• Tribology and Lubricants
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• 제17권6호
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• pp.459-466
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk on friction characteristics in various sliding conditions were investigated. AISI52100 steel ball was used for the substrate of coated ball specimens, which were prepared by depositing TiN coating with 1(m in coating thickness. AISI1045 steel was used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of two materials, the tests were performed both in air for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation. From the test results, the frictional characteristic between the two materials was predominated by iron oxide layer that formed on wear tract of counter-body and this layer caused friction transition and high friction. And the adhesive wear occurred from steel disk to TiN coated ball caused the formation of oxide layer on counter parts between the two materials.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.116-117
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• 2006

Conventional high-speed steels, which are carbide decentralized materials, are used for sliding parts, but they lack sufficient hardness for some applications. Improvement of surface hardness is possible for high-Cr steels through nitriding. However, nitriding P/M parts is not advisable without sealing the porosity before treatment, as they will become brittle. However, it is difficult to seal the pores with steam treatment, because high-Cr steel has a passive film on the surface. Controlling nitriding by decreasing the amount of oxygen on the surface to be nitrided, and grinding to decrease the porosity of the surface, makes it possible to produce a material that has reasonable and sufficient hardness in the required areas.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.67-68
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• 2002

The properties and mechanism of silicon protuberance and groove processing by diamond tip sliding using atomic force microscope (AFM) in atmosphere were studied. To control the height of protuberance and the depth of groove, the processed height and depth depended on load and diamond tip radius were evaluated. Nanoprotuberances and grooves were fabricated on a silicon surface by approximately 100-nm-radius diamond tip sliding using an atomic force microscope in atmosphere. To clarify the mechanical and chemical properties of these parts processed, changes in the protuberance and groove profiles due to additional diamond tip sliding and potassium hydroxide (KOH) solution etching were evaluated. Processed protuberances were negligibly removed, and processed grooves were easily removed by additional diamond tip sliding. The KOH solution selectively etched the unprocessed silicon area. while the protuberances, grooves and flat surfaces processed by diamond tip sliding were negligibly etched. Three-dimensional nanofabrication is performed in this study by utilizing these mechanic-chemically processed parts as protective etching mask for KOH solution etching.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.787-792
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• 1996

The method of manipulation by striking a part and letting it slide until it comes to rest, has been very little studied. However, the manipulation method is not uncommon in our daily lives. We analyze the dynamic behavior of a rigid polygonal part being striked and sliding on a horizontal surface under the action of fiction. There are two parts in this problem; one is the impact problem, and the other is the sliding problem. We characterize the impact and sliding dynamics with friction for polygonal parts, and present the possibility of reverse calculation for motion planning of striking operations. Using a high speed video camera, the computer simulation results are experimentally verified.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.222-226
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• 2009

The parts of building which has the most influence on thermal load are skins, outer walls and windows. Among them, window is the worst weak point of building even if it has many advantage of solar radiation gain than other parts. The present time, many researches on various performance of window and many types of system-window are being made. This study evaluates thermal performance of tilt & sliding system window by simulation program Therm 5.2 and Window 5.2. After making a sample model improving it's thermal weak point, this study evaluates real thermal performance of system window. As a result, this study understands manufacture ability condition of domestic company and proposes a research plan of system window.

• 지질공학
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• 제14권4호
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• pp.451-460
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• 2004

사면안정해석에 일반적으로 이용되는 2차원 한계평형해석에서는 활동면의 강도를 활동면 전체에 동일하게 설정한다. 그러나 사면의 활동면에서 저면부와 가장자리부의 강도는 다른 경우가 대부분이다. 4가지 절취모델을 이용한 3차원 사면안정해석의 결과에 따르면 활동면내에서 가장자리부의 저항력이 사면의 안정성에 크게 영향을 미치는 것으로 나타났다. 3차원 사면안정해석에서 활동면 강도를 저면부와 가장자리부로 구분하여 설정함으로써 지금까지 고려하지 못했던 사면 가장자리부의 전단강도가 사면안정에 미치는 영향을 정량적으로 파악할 수 있었다. 활동 저면부의 저항력이 낮은 경우에는 사면의 측부 절토에 의하여 안전율이 크게 저하되며, 저항력이 높은 경우에는 말단부 절토에 의하여 안전율이 저하되고 두부 절토에 의하여 안전율이 향상된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.799-804
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• 2003

Friction phenomenon can be described as two parts which are pre-sliding and sliding regions. In motion of the sliding region, friction forces depend on the velocity of the system and are known as Coulomb, stick-slip, stribeck effect and viscous friction. The pre-sliding region, which is before breakaway, depends on the position of the system. The motion of friction in the sliding region can be described as the LuGre model. But the pre-sliding motion of friction, which has hysteresis characteristics in general, is not known widely. Therefore, an improved friction model, which can describe the motion of friction in the pre-sliding region, is proposed in this paper. And simulation and experimental results show the effectiveness of the proposed friction model for precise tracking control systems.

• 제어로봇시스템학회논문지
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• 제13권1호
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• pp.15-18
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• 2007

We consider the problem of designing a static output feedback sliding mode control law for linear dynamical systems with mismatched uncertainties in the state matrix. We assume that an output dependent sliding surface guaranteeing the quadratic stability of the sliding mode dynamics is given, the reachability condition is not required to be satisfied globally, and the output feedback sliding mode control law complises both linear and discontinuous parts. We reduce the problem of designing the linear part of the sliding mode control law to a simple LMI problem which offers design flexibility for combining various useful convex design specifications. Our approach does not require state transformation and it can be applied to mismatched uncertain systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2290-2292
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• 2000

Robustness characteristics to the modelling imprecision and some disturbances could be achieved in sliding mode control. However, there are drawbacks such as discontinuous control and chattering. Recently, many researches have been developing to solve such the problems. In sliding mode control, overall control input could be divided into two parts which are equivalent control input and sliding mode control input. Sliding mode control input is a function of the switching surfaces and can be designed with their linear combinations. In this paper, the sliding mode control input is designed by TSK fuzzy model. The proposed method gives the continuous sliding control input and reject the chattering phenomenon.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1755-1762
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• 2004

Friction phenomenon can be described as two parts, which are the pre-sliding and sliding regions. In the motion of the sliding region, the friction force depends on the velocity of the system and consists of the Coulomb, stick-slip, Streibeck effect and viscous frictions. The friction force in the pre-sliding region, which occurs before the breakaway, depends on the position of the system. In the case of the motion of the friction in the sliding region, the LuGre model describes well the friction phenomenon and is used widely to identify the friction model, but the motion of the friction in the pre-sliding such as hysteresis phenomenon cannot be expressed well. In this paper, a modified friction model for the motion of the friction in the pre-sliding region is suggested which can consider the hysteresis phenomenon as the Preisach model. In order to show the effectiveness of the proposed friction model, the sliding mode controller (SMC) with hysteresis friction compensator is synthesized for a ball-screw servo system.