+44 (0)1509 263171
Please use this identifier to cite or link to this item:
|Title: ||Improvements in ultrasonically assisted turning of TI 15V3Al3Cr3Sn|
|Authors: ||Maurotto, Agostino|
Vibration assisted machining
|Issue Date: ||2013|
|Publisher: ||© Agostino Maurotto|
|Abstract: ||Titanium alloys have outstanding mechanical properties such as high hardness, a
good strength-to-weight ratio and high corrosion resistance. However, their low
thermal conductivity and high chemical affinity to tool materials severely impairs their
machinability with conventional techniques. Conventional machining of Ti-based
alloys is typically characterized by low depth of cuts and relatively low feed rates,
thus adversely affecting the material removal rates (MRR) during the machining
process. Ultrasonically assisted turning (UAT) is an advanced machining technique,
in which ultrasonic vibration is superimposed on a cutting tool. UAT was shown to
improve machinability of difficult-to-machine materials, such as ceramics, glass or
hard metals. UAT employment in the industry is, however, currently lacking due to
imperfect comprehensive knowledge on materials‘ response and difficulties in
obtaining consistent results.
In this work, significant improvements in the design of a UAT system were performed
to increase dynamic and static stiffness of the cutting head. Concurrent
improvements on depth-of-cut controls allowed precise and accurate machining
operations that were not possible before. Effects of depth of cut and cutting speed
were investigated and their influence on the ultrasonic cutting process evaluated.
Different cutting conditions -from low turning speeds to higher recommended levelwere
analysed. Thermal evolution of cutting process was assessed, and the
obtained results compared with FE simulations to gain knowledge on the
temperatures reached in the cutting zone. The developed process appeared to
improve dry turning of Ti-15-3-3-3 with significant reduction of average cutting forces.
Improved surface quality of the finished work-piece was also observed. Comparative
analyses with a conventional turning (CT) process at a cutting speed of 10 m/min
showed that UAT reduced the average cutting forces by 60-65% for all levels of ap
considered. Temperature profiles were obtained for CT and UAT of the studied alloy.
A comparative study of surface and sub-surface layers was performed for CT- and
UAT-processed work-pieces with notable improvements for the UAT-machined ones.
Two- to three-fold reductions of surface roughness and improvements of other
surface parameters were observed for the UAT- machined surfaces. Surface
hardness for both the CT- and UAT-machined surfaces was investigated by microindentation.
The intermittent cutting of the UAT-process resulted in reduction of
hardening of the sub-surface layers. Optical and electronic metallographic analyses
of cross-sectioned work-pieces investigated the effect of UAT on the grain structure
in material‘s sub-surface layers. Backscatter electron microscopy was also used to
evaluate the formation of α-Ti during the UAT cutting process. No grain changes or
α-precipitation were observed in both the CT- and UAT-machined work-pieces.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Sponsor: ||Marie Curie FP7|
|Appears in Collections:||PhD Theses (Mechanical, Electrical and Manufacturing Engineering)|
Files associated with this item:
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.