Papers by Author: Y. Bozkurt

Abstract: The feasibility of friction stir spot welding was studied on AA5754-H22 and AA2024-T3 aluminum alloys which have widespread applications in aircraft and automotive industries. The quality of the joint was evaluated by examining the characteristics of the joint as a result of lap-shear fracture load. Taguchi approach of the parameter design was used as a statistical design of experiment technique to set the optimal welding parameters. The experiments were arranged by using Taguchi’s L9 orthogonal array. The signal-to-noise ratio and the analysis of variance were utilized to obtain the influence of the friction stir spot welding parameters on the lap-shear fracture load. Finally, the results were confirmed by further experiments.

Abstract: Composites of calcinated bovine bone derived hydroxyapatite (BHA) doped 0.5 and 1 wt% CaF2 were prepared by sintering. The production of BHA from natural sources is preferred due to money and time saving reasons. Scanning electron microscopy (SEM) and X-ray diffraction analysis together with measurements of density and compression strength were carried out in the produced samples. The experimental results indicated that compression strength of the composites increase when sintering temperature increases. The best compression strength was achieved after sintering at 1200°C for 0.5% CaF2 addition. The results are in agreement with densification measurements and microstructure analysis. With regards to the amount of CaF2, the results indicate that small additions of F, lower than 0.5%, can further improve the mechanical properties of HA.