제22권2호
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• pp.8-14
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• 2007

In this study, tensile and fatigue crack propagation tests machined from actual wheels were performed. FEM analysis also was performed on the crack that was assumed to be 15 mm in depth under the wheel tread surface. The stress intensity factors K I and K II at the crack tip under the stress($P_{max}=911.5MPa$) due to a rolling contact were analyzed for crack growth characteristics. As a result, the perpendicular crack was found to be more dangerous compared to the parallel one. It is found that in the wheel fatigue crack, parallel to the wheel tread surface, the crack with its length 2a = 2.4mm starts to propagate due to the fact that the effective stress intensity factor access to the threshold stress intensity factor($K_{th}=16.04MPa{\sqrt{m}}$) of the wheel.

• 한국자기학회지
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• 제5권5호
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• pp.795-799
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• 1995

The magnetostriction versus field (${\lambda}-H$) curves for the melt-spun ribbons of $Dy_{x}{(Fe_{1-y}B_{y})}_{1-x}$ (x=0.2, 0.25, 0.3; y=0, 0.05, 0.1, 0.15, 0.2) alloys are measured systematically at various wheel speeds ranging from 10 to 50 m/sec. The ${\lambda}-H$ curves in most cases vary sensitively with the wheel speed and, in the wheel speed range where no amorphous phase is formed, the magnetic softness improves rather continuously with the wheel speed. This result is considered to be due to the reduced grain size with increasing wheel speed, which was confirmed by X-ray diffraction and transmission electron microscopy. In particular, homogeneous and ultrafine grains with size of about 10 nm are formed even in the as-spun state when the $Dy_{0.3}{(Fe_{1-y}B_{y})}_{0.7}$ alloys are quenched at the wheel speed of 30 m/sec (for the alloy with y=0.2) or 40 m/sec (for the alloys with $y{\leq}0.15$) and the ribbons having the nanocrystalline grain structure exhibit good magnetostrictive characteristics.

• 한국정밀공학회지
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• 제16권6호
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• pp.58-65
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• 1999

The spinning machine has been developed for a bus and truck wheel disc which is manufactured by spinning process method. This machine has the mechanical structure with bed, 2-column, cross head, 2-vertical slide, 2-horizontal slide with forming roller, clamp slide and main spindle similar to large size vertical lathe. Main spindle attached the mandrel is rotated about 500rpm drived by 280kW power DC motor, and a rotating black material pressed on the mandrel with the clamp slide is spinformed by 2-forming rollers which are attached inner end of the 2-horizontal slides. The 2-vertical and 2-horizontal slides are actuated by the hydraulic cylinder which is controlled by the servo valve individially, and these servo valves are controlled by control signal of the CNC controller which is computed with position signal feedbacked from the encoder sensor. The developed machine can manufacture wheel disc of various section profile without mandrel change because section profile is easily modified using program editing in the CNC controller processor. The wheel disc manufactured by spinning process method has many advantages that the endurance is increased by 2 times and the weight is decreased by 30% compared with a conventional disc.

• Journal of Astronomy and Space Sciences
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• 제34권2호
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• pp.171-182
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• 2017

In this study, the internal structure of a Heumgyeonggak-nu (欽敬閣漏) was designed, and the power transmission mechanism was analyzed. Heumgyeonggak-nu is an automated water clock from the Joseon Dynasty that was installed within Heumgyeonggak (欽敬閣), and it was manufactured in the $20^{th}$ year of the reign of King Sejong (1438). As descriptions of Heumgyeonggak-nu in ancient literature have mostly focused on its external shape, the study of its internal mechanism has been difficult. A detailed analysis of the literature record on Heumgyeonggak-nu (e.g., The Annals of the Joseon Dynasty) indicates that Heumgyeonggak-nu had a three-stage water clock, included a waterfall or tilting vessel (欹器) using the overflowed water, and displayed the time using a ball. In this study, the Cheonhyeong apparatus, water wheel, scoop, and various mechanism wheels were designed so that 16 fixed-type scoops could operate at a constant speed for the water wheel with a diameter of 100 cm. As the scoop can contain 1.25 l of water and the water wheel rotates 61 times a day, a total of 1,220 l of water is required. Also, the power gear wheel was designed as a 366-tooth gear, which supported the operation of the time signal gear wheel. To implement the movement of stars on the celestial sphere, the rotation ratio of the celestial gear wheel to the diurnal motion gear ring was set to 366:365. In addition, to operate the sun movement apparatus on the ecliptic, a gear device was installed on the South Pole axis. It is expected that the results of this study can be used for the manufacture and restoration of the operation model of Heumgyeonggak-nu.

• 대한기계학회논문집A
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• 제24권2호
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• pp.319-328
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• 2000

This paper presents a new design method of the 1 generation wheel bearing unit using a numerical optimization technique in order to increase bearing fatigue life. For calculating the fatigue life, a method of load analysis is studied on the automotive wheel bearing system. The design variables selected are ball size, initial contact angle, number of balls, pitch diameter, pre-load, and distance between ball centers. The method of feasible directions in ADS (Automated Design Synthesis) is utilized to automatically find the optimum design variables. To validate the design method, a computer program is developed and applied to a practical passenger car model. The optimum design results demonstrated the effectiveness of the proposed design method showing that the system life of the optimally designed wheel bearing unit is enhanced in comparison with that of the initial ones within the given available design space.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.43-47
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• 2002

In this study, through the experimental results of grinding ratio, grinding force and surface roughness with the obtained wear amount of diamond wheel and ceramic material during the grinding process, the following conclusions could be found. In the case of $Si_3N_4$, the wear of diamond wheel is large while the grinding force is stable and the range of change in surface roughness is small. for the case of $AL_2O_3$ and $ZrO_3$, while the wear of diamond wheel is getting smaller, the grinding force is increasing but the value of surface roughness is decreasing. For grinding with the vitrified bond wheel, it seems that the self-sharpening can be found for $Si_3N_4$ and the glazing effect of the cutting edge for $AL_2O_3$ and $ZrO_3$.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.18-24
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• 2010

철도차량의 동특성 해석을 위한 기존의 연구는 대부분 2차원 접촉해석에 근거한 근사해법에 의존해 왔다. 최근에 휠-접촉해석에 대한 정확한 해를 구하기 위해 3차원적 접근방법이 제시되고 있지만, 계산시간의 과다로 인해 실제 시뮬레이션 적용에는 효과적이지 못했다. 본 연구의 주요 관점은 효율적인 3차원 휠-레일 접촉 해석을 통해 휠-레일 접촉력을 계산하여 철도차량의 동특성 해석의 새로운 방법을 제시하고자 하는 것이다. 이를 통해, 3차원 휠-레일 접촉해석 및 휠셋의 동적 계산식이 제시된다.

• 동력기계공학회지
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• 제21권2호
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• pp.41-47
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• 2017

Boron steel (51B20) was cold forged using by new designed dies to apply for automotive aluminum wheel nut. The formability and mechanical properties of boron steel were compared with carbon steel(S45C) which has been used up to date for the wheel nut material. The formability was investigated on the dies designed with various types of punch nose using by FEM. The metal flow and compressive stress on the dies during cold forging were investigated and compared each other. The forging process with a new designed die showed the improved metal flow with a reduced forging load which resulted in the significant increase of the die life. It was recommended that the carbon steel for automotive wheel nut material could be substituted by the boron steel.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1995년도 춘계학술대회 논문집
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• pp.17-23
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• 1995

This paper describes investigation of the dressing time by laser in the surface grinding operation. Always dressing work is done before grinding operation. And then generates wear and roading on the wheel by contact between the grinding performance but also ground surfaces. On these states dressing work is needed. On this paper contour of the wheel by He-Ne laser is measured. It has also been found that the wheel deflection reduces the actual depth of cut and the roughness of the ground surface.

• 반도체디스플레이기술학회지
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• 제10권3호
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• pp.35-42
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• 2011

This paper describes the characteristics of high speed grinding and the influence of wheel surface speed V and a grindability of the grinding materials. The various fine ceramics pieces was ground by metal and vitrified bonded diamond wheel. The surface roughness of fine ceramics(Zirconia($ZrO_2$), Silicon Carbide(SiC), Silicon Nitride($Si_3N_4$), Alumina($Al_2O_3$)) decreases from $0.05{\mu}m(R_{max})$ to $0.025{\mu}m(R_{max})$ when the wheel speed at grinding point increases the wheel speed. Relation between the temperature at grinding point and surface roughness was linear. Abrasive jet machining(AJM), a specialized from of shot blasting, is considered one of the most helpful micro machining methods for hard and brittle materials such as glasses and ceramics by constant pressure grinding.