Ultrasonic assisted turning of Al alloys: influence of material processing to improve surface roughness

Abstract

Ultrasonic machining has been used over a decade to enhance the surface finishing and overall processing characteristics of conventional technologies. The benefits that are usually associated to this approach generate an increasing interest in both academic and industrial fields, especially in the turning operation due to its simple application. In this study, ultrasonic assisted turning is used to study the effect of intermittent tool contact on the surface quality of cast and wrought aluminium alloys. The resulting surface roughness and topography plots were evaluated through a three-dimensional (3D) optical profilometer. Additionally, stereo microscopy and detailed by scanning electron microscopy analyzed chip shape and morphology. The experimental results show that the appropriate use of an ultrasonic intermittent tool can improve the superficial quality up to 82% and reduce the maximum peak height by 59 % for a 0.045 mm/rev feed rate. When the feed rate is increased to 0.18 mm/rev, the surface roughness may be enhanced by 60% and the maximum peak height reduced by 76%. Furthermore, due to the introduction of a distinct cutting mechanism, the traditional chip shape is modified when the ultrasonic tool excitation is applied. A model is suggested to explain the chip growth and the fracture behaviour.