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Parametric investigation of rotary ultrasonic drilling of carbon fiber reinforced plastics

Carbon fiber reinforced plastics are used in various industrial applications for their excellent properties. Rotary ultrasonic drilling is the new machining process used to drill holes on fiber-reinforced plastics and has been attracting increased attention in recent years. Dimensional tolerances are very important in machining of carbon fiber reinforced plastics. Additionally, diamond core drills are simultaneously drilling and grinding fiber reinforced plastics. This paper aims to investigate thrust force and dimensional tolerances including roundness and cylindricity in rotary ultrasonic drilling of carbon fiber reinforced plastics using diamond core drill. To this end, a proper ultrasonic system for a core drill in ABAQUS is designed and fabricated. Thrust force in rotary ultrasonic drilling when compared to conventional drilling reduced by up to 30%. Besides, roundness and cylindricity decreased by up to 80% and 72%, respectively. Afterwards, analysis of variance demonstrated that vibration is more influential than other machining parameters in order to improve the hole accuracy. That is, obtained exponential regression models predict roundness and cylindricity through machining parameters with high accuracy. Feed rate of 30 mm/min and spindle speed of 1400 r/min by exerting vibration on the tool is considered to be the optimized condition.