In manually operated vehicle transmissions and their automated versions synchronizers are widely used to equalize gear speeds during shifting. For proper functioning friction and wear between the cones must be carefully controlled. Therefore the friction and wear behaviour of a coated tribological system with boundary and/or mixed lubrication was investigated. The system follows two main wear patterns and three regimes of wear: continuously mild wear, continuously severe wear and a bistable region. In this region, after a period of time with severe wear, the system switches to mild wear. This effect is mirrored by the friction coefficients. In the regime of severe wear, wear can be described by a semi-empiric model which is based on the energetic wear intensity, which means the wear volume per unit friction work or dissipated energy. The wear intensity is shown to depend on a single duty parameter. It is mainly a function of sliding velocity and contact pressure. The coefficients in the equation defining the duty parameter as well as in the equation relating this duty parameter to the specific wear are characteristic for each system. The duty parameter is assumed to reflect contact temperatures. The coefficients in its defining equation will therefore depend on the thermal properties of the system, that means essentially heat capacity and transfer specifics. The next step planned is to look more closely into the role of temperature in order to confirm the assumptions about the nature of the duty parameter as well as to include parameters like the oil sump temperature or varying cycle times. From there, indirect conclusions can be drawn on the contribution of boundary friction; a direct measurement, however, requires to concentrate on the microscopic real areas of contact. A combination of microscratch-testing and atomic force microscopy allowed to correlate the macroscopic measurements to microscopic surface properties.


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    Titel :

    Wear and friction of molybdenum coated synchronizers for truck transmissions


    Beteiligte:
    Poll, G. (Autor:in) / Spreckels, M. (Autor:in)


    Erscheinungsdatum :

    2001


    Format / Umfang :

    10 Seiten, 9 Bilder, 13 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch




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