• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.189-189
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• 2011

CrZrN 박막은 CrN 박막에 비해서 향상된 기계적 특성과 우수한 표면 조도특성을 가지고 있다. 그러나 $500^{\circ}C$ 이상에서 기계적 특성이 급격히 감소하는 현상이 알려져 있다. 본 연구에서는 CrZrN 박막에 Si를 첨가하여 Si 함량에 따른 고온에서의 기계적 특성을 CrZrN 박막과 비교하였다. $500^{\circ}C$에서 마모 실험한 결과 CrZrN 박막에 비하여 소량의 Si의 첨가만으로 고온에서의 마모 특성이 향상되는 것을 확인하였다. 이것은 Si 첨가에 따라 고온에서 안정한 비정질상의 형성 영향으로 판단된다.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.633-642
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• 2006

This study evaluated the surface changes such as surface average roughness(RA), surface free energy(SFE) and wear depth among groups treated with surface penetrating sealant(Fortify, Biscover), non treated polishing group before and after tooth-brushing, analyzing the influence of the sealants in filling of surface microdefects formed during the finishing and polishing procedures of composite resin. Results were as follow(p= 0.05) : 1. Ra was increased Biscover. Fortify and Polishing group. Before abrasion and in 6 months, all groups were statistically significant. In 1 month, 2 months and 3 months no statistical difference was noticed between Fortify and Biscover 2. SFE of Polishig and Biscover group. Fortify and Biscover group were statistically significant before abrasion. SFE of Polishing and Fortify group was statistically significant in 1 month. No statistical difference was noticed among groups in 2 months. SFE of Fortify and Biscover group was statistically significant in 3 months. Polishing and Fortify group, Fortify and Biscover group were statistically significant in 6 months. 3, Wear rate between Polishing and Fortify group was statistically significant in only 1 month. Wear rate between Polishing and Biscover group was statistically different in each month except for 2 month and so it was between Fortify and Biscover group. Considering film thickness of Fortify and Biscover, Fortify almost discappeared after 2 months and Biscover did after 6 months.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.4
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• pp.369-376
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• 2004

It is shown that the rate of wear can be related to on 'index of wear intensity'. Since both upper and lower specimens have used the same hardness values, equivalent hardness of 'index of wear intensity' used the mean hardness value of specimens. This index is derived from the external variables of load, sliding speed and the hardness of the sliding pairs. The wear behavior as the hardness of the sliding elements on the dry wear has been investigated using a disc on disc configuration. The materials of the specimens are used as ten kinds along their hardness. Using experimental data, we figured the relationship between wea rate and index of wear intensity. The result had been derived a newly wear equation in disc on disc wear system.

• Composites Research
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• v.30 no.5
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• pp.310-315
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• 2017

In this study, we have investigated microstructure, mechanical properties and wear characteristic of aluminum metal matrix composites with a high volume fraction and uniformly dispersed SiC particles which produced by a liquid pressing process. The volume fraction of bimodal SiC/Al7075 composite was 12% higher than that of the monomodal SiC/Al7075 composite and a compressive strength is increased about 200 MPa. As a result of the abrasion test, the wear width and depth of the bimodal SiC/Al7075 composite were $285.1{\mu}m$ and $0.45{\mu}m$, respectively. The coefficient of friction of bimodal SiC/Al7075 was 0.16.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.453-467
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• 2018

The excavation performance and the cutting tool wear prediction of shield TBM are very important issues for design and construction in TBM tunneling. For hard-rock TBMs, CSM and NTNU model have been widely used for prediction of disc cutter wear and penetration rate. But in case of soft-ground TBMs, the wear evaluation and the excavation performance have not been studied in details due to the complexity of the ground behavior and therefore few testing methods have been proposed. In this study, a new soil abrasion and penetration tester (SAPT) that simulates EPB TBM excavation process is introduced which overcomes the drawbacks of the previously developed soil abrasivity testers. Parametric tests for penetration rate, foam mixing ratio, foam concentration were conducted to evaluate influential parameters affecting TBM excavation and also ripper wear was measured in laboratory. The results of artificial soil specimen composed of 70% illite and 30% silica sand showed TBM additives such as foam play a key role in terms of excavation and tool wear.

• Composites Research
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• v.13 no.6
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• pp.1-8
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• 2000

The fabrication Process of $Al_2O_{3p}$/AC8A composites by pressureless infiltration technique and the effects of additive Mg content and volume fraction of particulate reinforcement on mechanical and wear properties were investigated. It was found that the bending strength decreased with increasing volume fraction of $Al_2O_{3p}$ particles. Whereas hardness increased with volume fraction of $Al_2O_{3p}$ particles. The decrement of strength in case of high volume fraction of $Al_2O_{3p}$ particles was attributed to high porosity level. In terms of additive Mg content, $Al_2O_{3p}$/AC8A composites containing around 5~7wt% of additive Mg indicated the highest strength, and hardness values increased with additive Mg contents. Wear resistance of AC8A alloy were improved by reinforcement of $Al_2O_{3p}$ particles especially at high sliding velocity. Wear property of $Al_2O_{3p}$/AC8A composites and AC8A alloy exhibited different aspects. $Al_2O_{3p}$/AC8A composites indicated more wear loss than AC8A alloy at slow velocity region. However a transition point of wear loss was found at middle velocity region which shows the minimum wear loss and wear loss at high velocity region exhibited almost same value as at slow velocity region, whereas wear loss of AC8A alloy almost linearly increased with sliding velocity. It was found that $Al_2O_{3p}$/AC8A composites containing $Al_2O_{3p}$ volume fraction of 20% exhibited abrasive wear surface regardless of sliding velocity and $Al_2O_{3p}$/AC8A composites containing $Al_2O_{3p}$ volume fraction of 40% showed slightly adhesive wear surface at low sliding velocity, and it progressed to severe wear as increasing the sliding velocity.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.38-39
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• 2007

Chromium nitrids(Cr-N)박막은 경질박막재료이며 특히 PVD법을 제조한 CrN 박막은 다른 이원계 박막에 비해 높은 내마모성을 갖는다고 알려져 있다. 본 실험에서는 CrN박막에 Zr을 첨가하여 3원계의 CrZrN 박막을 합성하여 박막의 Zr 함량에 따른 표면경도 및 조도를 측정하고 Ball-on-disk type의 마모실험과 습도제어 하에서의 마모실험을 실시하였다. 박막의 Zr 함량이 증가함에 따라 박막의 표면경도가 증가하고 표면조도는 낮아지는 것을 알수 있었고, 그에 따라 마찰계수 값 또한 낮게 측정되었다. 습도제어하에서는 마찰계수 값은 비슷한 경향을 보였으나 습도가 매우 낮은 건조한 환경에서는 박막의 마찰계수 값이 높게 나타나는 경향을 보였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.143-143
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• 2017

CrAlN 코팅은 높은 경도, 낮은 표면 조도 등의 상온에서의 우수한 기계적 특성 이외에 고온에서 안정한 합금상의 형성으로 인하여 우수한 내산화성 및 내열성을 보유하여 공구 코팅으로의 적용 가능성이 크다. 그러나 최근 공구사용 환경의 가혹화로 인하여 코팅의 내마모성 및 내열성 등의 물성 향상을 통한 공구의 수명 향상이 필요시 되고 있으며, 다양한 코팅 물질을 활용하여 다층 코팅을 합성함으로써 난삭재용 공구 코팅의 물성을 높이는 연구들이 진행되고 있다. 본 연구에서는 CrAlN 코팅과 WC-Co 6wt.% 모재 사이에 CrZrN, CrN, CrN/CrZrSiN 등의 중간층을 합성하여 CrAlN 코팅의 상온 및 고온 특성을 향상시키는 연구가 진행되었다. 합성된 코팅의 구조 및 물성을 분석하기 위해 field emission scanning electron microscopy(FE-SEM), nano-indentation, atomic force microscopy(AFM) 및 ball-on-disk wear tester를 사용하였다. 코팅의 고온 특성을 확인하기 위해 코팅을 furnace에 넣어 공기중에서 30분 동안 annealing 한 후에 nano-indentation을 사용하여 경도를 측정하였고, $500^{\circ}C$ annealing 코팅의 표면 조도 분석 및 $500^{\circ}C$에서 마찰마모시험을 실시하였다. CrAlN 코팅의 상온 특성을 분석한 결과, 모든 코팅의 경도(35.5-36.2 GPa)와 탄성계수(424.3-429.2 GPa)는 중간층의 종류에 상관없이 비슷한 값을 보인 것으로 확인됐다. 그러나, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 마찰계수는 0.33로 CrZrN 중간층을 증착한 CrAlN 코팅의 마찰계수(0.41)에 비해 향상된 값 보였으며, 코팅의 마모율 및 마모폭도 비슷한 경향을 보인 것으로 보아 코팅의 내마모성이 향상된 것으로 판단된다. 이것은 중간층의 H/E ratio가 코팅의 내마모성에 미치는 영향에 의한 결과로 사료된다. H/E ratio는 파단시의 최대 탄성 변형율로써, 모재/중간층/코팅의 H/E ratio 구배에 따라 코팅 내의 응력의 완화 정도가 변하게 된다. WC 모재 (H/E=0.040)와 CrAlN 코팅(H/E=0.089) 사이에서 CrN, CrZrSiN 중간층의 H/E ratio는 각각 0.076, 0.083 으로 모재/중간층/코팅의 H/E ratio 구배가 점차 증가함을 확인 할 수 있었고, 일정 응력이 지속적으로 가해지면서 진행되는 마모시험중에 CrN과 CrZrSiN 중간층이 WC와 CrAlN 코팅 사이에서 코팅 내부의 응력구배를 완화시키는 역할을 함으로써 CrAlN 코팅의 내마모성이 향상된 것으로 판단된다. 내열성 시험 결과, CrN/CrZrSiN 중간층을 증착한 코팅은 $1,000^{\circ}C$까지 약 28GPa의 높은 경도를 유지한 것으로 확인 되었다. $500^{\circ}C$ annealing 후 진행된 표면 조도와 마모시험 결과, 모든 코팅의 조도 값 및 마찰계수는 상온 값에 비해 증가하였으며 CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 변화량이 가장 낮은 값을 보였다. 이는 CrZrSiN 중간층 내에 존재하는 $SiN_x$ 비정질상이 고온 annealing시에 산소 차폐막 역할을 하여, 코팅내의 잔류 산소에 의한 산화작용을 효과적으로 방지함으로써 코팅의 고온 특성이 향상된 것으로 판단된다.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.83-88
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• 2010

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the wear resistance according to the change of apply load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and the wear test results exhibited as following ; The epoxy matrix composites showed lower coefficient of friction compared to the neat epoxy through the whole sliding distance. As increasing the sliding velocity the epoxy matrix composites indicated lower coefficient of friction, whereas the neat epoxy showed higher coefficient of friction as increasing the sliding velocity. The specific friction work of both materials were increased with apply load. In case of the epoxy matrix composites, the running in periods of friction were reduced as increase in apply load. The epoxy matrix composites were improved the wear resistance by adding the nano silica particles remarkably. It is expected that the load carrying capacity of the epoxy matrix composites will be improved by increase of Pv factor.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.117-127
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• 2007

The exposed aggregate PCC(EAP) pavements have been successfully used in Europe and Japan as low-noise pavements. Coarse aggregate are exposed on the pavement surface texture of EAP by removing mortar of surface. The pavement surface texture should maintain not only low-noise characteristic but also adequate skid resistance level during the performance period. Skid resistance decreased with wearing and polishing of tire and pavement surface due to the repetition of tire-pavement contact. Since the tires mainly contact the exposed coarse aggregate, the shape and rock type of coarse aggregate significantly influence wearing and polishing of EAP pavements. The test for resistance to abrasion coarse aggregate by use of the Los Angeles machine(KS F 2508) and the method of test for resistance to abrasion coarse aggregate by use of the Accelerated Polishing Machine(ASTM D 3319-90) are generally used to evaluate polishing characteristics of aggregate. In this study, polishing of coarse aggregate of different five rock types were evaluated by KS F 2508(LA abrasion test) and ASTM D 3319-90(PSV method). The results of LA abrasion test and PSV method were contrary to each other. Since LA abrasion test is estimated the quantity of abrasion by the impact of aggregate, it may not be adequate to evaluate the polishing of aggregate by the repetition of tire. In the case of PSV method, the resistance of polishing is estimated the skid resistance variation of polished aggregate after repetition of tire. The PSV method is adequate for the evaluation on polishing of coarse aggregate. From the test results of PSV method, it was founded that rock type, specific gravity, coarse aggregate angularity, flat or elongated particles in coarse aggregate are significant to the resistance characteristic of coarse aggregate.