• 한국기계가공학회지
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• 제6권3호
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• pp.38-46
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• 2007

Weight reduction for an automobile component has been sought to achieve fuel efficiency and energy conservation. In response to this trend, a new disc-brake called the circumferential friction disc-brake is suggested. This paper compares the mechanical performances of a conventional disc-brake and a suggested disc-brake, under the dynamic braking condition. The thermoelastic instability is considered to simulate the test condition. Furthermore, the metamodel using kriging interpolation method is introduced to obtain the optimum design of a suggested circumferential friction disc-brake. The design results obtained by the kriging method are compared with those obtained by the ANSYS.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.665-670
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• 2000

The paper presents the dynamic instability of a disc brake pad subjected to distributed friction forces. A brake pad can be modeled as a beam with two translational springs. The study of this prototypical model is intended to provide a fundamental understanding of disc brake pad instabilities. Governing equations of motion are derived form energy expressions and their corresponding solutions are obtained by employing the finite element method. The critical distributed friction force and the instability regions are demonstrated by changing two translational spring constants. Finally, the changes of eigen-frequencies of a beam determining instability types are investigated for various combinations of two spring constants.

• International Journal of Precision Engineering and Manufacturing
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• 제5권1호
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• pp.13-18
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• 2004

In precision mechanical components that experience sliding, it is important to reduce the friction to minimize surface damage. Particularly, new lubrication methods are needed to reduce friction in silicon based micro-systems applications. In this work, the tribological characteristics of PFPE (Perfluoropolyether) Zdol lubricant on silicon were investigated based on the thickness of the film. The lubricant was coated on silicon wafer specimens by the dip coating method. It was shown that the friction coefficient as well as stiction decreased as the thickness of the film increased. The results of this work may be applied to improve the tribological performance of silicon based micro-system components.

• 한국항공운항학회지
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• 제14권3호
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• pp.16-22
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• 2006

The friction and wear of tire determined by frictional behavior of tire tread that translate driving force, cornering force and braking force between automobile and road as a result of frictional behavior of each tread block. The tire tread block is representative case of rubber block doing frictional behavior. In this paper, frictional behavior of rubber block under compressive force and shear force was analytically obtained by using slip starting position parameter instead of friction coefficient which is uncertain to express exact value between rubber and other surfaces yet. And local coefficients of friction were calculated as a function of compressive force, shear force, shear modulus of rubber, shape factor and slip starting position.

• 한국전산구조공학회논문집
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• 제23권4호
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• pp.435-443
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• 2010

본 연구에서는 MR(Magneto-Reological)제어기가 설치된 단자유도 구조물의 응답을 예측하기 위하여 구조물의 운동방정식을 해석적으로 분석하고 주요변수를 파악하였다. MR제어기의 수치 모델로는 마찰 및 점성감쇠로 단순모델한 Bingham모델을 사용하였다. 자유진동과 조화진동일때의 응답감쇠를 결정짓는 주요변수가 각각 마찰력과 최대정적복원력의 비 $R_f$, 마찰력과 최대조화가진력의 비 $R_h$ 임을 파악하였다. 비선형 미분방정식을 등가의 선형 미분방정식으로 변환하기 위하여 마찰력에 의한 에너지 소산을 등가의 점성에너지로 치환하여 등가점성감쇠와 등가점성감쇠비를 유도하였다. 마지막으로 등가선형화과정을 검증하기 위하여 실제 지진에 대한 구조물의 응답을 비선형 미분방정식의 해와 비교하였다.

• 한국수소및신에너지학회논문집
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• 제26권6호
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• pp.659-665
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• 2015

In this study, an experimental investigation is performed for evaluation of a liquid pool spreading model with continuous release. The model considered in this study was developed based on a concept which means that the liquid pool spreading is governed by a balance between an inertia force from gravity and a frictional force from friction with the ground under the whole base of the liquid pool. For evaluation of the model, experimental study is performed. Experimental apparatus is setup for measuring release rate, spreading velocity, and evaporation rate from a liquid pool. The experimental results are compared with results from the model. By applying release and evaporation rates obtained from experiments to solving the model, liquid pool radius variation according to time can be obtained. For evaluation of an effect of friction force in the spreading model, results obtained from the models with and without the friction force are compared with those obtained from the experiments. As a result, it is shown that there exists a large deviation between the results obtained from the model without the friction force and the experimental results. On the other hand, the tendency of liquid pool radius variation according to time is similar between the results obtained from the model without the friction force and the experimental results.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.67-76
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• 1998

Friction materials for brake linings and clutches have severe performance requirements. The principal function of such frictional elements is to convert kinetic energy to heat, and then either to absorb or to dissipate heat. In order to achieve these objectives, the coefficient of friction must be as high as possible, independent of variations in operating conditions, and the necessary energy conversion must be accomplished with a minimum of wear on the contacting parts. In this study, Al powder, Al bronze powder and Mo powder used in general for automobile brake was sprayed on automobile brake disc to restrain rust and to maintain friction performance. Dynamo and corrosion tests have been carried out. It is concluded that the sprayed disc with Al bronze powder has the most improved frictional performance and anti-corrosive characteristics. The main results obtained can be summarized as follows; 1. From the corrosion current density test for gray cast iron and sprayed disc with powders of Al, Al bronze and Mo, it was cleared that the spray treatment with Al bronze powder showed the most superior anti-corrosive characteristics than other powders. 2. By anode polarization toward the noble direction from corrosion potential, corrosion current density with sprayed brake disc by Al-bronze powder was the lowest. 3. Mean frictional coefficients obtained from dynamo test are as follows : the sprayed disc with Al(99.99%) powder was 0.190 ; the sprayed disc with Al-bronze powder was 0.312 ; the sprayed disc with Mo powder was 0.257 ; the non-sprayed disc of gray cast iron was 0.331. In the case of the sprayed disc Al-bronze powder showed the most excellent frictional characteristics . 4. Amount of burnish quantity obtained from burnish test by dynamometer is as follows : the sprayed disc with Al-powder was 1.079 mm : the sprayed disc with Al-bronze powder was 0.155 mm : the sprayed disc with Mo powder was 0.253 mm : the non-sprayed disc of gray cast iron was 0.241 mm. Al-bronze powder also showed the most excellent burnish characteristics.

• 한국강구조학회 논문집
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• 제28권4호
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• pp.223-229
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• 2016

이 연구에서는 고무 스프링과 자력마찰을 조합한 스마트 댐퍼의 동적 실험을 수행하여 스마트 댐퍼의 깃발모양 (flag-shaped) 거동을 확인하고자 하였다. 스마트 댐퍼 동적실험을 수행하기 위하여, 네오디뮴 (NdFeB) 자석을 사용하였으며 $50mm{\times}50mm{\times}25mm$ ($B{\times}L{\times}H$)의 크기를 사용하였다. 또한 폴리우레탄 고무를 사용하였으며 길이 80mm 외경 80mm 내경 20mm의 크기의 원주형 고무스프링을 사용하였다. 동적 실험에서 자석의 개수와 진동수를 제어하여 수행하였으며, 자석의 개수는 0, 4, 8, 12개의 순서로 증가하였으며, 이는 자력 마찰력이 증가함을 의미하였다. 진동수는 0.1부터 2.0Hz까지 증가시키면서 진행하였다. 실험의 진행은 고무 스프링이 장착되지 않은 자력마찰 댐퍼의 자력 마찰력 평가 실험, 고무 스프링의 기압축량 평가 실험 및 최종적으로 자력 마찰력과 기압축 고무스프링이 합성된 스마트 댐퍼의 동적 실험 순서로 진행하였다. 실험 결과를 통하여 스마트 댐퍼의 깃발모양 거동을 평가하고 에너지 소산능력, 감쇠비를 평가하여 스마트 댐퍼로서의 성능을 확인하였다.

• 한국농공학회지
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• 제23권3호
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• pp.96-104
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• 1981

In order to investigate the characteristics of the shear strength of the unsaturated cohesive soils which has mean characters of sand and clay widely used for banking, I selected soil samples from An-sung district and, against it, performed direct shear test and unconfined compression test changing grain size, compaction energy and moisture content and also performed triaxial compression test under optimum moisture content. The results are as follows; 1.As the passing percent of the No. 200 sieve increased from 23.6% to 56.1%, cohesion increased from 0. 202kg/cm2 to 0. 398kg/cm2 under the direct shear test and from 0.38 kg/cm2 to 1. 05kg/cm2 under the tria4al compression test, internal friction angle decreased from 44. 78$^{\circ}$ to 34. 34$^{\circ}$ under the direct shear test and from 31. 88$^{\circ}$ to 13. 31$^{\circ}$ under the triaxial compression test. 2.Cohesion showed it's maximum value around OMC and internal friction angle showed a tendency to increase according to the decrease of water content but it's increasing ratio was relatively slow. 3.Decreasing ratio of cohesion and internal friction angle was relatively sensitive according to the decrease of compaction energy. 4.The smaller of the vertical stress and the coarser of the grain size of samples, changing of the volume showed a tendency to increase and as the increase of water content, the shear displacement (dh) at failure shear stress ($\tau$f) showed maximum and the $\tau$f-dh curve was gentle. 5.To synthesize the results of the direct shear test and the triaxial compression test, cohesion showed higher under the triaxial compression test and internal friction angle showed a tendeney to appear higher under the direct shear test. It seems that we can get correspondent results by removing the side friction of mold with soils and adjusting the vertical stress and shearing speed under the direct shear test.

• Geomechanics and Engineering
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• 제29권2호
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• pp.113-131
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• 2022

A rockburst is a common disaster in deep-tunnel excavation engineering, especially for high-geostress areas. An anomalously low friction effect is one of the most important inducements of rockbursts. To elucidate the correlation between an anomalously low friction effect and a rockburst, we establish a two-dimensional prediction model that considers the discontinuous structure of a rock mass. The degree of freedom of the rotation angle is introduced, thus the motion equations of the blocks under the influence of a transient disturbing force are acquired according to the interactions of the blocks. Based on the two-dimensional discontinuous block model of deep rock mass, a rockburst prediction model is established, and the initiation process of ultra-low friction rockburst is analyzed. In addition, the intensity of a rockburst, including the location, depth, area, and velocity of ejection fragments, can be determined quantitatively using the proposed prediction model. Then, through a specific example, the effects of geomechanical parameters such as the different principal stress ratios, the material properties, a dip of principal stress on the occurrence form and range of rockburst are analyzed. The results indicate that under dynamic disturbance, stress variation on the structural surface in a deep rock mass may directly give rise to a rockburst. The formation of rockburst is characterized by three stages: the appearance of cracks that result from the tension or compression failure of the deformation block, the transformation of strain energy of rock blocks to kinetic energy, and the ejection of some of the free blocks from the surrounding rock mass. Finally, the two-dimensional rockburst prediction model is applied to the construction drainage tunnel project of Jinping II hydropower station. Through the comparison with the field measured rockburst data and UDEC simulation results, it shows that the model in this paper is in good agreement with the actual working conditions, which verifies the accuracy of the model in this paper.