측면 에어 가이드 트랙을 이용한 새로운 운동마찰계수 측정장치의 개발

남형주 한국공학교육학회 2018 공학교육연구 Vol.21 No.3

In this study, a new experimental device was developed for measurement of the coefficient of kinetic friction using a photo gate timer system which have advantages of easy and accurate detection of motion. This device, consisting of a side air-guide track and a side friction-free glider, forces a friction sample to move in a straight line without producing unnecessary friction. The new device is compared to two conventional measuring methods of friction for four different friction samples: one is using a camera system and the other is using a force sensor. It is demonstrated that the developed friction device in this study is easier to operate and produces the most accurate and the least deviating results among them. On the basis of these results, we propose that friction experiment using the new friction device is included in general physics experiment, so that engineering students should have a chance to get correct understanding of classical mechanics including friction phenomenon.

Friction Characteristics of DLC and WC/C

Dong-Wook Kim(김동욱),Kyung-Woong Kim(김경웅) 한국트라이볼로지학회 2011 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.27 No.6

본 연구에서는 수직 하중과 미그럼 속도가 DLC(a-C:H)와 WC/C (a-C:H:W)의 마찰 특성에 미치는 영향을 파악하기 위해 ball-on-disk 형태의 마찰 실험 장치를 이용하여 실험을 수행하였다. 연구 대상 고체 윤활막인 DLC와 WC/C는 AISI 52100 steel ball의 표면에 증착되었으며, 상대 마찰면의 재질은 침탄 경화된 SCM 415 Cr-Mo steel이다. 실험은 상대 습도가 20~40% 이고 온도가 16~24℃인 대기 분위기에서 다양한 미끄럼 속도 (0.1, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50, 100 ㎜/s) 및 수직하중 (2.4, 4.8, 9.6 N) 조건에 대해 수행되었다. 실험 결과로 각각의 실험 조건에서의 DLC와 WC/C의 운동 마찰 계수를 얻었다. 실험 결과 DLC 와 WC/C의 운동 마찰 계수는 미끄럼 속도가 증가할수록 대체로 증가하였으며, 수직 하중에 관계없이 거의 일정한 갑을 보였다. 그리고 동일한 실험조건에서 DLC의 마찰 계수가 WC/C의 마찰 계수애 비해 대체로 낮은 값을 보였다. In this study, friction tests were performed in order to investigate the effect of sliding velocity and normal load on the friction characteristics of DLC (a-C:H) and WC/C (a-C:H:W) using a ball-on-disk type friction tester. DLC and WC/C were deposited on AlSI 52100 steel balls. Friction tests against carburized SCM 415 Cr-Mo steel disks were carried out under various sliding velocity (0.1, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 and 100 ㎜/s) and normal load (2.4, 4.8 and 9.6 N) conditions while the relative humidity was 20~40 % R.H. and air temperature was 16~24 ℃. As results, kinetic friction coefficients of DLC and WC/C were obtained under each test condition. The results show that the kinetic friction coefficients of DLC and WC/C generally increase with the increase in sliding velocity. And, under the same sliding velocity condition, the kinetic friction coefficients are almost constant regardless of normal load. In addition, the kinetic friction coefficients of DLC are lower than those of WC/C under the same test conditions.

Friction Characteristics of DLC and WC/C

김동욱,김경웅 한국트라이볼로지학회 2011 한국윤활학회지(윤활학회지) Vol.27 No.6

In this study, friction tests were performed in order to investigate the effect of sliding velocity and normal load on the friction characteristics of DLC (a-C:H) and WC/C (a-C:H:W) using a ball-on-disk type friction tester. DLC and WC/C were deposited on AISI 52100 steel balls. Friction tests against carburized SCM 415 Cr-Mo steel disks were carried out under various sliding velocity (0.1, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 and 100 mm/s) and normal load (2.4, 4.8 and 9.6 N) conditions while the relative humidity was 20~40 % R.H. and air temperature was 16~24 ℃. As results, kinetic friction coefficients of DLC and WC/C were obtained under each test condition. The results show that the kinetic friction coefficients of DLC and WC/C generally increase with the increase in sliding velocity. And, under the same sliding velocity condition, the kinetic friction coefficients are almost constant regardless of normal load. In addition, the kinetic friction coefficients of DLC are lower than those of WC/C under the same test conditions.

다물체 동역학 해석을 위한 마찰 접촉 모델링에 대한 연구

노현영(Hyun Young Roh),김범석(Bum Suk Kim),유홍희(Hong Hee Yoo) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This paper presents the method to remove the slip problem of the friction contact modeling employed in most of multibody dynamic analysis programs. Even if contact occurs between two rigid bodies with no slip condition, most of contact algorithms developed so far provide the results of low speed slip motion. The friction coefficient is defined as a spline function of relative velocities in most commercial codes. Such a function resolved the problem of the discontinuity in friction force. However, when the relative velocity approaches zero, friction coefficient approaches zero too. So, slip occurs when small force is applied. This problem of low speed slip is resolved in this study with a new modeling method.

다물체계의 자려진동 구현을 위한 마찰 모델링

노현영(Roh, Hyun-Young),유홍희(Yoo, Hong-Hee) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.6

This paper presents a friction model to realize self-excited vibration of multi-body systems. The friction coefficient is modeled with a spline function in most commercial codes. Even if such a function resolves the problem of discontinuity in friction force, it cannot realize self-excited vibration phenomena. Furthermore, as the relative velocity approaches zero, the friction coefficient approaches zero with the conventional model. So, slip occurs when small force is applied to the system. To avoid these problems a new friction model is proposed in this study. With the new friction model, the self-excited vibration can be realized since the friction coefficient changes with the relative velocity. Furthermore, the slip phenomena could be reduced significantly with the proposed model.

상해예방을 위한 무용슈즈 재질 변화와 바닥면과의 마찰 상관관계에 대한 정량적 연구

이효민,김선정,현준원 한국무용연구학회 2018 한국무용연구 Vol.36 No.2

This study includes the measurements of correlation coefficients of friction between the different materials of flooring and dance shoes using the sliding friction experiment (SG-9128). The aim of this study is to build a database applicable to various areas by procuring evidence through scientific experiments on the materials of flooring. Impact on dancer’s body in a variety of settings, and on the materials of dance shoes reduce damage to dancer’s body well-balanced, depending on dance shoe. Therefore, to determine correlations of friction among four types of flooring surface materials and three types of dance shoes, investigators measured coefficients of friction and intended the information helps dancers get optimum results. To control errors, two methods were applied. Results of this study found that the reasonable solution to reduce errors while experimenting on a slope was to insert weights at a constant weight of 380g in the dance shoes. 본 연구는 상해예방을 위한 무용슈즈 재질 변화와 바닥면과의 마찰 상관관계에 대한 정량적 연구를 위해 수행 되었다. 이러한 연구목적을 달성하기 위하여 무용연습실이나 실제 공연장 무대의 바닥면과 무용슈즈 재질간의 마찰계수를 측정하였다. 물리역학적 측정기구(sliding friction experiment, SG-9128)를 사용하여 미끄러지는 과정을 정확한 수치로 측정 하고, 제어 가능한 재질의 순위를 집계한 결과 다음과같은 결론을 도출하였다. 첫째, 오랜 기간 무용수들이 선택해온 재질이 합리적이었음을 과학적 데이터로 입증했다. 둘째, 마찰계수를 측정하고 무용수에게 과학적 데이터를 통하여 최적의 효과를 줄 수 있는 환경을 구축할 수 있게 정보를 제공하고자 하였다. 따라서 지속적인 연구를 한다면 더 좋은 재질을 개발해 낼 가능성이 있고, 무용슈즈 재질변화에 따른 바닥면 사이의 마찰에 대한 정량적 고찰을 함으로써 무용수들의심리적 안정감과 상해예방 차원에서 본 연구의 큰 의미를 찾아 볼 수 있다.

시료의 직선 운동이 가능한 마찰 계수 측정 실험 장치의 개발

남형주 한국물리학회 2016 새물리 Vol.66 No.7

A new experimental apparatus for friction, which enables easy and accurate calculation of the coefficient of kinetic friction by measuring the acceleration of a sample with a small error, has been developed. For this purpose, a friction track of optimum size and function, on which the guide rail was mounted so as to allow the sample to move linearly, was manufactured. Also, a glider that could move along this guide rail was manufactured. In addition, a photogate stand and a stanchion that work well without adjusting the photogate height or the angle for measuring the glider's acceleration were designed, and an easy way to attach and detach the sample to the bottom of the glider by using velcro tape was developed. Consequently, the coefficients of kinetic friction obtained from the new experimental apparatus were constant even for several experimental conditions: different angles or masses. 마찰 시료의 운동 가속도를 매우 작은 편차로 쉽고 정확하게 측정하여 운동 마찰 계수를 구할 수 있는 마찰 실험 장치를 개발하였다. 이를 위해 마찰 시료의 운동을 직선으로 제어할 수 있는 가이드 레일을 부착한 효율적인 크기와 기능의 마찰실험대를 제작하였다. 그리고 이 가이드 레일을 따라 운동할 수 있는 글라이더를 만들었다. 또한, 마찰실험대의 어떠한 경사각에서도 글라이더의 가속도를 측정하기 위한 포토게이트의 높이와 기울임의 조절이 필요 없는 편리한 새로운 포토게이트 스탠드와 지지대를 제작하였으며, 벨크로 테잎을 이용해 마찰 시료를 글라이더 바닥에 쉽게 탈 부착할 수 있는 방법을 개발하였다. 그리고 이 마찰 실험 장치로 각도와 질량의 조건을 달리하며 실험한 여러 실험에서 운동 마찰 계수는 상당히 일정한 값으로 측정되었다.

Agricultural Process and Food Engineering ; Moisture-dependent Physical Properties of Detarium microcarpum Seeds

( Ndubisi A. Aviara ),( Mary E. Onaji ),( Abubakar A. Lawal ) 한국농업기계학회 2015 바이오시스템공학 Vol.40 No.3

Purpose: Physical properties of Detarium microcarpum seeds were investigated as a function of moisture content to explore the possibility of developing bulk handling and processing equipment. Methods: Seed size, surface area, and 1,000-seed weight were determined by measuring the three principal axes, measuring area on a graph paper, and counting and weighing seeds. Particle and bulk densities were determined using liquid displacement and weight in a measuring cylinder, respectively. Porosity was computed from particle and bulk densities. Roundness and sphericity were measured using shadowgraphs. Angle of repose and static and kinetic coefficients of friction were determined using the vertical cylindrical pipe method, an inclined plane, and a kinetic coefficient of friction apparatus. Results: In the moisture range of 8.2%-28.5% (db), the major, intermediate, and the minor axes increased from 2.95 to 3.21 cm, 1.85 to 2.61 cm, and 0.40 to 1 .21 cm, respectively. Surface area, 1,000-seed weight, particle density, porosity, and angle of repose increased from 354.62 to 433.19 cm 2 , 3.184 to 3.737 kg, 1060 to1316 kg/m 3 , and 30.0% to 53.1%, respectively, whereas bulk density decreased from 647.6 to 617.2 kg/m 3 . Angle of repose increased from 13.9° to 28.4°. Static and kinetic coefficients of friction varied between 0.096 and 0.638 on different structural surfaces. Conclusions: Arithmetic mean, geometric mean, and equivalent sphere effective diameters determined at the same moisture level were significantly different from each other, with the arithmetic mean diameter being greatest. Surface area, 1,000-seed weight, particle density, porosity, and angle of repose all increased linearly with moisture content. Bulk density decreased linearly with moisture content. The coefficients of friction had linear relationships with moisture content. The highest values of static and kinetic coefficients of friction were observed on galvanized steel and hessian fabric, respectively, whereas the lowest values were observed on fiberglass.

Moisture-dependent Physical Properties of Detarium microcarpum Seeds

Aviara, Ndubisi A.,Onaji, Mary E.,Lawal, Abubakar A. Korean Society for Agricultural Machinery 2015 바이오시스템공학 Vol.40 No.3

Purpose: Physical properties of Detarium microcarpum seeds were investigated as a function of moisture content to explore the possibility of developing bulk handling and processing equipment. Methods: Seed size, surface area, and 1,000-seed weight were determined by measuring the three principal axes, measuring area on a graph paper, and counting and weighing seeds. Particle and bulk densities were determined using liquid displacement and weight in a measuring cylinder, respectively. Porosity was computed from particle and bulk densities. Roundness and sphericity were measured using shadowgraphs. Angle of repose and static and kinetic coefficients of friction were determined using the vertical cylindrical pipe method, an inclined plane, and a kinetic coefficient of friction apparatus. Results: In the moisture range of 8.2%-28.5% (db), the major, intermediate, and the minor axes increased from 2.95 to 3.21 cm, 1.85 to 2.61 cm, and 0.40 to 1.21 cm, respectively. Surface area, 1,000-seed weight, particle density, porosity, and angle of repose increased from 354.62 to $433.19cm^2$, 3.184 to 3.737 kg, 1060 to $1316kg/m^3$, and 30.0% to 53.1%, respectively, whereas bulk density decreased from 647.6 to $617.2kg/m^3$. Angle of repose increased from $13.9^{\circ}$ to $28.4^{\circ}$. Static and kinetic coefficients of friction varied between 0.096 and 0.638 on different structural surfaces. Conclusions: Arithmetic mean, geometric mean, and equivalent sphere effective diameters determined at the same moisture level were significantly different from each other, with the arithmetic mean diameter being greatest. Surface area, 1,000-seed weight, particle density, porosity, and angle of repose all increased linearly with moisture content. Bulk density decreased linearly with moisture content. The coefficients of friction had linear relationships with moisture content. The highest values of static and kinetic coefficients of friction were observed on galvanized steel and hessian fabric, respectively, whereas the lowest values were observed on fiberglass.

차량용 마그네틱 클러치의 마찰 특성

김동욱(Dong-Wook Kim),김경웅(Kyung-Woong Kim) 한국트라이볼로지학회 2009 한국윤활학회지(윤활학회지) Vol.25 No.4

A magnetic clutch consists of pulley and disk. It delivers and isolates the power needed for the operation of the compressor used in automotive air conditioning system. To improve the performance, efficiency and durability of automotive air conditioning system, appropriate design of pulley, disk and system working parameters(the magnitude of magnetic force, and so on) is necessary. For that goal, it is required to understand the friction characteristics of magnetic clutch for the initial operating time. In this study, friction tests were carried out in order to investigate the effect of sliding velocity on the friction characteristics of magnetic clutch using pinon-disk type friction and wear tester. For experiments, pulley and disk used in real automotive air conditioning system were considered. Friction experiments were conducted under various sliding velocities, and coefficients of kinetic friction were obtained. Under the experimental conditions considered in this study, the coefficients of kinetic friction increased with the increase of test number(sliding distance) and decreased with the increase of sliding velocity.