Analytical and experimental approaches to study elastic deflection of thin strip in ultrasonic-assisted drilling process

Abstract

During machining of thin material, workpiece endures deflection due to cutting forces that negatively influence dimensional tolerances and machined surface quality. An applicable method for the restriction of such problems is machining in the presence of ultrasonic vibration. However, understanding of how this improvement is caused by this type of vibration needs extensive studies. This paper presents a workpiece deflection model for conventional drilling and ultrasonic-assisted drilling of 1 mm thickness aluminum 7075. The workpiece considered was a thin beam and the deflection was determined by the use of beam vibration theory in continuous system. The deflection of workpiece during both the conventional and ultrasonic-assisted drilling processes were determined by means of developed model and compared with those derived from experiments. It was found that the average prediction error in worst case was less than 20%. Also, it is observed from both the experimental and theoretical approaches that applying ultrasonic vibration to drilling tool significantly reduces the workpiece deflection. Furthermore, from both approaches, it is identified that increase in vibration amplitude causes a decrease in beam deflection. Restriction of beam deflection by exerting high-amplitude ultrasonic vibration causes elimination of cap burr in the exit hole due to enhancement in the rigidity of workpiece.