Investigate the effect of tool conical angle on the bushing height, wall thickness and forming in friction drilling of A7075-T651 aluminum alloy

Abstract

Friction drilling process is a non-traditional hole drilling process formed by thermal friction having the most important features such as no pollution, short machining time and long tool life. In this process conical tool is used to generate heat by friction to soften and generate a thin workpiece and create a bushing without generating chips. In this friction drilling experimental study, the selected spindle speeds were 2400 rpm, 3600 rpm, and 4800 rpm, feed rates were 50 mm/min, 75 mm/min, and 100 mm/min and tool material was HSS tool with 24°, 36°, and 48° conical angles, 8 mm, 10 mm, and 12 mm cylindrical region diameters and 16 mm tool cylindrical region lengths. The specimens were A7075-T651 with thickness of 4 mm, and 6 mm. The effect of tool conical angle on the bushing height, bushing wall thickness, and bushing shape were analyzed. It was seen that for 4 mm and 6 mm materials thicknesses, according to the bushing height, the most optimum tool conical angle was 24° for all diameters. For 4 mm material thickness according to the bushing wall thickness 48° was the most optimum conical angle in friction drilling 8 mm diameter, 24° for friction drilling 10 mm and 12 mm diameters. The most optimum tool conical angle was 36° for 8 mm diameter, 24° for 10 mm and 12 mm diameters. With decreasing tool conical angle the bushing height was increased and bushing wall thickness was decreased. In the conditional low tool conical angles the softened material flow in the direction of tool motion in friction drilling, thus bushing height increased and wall thickness decreased. With increasing both tool conical angle and spindle speed the cracks in obtained bushing were advanced and the shape of bushing formed as petal. But with increasing feed rate the bushings shapes were not changed.

Keywords

• Friction drilling, tool conical angle, bushing height

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