ORIGINAL ARTICLE Effect of process parameters on chip formation during vibration-assisted drilling of Ti6Al4V R. Hussein 1 & A. Sadek 2 & M. A. Elbestawi 1 & M.H. Attia 2 Received: 30 July 2019 /Accepted: 31 October 2019 # Springer-Verlag London Ltd., part of Springer Nature 2019 Abstract Vibration-assisted drilling (VAD) of Ti6Al4V is typically used in the aerospace industry to enhance the performance of the machining process. A mix of continuous and saw-tooth chip formation is associated with VAD of Ti6Al4V. In this paper, a comprehensive experimental study is developed to examine the effect of process parameters on the dominant chip formation mechanisms and the associated effects on the thrust forces and machined surface finish. The results indicate a significant change of the chips free surface produced by VAD. The kinematics of VAD showed a direct relation between the VAD amplitude and the effective rake angle. In agreement with the theory of saw-tooth formation due to cyclic crack formation, the scanning electron microscopy (SEM) examination showed a gross crack (GC) and micro crack (MC) along the shear plane. The GC increased from 20 μm for conventional drilling to 224 μm for VAD at the highest amplitude. Moreover, increasing the VAD amplitude to 160 μm showed an obvious enhancement of the machined surface finish. In addition, the study presents the influence of VAD on the tool wear mechanisms through the composition analysis of the chips machined surface using Energy Dispersion X-ray Spectroscopy (EDS). Keywords Low-frequency vibration-assisted drilling . Ti6Al4V material . Advanced machining . Crack . Chip formation . Chip morphology Abbreviations VAD Vibration-assisted drilling LF-VAD Low-frequency vibration-assisted drilling CD Conventional drilling ASB Adiabatic shear band SB Shear band WC Tungsten carbide SD Segment degree GC Gross crack MC Micro crack Notations N Rotational speed [rpm] F Feed rate [mm/rev] A m Modulation amplitude [mm] F Frequency [Hz] W f Modulation frequency [oscillation/rev] h max Maximum saw-tooth height [μm] h min Minimum saw-tooth height [μm] Lc Deformed chip length [μm] S d Sliding distance [μm] Z Axial cutting edge position [mm] Zk(γ) Maximum height of the previous rotation [mm] γ Rake angle [°] γ' Effective rake angle [°] ƞ Resultant cutting force direction [°] V c Primary cutting speed [m/s] V f Dynamic feed speed [m/s] 1 Introduction The critical mechanical characteristics for a load-carrying structure, such as high strength to weight ratio and excellent fatigue life, increased the use of Ti6Al4V to more than 16% of the total weight of an aircraft. Conventional drilling of Ti6Al4V prior to the assembly process poses several * R. Hussein husser2@mcmaster.ca 1 Department of Mechanical Engineering, McMaster University, Hamilton, ON L8S 4L7, Canada 2 Aerospace Manufacturing, National Research Council Canada, Montreal, QC, Canada The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-019-04627-9