FRICTION CHARACTERISTICS OF A PAPER-BASED FRICTION MATERIAL

Gao, H.,Barber, G.-C.,Chu, H. The Korean Society of Automotive Engineers 2002 International journal of automotive technology Vol.3 No.4

A bench test set-up is employed to simulate the friction characteristics of a paper-based friction material operating against a steel plate. Dry friction tests are run as well as tests with transmission fluids. Glazed friction material produces a negative coefficient of friction versus sliding velocity (f-v) curve for both dry friction and lubrication with transmission fluids. At low sliding speeds, the coefficient of friction when operating in transmission fluids for glazed friction materials is greater than that under dry friction. An appreciable negative f-v slope occurs at low sliding speeds for glazed friction materials when running with the transmission fluid. The friction material after running in produces a constant f-v curve under dry friction and a negative slope when lubricated with transmission fluid. At low sliding speeds, the coefficient of friction of the run-in friction material is lower than that of the glazed wet material. On the other hand, the run-in friction material has a larger friction coefficient than does the glazed friction material at higher sliding speeds.

Tribological Properties of Brake Friction Materials with Steel Fibers

박성빈,조근형,Sola Jung,장호겸 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.1

The tribological properties of brake friction materials with and without steel fibers were investigated. The focus of this study was determining the effect of steel fibers on the speed sensitivity of the friction coefficient. The speed sensitivity of the friction coefficient is closely associated with the stick-slip phenomenon. The results indicate that the friction material containing steel filbers was more sensitive to sliding speed, exhibiting a highly negative μ-v relation. In particular, the friction material with steel fibers showed a larger vibration amplitude during brake applications, suggesting that the μ-v relation was strongly related to the friction-induced vibration. On the other hand, the wear resistance of the friction materials containing steel was significantly better than that without steel fibers, suggesting longer service life. A possible mechanism of the stick-slip by the steel fibers is discussed in terms of the physical properties of the steel fiber and the gray iron rotor. The tribological properties of brake friction materials with and without steel fibers were investigated. The focus of this study was determining the effect of steel fibers on the speed sensitivity of the friction coefficient. The speed sensitivity of the friction coefficient is closely associated with the stick-slip phenomenon. The results indicate that the friction material containing steel filbers was more sensitive to sliding speed, exhibiting a highly negative μ-v relation. In particular, the friction material with steel fibers showed a larger vibration amplitude during brake applications, suggesting that the μ-v relation was strongly related to the friction-induced vibration. On the other hand, the wear resistance of the friction materials containing steel was significantly better than that without steel fibers, suggesting longer service life. A possible mechanism of the stick-slip by the steel fibers is discussed in terms of the physical properties of the steel fiber and the gray iron rotor.

Pre-Sliding Friction Control Using the Sliding Mode Controller with Hysteresis Friction Compensator

Choi, Jeong Ju,Kim, Jong Shik,Han, Seong Ik The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.10

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.

Friction compensation control of a feed drive system operated in a vacuum

송원택,심재윤,김남현,채근병,이원균 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.11

In a feed drive system, friction is a typical nonlinear component that increases the complexity of the dynamic behavior. A feed drive system equipped with rolling contact components, such as ball screws and linear motion guides, undergoes complicated friction behavior. In this regard, various techniques have been proposed to decrease the effect of friction and thus achieve the precise control of the feed drive system. Friction compensation control is a widely used technique that cancels out the friction force by applying an additional driving force that corresponds to the friction estimated by a friction model. A variety of friction models have been proposed to estimate the friction force accurately for friction compensation control. However, conventional friction models have focused on estimating the friction force of a feed drive system operating in atmospheric pressure although air pressure affects the friction characteristics. The accuracy of the conventional friction models might decrease for a feed drive system operated in a vacuum. This paper presents a friction compensation controller on the basis of a new friction model that considers the effect of the vacuum pressure on friction. A vacuum chamber that can control the vacuum pressure and a vacuum-compatible feed drive system are constructed to measure the friction force at various vacuum pressures. The relationship between the friction characteristics and the vacuum pressure is investigated on the basis of the experimental results and applied to the friction model. A friction compensation controller based on the friction model and Kalman filter is designed and evaluated experimentally.

Effect of anodized coating on friction noise in aluminum

남재현,강재영 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4

This study looks at the frictional noise and vibration generated by the relative motion of steel with an uncoated Al pin and an anodized Al pin in a reciprocating system. Frictional noise occurred with both the uncoated and anodized Al pins near 2 kHz and 7.2 kHz. However, the onset of the frictional noise with the uncoated Al pin was generated relatively quickly. The sound pressure level of the two specimens was similar at the moment when the friction coefficient became similar. The results of the surface characteristics using scanning electron microscope (SEM)/energy dispersive spectroscopy (EDS) analysis shows that the uncoated Al pin sharply generated wear from the beginning of the test. And, adhesive wear occurred at the edge of the contact surface. When the friction continued, there were increases in the debris due to material transfer on the worn surface, as well as oxygen and Fe on the surface. This result suggests that the friction surface was further damaged. In contrast, the coating on the anodized Al pin protected the friction surface at the beginning of the test and delayed the damage of the surface due to friction. However, as the friction continued, the coating surface was damaged because the nickel and sulfur added in the post-processing of the coating were reduced, and the debris was increased by the material transfer. Thus, the friction coefficient gradually increased at the anodized Al pin. And, frictional noise was generated. Frictional noise at the anodized Al pin was generated by the gradual increase in the friction coefficient.

마찰력이 작용하는 동적 시스템의 점착 구현을 위한 마찰모델 제안 및 정확성 검증

최찬규(Choi, Chan-Kyu),유홍희(Yoo, Hong-Hee) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.8

Friction causes self-excited vibration, stick-slip vibration and any other friction-induced phenomena. That kinds of vibrations cause chatter and squeal. In order to predict such vibrations accurately, employing an accurate friction model is very important because a dynamic behavior of a system with friction is dominantly governed by a friction model. A Coulomb friction model is the most widely known model. Coulomb friction model is useful model to obtain analytical solutions of the system with friction and the model gives relatively good simulation result. However, defining a friction force at a stick state in simulation is hard because of the characteristic itself and a Coulomb friction model is discontinuous function between a static and a dynamic friction coefficient. Therefore, applying the Coulomb friction model to a simulation is not appropriate. In order to resolve these problems, an approximated Coulomb friction model was developed using simple and continuous function. However, an approximated Coulomb friction model cannot realize stick. Therefore, an approximated Coulomb friction model cannot describe friction phenomena accurately. In order to analyze a friction phenomenon accurately, a friction model for a simulation was proposed in this paper. A proposed friction model realizes stick and gives reasonably good results compared to results obtained by the simulation employing an approximated Coulomb friction model. Accuracy of a proposed friction model was verified by comparing experimental results.

외국인 주식보유의 마찰효과

선정훈 ( Jung Hoon Seon ) 아시아.유럽미래학회 2015 유라시아연구 Vol.12 No.4

본 논문에서는 유가증권시장(이하 KOSPI) 기업과 코스닥시장(이하 KOSDAQ) 기업에서 외국인 주식보유 증가가 시장 유동성에 미치는 부정적인 영향인 외국인 주식보유의 마찰효과(friction effect)가 나타나는지를 고찰하고자 한다. 어떠한 시장마찰(market friction)도 존재하지 않는 완전 자본시장(perfect capital market)에서는 외국인 투자자의 주식보유가 시장 유동성에 영향을 미치지 않는다. 하지만, 주문처리비용(order processing cost), 재고보유비용(inventory hoding cost), 정보비대칭비용(asymmetricinformation cost) 등 시장마찰이 존재하는 현실의 자본시장에서는 외국인 투자자의 주식보유 증가가 시장 유동성에 영향을 미칠 수 있다. Stoll(2000)에 의하면 전체 마찰효과는 실질마찰(real friction)과 정보마찰(information friction)의 두 가지 요소로 구성될 수 있다고 한다. 여기서 실질마찰은 주문처리비용, 재고보유비용 등과 연관되고, 유동성 제공자의 실질적인 자원을 소모하여 발생 된 부분이다. 반면, 정보마찰은 정보비대칭비용과 관련되고, 유동성 제공자의 실질적인 자원을 소모하지 않지만 투자자들 간에 부(wealth)의 재분배를 가져오는 부분이다. 본 논문에서는 이러한 Stoll(2000)의 관점에 따라,외국인 주식보유의 마찰효과를 실질마찰과 정보마찰의 두 가지 요소로 구분하고, 각 요소의 존재 유무를 검증한다. 우리나라 주식시장에서 외국인 주식보유의 마찰효과가 실질마찰 또는 정보마찰, 아니면 두 가지 요소 모두에 기인하는지에 대한 실증적인 분석은 외국인 주식보유가 어떤 경로를 통해 시장유동성에 영향을 미치는지에 대한 시사점을 제시할 것으로 기대된다. 즉, 외국인 주식보유의 실질마찰의 존재는 외국인 주식보유가 거래활동 경로를 통해 주식의 시장유동성에 영향을 미치는 것을 의미한다. 그리고 외국인 주식보유의 정보마찰의 존재는 외국인 주식보유가 정보환경의 변화를 통한 경로를 통해 주식의 시장유동성을 변화시킴을 의미한다. 본 논문은 2009년 1월부터 2013년 12월까지 60개월을 표본기간으로 하고, 표본기간 중 연속적인 시계열 확보가 가능한 KOSPI 기업 355개 및 KOSDAQ 기업 436개를 표본 종목으로 선정한다. 분석에 활용된 자료는 각 종목의 외국인 주식보유 변수의 월말 자료와 일별 거래활동 및 가격충격 변수의 월간 평균 및 표준편차 자료 등이다. 외국인 주식보유는 발행주식수 대비 외국인 보유주식수의 비중으로, 거래활동은 회전율 또는 거래량으로, 가격충격은 Amihud(2002) 지표로 각각 측정된다. 본 논문은 고정효과 패널모형을 이용하여 해당 월의 거래활동 및 Amihud(2002) 가격충격 변수와 직전 월의 외국인 주식보유 간의 관계를 고찰한다. 본 논문의 주요 결과는 다음과 같이 요약된다. 첫째, KOSPI 및 KOSDAQ 기업 모두에서 외국인 주식보유 증가가 주식 거래활동에 부정적인 영향을 미치며, 이는 외국인 주식보유의 실질마찰이 나타난다는 증거로 해석된다. 둘째, KOSPI 기업에서는 외국인주식보유 증가가 가격충격에 미치는 부정적인 영향인 전체 마찰효과가 나타나지만, 실질마찰을 통제하면 사라진다. 이에 따라 전체 마찰에서 실질마찰을 차감한 부분으로 정의되는 정보마찰이 존재하지 않는것으로 해석된다. 마지막으로, KOSDAQ 기업에서는 외국인 주식보유의 전체 마찰효과가 나타나지 않는다. 이상의 결과들을 종합하면, 우리나라 주식시장에서 외국인 주식보유 증가가 시장유동성에 미치는 부정적인 영향은 주로 거래활동을 경유하고 유동성 제공자의 실질적인 자원을 소모하여 발생함을 시사한다. This paper investigates whether there exist the friction effects of foreign ownership in the stocks listed on the Korea exchange. The friction effects of foreign ownership is defined as a negative effect of foreign stock ownership on the market liquidity. In a perfect capital market in which any market friction does not exist, foreign stock ownership should not affect market liquidity. However, market frictions such as order processing costs, inventory holding costs, and information asymmetric costs exits in real stock markets and thus the friction effects of foreign ownership may exist. According to Stoll (2000), any friction effects that might occur in imperfect markets can be decomposed into two components.real friction and information friction. The real friction is related to order processing costs and inventory holding costs and the component that consumes real resources of liquidity providers. Meanwhile, the informational friction is related with information asymmetry costs and the component that redistribute investors’ wealth without consuming real resources of liquidity providers. Following Stoll (2000)’s view, we decompose the friction effects of foreign ownership into two components: the real and informational frictions. The real friction is defined as the negative impact of an increase in foreign ownership on the trading activity of stocks. The informational friction is defined as the adverse impact of an increase in foreign ownership on theasymmetric information costs of a stock. The empirical studies on whether the friction effects of foreign stock ownership come from real friction, informational friction, or both might suggest through which channel foreign stock ownership affect on market liquidity in a stock market. The existence of real friction indicates that foreign stock ownership impact the market liquidity through trading activity. The existence of informational friction suggests that foreign stock ownership impact the market liquidity through the changes in information environment. This paper uses monthly panel data for 791 firms (355 KOSPI firms and 436 KOSPI firms) from January 2009 to December 2013. Using the monthly panel data and two-way fixed effect panel model, this paper examine the relationship among this month’s trading activity and Amihud(2002) price impact, and previous month’s foreign stock ownership using each stock’s share price, volatility of share price, and market capitalization as control variables. The foreign stock ownership of a stock is measured as the shares of foreign stock ownership divided by the number of shares outstanding at the end of each month. The trading activity of a stock is measures as the monthly average of turnover ratio and trading volume ratio. Amihud(2002) price impact of a stock is computed as the monthly average of the ratio of daily mean absolute return to daily volume for each month. This paper finds the results as follows. First, the inverse relationship between lagged foreign ownership and trading activity of stocks - the real friction of foreign ownership is observed for both the KOSPI and KOSDAQ firms. Second, the adverse impact of lagged foreign ownership on the Amihud (2002)’s price impacts of stocks - the total friction effect of foreign ownership is found for the KOSPI firms. The adverse impact, however, is disappeared, when real friction is controlled in the friction effect. Lastly, the total friction effect of foreign ownership is not observed for KOSDAQ firms. Overall, the results suggest that friction effect of foreign ownership is driven by the real friction and the informational friction plays no role in the friction effect.

Stochastic modeling of friction force and vibration analysis of a mechanical system using the model

강원석,최찬규,유홍희 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.9

The squeal noise generated from a disk brake or chatter occurred in a machine tool primarily results from friction-induced vibration. Since friction-induced vibration is usually accompanied by abrasion and lifespan reduction of mechanical parts, it is necessary to developa reliable analysis model by which friction-induced vibration phenomena can be accurately analyzed. The original Coulomb’s frictionmodel or the modified Coulomb friction model employed in most commercial programs employs deterministic friction coefficients. However, observing friction phenomena between two contact surfaces, one may observe that friction coefficients keep changing due tothe unevenness of contact surface, temperature, lubrication and humidity. Therefore, in this study, friction coefficients are modeled asrandom parameters that keep changing during the motion of a mechanical system undergoing friction force. The integrity of the proposedstochastic friction model was validated by comparing the analysis results obtained by the proposed model with experimental results.

CMP에서의 스틱-슬립 마찰특성에 관한 연구

이현섭,박범영,서헌덕,박기현,정해도,Lee, Hyunseop,Park, Boumyoung,Seo, Heondeok,Park, Kihyun,Jeong, Haedo 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.4

Stick-slip friction is one of the material removal mechanisms in tribology. It occurs when the static friction force is larger than the dynamic friction force, and make the friction curve fluctuated. In the friction monitoring of chemical mechanical polishing(CMP), the friction force also vibrates just as stick-slip friction. In this paper, an attempt to show the similarity between stick-slip friction and the friction of CMP was conducted. The prepared hard pa(IC1000/Suba400 stacked/sup TM/) and soft pad(Suba400/sup TM/) were tested with SiO₂ slurry. The friction force was measured by piezoelectric sensor. According to this experiment, it was shown that as the head and table velocity became faster, the stick-slip time shortened because of the change of real contact area. And, the gradient of stick-slip period as a function of head and table speed in soft pad was more precipitous than that of hard one. From these results, it seems that the fluctuating friction force in CMP is stick-slip friction caused by viscoelastic behavior of the pad and the change of real contact area.

개인정보 유형의 정보 민감도에 따른 모바일 서비스 UI 디자인 프릭션 분석

이예나(Yena Lee),김현석(Hyunsuk Kim) 한국디자인학회 2024 디자인학연구 Vol.37 No.1

Background : ‘Design Friction’ is a microinteraction design that intentionally creates points of friction to ensure the user’s attention. Interactions lacking design friction can cause problems such as reduced accuracy and incorrect selection, and thus must be considered during the user experience/user interface (UX/UI) design process. Despite its significance, there remains a lack of in-depth research regarding design friction. Moreover, the fact that the characteristics of design friction can shift depending on the inherent risks of tasks has not been adequately discussed. Therefore, this study aims to analyze the design friction factors applied to each user task, discussing the appropriate direction of design friction in mobile services associated with user privacy. Methods : Through an extensive literature research, this study identified the key attributes of design friction. Based on this foundation, a categorization matrix was developed. Rigorous measures were taken to ensure the reliability of the study, including expert reviews and inter-coder reliability. Then, a dataset of 630 interface screens was collected for each user task related to mobile services that utilize personal information. Subsequently, cluster analysis and categorization were performed. Results : As a result of the study, the categorization matrix composed of four categories and fourteen checklists was designed for the analysis of design friction. Moreover, the research identified four distinct types of friction: Absence of Friction, General Friction, Visual Friction, and Proactive Friction. Building on these findings, the study proposed guidelines for tailoring design friction according to the sensitivity of the information involved. Conclusions : The theoretical significance of this study lies in its detailed classification of the design friction concept, which had previously been approached comprehensively, through a combination of literature review and content analysis. Furthermore, this study holds practical significance by introducing a friction measurement framework. This framework empowers designers to systematically appraise and gauge elements of stability and credibility in real-world contexts.