• 한국정밀공학회지
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• 제15권7호
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• pp.61-68
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• 1998

The form accuracy of parts has become an important parameter. Therefore, dimensional tolerance and geometric tolerance are used in the design stage to satisfy required quality and functions of parts. But the informations on the machining conditions, which can satisfy the assigned geometric tolerance in design, are insufficient. The objectives of this research are to study the effects of the grinding parameters such as traverse speed, work speed, depth of cut, and dwell time on the after-ground workpiece shape, and to find out the major parameters among them. The results are as follows, The effects of work speed and depth of cut on workpiece shape are negligible compared with the effect of traverse speed. There is an optimal dwell time depending on the traverse speed. The optimal dwell time is decreasing as the traverse speed is increased.

• Steel and Composite Structures
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• 제17권5호
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• pp.687-704
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• 2014

A great number of moment-resisting steel structures collapsed due to ductile crack initiation at welded beam-column connections, followed by explosive brittle fracture in the Kobe (Hyogoken-Nanbu) earthquake in 1995. A series of experimental and numerical studies on cracking behaviors of beam-column connections in steel bridge piers were carried out by the authors' team. This paper aims to study the effect of post weld treatment on cracking behaviors of the connections during a strong earthquake event. Experiments of three specimens with different weld finishes, i.e., as-welded, R-finish, and burr grinding, were conducted. The experimental results indicate that the instants of ductile crack initiation are greatly delayed for the specimens with R-finish and burr grinding finishes compared with the as-welded one. The strain concentration effect in the connection is also greatly reduced in the specimens with post weld treatment compared with the as-welded one, which was also verified in the tests.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2005년도 국제학술대회
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• pp.326-329
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• 2005

A worker who grinded the inner parts of camshafts for automobile engines using water-soluble metalworking fluid (MWF) for 14 years was diagnosed with sinusitis. We postulated that the outbreak of sinusitis could be associated with exposure to microbes contaminated in water-soluble MWF during the grinding operation. To suggest responsible agents for this outbreak, quantitative exposure assessment for chemical and biological agents and prevalence of work-related respiratory symptoms by questionnaire were studied. The exposure ranges of MWF mist (0.59 $mg/m^3$to 2.12 $mg/m^3$) measured during grinding exceeded 0.5 $mg/m^3$ of the recommended exposure limit (REL). Grinder's exposures to bacteria, fungi and endotoxins were also generally higher than not only the proposed standards, but also those reported by several studies to identify the cause of respiratory effects. Statistical test indicated that the prevalence rate of reported symptoms related to nasal cavities showed no significant differences among the operations. Evaluation on grinding operation characteristics and quantitative exposure assessment indicated that repeated exposure to MWF mist including microbes contaminated from the use of water-soluble MWF may cause respiratory diseases like sinusitis or at least increase susceptibility to the development of sinusitis

• 한국기계가공학회지
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• 제11권5호
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• pp.60-67
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• 2012

In the study, the effect grinding condition on the workpiece arithmetical average roughness(Ra) to 10 steps leading to cutting each section with the spindle rotational speed 8000rpm and feed rate 150mm/min of grinding in GC(green silicon carbide) grinding processing after heat treatment and non heat treatment of SCM415 material. Also the following conclusions were obtained analysis of stress distribution displacement and finite elements method(FEM) on assemble parts with 3+2 axis simultaneous control through grinding and gave a load 11kg on ATC arm both sides gave a load of 11kg. For the centerline average roughness(Ra) in the heat and non-heat treatment work pieces, which were appeared the most favorable in the fifth section were $0.511{\mu}m$ and $0.514{\mu}m$, that were shown in the near the straight line section was the smallest deformation of curve. In addition, the bad surface roughness appeared on the path is too long by changing angle, the more inclined depth of cut, because the chip discharging is not smoothly.

• 한국정밀공학회지
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• 제30권12호
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• pp.1237-1243
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• 2013

This study has focused on the effect of ultrasonic vibration table in ELID grinding process of aluminum nitride ceramics. Aluminum nitride ceramics has superior physical and chemical properties and widely used in IC, LSI substrate, package and so on. To achieve the high effective machining of brittle and high strength ceramics as like aluminum nitride, machining method combined ELID grinding and ultrasonic vibration has been adopted in this study. From the experimental results, material removal rate, MRR has been increased maximum 36 percent and spindle resistance has been decreased in using ultrasonic table. Surface roughness of ground surface became a little worse in using ultrasonic table but was somewhat improved in feed direction.

• 대한금속재료학회지
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• 제50권5호
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• pp.383-387
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• 2012

The activation of Mg-10 wt%$Fe_2O_3$ was completed after one hydriding-dehydriding cycle. Activated Mg-10 wt%$Fe_2O_3$ absorbed 5.54 wt% H for 60 min at 593 K under 12 bar $H_2$, and desorbed 1.04 wt% H for 60 min at 593 K under 1.0 bar $H_2$. The effect of the reactive grinding on the hydriding and dehydriding rates of Mg was weak. The reactive grinding of Mg with $Fe_2O_3$ is believed to increase the $H_2$-sorption rates by facilitating nucleation (by creating defects on the surface of the Mg particles and by the additive), by making cracks on the surface of Mg particles and reducing the particle size of Mg and thus by shortening the diffusion distances of hydrogen atoms. The added $Fe_2O_3$ and the $Fe_2O_3$ pulverized during mechanical grinding are considered to help the particles of magnesium become finer. Hydriding-dehydriding cycling is also considered to increase the $H_2$-sorption rates of Mg by creating defects and cracks and by reducing the particle size of Mg.

• 한국기계가공학회지
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• 제18권4호
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• pp.69-75
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• 2019

Since gasoline engines are based on a combination of a cast iron liner and an aluminum block, which have different thermal properties and stiffnesses, bore shape distortion is likely to occur during honing due to uneven thermal deformation. To solve this problem, many tests and evaluations are needed to support the development of a high-performance honing stone with low heat generation. Moreover, performance evaluation, which depends on inspection and observation after work, often requires much trial and error to optimize tool design, due to challenges in the accurate interpretation of results. This study confirmed that the assessment of grinding capability was clarified by evaluating performance under severe work conditions and by in-situ measurement and recording of current consumption (workload) and heat generation during operation. As a result of using a honing stone with excellent grinding performance in engine block manufacture-in which cylinder bore distortion caused by thermal deformation during manufacture is a problem-a noticeable improvement in the degree of cylindricity was observed.

• 대한화장품학회지
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• 제30권4호
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• pp.543-548
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• 2004

메이크업 제품에 있어서 특히 아이섀도나 블러셔와 같은 포인트 메이크업 제품의 제조시 화사함이나 광택을 부여하기 위하여 사용되는 펄 안료에 대하여 분쇄시간에 따른 입도분포 변화와 결합제로 사용되는 바인더의 영향에 따른 입도분포의 변화에 대하여 검토하였다. 고속 회전형 믹서기를 사용하였으며 레이져 회절${\cdot}$산란법을 이용하여 입도분포를 측정하였다. 평균경 5 um의 펄 안료인 경우 120 s간 분쇄하였을시 4.5 um로 입자경의 변화 폭이 작지만, $45{\;}{\mu}m$인 경우 27 um로 현저히 작아지며 그에 따라 본래의 광택감도 떨어지는 것을 확인할 수 있었다. 바인더의 경우, raw material의 입자사이즈에 따라 분쇄시간과의 상관성을 확인하였으며, 바인더 함량에 따라 입자간의 응집에 의하여 발생하는 분립체의 입도분포의 변화에 대해서도 고찰하였다.

• Korean Chemical Engineering Research
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• 제56권2호
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• pp.191-203
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• 2018

이 연구는 각각 크기와 재질이 다른 3 가지 종류의 분쇄 매체를 이용하여 회전속도와 밀링 시간의 따른 구리 (Cu) 분말의 형상변화의 과정에 미치는 영향을 관찰하고, 볼 움직임의 DEM시뮬레이션을 행하였다. 전동볼밀에서 볼 움직임의 3차원 시뮬레이션을 통해 분쇄 메커니즘을 규명하기 위하여 분쇄매체의 힘, 운동에너지, 매체 운동속도 등을 계산하였다. 시뮬레이션에서는 회전속도, 볼 재질, 운동속도, 마찰계수 등을 실제 실험조건과 동일하게 조건을 맞추어 투입되는 에너지의 변화량도 계산하였다. 주사전자현미경 결과를 살펴보면 볼 직경이 작을 때 입자형상이 불규칙한 형태에서 구형 형태로 변화하는 것을 알 수 있었다.

• 한국재료학회지
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• 제9권2호
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• pp.111-116
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• 1999

The microstructure of vitreous bonded abrasives, which are used as the essential materials in the precise grinding, was investigated theoretically using two particle model. In this paper, a general equation applicable for a case in which there is a gap between abrasive grits is suggested. As a result, it was known that both the volume ratio of grit to glassy bond(V\ulcorner/V\ulcorner) and porosity(V\ulcorner) are the function of $\alpha$(the ratio of distance between grit to diameter of grit) and $\theta$(the angle from the center of pore to that of grit). Because the value $\alpha$ and $\theta$ can be get easily by using these suggested equations, the microstructure could be explained quantitatively. Also the raised error with the increasing amount of bond was modified by the simple assumption. As a result, in that case, both V\ulcorner/V\ulcorner and V\ulcorner were known to be the function of $\alpha$ and $\theta$(the ratio diameter of pore to that of grit).