Abstract
In this study, a special resolution V design and response surface methodology (RSM) were used to characterize the ultrasonic-assisted drilling (UAD) process of aluminum 6061. This characterization was done through developing mathematical models to study the effect of ultrasonic and drilling parameters including spindle speed, feed rate, and amplitude on thrust force, temperature, chip morphology, and power. The tests were done using an industrially hardened non-rotating UAD system mounted in a CNC turning center. The analysis of variance (ANOVA) was used to find significant parameters of thrust force, temperature, chip morphology and power. Then, for all responses, the optimum drilling parameters that provide desired solutions for all responses were obtained. This was followed by out-of-sample testing to verify the accuracy of the developed models. The results of this study showed that in UAD of aluminum, the minimum values of thrust force and chip size were obtained at low spindle speed, low feed rate and high amplitude. The results also showed that amplitude was not a significant parameter affecting the tool temperature and cannot be used to analyze the effect of ultrasonic vibrations on generated heat during UAD. Instead, the interaction of amplitude and feed rate was significant and should be considered in the analysis. Finally, minimum consumed power, specially at higher amplitudes, can be obtained using high spindle speed and low feed rate.
Highlights
Due to the strength-to-weight ratio as well as corrosion resistance of aluminum alloys, these alloys are widely used in various industries such as aircraft, aerospace, and automotive
The results of this study showed that in ultrasonic-assisted drilling (UAD) of aluminum, the minimum values of thrust force and chip size were obtained at low spindle speed, low feed rate and high amplitude
The results investigated in this study included thrust force, drill temperature, chip morphology, and the power consumed during the process
Summary
Due to the strength-to-weight ratio as well as corrosion resistance of aluminum alloys, these alloys are widely used in various industries such as aircraft, aerospace, and automotive. Of the several conventional processes used to machine this material, conventional drilling (CD) ranks as one of the most demanding machining processes. While aluminum alloys have been considered as one of the easy-to-machine materials, drilling this material has some limitations including low surface roughness of the drilled holes, built-up edge (BUE), and exit burr. A promising technique known as ultrasonic-assisted drilling (UAD) has attracted much attention because it can overcome the technological constraints just mentioned. The UAD process is a technology that applies high frequency vibrations (>20 kHz) at amplitudes of 2–20 μm in the feed direction to either the drill tip or work piece to improve drilling conditions and productivity. It should be noted that UAD is distinct from ultrasonic drilling (UD), which is known as rotary ultrasonic machining, where it uses an abrasive slurry to remove material from a workpiece
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