Friction brake materials are made from a mixture of materials with different properties in order to meet the brake performance requirement. Friction brake material contains a reinforcement fiber that serves to maintain the integrity of the material when subjected to loading. Natural fiber has the potential to be used as a reinforcement material for friction material due to some of its superior characteristics. In this research, friction brake materials using cantala fibers were developed to investigate their frictional characteristics. The volume fraction of the cantala fibers in the specimens was varied from 0%, 4%, 8%, to 12% of the total composition of the friction brake material. The manufacturing of the specimen was initiated by mixing the ingredients, followed by cold pressing of the mixture, hot pressing of the preform, and finally post-curing of the specimens. The frictional characteristics of the specimens were evaluated using pin-on-disc tribometer. The result showed that the cantala fibers contributed to the decrease in the coefficient of friction. An increase in contact pressure caused the coefficient of friction to increase, while the increase in sliding speed caused a decrease in the coefficient of friction. The addition of cantala fiber into the composite could increase wear resistance and stabilize the coefficient of friction of the friction brake material.
The film flow between the disks is the critical factor in the design of hydro-viscous drive. In the previous work dealing with the flow in the gap, few authors considered the effect of non-isothermal interface on the flow. In order to investigate the dynamic behavior of the oil film between non-isothermal friction pair in hydro-viscous drive, the flow field of the oil film between the disks is presented with consideration of four representative temperature models. Parameters related to the flow, such as temperature, pressure, velocity, shear stress and viscous torque are obtained by means of numerical simulation. The results show that non-isothermal interface results in temperature distribution profiles that diverge from the ideal parabolic curve. Both the discrepancies about film pressure and radial velocity at the outlet are vulnerable to temperature variation derived from a set of frictional pair. Tangential velocity profiles diverge from inlet to outlet due to the non-isothermal interface. Shear stress profiles show the opposite trend caused by the substantial variation about the oil viscosity. The research results lay a theoretical foundation for the reasonable designs of hydro-viscous drive.
In this paper, the variations of the squeeze elastohydrodynamic lubrication (EHL) oil film in unidirectional and bidirectional intermittent motions are investigated theoretically. For the unidirectional intermittent motion, the effects of stop time, deceleration, elliptical ratio and applied load are explored. It is found that the variation of the central pressure, central and minimum film thickness in intermittent motion resemble those in an impact-rebound process with shorter intermittent period. However, the shapes of the pressure curves versus time are also influenced by the elliptical ratio and the applied load. It is also found that the bidirectional intermittent motion is more detrimental to the contact metals so that special attention should be paid in the design.
In this paper, hydrodynamic lubrication behaviors of PAO (Polyalphaolefin) oils in a slider-on-disc conformal contact were measured with optical interferometry. The film thickness under different loads, speeds, oil viscosities and angles of inclination of slider were obtained. It was shown that under the working conditions employed the film thickness shows linear relationship with load, speed and viscosity at a log-log scale, and a film thickness equation was thus established with correction by the angle of inclination. The measured film thickness vs. speed was transferred to the curve of load-carrying capacity vs. convergence ratio, and it was shown that the load-carrying capacity does not exclusively depend on the contact geometry as predicted by classical theory.
The running-in process affects the friction and wear properties of sliding materials in machines. If it is not done correctly, serious problems such as machine seizure may occur. Diamond-like carbon (DLC) films are used in various fields as an excellent tribo-material because of their low friction coefficient and high wear resistance. However, their running-in behavior has not been clarified quantitatively in detail. In addition, previous studies have not adequately investigated changes in wear particles during the running-in process. In the present work, we investigated the correlation between the friction coefficient and the number of wear particles during the runningin process using an online particle counter. Then, we compared the sliding distance at the completion of running-in judged using the particle counter with that judged using the friction coefficient. As a result, the running-in behavior in the combination of a DLC film and AC8A Al alloy is well clarified. In the case of a DLC/AC8A sliding pair, the DLC surface showed no significant changes after wear tests. The AC8A surface became smooth by abrasion and plastic deformation during running-in, and the ratio of silicon occupying the surface area increased slightly.