الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Friction drilling is a chipless hole-making process that solves the problem of threaded joints in thin-walled structures by substantial welded nuts and riveted nuts through two simple steps friction drilling, followed by form tapping. Materials like stainless steel are difficult to cut due to its characteristic; therefore, lubricant should be used, but it is dangerous and affects human health. Friction drilling could perform different hole sizes with high quality in stainless steel and without any lubricant. Threaded joints are widely used in the assembly of mechanical parts according to their flexibility to disassembly, for example, maintenance or recycling, and also because of their high strength and rigidity. Therefore, this study investigated hole and thread quality performed by friction drilling followed by the form tapping process. Form tapping process is a cold forming process characterized by a strain-hardened effect and compressed grains, which realizes formed thread with high strength. Also, both processes are chipless without chip disposal problems. Therefore, they are rapid, clean, and ecologically safe. This study aims to improve friction-drilled holes and formed thread quality by investigating the influence of the input working parameters, such as the ratio of workpiece thickness (t) to friction drill diameter (d), rotational speed (N), and feed speed (f). The hole quality is assessed by studying the effect of those parameters on the hole diametral oversize (U), cylindricity error, and the height of the formed collar. Then, the micro-hardness test, metallographic examination, effective thread length measurements, diameters, and pitch errors of the formed thread were performed to assess the formed thread quality. Finally, A comparison was conducted to examine the difference between the ultimate tensile strength of the formed and cut threads. Based on the fractional factorial design experiments approach, the experiments were conducted on difficult-to-cut material 25x25mm square cross-sectional area AISI 304 stainless steel workpieces with (2 and 3 mm) wall thicknesses. Tungsten carbide friction drills with diameters (Ø9.2, Ø7.3, and Ø4.5 mm) were used to perform the experiments, followed by HSS form taps (M10x1.5, M8x1.25, and M5x0.8, respectively). The analysis of variance (ANOVA) showed that the t/d ratio was the most significant factor affecting the mean cylindricity error, the collar height, and the effective thread length. By comparing the performance of the three friction drills, it was noticeable that the friction drill Ø7.3 realized better results in terms of mean hole diametral oversize and mean cylindricity error. The mean hole diametral oversize (U) decreased by increasing the input working parameters for the investigated tools. The centering process was positively affecting the collar shape. The elevated temperature associated with high plastic deformation during the processes resulting in fine austenite grains surrounded by δ-ferrite stringers with high hardness values were observed at the heat-affected zone. The formed thread realized a higher ultimate tensile strength than the cut thread as a result of a longer effective thread length, strain hardening effect, and compressed grains.