Experimental Investigations of Improving Bushing Quality and Joining Sheet Metals in Friction Drilling
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Friction drilling is a novel hole-making process performed on thin-walled sheet metals. The friction between a rapid-rotating conical tool and a sheet metal generates heat to soften the work material and penetrate it to form a hole. The bushing is formed in situ from the workpiece. This experimental study investigated friction drilling process. Axial thrust forces during the process were measured by a dynamometer and data acquisition system. The thrust force curves and the cross-sectioned images of friction-drilled holes were characterized to study the effects of process parameters such as spindle speed, feed rate, workpiece thickness, and tool diameter. The results showed that either increasing spindle speed or decreasing feed rate can reduce the thrust forces. Generating a bushing with good quality has been a challenge in friction drilling. The lower die fixture was designed to improve the bushing shape in its cylindricality, cracks and petal formation. Threads were tapped to demonstrate the improvement of the bushing quality in practical application. Due to the similarities in friction stir welding and friction drilling, the feasibility of joining sheet metals in friction drilling was explored. Different coalescence conditions were observed. The potential of joining sheet metals by friction drilling was demonstrated.
Su, Kuan-Yu (2015). Experimental Investigations of Improving Bushing Quality and Joining Sheet Metals in Friction Drilling. Master's thesis, Texas A & M University. Available electronically from