الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
To conduct the experimental study in this project, variables process parameters were; cutting speed, feed rate and depth of cut. Three different types of insert were used during the experimental trials. Generated surface quality and cutting temperature were utilized as quality marks to assess the relative performance of different machining modes, high speed vs conventional, under a wide range of process parameters. The results showed that tangling of chip with workpiece has a negative effect on the resultant surface roughness. In addition, it was found that at low cutting speed, continuous helical chip was produced with a good result of chip evacuation for all values of depth of cut and feed rates and increasing feed rate and depth of cut encourages chip-up curling. Also, higher feed rate with small depth of cut found to achieve good results in chip breaking and evacuation at higher cutting speed. The results of SEMexamination of produced chips revealed different images of chip analysis by different chip curling mechanismswhich differ in chip shape based on the applied process variables. Chip-side curl formation showed different segmentation analysis along chip width while chip-up curl occurred by degradation of chip thickness to reach a its maximum value at one plane along chip width. High-speed machining showed a higher increase in cutting temperature by average of 65% compared with conventional machining. However, high-speed machining showed a better performance by turning Ti6Al4V compared with conventional machining in terms of improved surface quality and increasedmaterial removal rate (MRR), thus offering higher productivity. Furthermore, an inverse relationship between generated cutting temperature andsurface roughness was verified. This was mainly attributed to the positive influence of generated, but controlled, high cutting temperature on softening and thus decreasing localized strength of the material in the vicinity of the cutting zone which in turn enables smooth machining mechanisms and smother surface. CBN insert showed a good behavior for temperature dissipation during machining compared to coated ceramic insert with a reduction of temperature by 28% while coated ceramic insert showed excellent results of surface roughness with improvement by 34% compared with using CBN insert. Moreover, the results by both insert confirmed the positive effect of cutting temperature on improving surface roughness via the comparison between the performance of both insert at the same cutting conditions.