Modeling and optimization of thrust force, torque, and surface roughness in ultrasonic-assisted drilling using surface response methodology

Due to the high number of applications of aluminum alloys in aircraft and automotive industries, there is a great interest in machining and specifically drilling these materials. Even though aluminum is considered a machinable material, drilling this material has its own challenges including built-up edge (BUE), exit burr, and low surface roughness of the drilled holes. Ultrasonic-assisted drilling (UAD) process, a technology that applies high-frequency vibrations with low amplitudes has proven to have many benefits compared to conventional drilling. In this study, a special resolution V design as well as response surface methodology (RSM) were used to characterize the UAD process of Aluminum 6061. This characterization was done through the study of the effect of drilling parameters including spindle speed, feed rate, and amplitude on thrust force, torque, and surface roughness. The analysis of variance (ANOVA) was utilized to find significant parameters of thrust force, torque, and surface roughness. Then, the optimum values of drilling parameters that minimized these parameters were obtained. The results showed that in UAD of aluminum, the minimum values of thrust force and torque were obtained at low spindle speed, low feed rate, and high amplitude, while minimum surface roughness was obtained at high spindle speed, low feed rate, and high amplitude. Finally, out-of-sample testing was used to verify the adequacy of the mathematical models.