Influence of graphite particles distribution in cast-iron on its rubbing against composite material with aluminium alloy matrix
Andrzej Posmyk, Henryk Bąkowski
Quarterly No. 2, 2010 pages 159-164
DOI:
keywords: reinforcing particle, distribution of stresses and strains, composite, cast iron, graphite, wear
abstract The attempt to explain of the influence of graphite stereological parameters in cast iron piston ring on mechanism of wear in pairing cast iron EN-GJL-350/composite W6D.22A using of Finite Elements Method (FEM) has been presented in this paper. As a result of conducted metallographic and stereological investigations the graphite stereological parameters and its orientation to friction surface in cast-iron and stereological parameters of reinforcing phase of AlMC have been determined. Based on those results, two extreme models of pairing, i.e. with vertical and horizontal graphite orientation have been elaborated and simulating calculations have been conducted. The assumptions for that model are as follows: the average diameter of reinforcing particles d = 15 m, average distance between particles is 25 m, the surface fraction of alumina particles NA = 625 mm–2, friction in air (= 0.3). The stereological parameters of cast-iron are as follows: average graphite precipitation chord d = 5 m, average length L = 15 m, average distance between graphite particles 15 m. These models have been named “advanced”, compared to former simplified model, which does not consider graphite precipitates in cast-iron, i.e. cast-iron is isotropic. Two models of pairing with vertical and horizontal graphite precipitates localisation have been elaborated. Simulation calculations have shown that the maximum of stresses is in graphite precipitates at the contact line between pearlitic cast-iron matrix and the reinforcing phase. The maximal stresses in vertical graphite (82 MPa) are about 50% higher then the stresses in horizontal graphite (55 MPa). Comparing the stresses calculated using advanced and simplified models it should be stated that the average stresses in the contact zone between cast-iron and composite having aluminia reinforcing particles are between the both analysed extreme cases. The maximum stresses are 17÷27 times larger then the given load (3 MPa).