An experimental and analytical study of scuffing in aluminum based metal matrix composites

Scuffing is a surface damage phenomenon in tribology characterized by the formation of local welds between sliding surfaces. Many previous studies focused on scuffing of ferrous materials due to their extensive use in tribological systems. Information about scuffing behavior of Al metal matrix composites (MMC) is scarce, especially quantitative modeling of the effects of volume percentage, size as well as distribution of reinforcement particles. Therefore, it will broaden our understanding of scuffing in MMC's if the influences of these factors on scuffing behavior are clarified.; The objective of this study is to understand when scuffing will occur and the relationships of Al MMC's scuffing resistance with material characteristics and mechanical properties.; A new scuffing criterion for particulate reinforced MMG's was proposed in this study based on which an extensive finite element analysis (FEA) on MMC's behavior was carried out. This is the first FEA modeling work in this research field.; Various MMC's were tested experimentally in this study including SiC and Al{dollar}sb{lcub}2sb3{rcub}{dollar} ceramic particle reinforcements and Al 356, Al 6061 and Al 2014 matrices.; A special ring-on-block reciprocating test apparatus was developed to perform scuffing tests and simulate the interactions between piston ring and engine cylinder bore. Scuffing was detected by an abrupt increase in friction during experiments. Scuffing resistance is represented by scuffing pressure or scuffing initiating time. After scuffing tests, most of the MMC samples were examined with optical and/or scanning electron microscopy (SEM) to obtain information on surface topography changes.; The influence of a material's microstructural and mechanical properties (hardness, yield strength, percentage and size of reinforcements), surface finish and lubrication on scuffing were investigated. The conclusions can provide us a guidance in the selection of appropriate materials and machining processes for a tribological system. The major contribution of this study is the finding of an effective method (FEA) to predict scuffing resistance of MMC's quantitatively.; The FEA results on scuffing were compared with that from experiments and they show strong correlation.