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ISSN 1068-798X, Russian Engineering Research, 2018, Vol. 38, No. 2, pp. 130–134. © Allerton Press, Inc., 2018.
Original Russian Text © G.V. Shadskii, O.A. Erzin, S.V. Sal’nikov, 2017, published in STIN, 2017, No. 8, pp. 24–29.
Dynamic Aspects of Chip Formation
G. V. Shadskii*, O. A. Erzin**, and S. V. Sal’nikov***
Tula State University, Tula, Russia
*e-mail: chief.gennadiischadscky@yandex.ru
**e-mail: erzin79@mail.ru
***e-mail: sergeysalnikov@yandex.ru
Abstract—A multimass chain model of chip formation in the secondary deformation zone is proposed. The
influence of the frictional conditions and cutting conditions on the group motion of the chip elements over
the cutter’s front surface is shown. The dynamics of the motion of the chip’s free end has a significant influ-
ence on its fracture. In particular, the mass ratio of the last elements involved in the group motion (and posi-
tioned on the contact line at the cutter’s front surface) and the free end of the chip gives rise to considerable
dynamic splitting forces between the elements. The proposed approach offers broad scope for analysis of the
conditions of chip formation, including conditions with intensification of the cutting process by electrical
pulses.
Keywords: chip formation, cutting force, cutter, chain model, chip fracture
DOI: 10.3103/S1068798X1802017X
We know that the efficiency of cutting is largely
determined by processes in the secondary deformation
zone [1–6]. For a wide class of materials, segmented
chip is formed [7–12]. The segmentation coefficient
depends on the cutting conditions and the workpiece
characteristics. The elements of the chip have a dis-
tinct form. The deformation is greatest for the material
at the boundary of adjacent elements. This region dif-
fers in some respect from the main section of the seg-
ments, as indicated by high-speed video recordings
(Fig. 1) and oscillographic data for different cutting
conditions [3, 9, 12].
In extensive research, the main factor in the cutting
dynamics is assumed to be a stable periodic sequence
of disintegration of the material removed from the
workpiece. The dynamics of chip formation may be
considered as a three-stage sequence culminating in a
chip element [7, 8].
The first stage is characterized by limiting elastic
deformation of the chip element. The primary compo-
nent P
z
of the cutting force reaches a maximum during
elastic loading. The velocity of the chip relative to the
front cutting face is practically zero.
In the second stage, the chip element undergoes
shear and moves over the front cutting face. Its velocity
exceeds the cutting speed by an amount equal to the
rate of elastic unloading of the metal in the chip ele-
ment along the shear plane. The primary component
of the cutting force tends to a minimum.
The third stage consists of the elastoplastic forma-
tion of a chip element from the disintegrated material
corresponding to the second stage and the develop-
ment of the limiting deformed state corresponding to
the first stage.
During the formation of a chip element, the com-
ponents of the cutting force undergo cyclic variation.
Their direction of action remains constant. The stages
in which the components increase and decrease are
mutually opposed. The amplitude of the f luctuations
in the primary component may reach half of the max-
imum value.
Cyclic changes in the angle at which the cutting
force acts occur with constant front angle of the cutter.
That reflects the variability of the frictional conditions
in the formation of a chip element [7, 8]. Thus, the
amplitude and phase of the oscillation in the primary
component P
z
of the cutting force provide useful infor-
mation regarding chip formation.
Fig. 1. Chip microsections in turning KhN73MBTYu alloy
by means of a diamond–alloy Kiborit cutter at v = 5 m/s
[9] (a); and steel 45 by means of Т15K6 hard-alloy inserts
at v = 4.36 m/s [3] (b) and by means of TiAl6V4 alloy at
v = 90 m/s [12] (c).
LL
h
1
h
1
h
1
h
2
h
2
h
2
50 μm50
μm
50 μm
(a) (b) (c)
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