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Öğe Investigate the effect of pre-drilling in friction drilling of A7075-T651(Taylor & Francis, 2014-04-28) Demir, Zülküf; Özek, CebeliFriction drilling is a non-traditional hole achieving method that is a clean, chip-less process, which is called thermal drilling, form drilling, flow drilling, and friction stir drilling. In this study pre-drilling friction drilling was investigated for improving the bushing shape of A7075-T651, which is a brittle cast material. During the process, surface roughness and bushing shapes were analyzed and generated frictional heat was measured by the virtue of thermocouples. Experiments were carried out to 4mm and 6mm in thicknesses of A7075-T651 aluminum alloy at 1200, 1800, 2400, 3000, and 3600 rpm spindle speeds, 20, 40, 60, 80, and 100 mm/min feed rates with using high-speed steel rotating conical tool, whose diameter is 8 mm. Consequently, the bushing shapes were advanced without cracks and petal formation in pre-drilling Friction drilling in comparison with without pre-drilling process. With increasing pre-drilled hole diameter the generated frictional heat was decreased. The achieved temperature was realized to be 1/2-1/3 of the melting temperature of the workpiece. Surface roughness values were decreased with decreasing or increasing both spindle speed and feed rate correspondingly.Öğe Effect of temperature, force, and vibration on fatigue strength of friction stir-welded AA7075 aluminum alloy joints(SpringerLink, 2021-01-04) Çelik, Yahya Hışman; Kılıçkap, Erol; Çetkin, EdipIn this study, the AA7075 alloy pairs were welded by friction stir welding method by using conical- and triangular-type stirrer pins. Welding forces and moments, vibration, and temperature values have been measured during the jointing depending on the welding parameters. Finally, microstructures were examined and mechanical tests were carried out. Results obtained from the experiments revealed that at low spindle speed and welding feed rates, the temperatures formed on the surface of the alloy pair were high, the vibrations were low, and the welding force and moments were partially high. When the microstructures of the welded areas are examined, it was determined that the conical mixing pin has a better microstructure than the triangular mixing pin. In addition, it was determined that the mechanical properties of welded joints having a good microstructure were quite good. As a result, it was observed that forces during welding, temperature of welding, and vibration values have an effect on microstructure and mechanical properties.
