Table Of ContentMETAL
CUTT
MECHANICS
METAL
CUTTING
MEC ICS
Viktor P. Astakhov
0 CRC Press
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Preface
Except for casting, where the product forms directly from the liquid state,
many metal products are subjected to at least one metal-removing process
during their manufacture. The current rapid technological progress has forced
the theory of metal cutting into the forefront of engineering application and
design. The facts of economic life have made the efficient utilization of
material, labor, and time and a more efficient approach to design necessities
even for less sophisticated industrial applications. Therefore, today there is
a greater need for all industrial and manufacturing engineers to be familiar
with the fundamentals of metal cutting analysis, not only to be more numer-
ate and hence reduce the extent of empirical approach to problems, but also
to close the gap which exists between design and manufacture.
Although the theory of metal cutting has advanced considerably over the
last hundred years, rigorous solutions to many practical metal cutting prob-
lems are still not available. The common analyses of orthogonal cutting - a
simplified version of the practical cutting process, assuming idealized mate-
rials and boundary conditions - gives valuable insight into the effects of
cutting speed, feed, tool geometry, material properties, and various other
parameters on force, energy, and power requirements. However, there are
still many more questions than answers in regard to a great number of
particular cases.
The main differences between the author's work and the other works on
metal cutting include:
• A system engineering approach is taken to consider the cutting
process. For the first time, the cutting process is considered as taking
place within the cutting system, which is defined as consisting of the
following components: cutting tool, chip, and workpiece. Although
the known models of machining essentially include the same ele-
ments, they have never been considered as systems having the system
time frame; instead, they have always been considered as assemblages
without any time reference. Using the system approach, the basic
mechanisms governing the chip formation process are considered.
• The uniqueness of the cutting process, among other closely related
manufacturing processes, is identified by chip formation, which is
considered to be caused by the bending stress in the deformation
zone. The bending moment, which develops in the deformation zone
due to the interaction between the chip and tool rake face, causes the
bending stress in this zone. This bending stress combined with the
shear stress due to compression has been proven to be the cause for
chip formation and the consequent distinction of metal cutting from
other manufacturing processes. The presence, Significance, and varia-
tion of the bending stress in the deformation zone are proven both
theoretically and experimentally, resulting in the chief conclusion that
the cutting process has a cyclical nature. The dynamics of the cycles
are considered in terms of variation of the cutting force, cutting tem-
perature, chip structure, and other major cutting parameters.
• A distinctive move towards predictability of the metal cutting pro-
cess is suggested. At the present stage of development, the predict-
ability of a metal cutting theory depends entirely on the accuracy with
which it accounts for the properties of workpiece material, as the
design and geometry of the cutting tool along with the properties of
tool material are well known, and the cutting regime can be set at any
desirable level and/or can be varied according to any defined se-
quence. The resistance of workpiece materials to cutting is critical in
cutting mechanics; therefore, special attention is paid to the properties
of workpiece materials, with the main emphasis being placed on the
study of the thermomechanical behavior of these materials in cutting.
It has been proven that the shear flow stress, used as the primary
mechanical characteristic of workpiece material in cutting, is not a
relevant parameter to be used to predict the cutting process, and this
conclusion explains Significant discrepancies in reported results. The
reason for this is that the metal cutting process is always accomplished
by fracture - that is, by separation or fragmentation of a solid body
into two or more parts under the action of stress. Because fracture in
metal cutting processes is the result of plastic deformation, ductile
fracture is analyzed in details.
• Special attention is devoted to experimental methodology. Because
the theory of metal cutting is still in the early stages of development,
experimental study prevails as the essential instrument of know ledge
to reveal the influence of the cutting parameters on the processes'
outcomes as well as to prove certain aspects of developing theories.
Therefore, particular significance is given to the theory of similarity
and the theory (and practice) of simulation in their new, broader
sense, in which they are the basis for experimental procedures and
provide guidance as to the formulation of tests, as well as making it
possible to condense the resulting experimental information gained.
A number of new, original methods for experimental studies in metal
cutting are discussed. Special attention has been paid to the method-
ology of the cutting force measurements, simulation of orthogonal
cutting conditions, microhardness scanning procedure, and
fractography.
After a brief introductory chapter, the emphasis in the second chapter is
placed on the system approach in metal cutting. The mathematical theory of
system is employed to demonstrate that the cutting tool, workpiece, and tool
constitute the cutting system. Using the primary system properties, it has
been proven that the bending moment rising in the deformation zone due to
the interaction between the chip and tool rake face causes chip formation. A
definition of metal cutting is suggested to distinguish this process from other
closely related manufacturing processes. The third chapter gives a descrip-
tion of the model of chip formation having parallel boundaries. The approach
in this chapter is to apply, to the greatest extent possible, continuum mechan-
ics to the analysis of the chip formation process, with this model demonstrat-
ing that proper application of the theory leads to the proper velocity diagram
and to the conclusion that the deformation process in metal cutting cannot be
thought of as simple shearing. Although highly idealized, the model presents
a valuable starting point for further development. The fourth chapter consid-
ers the relevant properties of workpiece materials. This chapter is mainly
devoted to proving that the metal cutting process is purposeful fracture of
the workpiece material so that fracture toughness should be considered in
the analysis of the energy required. The strain at fracture is suggested to be
the main mechanical characteristic of workpiece material in cutting. Chapter
5 presents a finite element analysis of the cutting system. Little emphasis is
given to the computation side of the analysis, as it is covered sufficiently in
many books and papers. Instead, the main attention is given to physical
factors and aspects of analysis. Chapter 6 deals with experimental method-
ologies, experimental setups, data collection and acquisition procedures, and
analyses of the obtained results.
The book should be of particular relevant to researches in the field of
metal cutting and machine tool and tool design and to all practicing engi-
neers and metallurgists who are directly concerned with improving design
and efficiency in the manufacturing industry. Also, it should be of benefit to
graduate students and final year undergraduates specializing in manufactur-
ing processes.
I am deeply indebted to the following people for their help with the work
described in the book: Professor S. Shvets, for valuable help understanding
the chip formation process and its analysis; Professor Xinran Xiao, for her
supportive discussions and criticism of the material aspects of my work and
painstaking corrections of my earlier papers; Professor Jawahir, for the en-
couragement to write this book, constructive criticism, and his important
advice; Professor Milton Shaw, for his willingness to help, his open-minded
discussions, and his valuable advice; and Professor M.O.M. Osman, for his
support. I was greatly assisted by my graduate students, whose names
appear in the references throughout the text, and valuable assistance has
especially been provided by my graduate student, doctoral candidate
Mohammed Hayajneh, who has conducted a number of very sophisticated
cutting experiments included in the book. I wish to thank Thomas Hay for his
great help in careful checking of the manuscript. A special note of thanks is
due to the Manufacturing Engineering Division of the American Society for
Mechanical Engineers (ASME) for giving me the opportunities to organize
the symposium "Predictive Modeling in Metal Cutting as Means of Bridging
Gap Between Theory and Practice" in 1997 and the symposium "Machining
Science and Technology", in 1999.
Viktor P. Astakhov
The author
Viktor P. Astakhov, Ph.D., Dr.Sci., received his B.Eng. in manufacturing
from Odessa College of Industrial Automation (U.S.S.R) in 1972, his M.Eng.
in 1978 from the Odessa Polytechnic University (U.S.S.R), his B.Sc. and M.Sc.
in mathematics from Mechnicov's State University (Odessa, U.S.S.R), and
his Ph.D. from Tula Polytechnic University (U.S.S.R) in 1983. He was awarded
a Dr.Sc. designation in 1991 for his outstanding performance and profound
impact on science and technology. His first teaching appointment was in the
department of metal cutting and cutting tools at Odessa Polytechnic Univer-
sity in 1984, where he became a full professor and head of the deep-hole
machining center for the aerospace industry. He has served on national
scientific and planning committees and has also been an active consultant for
the machine tool building, aerospace, nuclear, and gas turbine industries.
Currently, he is an adjunct professor with Concordia University and a tech-
nical representative and senior consultant with American Heller Corpora-
tion.
Dr. Astakhov is the recipient of a "Bronze Medal for Achievements in
Development of Industry of the U.S.S.R" in 1984, a "Bronze Medal for
Achievements in Development of Industry of the Ukraine" in 1986, a certifi-
cate designating him "Professor of Ukraine" in 1994, and an ASME certificate
of appreciation and ASME's "BOSS" award in 1997.
Dr. Astakhov's principal research interest is in manufacturing, including
metal cutting theory, mechanical metallurgy, materials failure properties,
and cutting tool and machine tool design. He is also involved in teaching and
research of various manufacturing processes, machine design, and creativity
enhancement algorithms. Being active in both fundamental and industrial-
related research, he has published two books and more than 100 papers in
refereed journals and proceedings. Dr. Astakhov is the author of more than
40 patents. He has served as the organizer and contribution editor of the
"Predictable Modeling in Metal Cutting as Means of Bridging Gap Between
Theory and Practice" and "Machining Science and Technology" symposiums
held at the 1997 and 1999 International Mechanical Engineering Congress
and ExpOSition. He is serving as a board member and frequent reviewer for
several international scientific journals.
