여러 마찰온도에서 유기계마찰재 제동 시 전이막 형성 및 이로 인한 마찰계수의 영향

정진오(Jinoh Chung),고상렬(Sangryul Go),최종근(Jonggeun Choi),최희범(Heebum Choi),김향래(Hyangrae Kim) 한국자동차공학회 2018 한국 자동차공학회논문집 Vol.26 No.1

To study transfer film formation and its effect on the friction coefficients in the NAO friction material, friction tests, composed of 100 consecutive braking under constant temperature, were conducted at temperatures of 300˚C, 400 ˚C, 500 ˚C, and 600 ˚C, respectively. Counterpart disks used in the friction tests were collected to examinetransfer film formation. Friction test results showed that the friction coefficient did not change much with repeated braking under 500 ˚C, but the friction coefficient decreased with repeated braking at 600 ˚C. The transfer film was hardly detected under 400 ˚C, but it was well developed at high temperature of 600 ˚C. The hardness analysis of the transfer film showed that the transfer film was softer than the counterpart disk material, and its effect was considered to reduce friction coefficients. The decrease in friction coefficients with consecutive braking under 600 ˚C was attributed to the development of the transfer film with repeated braking.

디스크 브레이크의 제동마찰 및 마멸특성에 관한 실험적 연구

김청균(Chung Kyun Kim),이병관(Boung Kwan Lee),김한구(Han Goo Kim) 한국트라이볼로지학회 2006 한국윤활학회지(윤활학회지) Vol.22 No.3

This paper presents the braking friction and wears on the rubbing surfaces of a friction pad-disk brake. In this study, four friction disk specimens are sampled from unused and used disks in which are taken from the disk brake system when the friction induced vibration and noise problems have been occurred during a braking period at a running period of 10,000 ㎞, 20,000 ㎞, and 30,000 ㎞ in random. The experimental results indicate that the tribological characteristics of an unused disk brake shows equal and stable as a friction coefficient and temperature distributions during a braking friction/wear test period including a total friction mode from the start to running periods. But the used disk brake shows unstable and uneven friction modes between an outside and inside rubbing surfaces of a disk brake in terms of a friction coefficient and wears. This may lead to a friction induced friction vibration and noise problems of a used disk brake.

주행로봇 제어를 위한 험지의 최대마찰계수 추정

강현석(Hyun-Suk Kang),곽윤근(Yoon Keun Kwak),최현도(Hyun-Do Choi),정해관(Hae-Kwan Jeong),김수현(Soo-Hyun Kim) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.10

When mobile robots perform the mission in the rough terrain, the traversability depended on the terrain characteristic is useful information. In the travers abilities, wheel-terrain maximum friction coefficient can indicate the index to control wheel-terrain traction force or whether mobile robots to go or not. This paper proposes estimating wheel-terrain maximum friction coefficient. The existing method to estimate the maximum friction coefficient is limited in flat terrain or relatively easy driving knowing wheel absolute velocity. But this algorithm is applicable in rough terrain where a lot of slip occurred not knowing wheel absolute velocity. This algorithm applies the tire-friction model to each wheel to express the behavior of wheel friction and classifies slip-friction characteristic into 3 major cases. In each case, the specific algorithm to estimate the maximum friction coefficient is applied. To test the proposed algorithm’s feasibility, test bed(ROBHAZ-6WHEEL) simulations are performed, And then the experiment to estimate the maximum friction coefficient of the test bed is performed. To compare the estimated value with the real, we measure the real maximum friction coefficient. As a result of the experiment, the proposed algorithm has high accuracy in estimating the maximum friction coefficient.

Experimental investigation of friction noise on lubricated contact

남재현,백종수,도현철,강재영 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.12

In order to remove friction noise, a lubricant is normally applied on the friction surface either after cleansing the contact surface or without any surface treatment. As the friction continues, the lubrication performance deteriorates and the friction noise can reoccur in the both cases, but the cause of friction noise may be different. This study originally investigates the mechanism of friction noise under a lubricant on either the clean or contaminated surface. During the friction noise test, the vibration and sound pressure, the changes in friction coefficient and the characteristics of the contact surfaces are measured for the two lubrication scenarios. Particularly, the surface image and chemical state on the contact area are measured by SEM/EDS analysis in sequence. The results show that friction noise under the lubrication on the clean surface is induced by the reduction of the lubricant causing the increase of friction coefficient. For the lubrication on the contaminated surface by wear debris, the lubricant is mixed and contaminated with wear debris, and then friction noise eventually occurs with the negative slope of the friction-velocity curve in the absence of the increase of friction coefficient.

D2 공구강과 접촉시의 두 자동차체용 강판의 마찰 거동

김종민(Chongmin Kim),이정욱(Jeong-Uk Lee),Frederic Barlat,이명규(Myoung-Gyu Lee) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5

The application of advanced high strength steels generally makes it necessary to use higher tool-sheet contact pressures compared with those used for forming low-strength steel, and it will lead to changes in frictional behavior significantly, which in turn change the final product characteristics. In order to understand frictional behaviors between steel sheets and tool materials under high contact stresses present in real stamping conditions, a novel friction tester was conceived, fabricated and used. This tester can generate high normal loads, as high as 625 MPa, whereas traditional friction testers were limited to 10 MPa or less. A mild steel and a TRIP780 steel were paired with Cr-coated D2 tool steel, and friction behaviors were observed under various conditions, including the use of lubricants, different sliding speeds and different normal contact stresses. The coefficient of friction decreased at a low contact pressure as the sliding velocity increased. The contact pressure had a significant effect, albeit too complex to be explained by simple models. The magnitude of change of friction constant due to changes in experimental conditions was enough to affect spring-back of automotive body panels significantly, thereby revealing the inadequacy of the traditional Coulomb’s Law of Friction. It was also evident that lubricant effects must be studied coupled with the contact pressure and sliding speed.

Tribology Characteristics in 300 μm of Hexagonal Array Dimple Pattern

최혜진,권순홍,권순구,박종민,김종순,정성원,채영훈,최원식 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.6

In the tribological performance of materials, a textured surface reduces the friction coefficient and wear. This study investigates the effects of a pattern of 300 μm dimples in a hexagonal array on the tribological characteristics. Previous studies investigated 200 μm dimples by using a similar material and method. There are three frictional conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction. In this experiment, we investigated the frictional characteristics by conducting frictional tests at sliding speeds ranging from 9.6 rpm to 143.3 rpm and a normal load ranging from 13.6 N to 92 N. We used a photolithography method to create dimples for surface texturing. We used five specimens with different dimple densities 10%, 15%, 20%, 25%, and 30% in this study. The dimple density on the surface area is one of the important factors affecting the friction characteristics. The duty number graph indicates a fully developed fluid friction regime. Fluid friction occurs at a velocity of 28.7-143.3 rpm. We observed the best performance at a dimple density of 10% and a dimple diameter of 300 μm in the hexagonal array, the lowest friction coefficient at 0.0037 with 9.6 rpm 9.6N load, and the maximum friction coefficient at 0.0267 with 143.3 rpm 92N load.

FRICTIONAL CHARACTERISTICS OF STEEL SHEETS USED IN AUTOMOTIVE INDUSTRY

T. TRZEPIECI SKI,A. BAZAN,H. G. LEMU 한국자동차공학회 2015 International journal of automotive technology Vol.16 No.5

In this paper the results of experimental tests aimed to determine the friction coefficient in sheet metal forming operations for various sheet metal materials and at different operative conditions are presented. The research has considered the frictional characterization of three kinds of drawing quality steels that are commonly used in automotive industry. These are a drawing quality steel (DQ), a deep drawing quality steel (DDQ), and extra deep drawing quality steel (EDDQ). For measurement of the sheet surface topography, a 3D stylus instrument Alicona InfiniteFocus was used. To determine the friction coefficient three tribological tests, i.e. a strip drawing test, a draw bead test and a pin-on-disc tribometer, have been conducted. The experimental results have ascertained several relationships showing the effect of sheet metal surface roughness, lubricant conditions and sheet orientation on the value of friction coefficient in sheet metal forming processes. The results further showed that the surface topography and sample orientation in the rolling direction of the sheet are significant factors that influence the friction coefficient. It was found that the tested steel sheets, selected from automotive industry applications, exhibit anisotropic resistance to the friction corresponding to the measured orientation in relation to the rolling direction of the sheet.

Estimation of the Road Friction Coefficient Using a Particle Filter

Do Ui Hong,ChanHo Park,GiSung Gwak,Sung-Ho Hwang 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-

In vehicle driving safety, the friction coefficient is the important factor in deciding braking distance. The road friction coefficient manifests non-Gaussian states. In this paper, we use a particle filter, which is a simulation-based approach and which approximates the posterior Probability Density Function (PDF), to estimate the road friction coefficient. We derive the equation of the friction coefficient from the Free Body Diagram (FBD) of the vehicle. Using this equation, we find the μ-slip curve for each different road condition. Through the μ-slip curve, we can determine the road friction coefficient by interpolation. We perform the simulation by Carsim, and the result shows that the particle filter tracks the friction coefficient more accurately than before.

Tribology Characteristics in 300 μm of Hexagonal Array Dimple Pattern

Choi, H. J.,Hermanto, A. S.,Kwon, S. H.,Kwon, S. G.,Park, J. M.,Kim, J. S.,Chung, S. W.,Chae, Y. H.,Choi, W. S. Korean Tribology Society 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.4 No.1

In the tribological performance of materials, a textured surface reduces the friction coefficient and wear. This study investigates the effects of a pattern of 300 µm dimples in a hexagonal array on the tribological characteristics. Previous studies investigated 200 µm dimples by using a similar material and method. There are three frictional conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction. In this experiment, we investigated the frictional characteristics by conducting frictional tests at sliding speeds ranging from 9.6 rpm to 143.3 rpm and a normal load ranging from 13.6 N to 92 N. We used a photolithography method to create dimples for surface texturing. We used five specimens with different dimple densities 10%, 15%, 20%, 25%, and 30% in this study. The dimple density on the surface area is one of the important factors affecting the friction characteristics. The duty number graph indicates a fully developed fluid friction regime. Fluid friction occurs at a velocity of 28.7-143.3 rpm. We observed the best performance at a dimple density of 10% and a dimple diameter of 300 µm in the hexagonal array, the lowest friction coefficient at 0.0037 with 9.6 rpm 9.6N load, and the maximum friction coefficient at 0.0267 with 143.3 rpm 92N load.

마찰계수의 비접촉 추정을 위한 영상정보 활용방법

김두규(Doo-gyu Kim),김자영(Ja-young Kim),이지홍(Jihong Lee),최동걸(Dong-Geol Choi),권인소(In-So Kweon) 大韓電子工學會 2010 電子工學會論文誌-SP (Signal processing) Vol.47 No.4

본 논문에서는 마찰계수의 비접촉 추정을 위한 영상정보 활용방법을 제안한다. 마찰계수는 이동체의 도로주행 또는 장애물 극복에 있어 매우 중요한 요소이다. 이동체가 이동경로의 마찰계수를 미리 알 수 있다면 이동성향상을 기대할 수 있다. 본 논문의 마찰계수 추정방법은 영상정보를 활용하기 때문에 이동체가 지면과 접촉하기 전에 마찰계수를 추정 할 수 있다는 장점이 있다. 마찰계수의 비접촉 추정을 위한 영상정보 활용방법은 마찰계수측정실험과 물질그룹생성을 포함한 학습단계와 물질그룹 분류과정과 마찰계수 함수 활용을 포함한 마찰계수 추정단계로 구성되어 있으며 물질 조성비를 생성하는 영상처리는 두 단계에 모두 포함된다. 이 과정을 통해 얻은 마찰계수는 무인이동로봇이 이동경로 진입 전에 미끄러움을 판단하여 미끄럼지역을 회피 할 수 있도록 하며, 저속으로 이동이 가능한 경우 미끄럼이 발생하지 않는 적정속도를 계산하는데 확용 가능하다. 본 논문에서 사용한 지형의 마찰계수와 영상정보는 마찰계수 측정실험을 통해 취득하였다. 마찰계수 추정방법을 평가하기 위해 실험지형의 실제 마찰계수와 추정 마찰계수의 차이를 비교하였다. In this paper, we proposed an algorithm for utilizing visual information for non-contact predicting method of friction coefficient. Coefficient of friction is very important in driving on road and traversing over obstacle. Our algorithm is based on terrain classification for visual image. The proposed method, non-contacting approach, has advantage over other methods that extract material characteristic of road by sensors contacting road surface. This method is composed of learning group(experiment, grouping material) and predicting friction coefficient group(Bayesian classification .prediction function). Every group include previous work of vision. Advantage of our algorithm before entering such terrain can be very useful for avoiding slippery areas. We make experiment on measurement of friction coefficient of terrain. This result is utilized real friction coefficient as prediction method. We show error between real friction coefficient and predicted friction coefficient for performance evaluation of our algorithm.