• 청정기술
• /
• 제12권3호
• /
• pp.182-189
• /
• 2006

본 연구에서는 생산성 향상을 위하여 적용 분야가 점차로 확대되고 있는 고속 절삭가공의 경제성 및 환경비용을 평가하였다. 가공시간 및 가공비용이라는 절삭공정의 경제성 평가 모델과 더불어 수학적으로 모델링 된 절삭유제의 손실량 및 폐 유제 처리비용을 이용하여 환경비용을 고려한 절삭공정의 생산비용을 분석하였다. 분석에는 CBN 볼 엔드밀을 사용한 고속가공과 여러가지 냉각방식을 적용한 고속 선삭가공 공종에 대한 공수수명 및 공구마모 실험 데이터를 이용하였다. 고속 밀링가공에서 절삭속도가 높을수록 생산비용은 작아져서 고속가공의 장점을 그래도 보여주었다. 압축공기, 냉풍, 수용성 절삭유제, 건식 절삭의 네 가지 냉각방법을 사용한 선삭가공의 분석에서는 절삭유제를 이용한 냉각방식이 절삭유제를 사용하지 않은 방식에 비하여 공수수명의 향상으로 생산비용이 작았으나 환경비용을 고려하면 냉풍을 이용한 냉각방식이 생산성과 환경영향의 모든 면에서 가장 우수하였다.

• 한국가시화정보학회지
• /
• 제21권1호
• /
• pp.110-118
• /
• 2023

Characterizing the extensional rheological properties of non-Newtonian fluids is crucial in many industrial processes, such as inkjet printing, injection molding, and fiber engineering. However, educational institutions and research laboratories with budget constraints have limited access to an expensive commercial extensional rheometer. In this study, we developed a custom-made extensional rheometer using a CO₂ laser cutting machine and 3D printer. Furthermore, we utilized a smartphone with a low-cost microscopic lens for achieving a high spatial resolution of images. The aqueous polyethylene-oxide (PEO) solutions and a Boger fluid were prepared to characterize their extensional properties. A transition from a visco-capillary to an elasto-capillary regime was observed clearly through the developed rheometer. The extensional relaxation time and viscosity of the aqueous PEO solutions with a zero-shear viscosity of over 300 mPa·s could be quantified in the elasto-capillary regime. The extensional properties of the solutions with relatively small zero shear viscosity could be calculated using a smartphone's slow-motion feature with increasing temporal resolution of the images.

• 한국기계가공학회지
• /
• 제18권10호
• /
• pp.99-103
• /
• 2019

Recently, as the high-precision machinery industry has developed rapidly, peripheral equipment has been developed to improve machining efficiency. Peripheral equipment for machining includes cooling units, housings, oil separators, and much more. Oil, such as cleaning and cutting fluids, is used for machining. When waste oil is reused, the contamination of the workpieces and reduction in machining accuracy are generated by the waste oil, including sludge. Therefore, the development of an oil separator is necessary for efficiently separating oil, water, and sludge. The purpose of this study is to analyze the oil separation efficiency and flow characteristics of a high-speed centrifugal separator according to the rotation velocity and diffusion plate. The oil separation efficiency and flow characteristics were analyzed using hydrodynamic theory and computational fluid dynamics (CFD). The results of this study will be used as basic data for the development of a high-speed centrifugal separator.

• 한국정밀공학회지
• /
• 제17권4호
• /
• pp.209-219
• /
• 2000

A method is developed to evaluate machining process and to determine the optimal machining conditions considering the environmental effects. The method Is based on the evaluation attributes from the general LCA programs and the analysis technique of AHP from HHS. To assist the analysis. the mass models of cutting energy, tools, and fluids are developed. The models may be used for both quantitative prediction of the uses and disposed masses of materials and optimization of the machining conditions. The algorithm with the mass models is applied to the milling process planning. The process to survey the environmental data, calculate the used mass, and evaluate the alternatives is demonstrated. This demonstration illustrates the of the change of process conditions of the decision making.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2005년도 추계 학술대회논문집
• /
• pp.157-162
• /
• 2005

Parallel implementation and performance assessment of the grid assembly in a structured chimera grid approach is studied. The grid assembly process, involving hole cutting and searching donor, is parallelized on the PC cluster. A message passing programming model based on the MPI library is implemented using the single program multiple data(SPMD) paradigm. The coarse-grained communication is optimized with the minimized memory allocation because that the parallel grid assembly can access the decomposed geometry data in other processors by only message passing in the distributed memory system such as a PC cluster. The grid assembly workload is based on the static load balancing tied to flow solver. A goal of this work is a development of parallelized grid assembly that is suited for handling multiple moving body problems with large grid size.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.29-32
• /
• 2008

Dental high-speed air turbine handpieces have been used as a dental cutting tool in clinical dentistry for over 50 years, yet little study has been reported on their flow and performance analysis. Therefore it is necessary to investigate turbine for the performance improvements of an air turbine handpiece. This paper presents pressure on turbine rotor and flow analysis in air turbine handpiece using CFD (computational fluid dynamics). Characteristics on each flow and pressure for four various reflection angles of turbine rotor are presented, and then performance change is analyzed about air turbine handpieces by CFD results.

• 한국수의병리학회지
• /
• 제6권1호
• /
• pp.7-9
• /
• 2002

Case 1 was showed severe caughing and nasal discharge, who was one of 5-month-old 18 male sheep taking inspection for MCF experiment. Pathological examination of case 1 was conducted. Macroscopic observations were the foamy sticky fluids in nasal and tracheal cavity, the grey spots with 2-4 mm diameter on the surface of lung. Histopathological observations were severe eosinophil and other round cell infiltration in general organs including lung, trachea, small intestine, large intestine, liver. Also, in the lung, there were parasite-cutting lesions in some alveolar spaces and bronchioles. Following these observations, case 1 was diagnosed as ovine lungworm infection.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1999년도 춘계 학술대회논문집
• /
• pp.35-47
• /
• 1999

The development of a parallelized aerodynamic simulation process involving moving bodies is presented. The implementation of this process is demonstrated using a fully systemized Chimera methodology for steady and unsteady problems. This methodology consist of a Chimera hole-cutting, a new cut-paste algorithm for optimal mesh. interface generation and a two-step search method for donor cell identification. It is fully automated and requires minimal user input. All procedures of the Chimera technique are parallelized on the Cray T3E using the MPI library. Two and three-dimensional examples are chosen to demonstate the effectiveness and parallel performance of this procedure.

• 공업화학
• /
• 제16권6호
• /
• pp.834-841
• /
• 2005

아디픽산 및 세바식산의 이염기산을 폴리에틸렌글리콜(PEG)과 축합 반응하여 여러종류의 PEG-ester를 합성하였다. 합성된 PEG-ester의 화학적 구조 및 분자량을 FT-IR, $^1H-NMR$, HPLC 및 GPC에 의하여 분석하였다. 또한, 임계미셀농도(CMC), 표면장력, 알루미늄판에 대한 접촉각 등을 통하여 수용액상에서 계면활성제의 역할을 함을 알 수 있었다. PEG-ester의 농도에 따라 표면장력은 72.5에서 45~50 dyne/cm로 감소함을 알 수 있었고, 세바식산을 사용하여 합성한 PEG-ester가 아디픽산을 사용하여 합성한 PEG-ester보다 같은 농도에서 낮은 표면장력을 나타내었다. CMC는 구조에 따라 차이를 나타내었는데 세바식산을 함유한 PEG-ester의 CMC는 $0.9{\times}10^{-5}{\sim}5.3{\times}10^{-3}mol/L$로 폴리옥시알킬렌 단위체가 길어질수록 증가하였으며 아디픽산을 함유한 PEG-ester의 경우, 변곡점을 뚜렷하게 관찰할 수가 없었다. 알루미늄에 대한 젖음성을 알루미늄 시편에 대한 접촉각을 측정하여 검토하였는 바, PEG-ester의 농도가 증가할수록 작아짐을 알 수 있었고 임계점을 관찰할 수가 있었다. 2.5 wt% PEG-ester를 함유한 수용액의 알루미늄에 대한 접촉각은 $45{\sim}53^{\circ}$이었으며 알루미늄 가공 절삭시간은 CMC를 나타내는 농도에서 가장 짧게 관찰되었으며 CMC 농도보다 큰 농도에서 길게 나타났다. 즉, 알루미늄을 가공할 때 PEG-ester의 CMC가 절삭성능에 중요한 영향을 미치는 것으로 판단되었다.

• 한국전산유체공학회지
• /
• 제13권4호
• /
• pp.1-7
• /
• 2008

In the process of continuous hot-dip galvanizing, it is well known that the gas wiping through an air knife system is most effective because of its uniformity in coating thickness, possibility of thin coating, workability in high speed, and simplicity of control. However, gas wiping used in the galvanizing process brings about a problem of splashing at the strip edge above a certain high speed of process. It is also known that the problem of edge splashing is more harmful than that at the mid strip surface. For a given liquid(of a certain viscosity and surface tension), the onset of splashing mainly depends upon the strip velocity, the gas-jet pressure, and the nozzle's stand-off distance. In these connections in the present study, we proposed three kinds of air knife system having nozzles of constant expansion rate, and compared the jet structures issuing from newly proposed nozzle systems with the result by a conventional one. In numerical analysis, the governing equations are consisted of two-dimensional time dependent Navier-Stokes equations, and the standard k-${\varepsilon}$ turbulence model is employed to solve turbulence stress and so on. As the result, it is found that we had better use the constant expansion-rate nozzle which can be interpreted from the point view of the energy saving for the same coating thickness. Also, we better reduce the size of separation bubble and enhance the cutting ability at the strip surface, by using an air-knife having constant expansion-rate nozzle.