The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Ho Jang - One of the best experts on this subject based on the ideXlab platform.
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wear and Friction induced vibration of brake Friction Materials with different weight average molar mass phenolic resins
Tribology Letters, 2015Co-Authors: M W Shin, Ho JangAbstract:The Friction and wear of brake Friction Materials containing phenolic resins with different weight average molecular masses (M w = 2.2–6.1 kg/mol) were investigated using a Krauss-type tribometer and a reduced-scale dynamometer. The results demonstrated that the Friction level, wear rate, and Friction instability were strongly affected by the M w of the phenolic resin, attributed to the different shear strengths of the Friction Materials. The high-M w phenolic resin exhibited an increased Friction level while reducing the wear rate, with both effects more pronounced at temperatures above the phenolic resin decomposition temperature. The Friction Materials containing the higher-M w phenolic resins also showed an improved Friction instability, revealing a lower critical velocity for the incidence of Friction oscillation. The stiffness measured from the Friction Material revealed that the M w did not change the surface stiffness after the Friction tests, indicating that the improved Friction-induced vibration of the Friction Material with the high-M w phenolic resin was attributed to an increased matrix stiffness rather than to the sliding surface.
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Friction induced intermittent motion affected by surface roughness of brake Friction Materials
Wear, 2013Co-Authors: M W Shin, Ho JangAbstract:Abstract The effect of the surface roughness of the brake Friction Material on Friction-induced instability was studied. Commercial Friction Materials with different surface roughness levels were tested using a scale brake dynamometer to find a correlation between the surface roughness and Friction oscillation. The results showed that the normal contact stiffness was strongly affected by surface roughness and played a significant role in determining the Friction oscillation pattern. The Friction force oscillation changed from stick-slip to sinusoidal oscillation and steady sliding as the sliding velocity increased, and the velocity ranges for different oscillatory patterns were changed by the surface roughness. A smooth surface with glazed patches produced Friction oscillation with larger amplitudes, and the oscillation was maintained over a wider range of sliding velocities due to the high contact stiffness. The correlation between the contact stiffness and surface roughness suggested that Friction-induced instability might be avoided by designing the Friction Material to have low surface stiffness.
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effect of surface contact conditions on the stick slip behavior of brake Friction Material
Wear, 2012Co-Authors: S W Yoo, M W Shi, W G Lee, Ho JangAbstract:Abstract Brake-induced stick–slip, which determines the propensity of a brake system to generate noise, was investigated by analyzing the Friction oscillation at different loads, speeds, and surface topographies. The Friction characteristics at the sliding interface were obtained using a pad-on-disk type tribometer and a 1/5-scale brake dynamometer. Results showed that the size and stiffness of the surface contact plateaus significantly affect the propensity of stick–slip and wear. The stick–slip amplitude increased with normal load and decreased with sliding speed. Contact stiffness of the Friction Material, which was modified by producing shallow slots on the rubbing surface, also strongly affected the stick–slip propensity, whereas Δμ(= μ s − μ k ) was not changed by the surface modification. The strong effects from the contact stiffness suggest that the height distribution of the surface plateaus can change the stick–slip propensity of a brake Friction Material.
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tribological performance of brake Friction Materials containing carbon nanotubes
Wear, 2010Co-Authors: H J Hwang, S L Jung, Ho JangAbstract:Abstract This study examined brake Friction Materials containing multi-wall carbon nanotubes (CNTs) to determine their effect on the braking performance. The Friction Materials were produced using conventional dry mixing methods by substituting barite with CNTs (1.7, 4.7, and 8.5 wt.%). Their tribological properties were examined using both a Krauss type tester and a 1/5 scale brake dynamometer. The physical and tribological properties were affected considerably by the CNT content in the Friction Material. In particular, the CNT-added Friction Materials showed improved fade resistance and Friction stability. Moreover, the CNTs decreased the Friction force oscillation during brake application, which was attributed to the increased damping capacity of the Friction Materials. However, the CNTs decreased the Friction effectiveness owing to the lubricating nature of undispersed CNT bundles, and decreased the thermal conductivity of the Friction Material due to interfacial coupling effects.
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effects of ingredients on tribological characteristics of a brake lining an experimental case study
Wear, 2005Co-Authors: Min Hyung Cho, Seong Jin Kim, Daehwan Kim, Ho JangAbstract:Abstract A brake lining containing 16 ingredients was investigated to study the effect of ingredients on various aspects of Friction properties. The composite was developed for a non-asbestos organic based Friction Material for an automotive brake system and contained typical ingredients for commercial brake Friction Materials. Based on a basic formulation, 32 different Friction Material specimens were produced according to an experimental design. The influence of the ingredients on wear rate, fade (loss of Friction), Friction-induced vibration, and noise propensity was examined using a scaled Friction tester. This investigation confirmed that the specimen with high porosity and compressibility had low noise propensity. Results also showed that the Friction Materials with higher contents of phenolic resin, rockwool, zirconium silicate (zircon), MgO, and Ca(OH) 2 had high noise propensity and cashew resin reduced the noise occurrence. Wear resistance of the Friction Material was strongly affected by the relative amounts of magnesia, rockwool, calcium hydroxide, and zirconium silicate.
Jayashree Bijwe - One of the best experts on this subject based on the ideXlab platform.
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nao Friction Materials with various metal powders tribological evaluation on full scale inertia dynamometer
Wear, 2010Co-Authors: Mukesh Kumar, Jayashree BijweAbstract:Abstract A right selection of filler, its type, shape, size, amount and its compatibility with other co-fillers contribute to the performance of a Friction Material. Among various types of fillers, metallic fillers are very important and multifunctional. In spite of well-accepted fact that these affect all performance properties of Friction Materials, in depth studies and systematic evaluation as per standard procedure are not documented. Hence, in this work three Friction composites were developed in the laboratory with identical parent composition (90 wt.%) except metallic filler (10 wt.%) viz. brass, copper and iron powders while one more composite was developed without any metal contents for comparison's sake. These were characterized for physical, thermo-physical, chemical and mechanical properties. For tribo-evaluation inertia brake-dynamometer testing which reflects the most realistic performance was selected. The various performance properties like Friction, μ sensitivity to load, speed and temperature were studied as per industrial schedule. It was concluded that inclusion of metal contents, improved almost all the performance properties and copper containing composite showed best tribo-behavior followed by brass and then iron powder containing composite. Composite without metal powder proved poorest. Worn surface analysis and wear mechanism are also discussed in detail.
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role of different metallic fillers in non asbestos organic nao Friction composites for controlling sensitivity of coefficient of Friction to load and speed
Tribology International, 2010Co-Authors: Mukesh Kumar, Jayashree BijweAbstract:Abstract Sensitivity of μ (coefficient of Friction) of Friction composites towards load and speed is composition specific. For an ideal Friction Material, it should be zero. It was of interest to examine the influence of increasing amount of three commercially popular metallic fillers (steel fiber, brass fiber and copper powder) on the tribological performance of Friction composites including sensitivity of μ towards load and speed. Three series of non-asbestos organic (NAO) Friction composites comprising of seven composites in the form of brake pads were developed in the laboratory using three metallic fillers as a single variant. All composites were characterized for physical, chemical and mechanical properties. These were further tribo-tested on reduced scale prototype (RSP) for Friction, wear and sensitivity of Friction coefficient (μ) towards load and speed characteristics. It was concluded that inclusion of metal contents led to enhancement in Friction performance of the composites but at the cost of wear resistance, in general. From μ sensitivity point of view, composites with higher metallic contents and hence thermal conductivity (TC) showed better performance. Overall it was observed that copper powder based composite (with 10%) proved as the best performer from both Friction and wear point of view.
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influence of modified phenolic resins on the fade and recovery behavior of Friction Materials
Wear, 2005Co-Authors: Jayashree Bijwe, N Majumdar, Bhabani K SatapathyAbstract:Abstract The formulation of a Friction Material requires the optimization of multiple performance criteria. These include achieving a stable and adequate coefficient of kinetic Friction (μ) and minimizing its sensitivity to the brake operating parameters in order to produce low fade and high recovery characteristics. Low wear rates and a resistance to objectionable noise and vibration must be coupled with good strength through appropriate fabrication practices. Among the foregoing requirements, resistance to fade is particularly difficult to achieve. Resin is one of the most important ingredients in Friction Materials because it binds the ingredients firmly and allows them to contribute effectively to the desired performance. Ideally, there should be no significant deterioration in the function of the binder when the brake is operated under diverse conditions. However, when excessive Frictional heat is generated, changes in the resin can deteriorate performance. Consequently, a Friction Material's thermal stability, its capacity to retain mechanical properties, and its ability to hold its ingredients together under adverse conditions all depend on the resin. Despite this, little or no information on the effects of resin chemistry on Friction braking under adverse conditions has been reported in the open literature. Hence, the current work investigates the characteristics of five resins: (i) straight phenolic resin, (ii) alkyl benzene modified resin, (iii) cashew nut shell liquid modified resin, (iv) NBR modified resin, and (v) linseed oil modified resin. The same weight percent of each resin (10%) was used to make Friction Materials containing similar additions of 10 additives. The mechanical properties of these Materials were characterized using ASTM standards. Fade and recovery studies were carried out on a Krauss testing machine following the Economic Commission for Europe regulation for replacement brake linings (ECE R-90). Friction and wear characteristics varied with the type of resin, and no resin proved best for all the selected performance parameters. Alkyl benzene modified resin composite proved best in terms of strength, Friction, fade and recovery, but was poorest in wear performance. Results for linseed oil based phenolic resin composites showed exactly the opposite behaviour. Scanning electron microscopy was used to help understand the wear mechanisms and the causes for these differences.
Hendrik Van Brussel - One of the best experts on this subject based on the ideXlab platform.
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distinguishing the effects of adhesive wear and thermal degradation on the tribological characteristics of paper based Friction Materials under dry environment a theoretical study
Tribology International, 2015Co-Authors: Agusmian Partogi Ompusunggu, Hendrik Van BrusselAbstract:Abstract Adhesive wear and thermal degradation are the main aging mechanisms of paper-based Friction Materials. However, how these aging mechanisms affect the tribological characteristics of such Materials is not fully understood. In this paper, the respective influences of the two aging mechanisms on the tribological characteristics of the Friction Materials are investigated through simulation. It is assumed that adhesive wear pre-dominantly affects the surface topography, while thermal degradation significantly affects the mechanical properties of the Friction Material. The simulation results show that the static Friction coefficient and both normal and tangential contact stiffnesses increase due to adhesive wear, but decrease due to thermal degradation. These trends are qualitatively in agreement with experimental observations reported in the literature and our previous work.
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contact stiffness characteristics of a paper based wet clutch at different degradation levels
Proceeding of the 17th International Colloquium Tribology 2010 Solving Friction and Wear Problems, 2010Co-Authors: Agusmian Partogi Ompusunggu, Hendrik Van Brussel, Thierry Janssens, Farid Albender, Steve VandenplasAbstract:After clutch engagement in the post-lockup phase, the contact stiffness between Friction Materials and separators plays an important role in the dynamic behaviour of an Automatic Transmission (AT). The Friction Material deteriorates progressively during the service-life of a clutch, thus affecting the contact stiffness. The deterioration therefore changes the dynamic behaviour of the AT. In order to be able to predict the dynamic behaviour of the latter in the post-lockup phase, the contact stiffness characteristics at different degradation levels must be investigated. Consequently, this change in the dynamic behaviour can be used as a means to monitor clutch degradation. In this paper, both simple elastic contact model of rough surfaces, and experimental-setup tests are presented. Three identical paper-based Friction Materials with different degradation levels were used. Disc-on-disc experiments were performed on a newly developed rotational tribometer to simulate the representative post-lockup phase. In the experiments, those identical specimens were immersed in a fresh Automatic Transmission Fluid (ATF). The experimental results qualitatively agree with the presented model. In general, it can be concluded that, due to the Friction Material degradation, normal contact stiffness exhibits an increasing trend; in contrast, tangential contact stiffness exhibits a decreasing trend.
Agusmian Partogi Ompusunggu - One of the best experts on this subject based on the ideXlab platform.
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distinguishing the effects of adhesive wear and thermal degradation on the tribological characteristics of paper based Friction Materials under dry environment a theoretical study
Tribology International, 2015Co-Authors: Agusmian Partogi Ompusunggu, Hendrik Van BrusselAbstract:Abstract Adhesive wear and thermal degradation are the main aging mechanisms of paper-based Friction Materials. However, how these aging mechanisms affect the tribological characteristics of such Materials is not fully understood. In this paper, the respective influences of the two aging mechanisms on the tribological characteristics of the Friction Materials are investigated through simulation. It is assumed that adhesive wear pre-dominantly affects the surface topography, while thermal degradation significantly affects the mechanical properties of the Friction Material. The simulation results show that the static Friction coefficient and both normal and tangential contact stiffnesses increase due to adhesive wear, but decrease due to thermal degradation. These trends are qualitatively in agreement with experimental observations reported in the literature and our previous work.
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contact stiffness characteristics of a paper based wet clutch at different degradation levels
Proceeding of the 17th International Colloquium Tribology 2010 Solving Friction and Wear Problems, 2010Co-Authors: Agusmian Partogi Ompusunggu, Hendrik Van Brussel, Thierry Janssens, Farid Albender, Steve VandenplasAbstract:After clutch engagement in the post-lockup phase, the contact stiffness between Friction Materials and separators plays an important role in the dynamic behaviour of an Automatic Transmission (AT). The Friction Material deteriorates progressively during the service-life of a clutch, thus affecting the contact stiffness. The deterioration therefore changes the dynamic behaviour of the AT. In order to be able to predict the dynamic behaviour of the latter in the post-lockup phase, the contact stiffness characteristics at different degradation levels must be investigated. Consequently, this change in the dynamic behaviour can be used as a means to monitor clutch degradation. In this paper, both simple elastic contact model of rough surfaces, and experimental-setup tests are presented. Three identical paper-based Friction Materials with different degradation levels were used. Disc-on-disc experiments were performed on a newly developed rotational tribometer to simulate the representative post-lockup phase. In the experiments, those identical specimens were immersed in a fresh Automatic Transmission Fluid (ATF). The experimental results qualitatively agree with the presented model. In general, it can be concluded that, due to the Friction Material degradation, normal contact stiffness exhibits an increasing trend; in contrast, tangential contact stiffness exhibits a decreasing trend.
H J Hwang - One of the best experts on this subject based on the ideXlab platform.
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tribological performance of brake Friction Materials containing carbon nanotubes
Wear, 2010Co-Authors: H J Hwang, S L Jung, Ho JangAbstract:Abstract This study examined brake Friction Materials containing multi-wall carbon nanotubes (CNTs) to determine their effect on the braking performance. The Friction Materials were produced using conventional dry mixing methods by substituting barite with CNTs (1.7, 4.7, and 8.5 wt.%). Their tribological properties were examined using both a Krauss type tester and a 1/5 scale brake dynamometer. The physical and tribological properties were affected considerably by the CNT content in the Friction Material. In particular, the CNT-added Friction Materials showed improved fade resistance and Friction stability. Moreover, the CNTs decreased the Friction force oscillation during brake application, which was attributed to the increased damping capacity of the Friction Materials. However, the CNTs decreased the Friction effectiveness owing to the lubricating nature of undispersed CNT bundles, and decreased the thermal conductivity of the Friction Material due to interfacial coupling effects.
