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The purpose of this paper is to investigate surroundings for transfer film formation and removal, the effect of the transfer film formation on friction coefficients, the effect of four different abrasive components, ZrO₂, ZrSiO₄, Al₂O₃ and Fe₃O₄, on transfer film formation and the effect of lubricating component MoS₂ on transfer film formation and friction coefficients.

Two different MoS₂ contents of 5.5 and 8.5 per cent were added to friction materials with no MoS₂ content, which have four different abrasive components, ZrO₂, ZrSiO₄, Al₂O₃, Fe₃O₄. Friction tests composed of three different stages were conducted for those materials, and the friction surfaces of the counterpart disks were examined by scanning electron microscopy (SEM) to access the formation of transfer film at each stage.

For the transfer film formation, high temperature was a prerequisite, but the magnitude of deceleration rate was not important. The effect of the transfer film formation was to reduce the friction coefficients for most friction materials. Friction coefficients of materials which contain lubricating component MoS₂ were higher than those which contain no MoS₂ for most friction materials. The effect of the lubricating component MoS₂ was to suppress the formation of transfer film, thus resulting in increase in friction coefficients.

The transfer film was rather thin, with thickness of 1-2 µm for most friction materials. That hindered the examination of mechanical properties of the transfer film, such as hardness.

This research explained the surroundings for transfer film formation, and its effect on friction coefficients. The research suggests to suppress the formation of transfer film to make friction materials with high friction coefficient, and the lubricating component MoS₂ can be used for the purpose.

Development of high-friction-brake materials conventionally depends on the use of strong abrasive components, which may induce attacking of counterpart disks. The enhancement of friction coefficients with addition of MoS₂ content is expected to open a new prospect in development of high-performance friction materials, which can be applicable to brake pads for racing cars.

The study is in pursuit of the transfer film formation in successive friction stages, which revealed the conditions for transfer film generation and removal. Specimen preparation for SEM observation of cross section of friction surface was painstaking to not damage the developed friction surface. The study revealed the effect of different abrasive components on transfer film formation and the effect of lubrication contents of MoS₂ on transfer film formation and friction coefficients.

The purpose of this paper is to investigate the friction coefficients of aramid and acrylic fibers on brake pads.

Fiber components used in the present pads are aramid and acrylic fibers, respectively, while keeping other components, such as binders, lubricants, abrasives, fillers the same. Disk FC25 and disk FC17 are used for rotor rubbing test to investigate the friction coefficients with brake pads. The pads are tested by 1/5 scale brake dynamometer, and test mode is modified JASO C406‐P1. The results are analyzed with the friction coefficient and the temperature, transfer film, roughness, and photomicrograph of worn surface on rotors.

The friction coefficient was mainly determined by the pad material rather than the rotor material, and pads made of aramid fiber had high‐friction coefficient, while pads made of acrylic fiber had low‐friction coefficient, especially under high temperature. Temperature change during braking process was directly related to the initial speed only, and was indifferent to materials or decelerations imposed. In the fade test, the reversal of friction coefficients between the aramid fiber and acrylic fiber pads is determined by the amount of remained amount of respective fiber above 520°C.

Effect of different fiber components, aramid and acrylic fibers, on friction characteristics of pad is sought. Reversal of friction coefficients is determined by the thermal stability of fibers used for pads.