• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.19-24
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• 1997

The operating torque and tribological characteristics of the cam/tappet system in an I.C. engine have an important effect on engine efficiency. In this paper, we measured the torque of cam/tappet system with respect to the oil temperature and camshaft speed to characterize the tribological behavior. Also, accelerated test was performed to analyze the wear characteristics of cam/tappet interface. The torque of the cam/tappet system decreased with respect to camshaft speed and was not significantly affected by the oil temperature. The results of accelerated test showed that the running-in wear occurred during the tests and the center of the tappet was mainly damaged by the rolling and sliding friction.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2153-2162
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• 2011

The goal of this Paper is to reduce rail's wear in curved track by applying an additional surface layer material(High hardness and High resistance capacity of wear) on the top of the railhead. In order to evaluate appropriation of a coating material, experimental tests such as the varieties of fundamental properties tests (hardening, wear, tensile, and bending) and RCF(rolling contact fatigue)test were performed to establish fatigue wear and damage mechanism. As a result, wear performance of coating rail is better than heated rail about 6times and normal rail about 8~9times.

• 열처리공학회지
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• 제21권1호
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• pp.10-19
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• 2008

To investigate the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue and residual stress properties of bearing steels, this paper carried out a rolling contact fatigue test, measured residual stress and retained austenite, performed a wear test, observed microstructure, measured micro hardness, and analyzed surface topology. After the UNSM treatment, it was found that the surface became minute by over $100{\mu}m$. The micro surface hardness was changed from Hv730~740 of base material to Hv850~880 with about 20% improvement, and hardening depth was about 1.3 mm. The compressive residual stress was measured as high as -700~-900 MPa, and the quantity of retained austenite was reduced to 27% from 34%. The polymet RCF-6 ball type rolling contact fatigue test showed over 4 times longer fatigue lifetime after the UNSM treatment under 551 kgf load and 8,000 rpm. In addition, this paper observed the samples, which went through the rolling contact fatigue test, with OM and SEM, and it was found that the samples had a spalling phenomenon (the race way is decentralized) after the UNSM treatment. However, before the treatment, the samples had excessive spalling and complete exploration. Comparison of the test samples before and after the UNSM treatment showed a big difference in the fatigue lifetime, which seems to result from the complicated effects of micro particles, compressive residual stress, retained austenite, and surface topology.

• 한국철도학회논문집
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• 제20권4호
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• pp.512-520
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• 2017

일반적인 철도에서는 차륜과 레일의 마찰력을 이용하여 열차가 주행하게 된다. 차륜과 레일 사이에는 접촉압력이 발생하게 되고, 차량의 중량, 속도, 사행동, 접촉점 등에 따라 접촉압력의 크기가 변화하게 된다. 본 연구에서는 곡선부 차륜/레일에 대한 유한요소해석을 통해 접촉특성을 분석하였으며, 구름접촉피로시험을 통해 접촉압력에 따른 차륜/레일의 피로손상 및 마모율을 분석하였다. 구름접촉피로시험결과, 일반 및 열처리레일은 차륜에 비해 마모율이 높았으며, 일반 및 열처리레일마모율은 일정한 반복횟수 이상에서 급격히 증가하는 것으로 분석되었다. 또한, 일반레일이 열처리레일 보다 약 7~15% 마모율이 높았으며, 접촉압력 900~1,500MPa 범위에서 접촉압력에 따른 레일마모율에 대한 회귀분석식을 제시하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2003년도 추계학술발표회초록집
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• pp.118-118
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• 2003

In a rolling wire probe, a key component of an inspection apparatus for PDP electrode patterns, the electric performance of it is known to be strongly dependent on the surface condition of a collet pin, a needle pin, and a wire. However, the collet and needle pins rotate very rapidly in contact with each other, which results in the degradation of the surface by the heat and friction and finally the formation of black wear marks on the surface after a several hundred hours test. Once the black wear marks appear on the surface, the electric resistance of the probe increases sharply and so the integrity of the probe is severely damaged. In this experiment, TiN coating, which has excellent electric conductances and good wear-resistance, has been applied on the surface of collect and needle pins for preventing the surface damages. In order to achieve the homogeneous coating with a good adhesion property, special coating substrate stages and jigs were designed and applied during coating. TiN has been deposited using 99.999% Titanium target by a DC reactive sputtering method. According to the components and jigs, processing parameters, such as DC power, RF bias and the flow rate ratio of Ar and N$_2$ used as reactive gases, has been controlled to obtain good TiN films. Detailed problems and solutions for applying the new substrate stages and jigs will be discussed.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.118-126
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• 2003

In the present study, the residual stresses can have a significant on the life of structural engineering components. Residual stresses are created by the surface treatment such as shot peening or deep rolling. The objective of this experimental investigation is to study the influence of friction and wear characteristics due to residual stress under dry sliding condition. Friction and wear data were obtained with a specially designed tribometer. Test specimens were made of SUP9(leaf spring material) after they were created residual stress by shot peening treatment. Residual stress profiles were measured at surface by means of the X-ray diffraction. Sliding tests were carried out different contact pressure and same sliding velocity 0.035m/s(50rpm). Leaf spring assembly test used to strain gauge sticked on leaf spring specimen in order to measure interleaf friction of leaf spring. Therefore, we were obtained hysteresis curve. As the residual stresses of surfaces increased, coefficient of friction and wear volume are decreased, but the residual stresses of surfaces are high, and consequently wear volume do not decreased. Coefficient of friction obtained from leaf spring assembly test is lower than that obtained from sliding test. From the results, structural engineering components reduce coefficient of friction and resistant wear in order to have residual stresses themselves.

• 한국주조공학회지
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• 제24권2호
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• pp.108-114
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• 2004

$Al_2O_3$, SiC reinforced Al matrix composites were fabricated by centrifugal spray casting method and their wear resistance characteristics have been studied. Particles are generally uniformly distributed in the microstructure of as-cast specimens. In order to investigate the effect of secondary deformation, hot rolling was performed for each specimen of pure Al matrix composites with a reduction of 10, 20, 30, 40 and 50% at $400{\sim}500^{\circ}C$, respectively. Microstructure of specimen showed that particle distribution density and hardness increased because of increasing of reduction ratio. Wear test with a various sliding velocity of 1.98, 2.38, 2.88 and 3.53m/sec showed that the wear resistance characterization of composite improved remarkably compared to the normal alloy and performs without reinforced particles. Microstructural observation for the worn surface of pure Al specimens without particles showed that a change in wear mechanism seemed to separate layer by surface fatigue. In other case of Al composite reinforced with $Al_2O_3$ and SiC, the grinder type of wear mechanism was shown.

• Elastomers and Composites
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• 제46권1호
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• pp.70-77
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• 2011

슬러리와 접하는 환경에서 사용되는 고무 소재의 슬러리 마모 거동을 평가하기 위해 새로운 형태의 슬러리 마모시험기(Slurry Wear Tester; SWT)가 본 연구에서 제안되었다. 슬러리 마모 거동을 평가하기 위한 기본 매트릭스로 천연고무(NR)와 클로로프렌고무(CR)가 선정되었다. SWT 장치의 챔버를 채우기 위한 유체로는 35% HCl 용액과 NaCl 용액이 사용되었다. SWT의 결과는 기존의 고무 마모시험 방법들중의 하나인 건식 상태에서 시험이 진행되는 Akron 마모시험의 결과와 비교를 하였다. Akron 마모 시험의 결과에 따르면 CR이 NR 보다 더 빠른 속도로 마모가 됨을 알 수 있었으며 재료의 히스테레시스 특성이 마모에 영향을 미침을 알 수 있었다. 그러나 SWT 결과에 따르면 CR과 NR의 슬러리 마모거동은 큰 차이가 없었으며 더구나 산의 농도와 HCl 용액과 NaCl 용액에 침지된 시간에 따라서도 슬러리 마모속도에는 큰 영향이 없었다. 이는 슬러리에 포함된 유체가 마모지와 시편 사이의 마찰을 감소시켰기 때문이라고 사료되었다. 또한 Akron 마모 시험의 경우 고무 소재의 히스테레시스가 마모에 영향을 미쳤지만, SWT의 경우 유체는 반복 변형에 의해 발생되는 열을 감소시키고 마모지 표면에 남아있는 마모 찌꺼기들을 제거하였기 때문에 Akron 마모 시험의 결과와는 다른 결과를 나타내었다. 따라서 슬러리에 의한 고무 소재의 마모를 평가하는데 있어서 기존의 방식인 건식방법으로 마모 거동을 평가할 경우 잘못된 결과를 초래할 수 있음을 알 수 있었다.

• Tribology and Lubricants
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• 제27권6호
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• pp.321-325
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• 2011

Nanodiamond was dispersed in paraffin liquid oil to investigate the effects of nanodiamond at the marginally lubricated condition. Scuffing test and immediate loading sliding wear test were conducted using the fabricated nanodiamond oil. As a result, dispersion of nanodiamond in oil leads to increase in scuffing life, and nanodiamond contents affects the scuffing life. In case of immediate loading sliding wear test, the result was different according to hardness of specimen. If hardness of specimen was low, abrasion of nanodiamond occurred actively. If hardness of specimen was increased, however, nanodiamond can act as a spacer or rolling between contacting surfaces.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 제7회 압연 심포지엄
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• pp.65-71
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• 2009

The process of cold rolling is becoming more severe with the increase in the production of high tensile steel strip as a result of increased demand. Consequently, there is a need to develop work roll materials with better resistance to wear and roll failure. DOOSAN has developed an improved in-house 5%Cr alloy, New HSR1, with properties superior to the existing in- house 5%Cr alloy, Old HSR1. Test alloys were designed with controlled amounts of Si and Mn based on Old HSR1 and an optimum alloy was chosen based on thermal shock tests. A prototype work roll was manufactured with New HSR1, and properties of test specimens were evaluated. The results indicated that New HSR1 has better properties than Old HSR1. After application of New HSR1 work rolls, productivity increased due to advanced resistance to wear and roll failure.