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  • Effects of the contact surface properties on the flash temperature calculation and wear behaviour [Elektronski vir]
    Kalin, Mitjan ; Vižintin, Jože
    Tribochemical reactions with phase transformations between ceramics and metals under various sliding or fretting conditions have been reported many times to critically determine the wear and friction ... behaviour. Although their strong dependence on environmental and operating conditions was confirmed, details of the mechanisms and chemical reactions are still not fully understood. In particular, different and contradictory assessments of the importance of thermal and mechanical effects on the tribochemical reactions have been reported in literature so far. The reason is mostly due to simultaneous action of both, thermal and mechanical parameters and consequently use of only indirect methods to determine the actual key-governing factors. These include studies of phase transformations, surface chemistry, thermodynamic and flash temperature calculations and sometimes contact temperature measurements. Typically, the significant discrepancies in the calculated contact temperatures and observed surface changes are obtained in slow sliding applications. The transformation of frictional energy to heat, is responsible for increases in the contact temperatures of the sliding bodies, and can have a significant influence on the friction and wear behavior. However, the temperature generated at the contact is more or less an estimation, based on experimental evidence or calculations, since in both cases many problems are still unsolved. This paper focuses on the impact of some of the actually unknown contact parameters, i.e. thermal conductivity and real contact area on the calculation of the maximum contact temperature rise. Ten theoretical models for the contact temperature calculation were selected for this purpose. Wherever this was applicable, pre-set or measured values from high frequency fretting experiments in unlubricated and boundary lubricated contacts between steel and silicon nitride ceramics were used. The results confirmed that when more realistic contact conditions are used for the calculations instead of the nominal values, calculated temperatures at the spot-to-spot contacts in the gross slip regime can be very high, much higher than 1000°C. Furthermore, results showed the critical differences between selected models, according to which, the temperature couldvary for more than 100%. In order to compare the theoretical flash temperature calculation results with surface changes tribochemical phase transformations were investigated based on the SEM, EDS, AES and TEM results.
    Source: Materials Week 2001 Proceedings [Elektronski vir]. CD 2 (Str. 1-7 [mw2001_288.pdf])
    Type of material - conference contribution
    Publish date - 2002
    Language - english
    COBISS.SI-ID - 5134107

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