• 한국정밀공학회지
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• 제20권10호
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• pp.74-81
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• 2003

This paper describes that the micro-cutting of WC-Co using PCD (Polycrystalline Diamond) and PcBN (Polycrystalline Cubic Boron Nitride) cutting tools are performed with SEM(Scanning Electron Microscope) direct observation method. The purpose of this study is to present reasonable cutting conditions to obtain precise finished surface and machining efficiency. Summary of the results are shown below: (1) The thrust cutting forces tend to increase more than the principal forces as the depth of cut and the cuttlllg speed are increased preferably on orthogonal microcutting. (2) The tool wear in the flank face was formed larger than that in the rake face on orthogonal micro cutting. (3) The wear appearance for PCD tools is abraded by hard WC particles of the work materials, which lead diamond grain to be detached from the bond.

• ETRI Journal
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• 제41권1호
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• pp.73-83
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• 2019

This paper describes in detail the processing path leading to successful phase images stitching in digital holographic microscope for the extension of the field of view. It applies FIJI Grid/Collection Stitching Plugin, which is a general tool for images stitching, non-specific for phase images. The FIJI plugin is extensively supported by aberration and phase offset correction. Comparative analysis of different aberration correction methods and data processing strategies is presented, together with the critical analysis of their applicability. The proposed processing path provides good background for statistical phase analysis of cell cultures and digital phase pathology.

• 한국정밀공학회지
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• 제13권1호
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• pp.53-61
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• 1996

A clear understanding of the surface formation mechanism due to cutting is very important to help produce a good quality surface. Much of the roughness along the length of a bar being cut in a lathe can be explained in terms of macroscopic tool shape and feed rate. However, the roughness along the direction of cutting requires a different explanation. The formation of surface roughness is a problem in flow and fracture of materials in the vicinity of the tool edge. On a microscopic scale the cutting edge is rounded because it is impossible to grind a perfectly sharp cutting edge. Even if a perfectly sharp cutting edge were obtained it would soon become dull as a result of rapid breakdown and wear of the cutting edge. A research project is proposed in which in the main object is to model the surface formation mechanism due to cutting. The tool was assumed to be dull, that is, its edge has a finite radius. In order to study the effect of the radius of cutting edge on the surface formation, tools having different cutting edges were used. For orthogonal cutting experiment, cast iron and glass were chosen as brittle materials. Plowing forces acting in the cutting edge were estimated and its effect on the surface roughness was studied by observing the machined surface using optical microscope.

• Advances in nano research
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• 제14권2호
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• pp.117-126
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• 2023

This experimental study investigated friction stir welding (FSW) of the acrylonitrile-butadiene-styrene (ABS) T-joint in the presence of various nano-silica levels. This study aim to handle the drawbacks of the friction stir welding (FSW) of an ABS T-joint with various quantity of nanoparticles and assess the performance of nanoparticles in the welded joint. Moreover, the relationship between the nanoparticle quantity and FSW was analyzed using response surface methodology (RSM) Box-Behnken design. The input parameters were the tool rotation speed (400, 600, 800 rpm), the transverse speed (20, 30, 40 mm/min), and the nano-silica level (0.8, 1.6, 2.4 g). The tensile strength of the prepared specimens was determined by the universal testing machine. Silica nanoparticles were used to improve the mechanical properties (the tensile strength) of ABS and investigate the effect of various FSW parameters on the ABS T-joint. The results of Box-Behnken RSM revealed that sound joints with desired characteristics and efficiency are fabricated at tool rotation speed 755 rpm, transverse speed 20 mm/min, and nano-silica level 2.4 g. The scanning electron microscope (SEM) images revealed the crucial role of silica nanoparticles in reinforcing the ABS T-joint. The SEM images also indicated a decrease in the nanoparticle size by the tool rotation, leading to the filling and improvement of seams formed during FSW of the ABS T-joint.

• 한국산학기술학회논문지
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• 제15권9호
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• pp.5434-5439
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• 2014

금속의 표면관리는 공구 현미경이나 표면 조도 측정기를 이용하고 있다. 이러한 방법은 구조적인 문제로 인하여 생산현장에서 금형의 표면 상태 확인을 하기에는 효율성이 떨어진다. 이런 이유로 완성된 금형의 노후화에 따른 마모, 흠집 및 표면 상태를 관리할 수 있는 분석시스템 또는 측정시스템이 필요하다. 본 연구는 금형이나 가공품의 자동분석 및 기준화를 위한 표면상태 분석 소프트웨어를 개발하였다. 소프트웨어는 기본적으로 원, 점, 선 등의 요소들을 측정할 수 있게 개발하였으며, 캡처한 사진을 3차원 이미지로 구현하여 금형에 생긴 홈의 깊이와 단면 프로파일을 추정할 수 있도록 중점을 두었다. 실험분석결과 표면 조도는 93.2%이상의 정확도를 나타냈으며, 조명밝기에 대한 표면 조도의 최대편차는 $3{\mu}m$ 이내로 매우 정밀하였다. 이런 결과로 금형의 측정 및 표면분석을 통한 품질관리의 효율성을 확인 할 수 있었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.533-537
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• 2003

Compared to sintered polycrystalline diamond (PCD), the deposited thin film diamond has a great advantage on the fabrication of cutting tools with complex geometries such as drills. Because of high performance in high speed machining non-ferrous difficult-to-cut materials in the field of automobiles industry, aeronautics and astronautics industry, diamond-coated drills find large potentialities in commercial applications. However, the poor adhesion of the diamond film on the substrate and high surface roughness of the drill flute adversely affect the tool lift and machining quality and they become the main technical barriers for the successful development and commercialization of diamond-coated drills. In this paper, diamond thin films were deposited on the commercial WC-Co based drills by the electron aided hot filament chemical vapor deposition (EACVD). A new multiple coating technology based on changing gas pressure in different process stages was developed. The large triangular faceted diamond grains may have great contribution to the adhesive strength between the film and the substrate, and the overlapping ball like blocks consisted of nanometer sized diamond crystals may contribute much to the very low roughness of diamond film. Adhesive strength and quality of diamond film were evaluated by scanning electron microscope (SEM), atomic force microscope (AFM), Raman spectrum and drilling experiments. The ring-block tribological experiments were also conducted and the results revealed that the friction coefficient increased with the surface roughness of the diamond film. From a practical viewpoint, the cutting performances of diamond-coated drills were studied by drilling the SiC particles reinforced aluminum-matrix composite. The good adhesive strength and low surface roughness of flute were proved to be beneficial to the good chip evacuation and the decrease of thrust and consequently led to a prolonged tool lift and an improved machining quality. The wear mechanism of diamond-coated drills is the abrasive mechanical attrition.

• International Journal of Precision Engineering and Manufacturing
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• 제8권2호
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• pp.54-58
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• 2007

This paper describes an atomic force microscope (AFM)-based instrument for measuring the nanoscale cutting edge profiles of diamond cutting tools. The instrument consists of a combined AFM unit and an optical sensor to align the AFM tip with the top of the diamond cutting tool edge over a submicron range. In the optical sensor, a aser beam is emitted from a laser diode along the Y-axis and focused to a small beam spot with a diameter of approximately $10{\mu}m$ at the beam waist, which is then received by a photodiode. The top of the tool edge is first brought into the center of the beam waist by adjusting it in the X-Z-plane while monitoring the variation in the photodiode output. The cutting tool is then withdrawn and its top edge position at the beam center is recorded. The AFM tip can also be positioned at the beam center in a similar manner to align it with the top of the cutting edge. To reduce electronic noise interference on the photodiode output and thereby enhance the alignment accuracy, a technique is applied that can modulate the photodiode output to an AC signal by driving the laser diode with a sinusoidal current. Alignment experiments and edge profile measurements of a diamond cutting tool were carried out to verify the performance of the proposed system.

• 대한의용생체공학회:의공학회지
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• 제33권2호
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• pp.53-58
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• 2012

Intraoperative surgical microscope is an essential surgical equipment. However, it has a restriction to classify the retina layers because of the contrast differences. To solve this problem, operators use surgical instrument such as an intraocular mirror. In this case, it has to amputate the patient's eye. In this study, we developed a probe the intraoperative surgical optical coherence tomography. We expect that the developed OCT probe can overcome the limit of OCT and be applied as a real-time surgical tool. In this paper, we demonstrate applicability of the probe through rabbit's experimentation.

• 한국음향학회지
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• 제9권2호
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• pp.5-13
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• 1990

본 연구에서는 수 파장 이상의 깊이에 존재하는 결함을 탐상하기 위하여 50MHz의 중심주파수에서 동작하는 small aperture형 초음파현미경을 구성하였고 다층구조 샘플에 대한 영상을 연구분석하였다. 다층구조물에서의 출력특성을 음향감쇠, 수차, 렌즈형태, 샘플의 특성에 영향을 받으며 이것은 다층구조 I.C.와 bonding층 탐상에 이용할 수 있다. 실험결과, small aperture형 초음파현미경은 large aperture형 시스템에 비하여 두꺼운 샘플의 탐상에 유리하며 타 도구에서 관찰이 어려운 다층구조의 층별 탐상과 내부구조의 변형상태등을 2차원 영상으로 탐상할 수 있는 유용한 도구임을 확인하였다.

• Journal of Pharmaceutical Investigation
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• 제41권1호
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• pp.45-50
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• 2011

Nonclassical pathway of crystallization has been utilized to modify the properties and morphologies of inorganic and organic/inorganic materials. In here, the polymer-directed crystallization method has been applied to the pharmaceutical active ingredient to assess the applicability for as a particle engineering tool. The polymer-directed crystallization was successful to modifying the crystal size, habit and morphology, but it was not effective to discover the novel polymorphs of Sibutramine (SB). SB was selected as a model drug and polyacrylic acid (PAA), polyethylene imine (PEI) and chitosan (CHI) were added as a crystallization pathway modifier. SB was crystallized via drowning crystallization using methanol or ethanol as a solvent and water as a non-solvent. The significant interactions between polymer and the drug were confirmed by measuring the solubility of the drug in presence of polymer during the crystallization. The crystal forms of SB are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and optical microscope (OM). The polymer-directed crystallization seems to be able to modify the crystal properties of pharmaceutical active ingredient, which is critical in determining the bioavailability, processability, and stability.