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In this study, the solid particle erosion behavior of solutionized, articially aged (T6) and annealed aluminum alloy AA7075 has been investigated. The samples were eroded in solid particle erosion test equipment at 45• impingement angle and 75 m/s impingement velocity with 180 mesh garnet erodent particles. Afterwards, microstructures of solutionized, articially aged and annealed samples of AA7075 alloy were analyzed. In order to gure out the eect of ductility on erosion rates, the Brinell hardness of the samples was measured. The surface morphology images of the samples were taken before and after the erosion test by using scanning electron microscope (SEM). The eects of the microstructures and the hardness on the erosion behavior of the dierent heat treated specimens were examined. Finally, SEM images of the samples were deeply analyzed and the erosion mechanisms which occurred on the surfaces of the samples were discussed.

In this study, a fuzzy mathematical model is developed using a multi-response surface methodology with fuzzy logic to optimize all response variables simultaneously. The model has the flexibility to weight the response factors depending on the decision maker's choices. The model has been applied to the drilling process using a high speed steel drill bit on PVC samples in an upright drill. The aim of the study is to minimize surface roughness and cutting forces. The input variables and their experiment intervals are determined as cutting speed (360-1080 rev/min), feed rate (0.10-0.30 mm), and material thickness (15-45 mm). Surface roughness, radial force-X and radial force-Y are chosen as response variables. According to the experiments and statistical analysis, the optimum levels of cutting speed, feed rate, and material thickness were calculated as 1068 rev/min, 0.1195 mm, and 21.33 mm respectively.

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