Abstract
Longitudinal torsional coupled rotary ultrasonic–assisted drilling (LTC-RUAD) technology is introduced to improve the surface roughness of the hole-wall and solve the tear, burr, and delamination of carbon fiber–reinforced polymers (CFRPs) induced by large thrust force and torque during conventional drilling (CD). An experiment and scale-span numerical investigation of drilling CFRPs were presented for both the CD and LTC-RUAD processes in this study. A drilling experimental platform using the LTC-RUAD was built via a novel independently designed and manufactured LTC-RUAD vibration actuator, while the drilling experiments involving T700S-12 K/YP-H26 CFRP specimens with different process parameters were carried out by adopting the different ultrasonic vibration amplitude (UVA) in the longitudinal and torsional directions. Then, a three-dimensional (3D) scale-span FE simulation model of the CD and LTC-RUAD which applied the different UVA using tapered drill-reamer (TDR) is developed to find more details about the effects of machining quality of the holes. Experimental and simulation results revealed that the maximum average thrust force reduction is observed to be as high as 30% under certain drilling conditions, and the maximum average thrust force and the delamination factor of the drilled hole shows a “concave” trend with the increase of the UVA. The quality at the exit of the drilled hole is best when adopting Sr = 2000 rpm, Sf = 0.01 mm/rev, Alon = 7.02 μm, and Ator = 9.29 μm in the LTC-RUAD. The delamination factor is only 0.054, and the damage factors are reduced by 69.67% compared with CD.
Highlights
Carbon fiber reinforced polymers (CFRPs) are being widely used in aerospace industry and automobile industries and several other structural applications owing to their superior mechanical and physical properties [1,2]
Sadek et al [10] investigated the RUAD process to reduce thermal and mechanical defects associated with drilling of CFRPs, the results revealed that the optimized RUAD condition can reduce the machining temperature by 50%, the thrust force by 40% and produce delamination-free holes, without affecting productivity
For the sake of allowing a better comparison of the experimental and simulated thrust force, torque and the damage in entrance, hole-wall and exit of the performed hole using conventional drilling (CD) and LTC-RUAD, a typical feed rate of Sf=0.03mm/rev was chosen from the experimental feed data with a spindle speed Sr=2000rpm
Summary
Carbon fiber reinforced polymers (CFRPs) are being widely used in aerospace industry and automobile industries and several other structural applications owing to their superior mechanical and physical properties [1,2]. Compared with CD, RUAD is shown to be beneficial for drilling holes in brittle materials [8] and has many documented advantages, for instance, reduction in thrust force, improved surface finish, better hole quality, elimination of burrs and lower tool wear [9]. Thomas et al.[14] investigated the drill bit’s vibrational characteristic, the experimental and simulation results showed that there are several well-documented advantages of RUAD over CD techniques such as reduction in thrust forces and torque, better surface finish, low tool wear and elimination/reduction in burr formation. Compared with the one-dimensional longitudinal vibration drilling, the LTC vibration was discovered to improve the machining efficiency These above studies showed that there are several advantages of RUAD over CD such as reduction in drilling forces and torque, better surface finish, low tool wear and elimination in burr formation. Ltd after waterjet cutting, such as delamination and burr, etc
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