Non-asbestos Organic Friction Materials Research Articles

Cyclic behavior and seismic control performance of SMA friction damper

Using superelastic shape memory alloy (SMA) bars and non-asbestos organic friction material, this study developed an innovative self-centering friction damper (SCFD). This hybrid passive control device consists of the self-centering device using SMA bars and the friction energy dissipation device which can provide excellent self-centering ability and energy-absorbing ability to meet the requirements of civil engineering applications. To explore the feasibility and hysteretic properties of the SCFD, experimental tests under cyclic loading were conducted. According to the experimental results, the proposed SCFD exhibited a stable and repeatable flag-shaped hysteretic response, which can achieve the recovered displacement of 76.07% and dissipated energy of 6.04 kJ at 42 mm. The finite element model of the SCFD using ABAQUS software was established and validated by experimental results. And a series of numerical simulations with different parameters were performed, which enables a more in-depth interpretation of the SCFD. Additionally, a system-level nonlinear time-history analysis was performed on a three-story steel frame equipped with and without SCFDs. The dynamic analysis results indicated that the SCFDs could effectively reduce structural damage and enhance post-earthquake recoverability under rare earthquakes.

Development and investigation of non-asbestos organic friction materials with coconut shell powder as filler

The development of eco-friendly friction material (FM) with enhanced tribological and mechanical properties is a challenge to industrial engineers. This work presents an effort towards the developm...

Development and investigation of non-asbestos organic friction materials with coconut shell powder as filler

Development and investigation of non-asbestos organic friction materials with coconut shell powder as filler

Synergistic effect of Steel Slag-Molybdenum disulfide particles on fade-recovery performances of non-asbestos organic friction material

Purpose This paper aims to deal with the synergistic effect of steel slag-molybdenum disulfide particles on fade-recovery performances of non-asbestos organic friction material. Design/methodology/approach The brake friction materials were developed by using steel slag and molybdenum disulfide particles as individual and combination in the formulation. The brake friction materials were developed in the form of standard brake pads as per the industrial practice. The physical, mechanical and thermal properties of the developed brake pads were tested as per the industrial standards. The tribological properties were analyzed using the Chase test as per IS2742-Part-4. Worn surface analysis was done using a scanning electron microscope. Findings The experimental results indicate that the brake pads filled with a combination of steel slag and molybdenum disulfide showed stable friction and less wear rate due to the synergetic nature of abrasive and lubricant. Originality/value This paper explains the influence of steel slag and molybdenum disulfide particles as individual and combined in brake pads formulation to enhance the tribological performance by producing stabilized friction with undulations. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2020-0216/

Fade and recovery characteristics of commercial disc brake friction materials: a case study

Friction materials are usually evaluated according to their friction performance at high temperatures, i.e. fade performance. In the present study, the vehicle under consideration is a sport utility vehicle. An experimental investigation is carried out to find out fade and recovery characteristics of four commercial disc brake friction materials using a four-wheeler inertia brake dynamometer. For these four grades naming is given i.e. FC1, FC2, FC3, and FC4. The Grade FC1 is without steel content. FC2 is with low steel content, FC3 is low steel content with organic brake friction material, and FC4 is non-asbestos organic friction material. SEM-EDX analysis is carried out for finding different elements and microstructural characterisation of brake friction material. Grade FC2 attained the highest temperature, and FC4 attained the lowest temperature during the fade test. Grades FC1 and FC4 show better recovery characteristics as compared to other grades.

Effect of Carbonaceous Components on Tribological Properties of Copper-Free NAO Friction Material.

Copper helps to accelerate heat transfer during the braking process, allowing the brake materials to produce a stable coefficient of friction (COF), which in turn reduces wear loss and braking noise. However, its properties are also quite harmful to aquatic organisms. Finding a suitable replacement that fits all functions of copper for brake materials is not an easy feat. In this paper, six different carbonaceous components (coke, carbon black, carbon fiber, artificial graphite, natural graphite and expanded graphite) were substituted for copper in non-asbestos organic (NAO) friction materials. The hardness, thermal conductivity and tribological behaviors of these copper-free NAO friction materials were examined. Experimental results indicate that carbonaceous components improve lubrication and assist the friction composites with generating friction layers on the worn surface. Specimens containing coke, carbon black or carbon fiber exhibit broken friction layers, whereas specimens containing artificial graphite, natural graphite or expanded graphite exhibit quite adherent and smooth friction layers. Among all the copper-free carbon containing specimens, the specimen containing expanded graphite appears to be the best choice. It has the highest thermal conductivity, a relatively low wear loss and a relatively high and stable COF.

Exploration of plasma treated stainless steel swarf to reduce the wear of copper-free brake-pads

Abstract In recent few years, the environmental issues especially related to the aquatic life are pushing the Friction Industry to develop NAO FMs (non-asbestos organic friction materials) without Cu. Stainless-steel swarf (SSS) having good corrosion resistance was tried as one of the replacing ingredients for Cu in FMs in Authors’ laboratory in earlier work. It proved to have a great potential for Cu replacement almost in all the performance properties but at the cost of slightly lower wear resistance and hence the theme of current research was to enhance the wear resistance capability of SSS. Hence, in the present study SSS were treated with air-plasma and used in brake-pads. Thus, two types of brake-pads with the identical composition but differing in type of SSS 10 wt % (treated and untreated) were tribo-evaluated on a full-scale brake inertia dynamometer and treated SSS containing pads exhibited higher wear resistance (approx. 10%) confirming success of the treatment, first time explored for the friction materials. Enhanced adhesion with resin was the main cause for the improved tribo-performance.

High performance aramid pulp/carbon fiber-reinforced polybenzoxazine composites as friction materials

The objective of this work is to develop aramid pulp/carbon fiber-reinforced polybenzoxazine composites as high performance friction materials. Effects of aramid pulps and carbon fibers on thermal stability, mechanical properties, and tribological performances of the composites are investigated. Aramid pulps could enhance friction coefficient and friction stability of the composites, while thermal stability, mechanical properties, and wear resistance of the composites are improved with an addition of carbon fibers. The composites exhibit high thermal degradation and glass transition temperatures, high and stable friction coefficient, and good wear resistance. The developed polybenzoxazine composites could be applied as non-asbestos organic friction materials.

Conditions for Transfer Film Formation and Its Effect on Friction Coefficients in NAO Friction Materials Containing Various Abrasive Components

The non-asbestos organic friction materials with various abrasives such as ZrO2, ZrSiO4, Al2O3, Fe3O4 were manufactured and underwent friction tests to find conditions for transfer film formation and their effect on friction coefficients, and also the effect of different abrasive components was analyzed. Friction tests were composed of the effectiveness test and the fade & recovery test successively and counterpart disks were examined at each stage to find transfer film distribution changes. Friction surface observation by SEM revealed that the transfer film was formed not in the effectiveness stage which simulated the normal braking condition, but in the fade stage when temperature rose up to 600°C. The level of friction coefficients for most friction materials turned out to be opposite to the quantity of transfer film formation implying that the transfer film reduced the friction coefficient. High temperature condition was requisite for transfer film generation, but the transfer film was hardly formed irrespective of the magnitude of deceleration rate under moderate operating conditions where temperature stayed below 350°C. Among the friction materials tested, friction material which contained Al2O3 produced the least transfer film but showed the highest friction coefficient throughout the entire stages of the friction test.

Development of a Composite Friction Material with Excellent Fade Resistance by Employing Oversized Ceramic Particles

Non-asbestos organic friction materials have historically been developed through a series of trial-and-error experimental procedure. But in this work, the friction theory was used to design and prepare a new composite friction material with excellent fade resistance. Oversized (3.0 ± 0.5 mm) SiO2-based particles with the great thermal stability and large contact area against the disc were used to reinforce the resin matrix. The effectiveness of the oversized particles relative to particles of other sizes was evaluated using an established test procedure. The results showed that the oversized particles improve the fade resistance and wear resistance of materials, but not followed with excessive disc wear.

Pin-on-disc study of brake friction materials with ball-milled nanostructured components

Copper is an ingredient of the automotive disc brake pads with important functional role. On the other hand, copper is regarded as one of the most hazardous component of the particulate matter released by the brake linings. Legislation in several countries is progressively reducing the tolerated amount of copper in friction materials. In this work, a possible approach to the reduction of copper in brake friction materials is presented. Starting from a commercial, state-of-the art, non-asbestos organic friction material, different formulations have been prepared, changing the microstructure of some of the ingredients, namely copper and zirconia using high energy ball-milling. The wear behavior of the newly developed materials has been tested and validated using pin-on-disc wear tests. One interesting aspect observed is that the wearing out of copper fibres produces fine copper particles entering the friction layer, thus contributing to its compaction. This observation implies that copper powder is not strictly required as a component in the starting friction material to achieve anyway a satisfactory tribological behavior associated with a stable friction layer. Furthermore, the addition of milled components provided interesting indications to be explored further in view of the replacement of copper in brake friction materials.

Role of combination of hexagonal boron nitride and graphite in NAO friction material

Copper is added in non-asbestos organic (NAO) friction materials (FM) to increase the thermal conductivity and to enhance the lubricity at high temperature apart from the well-accepted fact that it influences tribological performance also. Copper is being phased out slowly in FM formulations because of its proven threat to the aquatic life. Nowadays, the research in this area is being focussed on finding alternatives to Cu. Hexa-boron nitride (hBN) also known as white graphite is a ceramic powdery filler, having crystalline structure similar to that of graphite along with various desirable properties (such as higher thermo-oxidative stability and thermal conductivity) which could be possibly suitable for developing Cu-free FMs. Hence, it was thought worthwhile to explore hBN as a potential ingredient in FM formulation for replacing copper. Five FMs in the form of brake shoes were developed, keeping all other ingredients identical and varying combinations of two solid lubricants viz. graphite and hBN systematically. The amount of these two solid lubricants was purposefully kept high (20%) so that the effect on performance properties could be visible clearly. Samples were tribo-evaluated using chase test rig as per IS 2742 standard. The paper discusses on the influence of these solid lubricants on performance properties of the series of five FMs.

Airborne brake wear particle emission due to braking and accelerating

Abstract The emission of airborne brake wear particles due to non-asbestos organic friction material was studied for two passenger cars and a middle class truck. The emission of airborne brake particulates was tested with a brake dynamometer with a constant volume sampling system and real-time mass measurements were made. The particles emissions under constant driving were calculated in terms of initial wheel speed and deceleration. Time series mass emissions were obtained by real-time dust monitors for PM2.5 and PM10 (i.e., particles with a 50% cutoff aerodynamic diameter of 2.5 and 10 μm, respectively). The airborne brake wear particles emission occurred at deceleration and acceleration, suggesting resuspension of wear particles from friction on the surface of brakes and grooves at acceleration. The resuspended brake wear particles, whose emission during acceleration tended to increase with the initial speed, significantly contributed to the total emission. Therefore, they must be included in emission measurements of PM2.5 and PM10 during brake abrasion tests. Further measurements under a wide range of driving conditions, such as tailpipe emission test cycles, are required to obtain national and regional specific emission parameters for the development of inventories.

Special grade of graphite in NAO friction materials for possible replacement of copper

The main focus of current research in non-asbestos organic (NAO) friction materials (FMs) is on searching replacement of copper which is a recently proven hazard to the aquatic life. Cu is almost invariably used in the various forms in FMs mainly because it enhances thermal conductivity of a composite which helps to dissipate frictional heat efficiently from the friction surface and thus resists the negative impact on performance especially on fade. Moreover, it also acts as a solid lubricant at high temperature. The replacement is not easy and perhaps will have to be done by a package of ingredients. The search for newer ingredients hence is continuing. In this paper, newly commercialized graphite which is more conducting than the ordinary graphite is explored for possible replacement. During preliminary work presented in this paper, efforts were focussed on investigating the influence of amount of this graphite on tribo-properties. Three realistic composites containing all essential ingredients of FMs were developed which differed only in amount of new graphite (TG) (5%, 10% and 15%). The brake-shoes were tested against drum on chase machine as per IS 2742. Initial studies confirmed that 10% is the optimum amount of TG, where most of the performance properties were best. SEM studies were done to understand correlation between wear and wear mechanisms through topography studies.