• 한국산업융합학회 논문집
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• 제4권3호
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• pp.237-242
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• 2001

Ti-6Al-4V alloy can be obtained the stability of organization and product treasure, the evaluation of the cutting ability and the mechanical characteristics after the heat treatment of annealing, solution and aging. The difficulty in machining titanium alloy is how treat the heat generated during the process. Because the heat conductivity of titanium alloy is regardfully low, the heat generated during grinding is accumulated in workpiece. and it causes the increasing of grinding wheel grits' wear and makes the ground surface rough. So, these characteristics in grinding of titanium alloy will change the mechanical properties of the titanium alloy. From this study. the mechanical characteristics of annealed one and solution and aging one treated Ti-6Al-4V alloy after grinding was concerned with checking out the bending strength and hardness. For the result, both of bending strength and hardness were increased at the burned area on the surface. Roughness value was remarkably high at the table speed of 10m/min.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.403-403
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• 2008

This article reports changes in the mechanical properties of chromium steel after nitrogen implantation at high temperature. The samples are implanted with 120keV N-ion at doses ranging from $1\times1080$ to $4\times1080ions/cm^2$ and at substrate temperature ranging from 25 to $400^{\circ}C$. Nano-hardness and AES(Auger electrons spectroscopy) were measured from nitrogen ion implanted layer. The sliding wear and impact wear properties of the implanted samples were also measured. The results revealed that the hardness and mechanical properties of ion implanted samples depend strongly on the ion doses and implantation temperature. The hardness of the nitrogen implanted sample with 120keV, $4\times10^{18}ions/cm^2$, $335^{\circ}C$ was measured to be approximately 20 GPa, which is approximately 5 times higher than that of un-implanted sample (H=3.8 GPa). Also, the sliding wear and impact wear properties of nitrogen implanted samples were greatly improved. Detailed experiment results will be presented.

• 전기화학회지
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• 제3권4호
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• pp.196-199
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• 2000

무전해 도금은 내식성, 내구성, 전도성 특별히 비전도성 물질의 도금이 요구되는 모든 재료에 폭 넓게 사용되는 우수한 표면 처리 방법이다. 무전해 니켈 도금은 비자성, 무정형 구조,내구성, 내식성 그리고 열정 안정성 등의 많은 장점을 갖는다. 본 연구에서는 무전해 니켈 도금의 열처리에 따른 무전해 니켈-인 도금의 경도와 내식성의 변화를 연구하였다. 가장 높은 경도 값은 $500^{\circ}C$열처리에서 얻어졌다. $300^{\circ}C$에서 열처리한 도금의 내식성이 60시간 동안 1몰의 황산 수용액에서 테스트 한 결과 가장 우수하였다.

• 한국정밀공학회지
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• 제19권1호
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• pp.186-195
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• 2002

The mechanism of micro machining of reacted layer on silicon surface were proposed. The depth of reacted layer and the change of mechanical property were measured and analyzed. Depth of hydrated layer which is created on the surface of silicon by potassium hydrate was analyzed with SEM and XPS. The decrease of the micro victors hardness of silicon surface was shown with the increase of the concentration of potassium hydrate and the change of the dynamic friction coefficient by chemical reacted layer was measured due to the readiness of machining. The experiment of groove machining was done with 3-axis machine with constant load. With chemical mechanical micro machining the surface crack and burrs generated by both brittle and ductile micro machining were diminished. And the surface profile and groove depth was shown in accordance with the machining speed and reaction time with SEM and AFM.

• 한국환경복원기술학회지
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• 제10권2호
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• pp.34-43
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• 2007

To investigate the restoration procedure on soil physical properties and vegetation at the surface of strip road affected by timber harvesting operation. This study was carried out at strip roads constructed between 1989 and 1994 in Mt. Baekun, Kwangyang, Chollanam-Do. Soil hardness of the surface layer was improved with change of time after strip road construction, but that of 7.6~15 cm depth from the surface was not improved. According to linear regression analysis, it was estimated 16.6 years in 0~7.5 cm and 16.9 years in 7.6~15 cm soil depth to be restored to natural forest lands. The amount of surface soil erosion was 0.045$m^3$/km/yr on strip roads constructed in 1989 and 1990, and road constructed in 1994 showed the highest value (4.5$m^3$/km/yr). Vegetation coverage rates of road surface were 96.7% in strip roads constructed in 1990. Those of cutslope and fillslope were highest in roads constructed in 1990. The results indicated that strip roads were restored with change of time after road construction.

• 펄프종이기술
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• 제30권4호
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• pp.49-58
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• 1998

The SPM could image the most detailed microstructure of a sample in a wet and dry state by measuring the interaction between the atoms on the sample surface and the extremely sharp probe tip. The refined fibre exhibited large wrinkles formed by fibrillar bundles, the disintegrated fibres extensively showed “scale-like features”. By using the Non-Contact Atomic Force Microscopy (NC-AFM) and Contact Atomic Force Microscopy (C-AFM) including Phase Detection Microscopy (PDM) and Force Modulation Microscopy (FMM), it was possible to investigate surface topography, surface roughness and mechanical property (hardness or visco-elasticity) of fibre surface in detail. The PDM and FMM images showed that the disintegrated only fibre displayed uniform mechanical properties, whereas the refined one did not. The surface roughness of pulp fibres was higher in refined fibres than in disintegrated fibres due to the presence of external fibrils. These SPM images would be used to provide visual evidence of morphological change of a single fibre created during mechanical treatments such as refining, drying, calendering and so on.

• 한국표면공학회지
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• 제36권6호
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• pp.475-479
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• 2003

In this study, to investigate the effects of 2-step shot peening at the surface of spring steel, tests are conducted on spring steel and shot peened specimens. Various tests are accomplished to evaluate mechanical properties influenced by shot peening process, and fatigue tests are also performed to evaluate the improvement of fatigue strength. And then the residual stresses are examined. The mechanical properties of material did not change so much by shot peening. However, the fatigue strength of notched specimen remarkably increased. In the case of 1-step shot peening, fatigue strength increased by about 20％ than unpeened specimen. Especially, in the case of 2-step shot peening, fatigue strength increased by about 40％, because the residual compressive stress at surface was higher than that of 1-step shot peened specimen. The fatigue strength and life are closely related to the value and position of maximum compressive residual stress by shot peening.

• 치위생과학회지
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• 제11권5호
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• pp.397-404
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• 2011

최근 구강관리에 대한 관심이 증가하면서 시판되고 있는 구강양치용액의 종류도 다양해지고 있고 휴대가 간편하여 쉬운 사용방법으로 활용이 급진적으로 증가하고 있다. 본 연구에서는 시판 중인 구강양치용액의 pH를 측정하여 고유 산도가 법랑질 표면의 색조변화, 미세경도, 미세구조 변화, 거칠기 측정 등에 관한 실험방법을 통하여 구강양치용액의 효과를 평가하였다. 1. 색조변화는 Nextcare와 Listerine에서 light-dark를 나타내는 $L^*$값은 0에 가깝게 어두워졌으며 yellow-blue를 나타내는 $b^*$값은 초기값과 비교하여 채도가 낮아졌다. 특히 Listerine에서 ${\Delta}L^*$, ${\Delta}b^*$ 각각 -6.70, -7.20으로 가장 큰 변화를 보였다. 2. 표면경도 측정에서는 Nextcare와 Listerine에서 모두 통계적으로 유의한 감소를 보였다(p<0.05). 또한 표면의 형상과 거칠기에서도 Nextcare와 Listerine에서 다른 실험군과 비교하여 법랑질 표면의 붕괴 및 침식양상과 함께 거칠기가 매우 높아졌음을 알 수 있었다. 결론적으로, 현재 시판 중인 구강양치용액의 pH를 측정하여 고유 산도가 치아 경조직에 미치는 영향에 대해 알아본 결과, 산성의 pH를 가진 구강양치용액을 장기간 사용시 치면 착색 및 법랑질 표면의 영향을 줄 수 있으므로 적절한 사용법을 숙지하여 단기간 사용하는 것이 안전할 것으로 사료된다.

• 공업화학
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• 제28권1호
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• pp.57-63
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• 2017

본 연구에서는 다양한 NCO index에서 물 함량 변화가 자동차용 폴리우레탄 시트 폼 패드의 정적 안락감에 미치는 영향을 알아보았다. 정적 안락감에 영향을 미치는 요인을 파악하기 위해 UTM을 사용한 정하중 특성 시험을 통하여 히스테리시스 곡선을 나타냈으며, 이를 통해 25% 변형 시 경도와 65% 변형 시 경도, hysteresis loop area, hysteresis loss (%), 그리고 Sag factor를 구하였다. 동일한 NCO index에서 물 함량이 증가함에 따라 우레아 결합의 증가로 경도가 증가하고, 가교밀도가 증가하는 경향을 swelling ratio 측정으로 확인하였으며, 이에 따라 복원력은 감소하는 경향을 확인하였다. 또한 표면 경도의 증가로 인해 Sag factor가 감소하는 경향을 확인하였다. 동일한 물 함량에서 NCO index가 증가함에 따라 우레탄과 우레아 결합이 이소시아네이트와 추가 반응하여 가교도와 경도가 증가하고 이에 따라 복원력이 감소함을 확인하였다.

• 대한치과기공학회지
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• 제32권3호
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• pp.195-207
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• 2010

Purpose: The purpose of this study was to observe the microstructural changes of surface in the specimens, performing the shear bond strength testing. The currently most used non-precious alloys are nickel-chromium based alloys with or without beryllium. However, their biocompatibility has been questioned concerning possible damages to the health of the patient and professionals involved in the fabrication of prosthesis caused by long exposure to Ni and Be. An option to nickel-chromium alloys is the cobalt-chromium alloy, an alternative that does not sacrifice the physical properties of the metal porcelain systems. Studies in the animals substantially show that the cobalt-chromium alloys are relatively well tolerated, being therefore more biocompatible than the nickel-chromium alloys. Methods: Non-addition Be to nickel-chromium based alloy(Bellabond plus) and cobalt-chromium alloy which has been widely used(Wirobond C) fused with ZEO light porcelain classified control group and cobalt-chromium alloy which is developing alloy of Alphadent company in Korea(Alphadent alloy) fused with ZEO light porcelain classified experimental group. The specimens of $4mm{\times}4mm{\times}0.5mm$ were prepared as-cast and as-opaque to cast body to analyze the mechanical characteristic change, the microstructure of alloy surface. The phase change was used to observe through XRD analysis and OM/SEM was used to observe the surface of specimens as-cast and as-opaque to cast body. Chemical formation of their elements was measured with EDS. Then hardness was measured with Micro Vicker's hardness tester. Shear bond strength test thirty specimens of $10mm{\times}10mm{\times}2mm$ was prepared, veneered, 3mm high and 3mm in diameter, over the alloy specimens. The shear bond strength test was performed in a universal testing machine(UTM) with a cross head speed of 0.5mm/min. Ultimate shear bond strength data were analyzed with one-way ANOVA and the Scheffe's test (P<0.05). Within the limits of this study, the following conclusions were drawn: The X-ray diffraction analysis results for the as-cast and as-opaque specimens showed that the major relative intensity of Bellabond plus alloy were changed smaller than Wirobond C and Alphadent Co-Cr based alloys. Results: Microstructural analysis results for the opaque specimens showed all the alloys increased carbides and precipitation(PPT). Alphadent Co-Cr based alloy showed the carbides of lamellar type. The Vickers hardness results for the opaque specimens showed Wirobond C and Alphadent Co-Cr based alloys were increaser than before ascast, but Bellabond plus alloy relatively decreased. The mean shear bond strengths (MPa) were: 33.11 for Wirobond C/ZEO light; 25.00 for Alphadent Co-Cr alloy/ZEO light; 18.02 for Bellabond plus/ZEO light. Conclusion: The mean shear bond strengths for Co-Cr and Ni-Cr based alloy were significantly different. But the all groups showed metal-metal oxide modes in shear bond strengths test at the interface.