Automotive Friction Materials Research Articles

Experimental Comparison of Manufacturing Parameters in Automotive Friction Materials

In this study, a fixed automotive friction material content was determined and the mechani-cal and tribological effects of manufacturing parameters on friction materials were investigat-ed. Parameters; pre-forming time (1-3-5 min) and pre-forming pressure (8-10-12 MPa), hot pressing time (5-10-15 min) hot pressing pressure (8-10-12 MPa) and hot pressing temperature (125-150-175 °C), curing time (4-8-12 h) and curing temperature (120-150-180 °C) were de-termined. The friction test of the produced samples was carried out under 0.551 MPa pressure and 7 m/s rotation speed for 90 min. In addition, the average COF, friction stability, specific wear rate, density and hardness values of the samples were calculated. According to the results obtained, the average COF value increased as the pre-forming time and pressure increased. With the increase in hot pressing time, the tribological properties of friction materials improved. Although there was an increase in the average COF value with increasing hot pressing pressure and temperature, the specific wear rates increased in these parameters. The specific wear rate increased with the increase in curing time and temperature. The highest specific wear rate among all samples was obtained in the sample cured at 180 °C. Finally, it has been suggested that 3 min for pre-forming time, 12 MPa for pre-forming pressure; 15 min for hot pressing time, 12 MPa for hot pressing pressure, and 150°C for hot pressing temperature; and a curing time of 8 h and curing temperature of 150 °C may be sufficient.

The effect of sintering time on the tribological properties of automotive brake pads

In this study, the effect of sintering temperature on the physical, chemical and tribological effects of sintered automotive friction materials was investigated. Using the powder metallurgy method, 3 different samples were produced with the codes A1, A6 and A11. Mixing, pressing and sintering processes were applied respectively as production steps. Mixing time is 90 minutes, speed is 15 rpm. The pressing pressure is 250 MPa and the duration is 1 min. The sintering temperature was 800 °C and the sintering time was 1, 6 and 11 hours, respectively. The sintering process was carried out in the sintering mold using Argon gas. As the sintering time increased, it was observed that there was an increase in the time-dependent friction coefficients of the samples. Increasing the sintering time also increased the density of the samples. As the sintering time increased, the gap in the sample decreased, as it provided better bonding of the dustsers.

Synthesis and Thermal Adsorption Characteristics of Silver-Based Hybrid Nanocomposites for Automotive Friction Material Application

Advances in friction materials are imposed on developing multiceramic reinforced hybrid nanocomposites with superior tribomechanical properties. The silver-based matrix metals are gained significance in various applications like bearing, ratchet, and electrical contacts due to their high frictional resistance and good thermal and chemical stability compared to traditional metals. The present research is to develop silver-based hybrid nanocomposites containing alumina (Al2O3) and silicon carbide (SiC) nanoparticles of 50 nm mixing with the ratio of 0 wt% Al2O3/0 wt% SiC, 5 wt% Al2O3/0 wt% SiC, and 5 wt% Al2O3/5 wt% SiC via the semisolid vacuum stir-cast technique. The vacuum technology minimizes casting defects and increases composite properties. The casted composite samples are subjected to study the effect of reinforcement on thermal adsorption, conductivity, diffusivity, and frictional resistance. The composite containing 5 wt% Al2O3np/5 wt% SiCnp is to find optimum thermal and frictional behaviour. The thermal adsorption and frictional resistance are increased by 30% and 27% compared to unreinforced cast silver. The Ag/5 wt% Al2O3np/5 wt% SiCnp hybrid nanocomposite is recommended for automotive friction-bearing applications.

Optimizing tribological performance in elevated temperature of TiC reinforced A356 matrix composites designed as automotive friction materials using dragonfly algorithm

The objective of this study designed in three steps is to evaluate the optimization of tribological performance in the elevated temperature of TiC reinforced A356 matrix composites, produced by mechanical alloying (MA), using the dragonfly algorithm (DA). In the first step, an experimental design is created to formulate the problem as an optimization problem with the help of regression modeling, and wear tests by adding a temperature module according to ASTM G99-05 standards are performed at various reinforced rates, operating temperatures, and loads. In the second step, regression models are fitted to the experimental results. In the third step, the dragonfly algorithm (DA) – one of the recent nature inspired metaheuristic optimization algorithms – has been adapted to optimize the formulated problem. The results of DA indicate that the optimum factor levels for the reinforced rate, operating temperature, and load are determined as 7%, 10°C, and 20 N respectively to optimize the responses, namely weight loss, wear rate, and friction coefficient.

Performance analysis of automotive braking friction materials based on surface roughness

Performance analysis of automotive braking friction materials based on surface roughness

Effect of copper fiber on performance of automotive friction materials

Effect of copper fiber on performance of automotive friction materials

Tribological and Emission Behavior of Novel Friction Materials

The tribological behavior and the related airborne particles emission of three copper-free automotive friction materials are investigated. The tests were conducted using a pin-on-disc tribometer equipped with a specifically designed clean-enclosure chamber for the emission measurement. Particle number concentration from particle size 0.3 µm up to 10 µm and the mass of emitted particles between 1 µm to 10 µm were measured. Particular emphasis was given to the chemical composition of the bulk materials, the friction layers and the emissions, in order to explain the acting wear mechanisms, and the recorded emission of airborne particles. The results indicate that the recorded emissions do not correlate with the friction coefficient and the wear rates, since the wear mechanisms exert a different influence on the tribological and emission behavior of the materials under study.

The role of scorching treatment on the wear and emission behavior of friction materials with and without copper

The present work aims at investigating the correlations between friction, wear and particle matter emission in copper-containing and copper-free automotive friction materials with particular emphasis on the effect of the scorching treatment. The tribological tests have been conducted using pin-on-disc laboratory equipment, and the airborne particles were measured in terms of number and mass. The results indicate that the number concentration of the airborne particles correlates well with friction coefficient, whereas their mass correlates better with the system wear rate. In addition, the copper-free material displayed a lower friction and wear and lower emissions than the copper-full. For this material, scorching was also found to reduce the friction coefficient, wear rate and emissions with respect to the pristine un-scorched condition, whereas no similar effects were found for the copper-full material. The results are discussed considering the characteristics and relevant role of the friction layers forming onto the pin surface.

Modified automotive organic friction materials through infiltration of liquid carbon precursors

This research combines the liquid carbon precursor infiltration process for carbon/carbon composites with the fabrication procedure for organic, carbon-matrix friction materials in automotive. In the densification process, different liquid carbon precursors and numbers of densification cycle are adopted to investigate the influence on physical and mechanical properties, microstructure and tribological behavior. Experimental results indicate that the infiltration of liquid carbon precursors could improve the physical, mechanical properties and tribological performances of organic friction materials. The open porosity decreases with the number of densification cycle. Both bulk density and hardness increase with the number of densification cycle. The resin-based specimens show higher hardness and lower open porosity than those of the pitch-based specimens after each densification cycle. The tribological measurement of specimens with different carbon precursors shows that the pitch-based specimen shows lower and more stable friction coefficients and exhibits lower weight losses in comparison with other carbon precursors. Morphological observations show that a large area of smooth lubricative film was easily presented on the worn surfaces of the pitch-based specimens, whereas it was seldom observed on the worn surfaces of the preform specimen and resin-based specimens.

Release of volatile organic compounds by oxidative wear of automotive friction materials

Contribution of friction processes to the environmental pollution was proven in several studies, especially with respect to release of particulate emissions containing metals. Not too many researchers pay attention to volatile organic compounds formation during braking, although it is very relevant topic. When organic friction materials are used, the oxidative processes and thermal degradation always accompanies the friction processes during braking.A low-metallic, brake lining formulation was tested using the ISO 26867 friction evaluation standard procedure in an automotive full-scale brake dynamometer. Sampling of non-airborne debris, suspended airborne particles (PM10) and air was performed directly in the environmental chamber. Released volatiles and semi volatile organics were analyzed using GC/MS, Pyr/GC/MS, FTIR and carbon phase analysis. Occurrence of important groups of volatile organic compounds as PAHs and BTEXs with possible adverse effects on living organisms was confirmed.

Impact of humidity on wear of automotive friction materials

Relevance of wear occurring in brakes increased with relation to the released chemicals and health and environmental hazards. Wear of brakes leads to formation of complex chemicals that are released into environment. Humidity can considerably modify the adhesion of surfaces by creating menisci and increasing the contact area. This paper addresses the impact of humidity on two commercial brake material types: "non-asbestos organic" and "semi-metallics" rubbed against pearlitic gray cast iron used in vehicles worldwide. The friction and wear tests were performed with the “UMT Lab Tester” manufactured by Bruker and the wear surfaces/mechanisms were studied by using of scanning electron microscopy, energy dispersive X-ray microanalysis, and optical topography methods. Both materials wore noticeably less at increased humidity. This was ascribed to a better capacity to form a protective friction layer. It was incorrectly assumed that humidity would be desorbed above the boiling point of water. The chemistry, morphology and phase composition of the friction layers formed on the surfaces during braking could play a determining role when amounts of adsorbed water are concerned. The wear mechanisms including abrasive, adhesive, fatigue, and corrosion wear were observed on both material types, irrespectively of humidity levels.

The effect of using heat treated ulexite and cashew in automotive friction materials

Abstract In this experimental study, the use of heat treated ulexite and cashew as a new material in brake pads was investigated. The change of friction coefficient, the temperature of friction surface and amount of wear were examined to assess the performance of these samples. Additionlly, microstructural characterizations of braking pads were carried out using scanning electron microscopy. The results showed that the heat treated samples containing ulexite and cashew have an important effect on friction stability and fade resistance. It can be concluded that heat treated ulexite and cashew can be used as friction materials in the automotive brake pads.

Numerical Simulation and Process Optimization of Automotive Friction Materials in Warm Pressing Forming

Warm pressing forming technology has been gradually applied to the forming of automotive friction materials. How to ensure product performance to achieve the target at the same time achieve the maximum energy saving is the research focus of this study. In this paper, by using finite element method, the field of automotive friction materials in warm pressing forming was analyzed, reveals the relationship between the temperature field and the heating temperature/heating time. Furthermore, the energy consumption was analyzed and compared it with hot pressing forming process. The results will have significant guiding to the process optimization in warm pressing forming.

Friction and wear of friction composites reinforced by natural fibres

AbstractIn the present work, friction material composites were proposed to be used as automotive friction materials. The composites were reinforced by agricultural fibres of corn, palm, and sugar bars. The conventional friction materials based on asbestos cause serious lung diseases and being cancerous potential. The aim of the present work is to replace them by the proposed composites because they are environmentally friendly friction material for brake lining and clutch facings. Agricultural wastes of sugar bars, corn and palms fibres were prepared to obtain fibres of length less than 5 mm. The fibre materials were mixed by carbon, barium sulfate, silica, metallic powders and phenol formaldehyde. The proposed composites were pressed in the die at 105°C temperature. The produced specimens were subjected to machining processes to obtain the cylindrical form of 8 mm diameter. Experiments were carried out using test rig designed and manufactured to measure both friction and wear. It consists of a rotating hollow flat disc made of carbon steel, with an outside diameter of 250 mm and 16 mm thickness. The experiments investigated the effect of agriculture fibre wastes (corn, sugar bars, and palms fibres) on friction coefficient and wear. Wear mechanisms of the proposed composites were characterized by scanning electronic microscopy. The tribological properties of the proposed composites materials were compared to three commercial brake linings. Based on the experimental results it was found that, addition of agriculture fibre wastes (corn, sugar bars, and palms fibres) to composites materials increased friction coefficient and decreased wear. Friction coefficient slightly increased, while wear drastically decreased with increasing fibres content. The maximum friction value (0.58) was obtained by composites containing 30 wt.% iron and 25 wt.% sugar bar fibres. The corn fibres were more compatible with aluminum powder where it gave the highest friction coefficient and relatively lower wear compared to other composites. Wear resistance of the tested composites containing bunches and aluminum represented the lowest values among composites containing corn and bunches fibres. The lowest wear values were observed for composites containing 25 wt.% corn fibres and 30 wt.% aluminum and composites containing 20–25 wt.% sugar bar fibres.

Micro-tribological interface model for friction-induced cold start-up running dynamics

The robustness and noise warranty costs of many automotive friction materials like transmission belts or brake pad are directly affected by the frictional properties in cold start-up running. This paper presents a friction model for start-up running under cold conditions. The absorbed water, phase changes and variable lubrication regimes in cold start-up running are taken into account. The model includes the breakage of ice adhesion, ice–ice friction between the ice films on friction pairs, melting water-mediated mixed lubrication and boundary lubrication, friction elevation due to capillary adhesive effect, as well as dry contact in the end of cold start-up running. Thermal analysis is applied in conjunction with the friction model to estimate the parameters in phase transitions. A meniscus model is also integrated into the friction model to address the friction elevation due to the variation of water film thickness. It is illustrated that if the thickness of surface ice film is larger than a critical value, the static friction coefficient could be close to 1; if the thickness of melting water film is higher than the average roughness of the surface, static friction could increase due to capillary effect, and kinetic friction could decrease due to mixed lubrication resulting in wide modulation of friction during intermittent start-up transitions. This paper also presents the application of the model to elucidate the friction mechanisms in cold brake noise where the cold wet coefficient of friction (cof) could be substantially higher than the dry cof. The effects of temperature, roughness and load on cof are also characterized.

The Applications of Basalt Fiber in the Automotive Industry in the Future

This paper describes the characteristics of basalt fiber, lists the excellent performances of basalt fiber, the good sound insulation, high thermal stability, high temperature filtration, described the future of basalt fiber used in the automotive friction materials, filter materials and interior materials.

Friction Characteristics of Automotive Friction Materials with Ceramic Powder Contents

The friction characteristics of automotive brake friction materials that contained different ceramic content were investigated. Several kinds of raw materials, such as resin-based binder, reinforcing fiber, friction restraint, abrasive, and filling materials were mixed, pressed, and heated in order to make the brake friction materials. The contents of SiC and changed from 5 vol% to 20 vol%, respectively. In addition to this, the content of adjusted from 1 vol% to 16 vol%. The surface morphology of the SiC containing sample appeared rough while more debris was observed when the contents of SiC increased. This implies that the SiC containing brake composite was not adequate for the automobile. However, the relatively smooth surface was observed in samples that contained the . But the roughness was low with a content of 11 vol% compared to the other samples. This is consistent with the abrasive properties of the samples. In the case of containing samples, the smoothes surface was observed in the contents of 15 vol% . Thus, it was concluded that the 11 vol% and 15 vol% containing composite would be the optimum content for the brake composite. Similar to the results of the surface morphology, the abrasion resistance consistently decreased when the content of SiC increased. On the contrary, the sample that contained 11 vol% and 15 vol% showed the highest abrasion resistance compared to the other samples.

Wear residues of aramid fibre formation in friction materials

Friction and wear characteristics of aramid fibres in the automotive friction material are investigated using a pad on disc type friction tester. By means of SEM and X-ray analysis, the melting aramid fibre and its residues are detected and observed on the rubbing surfaces and lateral surfaces. The aramid fibres suffer the chemical and physical changes due to severe heating induced during braking. When the temperature of the rubbing surfaces of aramid fibres reaches or exceeds the melting point, the fibres on the surface move in the melting state. The melting particles of aramid fibres act as an interface lubricant. So it does not only lead to good wear resistance of the frictional materials, but also causes the coefficient of friction to reduce. The friction and wear mechanism of aramid fibre is discussed and analysed.

Fade performance prediction of automotive friction materials by means of artificial neural networks

Temperature sensitivity of friction materials has always been a critical aspect while ensuring their smooth and reliable functioning, and that sensitivity need to be constantly optimized. The performance of friction materials at elevated temperatures is defined by their fading performance. In this paper, possibilities for predicting the fading performance of the friction materials, regarding their formulation and manufacturing conditions, have been investigated by means of artificial neural networks. The neural modelling of the friction materials behaviour at elevated temperatures has been based on the two different training data sets regarding the number, type, and distribution of the stored data. The first training data set is consisted by 360 data related to cold, fading, and recovery performance. These data have been used for developing of the neural model for predicting not only the fading performance but also cold and recovery performance. The second training data set, consisted by 120 data, has been used for developing the neural model that is going to be only used for predicting the fading performance of the friction materials. In this paper, 18 neural networks have been trained by the 5 training algorithms. These networks have been tested by the testing data set formed using the parameters of formulating, manufacturing, and testing of the two friction materials which input parameters were completely unknown for the networks.

Asbestos Products, Hazards, and Regulation

Asbestos is present in the United States in a multitude of products used in past decades, and in some products that continue to be imported and domestically produced. We have limited information on the hazards posed by some of these individual products and no information at all on most of them. Legal discovery of corporate documents has shed some light on the use of asbestos in some products and exposures from asbestos in others, sometimes adding considerably to what was in the published literature. But liability concerns have motivated corporate efforts to curtail governmental public health guidance on long-recognized hazards to workers. Liability considerations have also evidently led, in the case of asbestos brake linings, to the support of publication in the scientific literature of review articles denying in the 21st century what had been widely accepted and established in health policy in the 20th century. This report is an effort to illustrate the suppression and emergence of scientific knowledge in a climate of regulation and liability. Examples discussed are vinyl-asbestos flooring, feminine hygiene products, automotive friction materials, and asbestos contamination of other minerals such as talc and vermiculite. Global efforts to deal with the hazards of continuing marketing of asbestos products are also discussed.