Thermal phenomena during friction of composite materials
Andrzej Posmyk*, Grzegorz Służałek*, Jerzy Myalski** *Uniwersytet Śląski, Wydział Informatyki i Nauki o Materiałach, ul. Śnieżna 2, 41-200 Sosnowiec **Politechnika Śląska, Wydział Inżynierii Materiałowej i Metalurgii, ul. Krasińskiego 8, 40-019 Katowice
Annals 4 No. 10, 2004 pages 179-183
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abstract In this paper thermal properties of composite materials with aluminium and their alloys matrix used for tribological testing are presented (Tables 1 and 2). The tribological tests with measurement of temperature near the friction zone in pairing of cast iron against chosen matrix and composite materials were made. Aluminium alloy AK12 reinforced with aluminium oxide (Al2O3) and amorphous carbon (WS) were tested. The results are presented in Table 3. The simulation of the heat flow generated through the friction under the assumption of one-point heat source was made. The results are presented in Figure 5. For the statistical estimation of the contact surface between the sliding parts measurements of the stereological parameters of the reinforcing phase (RP) were made using the 3D profilmeter (Figs. 2 and 3). Friction generated heat comes from the point sources number of, which depends on the topography and stereological parameters of the reinforcing phase. Quantity of the friction generated heat depends on the friction coefficient, which depends on topography and chemical composition of the surfaces of sliding parts. The heat flow carried away from the friction area depends on the thermal properties of the contacting parts. The reinforcing parts project over the matrix surface more then 1 μm (Fig. 3) and they are in contact with the sliding partner. As a results the local stresses and strains increase in cast iron as well as the friction coefficient does. The thermal conductivity coefficient of aluminia (Al2O3) is considerably lower then the one of aluminium. Therefore local thermal peaks take place in the friction area of the cast iron, wearing against composite materials. They are much higher then the ones during wearing against aluminium or silumin (AlSi alloy, Table 3). On the base of the test the significant differences between the temperatures near the friction area were found (Table 3). Some results were obtained by theoretical simulation based on Fourier-Kirchhoff heat transfer function (Fig. 5). These differences depended on the type of the reinforcing phase and its stereological parameters. The highest temperature was measured in case of aluminia, and the lowest in case of pure aluminium. Key words: thermal phenomena, sliding friction, thermal conductivity, one-point hit source, composite materials, aluminia, glassy carbon