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Abstract
Polymeric materials, many years ago, are being used increasingly in numerous mechanical and medical applications due to its excellent mechanical and tribological properties. This encouraged the designer and developer of mechanical and biomedical systems to study its behavior under different operating conditions.
\Vt.’ur is one of the commonly failure mode associated with hardware. Reduction and control of wear tend to be a great challenge because of the complexity of wear behavior and the lack of a unifying theory or model, such as those used for fracture and fatigue. Many intensive studies, over the last decays, have been developed to investigate the influence of different factors allecling wear in polymers in order to clear this feature.
Many applications of polymer-metal contact surfaces in dry or wet conditions such as bearings, gears, car tires and others may have some surface cracks or subsurface cracks. The presence of these cracks may increase or decrease the wear rate of polymer. On the other hand, these cracks may propagate or worn completely due to wear.
The present thesis studies the wear-crack interaction of polymethylmethacrylate (PMMA) sliding on steel counterfaces. The polymer was tested under constant load, constant speed and under dry or wet conditions. The polymer specimens had many configurations, specimens without crack and specimens with crack. The cracks were vertical with different lengths, angles and tip shapes. The polymer was, first, tested with different contact areas and simulated angles to study the effect of contact area and discontinuity on the wear rate and wear factor. Then, tests were performed to study the effect of crack, with different parameters, (lengths, angles and tip shapes), on the wear and also the effect of wear on crack propagation. Moreover, additional tests were performed to study the wear under wet condition. Finally, an explorer tests were conducted to investigate the effect of the type of steel used as a counterface.