Investigate the Effect of Pre-drilling in Friction Drilling of A7075-T651

摘要

Friction 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 4 mm and 6 mm in thicknesses of A7075-T651 aluminum alloy at 1200, 1800, 2400, 3000, and 3600 rpm spindle speeds, 20, 40, 60, 80, and 100mm/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.