Vibration analysys

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ARTICLE IN PRESS
International Journal of Machine Tools & Manufacture 50 (2010) 65–74

Contents lists available at ScienceDirect

International Journal of Machine Tools & Manufacture
journal homepage: www.elsevier.com/locate/ijmactool

Vibration analysis of cutting force in titanium alloy milling
Armando 
Italo Sette Antonialli a,Ã, Anselmo Eduardo Diniz b,1, Robson Pederiva b,1
a
b~
~
Materials Engineering Department, Federal University of Sao Carlos, 13565-905 Sao Carlos, SP, Brazil
Faculty of Mechanical Engineering, State University of Campinas, C. Postal 6122, 13083-860 Campinas, SP, Brazil

article info

abstract

Article history:
Received 16 June 2009
Received in revised form
1 September 2009
Accepted 8 September 2009
Available online 16 September 2009Machining processes such as milling, which are characterized by interrupted cutting, are often
susceptible to problems involving vibration of the machine-tool-workpiece fixation device system
because of the proximity between their natural frequency harmonics and the frequency of tool entry on
the workpiece. This phenomenon is particularly important in the milling of titanium alloys, becausethese materials show a low Young modulus, and hence, an extended elastic behavior, which means
tremendous variations in chip thickness and fluctuating cutting forces. Moreover, very low heat
conductivity causes the formation of serrated chips, which further increase the fluctuation in cutting
forces. The purpose of this work is to study the influence of the tool entering angle on the stability ofthe
process and on tool life based on a time and frequency domain analysis of the cutting forces. The results
show that lower entering angles may provide stabler cutting, as indicated by the regular tool wear
instead of the microchipping resulting from the use of a higher value of this angle. Although cutting
forces are larger at lower entering angles, the tool life is much longer, since mostof this load is
associated with low frequencies, at which the tool behaves like a rigid body.
& 2009 Elsevier Ltd. All rights reserved.

Keywords:
Machining
Milling
Vibration
Cutting forces
Titanium alloys

1. Introduction
Although titanium alloys have outstanding mechanical properties such as high hot hardness, good strength-to-weight ratio, and
high corrosion resistance, their lowthermal conductivity, high
chemical affinity to tool materials and low Young modulus
severely impair their machinability [1].
First and foremost, titanium alloys are poor heat conductors.
Their thermal conductivity is almost 7 W/m K, while that of
stainless steels is about 18 W/m K and that of carbon steels is
about 50 W/m K [2]. Therefore, the heat generated during
machining processes isconcentrated mainly at the tool’s cutting
edge, causing it to lose hardness and mechanical resistance and
leading to its plastic deformation and/or rapid wear [3].
Titanium alloys have chemical affinity for all known tool
materials, which, along with high temperatures generated in the
cutting zone, provides strong adhesion of workpiece material over
the tool edge. Mechanisms of attrition anddiffusion can
accelerate tool wear and lead to edge breakage [4].
Because of its low Young modulus, the volume of workpiece
material in the vicinity of the machined surface undergoes
excessive elastic deformation during machining, preventing a
à Corresponding author. Tel.: + 55 16 33518513.

E-mail addresses: antonialli@ufscar.br (A. 
Italo Sette Antonialli),
anselmo@fem.unicamp.br (A.Eduardo Diniz), robson@fem.unicamp.br
(R. Pederiva).
1
Tel.: + 55 19 3521 3292.
0890-6955/$ - see front matter & 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ijmachtools.2009.09.006

good finish, particularly in the case of thin walls [5]. In milling or
other processes associated with interrupted cutting, a low Young
modulus causes major variations in chip thickness, i.e., high...
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