Acoustic Horn Design, Numerical and Experimental Investigations of Ultrasonic Vibration Assisted Turning of Ti-6Al-4V

Abstract

Titanium alloys have got wide ranges of applications in the field of aerospace, biomedical, and marine industries owing to its unique properties like high strength, exceptional corrosion resistance, and high strength to weight ratio. Still, characteristics like redduced thermal conductivity and high affinity towards the cutting tools limit the machinability of these alloys making these as the hard to cut alloys. Ultrasonic vibration assisted turning (UVAT) is one of the novel machining processes enhancing the machinability of titanium alloys compared to the conventional turning (CT). The process allows us to impose an ultrasonic vibration of 20 kHz with small amplitude of vibration on the cutting insert to get an intermittent cutting, unlike the conventional turning. The present work consists of three parts (i) design and analysis of acoustic horn along with its fabrication (ii) finite element model for both of the processes and experimental investigation with the discussions, and (iii) machinability investigations of both the processes studying chip morphology, surface integrity and tool wear. The first part includes designing and modeling of the horn that will act as the tool holder in UVAT process, using Ansys v15®, along with the fabrication of the parts based on the analysis. The tool holder is stepped type made of stainless steel (Grade SS304) with flexible attachments for the cutting inserts. The later part of the thesis includes preparation of 3D thermo-mechanical finite element model for both the processes using Deform 3D®. Experimental investigations of both the machining processes were carried out to study the machinability of titanium Grade 5, TI-6Al-4V. The dependence of results (cutting force, surface roughness, tool temperature, chip morphology etc.) on the input parameters were investigated and compared. UVAT showed significant reductions in cutting forces with improved surface finish of the workpiece. In the third section, machinability indices like chip morphology, surface integrity, and tool wear were observed. The results confirm the suitability and advantages of the UVAT process compared to the CT process to machine hard to cut metal Ti-6Al-4V.