An experimental and analytical investigation of flow instability and shear localization in the orthogonal machining of grade 2 commercially pure titanium was made. A criterion for thermo-plastic instability was developed from torsion test results and applied to the analysis of the chip formation process. It was shown that flow instability followed by flow localization occurs when machining titanium at all cutting speeds and that a transition in the chip type from uniform to segmented does not occur. Orthogonal machining experiments were conducted in the speed range from 8.75 × 10−5 to 3.20 m/s for various depths of cut and the shear strain in the chip was calculated. It was shown that shear localization occurred in the chip formation process when the uniform shear strain involved in producing a chip segment reached a critical value and that this critical shear strain correlates fairly well with the instability shear strain predicted by the thermo-plastic instability criterion.

1.
Batra
R. C.
, and
Kim
C. H.
,
1992
, “
Analysis of Shear Banding in Twelve Materials
,”
Int. J. Plasticity
, Vol.
8
, p.
425
425
.
2.
Brown, C. J., and Hinds, B. K., 1985, “Force and Temperature Effects When Machining Titanium,” Manufac. Eng. Trans. SME, p. 238.
3.
Cook, N. H., 1953, “Chip Formation in Machining Titanium,” Proc. Symp. on Machining and Grinding Titanium, Watertown Arsenal, Watertown, MA, March 31.
4.
Duffy
J.
, and
Chi
Y. C.
,
1992
, “
On the Measurement of Local Strain and Temperature During the Formation of Adiabatic Shear Bands
,”
Materials Science and Engineering
, Vol.
A157
, p.
195
195
.
5.
Johnson, G. R., and Cook, W. H., 1983, “Dynamic Analysis of a Torsion Test Specimen Including Heat Conduction and Plastic Flow,” Proc. 7th Int. Sym. on Ballistics, The Hague, The Netherlands, p. 541.
6.
Komanduri
R.
, and
von-Turkovich
B. F.
,
1981
, “
New Observations on The Mechanism of Chip Formation When Machining Titanium Alloys
,”
Wear
, Vol.
69
, p.
179
179
.
7.
Komanduri
R.
,
1982
, “
Some Clarification on The Mechanism of Chip Formation When Machining Titanium Alloys
,”
Wear
, Vol.
76
, p.
15
15
.
8.
Lemaire
J. C.
, and
Backofen
W. A.
,
1972
, “
Adiabatic Instability in the Orthogonal Cutting of Steel
,”
Metallurgical Transactions
, Vol.
3
, p.
477
477
.
9.
Loewen
E. G.
, and
Shaw
M. C.
,
1954
, “
On the Analysis of Cutting Tool Temperature
,”
Transactions of the ASME
, Vol.
76
, p.
217
217
.
10.
Manyindo
B. M.
, and
Oxley
P. L. B.
,
1986
, “
Modeling of The Catastrophic Shear Type of Chip When Machining Stainless Steel
,”
Proc. Instn. Mech. Engrs.
, Vol.
200
, No.
C5
, p.
349
349
.
11.
McQuillan, A. D., and McQuillan, M. K., 1955, Titanium, Butterworths Pub. Ltd., London.
12.
Molinari
A.
, and
Clifton
R. J.
,
1987
, “
Analytical Characterization of Shear Localization in Thermoviscoplastic Materials
,”
ASME Journal of Applied Mechanics
, Vol.
54
, p.
806
806
.
13.
Recht
R. F.
,
1964
, “
Catastrophic Thermoplastic Shear
,”
ASME Journal of Applied Mechanics
, Vol.
31E
, p.
189
189
.
14.
Semiatin
S. L.
, and
Rao
S. B.
,
1983
, “
Shear Localization During Metal Cutting
,”
Materials Science and Engineering
, Vol.
61
, p.
185
185
.
15.
Semiatin, S. L., Lahoti, G. D., and Oh, S. I., 1982, “The Occurrence of Shear Bands in Metalworking,” Material Behavior Under High Stress and Ultrahigh Loading Rates, J. Mescall and V. Weiss, eds., p. 119.
16.
Shaw, M. C., Dirke, S. O., Smith, P. A., Cook, N. H., Loewen, E. G., and Yang, C. T., 1954, “Machining Titanium,” MIT Report.
17.
Shaw
M. C.
, and
Vyas
A.
,
1993
, “
Chip Formation in the Machining of Hardened Steel
,”
Annals of the CIRP
, Vol.
42/1
, p.
29
29
.
18.
Sheikh-Ahmad
J.
, and
Bailey
J.
,
1995
a, “
A Constitutive Model for Commercially Pure Titanium
,”
J. Mat. Eng. and Technology
, Vol.
117
, p.
139
139
.
19.
Sheikh-Ahmad
J.
, and
Bailey
J.
,
1995
b, “
Flow Instability in the Torsional Straining of Commercially Pure Titanium
,”
J. Mat. Eng. and Technology
, Vol.
117
, p.
255
255
.
20.
Turley
D. M.
,
Doyle
E. D.
, and
Ramalingam
S.
,
1982
, “
Calculation of Shear Strains in Chip Formation in Titanium
,”
Materials Science and Engineering
, Vol.
55
, p.
45
45
.
21.
von-Turkovich, B. F., and Durham, D. R., 1981, “Machining of Titanium and its Alloys,” Proc. of the Symp. on Advanced Processing Methods for Titanium, Met. Soc. AIME Conference, p. 257.
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