Friction Lining Research Articles

Mathematical model for determining maximum stress in friction winder rope

Multi-rope winders are quite possibly the most important means of conveyance in deep underground mines. The drive is transmitted to the rope by pure friction; each end of the rope is connected to each of the conveyances—the drive effected by contact with a drum having friction lines on its peripheral surface. The wire ropes used in such a system are costly and need to be replaced from time to time throughout the life of the winder. It is thus essential to have knowledge of the working stresses generated in wire ropes; to ignore this will risk premature failure of the rope with all its consequential hazards.

Beyond Atlanta: the struggle for racial equality in Georgia, 1940-1980

The first comprehensive history of the civil rights movement in Georgia This sweeping history of the civil rights movement in the South's largest state tells of many Georgias. On one extreme is Atlanta, a metropolitan center of relative prosperity and training ground of many movement leaders. On another is Albany. A city deep in the black belt of the plantation South, it is the site of Martin Luther King Jr.'s greatest civil rights setback. Somewhere in between is yet another Georgia, a Georgia whose communities once constituted hundreds of Jim Crow fiefdoms where black-white relations were as crude or as nuanced as the outlook of the local sheriff. Beyond Atlanta draws on interviews with almost two hundred people - and white - who worked for, or actively resisted, the freedom movement. Among the topics Stephen Tuck covers are the absence of consistent support from the movement's national leadership and the frustration and innovation it alternately inspired at the local level. In addition, Tuck reveals friction, along urban-rural and poor-prosperous lines, about movement goals and tactics, and he highlights the often unheralded roles played by African American women, veterans, masons, unions, neighborhood clubs, and local NAACP branches.

Fracture of Friction Lining of the Brake System at Car Braking

The problem of fracture mechanics for friction lining of the brakesystem has been considered. It is assumed that at a multifold brakingthe fracture of materials caused by a contact interaction and accompanied by joint action of power load and temperature takes place with friction. It is considered that there are cracks near the surface of the friction lining contact. By the methods of analytical function theory the problem considered is reduced to the system of singular integral equations and to the infinite system of linear algebraic equations. The procedure of defining stress-intensity factors is shown. In the calculations the function describing the roughness of the friction lining surface has been assumed to be a stationary random function with a zero average value and known dispersion.

The running-in behaviour of friction linings

Brand-new friction linings exhibit a typical running-in behaviour. At the end of this process, the lining achieves its full load transmission capacity. This article by the Technical University of Berlin presents a new procedure for assessing the running-in behaviour of friction linings.

The impedance method of monitoring the degradation of rubber linings in applications where progressive deterioration is the predominant failure mechanism

A method has been proposed for testing rubber linings in industrial conditions based on a proposed model of coating penetration. The depth of penetration of rubber lining by water has been determined on the basis of investigation results by electrochemical impedance spectroscopy. Verification of the proposed procedure has been performed by comparing the obtained results of electrochemical investigations with determination of the water content in rubber by the gravimetric method. It has been confirmed that the values calculated in accordance with the penetration model correlate with the water content in rubber. Investigation results confirm views on the corrosion aggressiveness of media in different zones of a scrubber working as part of the flue gas desulphurisation installation.

Ceramics for use in brakes and clutches

A further increase in the power density of clutches and brakes is hardly possible using conventional friction materials. Although friction linings on the basis of sintered metals allow higher power densities than organic linings, they have serious disadvantages with regard to comfort, which means that that they cannot be used in vehicles. The use of innovative ceramic materials here is promising, as is shown by the following article from the Institute of Machine Design and Automotive Engineering of the University of Karlsruhe.

An Optimization Study for the Bow Form of High-Speed Displacement Catamarans

ABSTRACT Interest in high-speed marine transportation has acquired a wide variety of hydrodynamic research activities on catamarans, including shape optimization for minimum total resistance. This study attempts to utilize the mathematical programming in optimizing the bow form of twin hulls for minimum total resistance as well as in analyzing the optimization by physical model tests. The total resistance is assumed to be composed of wave-making and frictional components, which are formulated using Michell's thin-ship theory and ITTC-1957 friction line, respectively. The optimized hull form is analyzed by means of a computational flow solver before going through the experimental analysis. The study demonstrates the capabilities of the optimization procedure, presented for catamarans, in reducing the total resistance, as well as its limitations to be used as a design tool in a relatively high-speed zone.

Finite Element Analysis of Air Springs with Fiber-Reinforced Rubber Composites Using 3-D Shell Elements

This paper is concerned with the orthotropic problem of diaphragm-type air springs which consist of rubber linings, nylon reinforced rubber composite and bead ring. The analysis is carried out with a finite element method developed to consider the orthotropic properties, geometric nonlinearity using four-node degenerated shell element with reduced integration. Physical stabilization scheme is used to control the zeroenergy mode of the element. The analysis includes an inflation analysis and a lateral analysis of an air spring for the deformed shape and the spring load with respect to the vertical and l ateral deflection. Numerical results demonstrate the variation of the outer diameter, the fold height, the vertical force and the lateral force with respect to the inflation pressure and the lateral deflection.

Frictionally Excited Thermoelastic Instability in Multi-Disk Clutches and Brakes

The propensity toward thermoelastic instability (TEI) in multi-disk clutches and brakes is investigated by introducing a new bidimensional analytical model, where metal and friction disks are replaced by two-dimensional layers of finite thickness. This new model permits to estimate the effect of the thickness ratio a1/a2, between friction and metal disks, on the critical speed, critical wave parameter and migration speed of the sliding system. It is found that as the thickness ratio a1/a2 decreases the critical speed reduces significantly taking up values about 80 percent smaller than that predicted by previous two-dimensional models for commonly used ratios 0.1<a1/a2<1, whilst the critical wave parameter slightly increases. Therefore, not only the susceptibility towards TEI can be reduced by changing the material properties of the friction lining but also by adjusting suitably the thickness ratio of the disks. The two-dimensional model is also employed to determine the critical speed in a real multi-disk clutch, and the results are compared with a three-dimensional finite element code. It is shown that the critical speed estimated by the present two-dimensional plane strain model is in good agreement with that determined by the FE code for sufficiently large radial thickness of the disks, whilst the two-dimensional plane stress solution has to be used for relatively small radial thickness ratios. Also, it is found that the critical number of hot spots is independent of the radial thickness ratio and it is correctly predicted by the two-dimensional model.

Applied Rubber Linings wins moulding patent

Applied Rubber Linings wins moulding patent

Optimizing the mill lining and the grinding media in tumbling mills

The grinding mill is probably the most common unit operation in mineral processing. There is, however, much that can still be done in the way of optimization. This paper discusses the results of a well-controlled pilot-scale test in which the performance of a tumbling mill equipped with a conventional rubber lining and lifter bars was compared to a tumbling mill equipped with a smooth rubber lining of the magnetic type. The results indicate that the smooth lining is about 14% more effective with respect to energy consumption. By optimizing the size of the grinding media, the mill capacity can be increased in many grinding operations. In this specific case, grinding with a −20-mm ball charge required 26% less grinding energy than grinding with a −30-mm ball charge. The energy savings can, in most cases, be converted to an increase in capacity. The wear of the grinding media is difficult to assess over a short test period, but the results suggest that the wear is somewhat less when a smooth lining is used. A determination of the wear of the linings was not included in this study, but it is generally accepted that the use of magnetic linings reduces the lining costs dramatically. Computer simulation using the Millsoft code developed by Mishra et al. confirms and explains the increased effectiveness of comminution when a smooth lining and smaller grinding balls are used.

Numerical simulation of crossing-shock-wave/turbulent-boundary-layer interaction using a two-equation model of turbulence

A crossing-shock-wave/turbulent-boundary-layer interaction is investigated using the k–ε turbulence model with a new low-Reynolds-number model based on the approach of Saffman (1970) and Speziale et al. (1990). The crossing shocks are generated by two wedge-shaped fins with wedge angles α1 and α2 attached normal to a flat plate on which an equilibrium supersonic turbulent boundary layer has developed. Two configurations, corresponding to the experiments of Zheltovodov et al. (1994, 1998a, b), are considered. The free-stream Mach number is 3.9, and the fin angles are (α1, α2) = (7°, 7°) and (7°, 11°). The computed surface pressure displays very good agreement with experiment. The computed surface skin friction lines are in close agreement with experiment for the initial separation, and are in qualitative agreement within the crossing shock interaction region. The computed heat transfer is in good agreement with experiment for the (α1, α2) = (7°, 7°) configuration. For the (α1, α2) = (7°, 11°) configuration, the heat transfer is significantly overpredicted within the three-dimensional interaction. The adiabatic wall temperature is accurately predicted for both configurations.

On the form factor scale effect

Four geosim families, with fully available resistance test results, have been re-analyzed to check the possible scale effect on the form factor. The form factor determined by Prohaska's method, with exponent n=4 and ITTC'57 correlation line, increases with the model size in all four cases analyzed. Because of its high correlation coefficient, a linear variation of the form factor with the scale is assumed. It is possible to have a first estimation of the ship's form factor extrapolating for λ=1 in the regression line. Form factor Reynolds number dependency will always be associated with a friction line. Using the ITTC'57 correlation line, the following equation K S− K M=1.91·( λ−1)·10 −3 can be used to estimate the scale effect on the form factor. Calculations carried out, for axisymetric bodies, with some CFD codes are in good agreement with the experimental findings.

Comparative hazards of chrysotile asbestos and its substitutes: A European perspective.

Although the use of amphibole asbestos (crocidolite and amosite) has been banned in most European countries because of its known effects on the lung and pleura, chrysotile asbestos remains in use in a number of widely used products, notably asbestos cement and friction linings in vehicle brakes and clutches. A ban on chrysotile throughout the European Union for these remaining applications is currently under consideration, but this requires confidence in the safety of substitute materials. The main substitutes for the residual uses of chrysotile are p-aramid, polyvinyl alcohol (PVA), and cellulose fibers, and it is these materials that are evaluated here. Because it critically affects both exposure concentrations and deposition in the lung, diameter is a key determinant of the intrinsic hazard of a fiber; the propensity of a material to release fibers into the air is also important. It is generally accepted that to be pathogenic to the lung or pleura, fibers must be long, thin, and durable; fiber chemistry may also be significant. These basic principles are used in a pragmatic way to form a judgement on the relative safety of the substitute materials, taking into account what is known about their hazardous properties and also the potential for uncontrolled exposures during a lifetime of use (including disposal). We conclude that chrysotile asbestos is intrinsically more hazardous than p-aramid, PVA, or cellulose fibers and that its continued use in asbestos-cement products and friction materials is not justifiable in the face of available technically adequate substitutes.

Theoretical and experimental studies on the interface phenomena during the engagement of automatic transmission clutch

Mathematical models for predicting the temperature and thermal degradation have been developed, which include all important phenomena during the engagement of wet friction clutch. The thermal model consists of heat balance for the separator, friction lining, core plate, and ATF in the clearance. The degradation mechanism and constants for the selected friction material obey the zeroth order reaction. The model predictions show good agreement with experimental measurements.

Control of 3D turbulent boundary layer separation caused by a wing–body junction

Abstract In three-dimensional flows, boundary layer separation leads to the formation of vortical structures formed by the rolling up of the viscous flow sheet previously confined in a thin layer attached to the wall. Several characteristics of the vortex flow development have negative effects; for example, it may be responsible for unsteadiness or generating unwanted vibration or noise. There are several ways to alter the properties of the vortex or to eliminate it as an organized structure. The objective of this paper is to present two different vortex control approaches. The first solution involves a modification of the pressure field induced by the obstacle by altering its geometry with a strake. The second solution, which can be called active control, consists of suction through an aperture located near the separation line. In this study, we have considered the incompressible three-dimensional boundary layer separation induced by an obstacle mounted perpendicular to a flat plate. The tests were conducted in the F2 subsonic wind tunnel of the ONERA Fauga-Mauzac center. The test section has a cross sectional area of 1.8 × 1.4 m2 and the upstream velocity of the flow was 50 m/s. The surface flow properties have been characterized by using a viscous coating which allows the visualization of the skin friction line patterns. The essential part of the study has been devoted to Laser Doppler Velocimetry (LDV) measurements. The plane of symmetric flow ahead of the leading edge has been qualified by using 3D laser velocimetry in the forward scatter mode. Results show that the geometrical extent of the separation region is reduced and the primary separation line is much closer to the model's leading edge when considering the configuration with a strake. Using an active control system, with suction through a hole located in the plane of symmetry in front of the obstacle's leading edge, the vortex size is reduced and its location displaced towards the origin of the obstacle.

Noise damped brake pad assembly

A disk brake pad assembly includes a rigid metal backing plate, a brake friction lining pad and a damping structure including a viscoelastic material disposed between the backing plate and the friction lining pad and fixed to each. In one embodiment the damping structure is a perforated metal plate having perforations filled with viscoelastic damping material. The damping plate may be provided along its opposite sides with constraining layers. Such a perforated damping structure may be disposed on either side of the backing plate.

Three-dimensional separation in the neighborhood of roughness on the surface of an axisymmetric body

Steady-state viscous incompressible fluid flow past an axisymmetric slender body is considered at high Reynolds numbers in the regime with vanishing surface friction in a certain cross-section. In a small neighborhood of this cross-section interaction between the boundary layer flow and the external irrotational stream develops. In order to study the structure of the three-dimensional flow with local separation zones it is assumed that there is three-dimensional roughness on the surface of the body with the scale of the interaction zone. For this zone a numerical solution of the problem is obtained and its nonuniqueness is established. The surface friction line (limiting streamline) patterns with their inherent features are constructed.

Dry sliding wear of particulate-reinforced aluminium alloys against automobile friction materials

Two magnesium/silicon aluminium alloys each reinforced with 20 vol.% SiC particulates have been worn against three makes of automobile friction linings (brake pads). Two of the friction linings are commonly used against cast iron rotors in automobile braking systems while the third has been specifically formulated for use against aluminium metal matrix composite (MMC) brake rotors. Wear processes at the interfaces of the specific rotor-pad combinations have been characterised through the analysis of friction traces and the use of electron microscopy. For aluminium MMCs sliding against organic pads formulated for use against cast iron, wear rates are low and friction traces constant due to the formation of a solid lubricant graphitic layer at the wear interface. When these MMCs are worn against semi-metallic pads formulated for use against cast iron, wear rates are extremely high due to three body abrasion which leads to subsurface delamination and early melt wear in the MMC. For an aluminium MMC developed for its use in automobile brake rotors sliding against a semi-metallic pad specifically formulated for its use against MMC brake rotors, wear rates at low loads are low although friction traces are highly irregular and fracture of the SiC particulates occurs at the lowest load and sliding velocity. This fracture of SiC is induced by the abrasive action of hard alumina particles within the pad. At high loads and sliding velocities cohesiveness of materials within the pad is poor and the wear rate of the MMC is extremely high. If the structure and composition of friction linings are arranged correctly, the wear resistance and frictional properties of aluminium MMC brake rotors are superior to those of cast iron brake rotors.

Dry sliding wear of particulate-reinforced aluminium alloys against automobile friction materials

Two magnesium/silicon aluminium alloys each reinforced with 20 vol.% SiC particulates have been worn against three makes of automobile friction linings (brake pads). Two of the friction linings are commonly used against cast iron rotors in automobile braking systems while the third has been specifically formulated for use against aluminium metal matrix composite (MMC) brake rotors. Wear processes at the interfaces of the specific rotor-pad combinations have been characterised through the analysis of friction traces and the use of electron microscopy. For aluminium MMCs sliding against organic pads formulated for use against cast iron, wear rates are low and friction traces constant due to the formation of a solid lubricant graphitic layer at the wear interface. When these MMCs are worn against semi-metallic pads formulated for use against cast iron, wear rates are extremely high due to three body abrasion which leads to subsurface delamination and early melt wear in the MMC. For an aluminium MMC developed for its use in automobile brake rotors sliding against a semi-metallic pad specifically formulated for its use against MMC brake rotors, wear rates at low loads are low although friction traces are highly irregular and fracture of the SiC particulates occurs at the lowest load and sliding velocity. This fracture of SiC is induced by the abrasive action of hard alumina particles within the pad. At high loads and sliding velocities cohesiveness of materials within the pad is poor and the wear rate of the MMC is extremely high. If the structure and composition of friction linings are arranged correctly, the wear resistance and frictional properties of aluminium MMC brake rotors are superior to those of cast iron brake rotors.