1
Study on Fracture Mechanism of Rock Cutting
2
Xin Wei, Chengyong Wang and Hui Yuan
3
4
Faculty of Mechanical & Electronic Engineering,
Guangdong University of Technology, Guangzhou 510090 P. R. China
5
Keywords: Rock, Granite, Diabase, Cutting mechanism
6
7
8
9
10
11
12
Abstract. This paper presents a review of the authors’ investigation in the cutting processes of
diabase and granite. The formation of crushed zone and the propagation of microcracks and cracks
under different cutting conditions have been observed in detail by means of a workshop microscope
and a polarization microscope. The fracture mechanism is analyzed by measuring the cutting strain
field using laser speckle interferometry and comparing the fractography of the cutting chips with
those of the samples of tensile test and shear test. The cutting mechanism models of diabase and
granite are proposed respectively.
13
Introduction
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Rock cutting has been widely used in the fields of machining natural slabs, basic components of
precise instruments, etc. Rock cutting processes have been studied since 1950’. Several physical
models of rock cutting mechanism have been proposed based on experimental study and finite
element analysis. It is well known that the process of rock fracture under indentation generally
includes the following stages: building up of the stress field, formation of an inelastic deformation
zone or a crushed zone, chipping and crater deformation of surface, and formation of subsurface
cracks [1, 2, 3]. But there are some differences between the research results relating to the
formation of crushed zone and the formation and propagation of cracks and chipping. Based on coal
cutting process, Evans (1958) supposed that the chipping crack is formed by the action of tensile
stress [4]. Gray (1982) considered that the chipping trajectory takes a logarithmic contour and the
initial cracks are formed by shear stress [5]. Hood (2000) indicated that the cutting tool (either a
drag bit or an indenter) induces tensile cracks in the rock and these cracks propagate to form
fragments or rock chips, and the wedging action of sharp drag bits produces tensile stress in the
rock in a fairly direct manner [6]. On the other hand, some researchers think the chipping crack is a
mixed tensile and shear mode crack [3].
Regarding to the formation of crushed zone, Lindqvist (1983) concluded from the indentation
experiments that the crushed zone in marble is formed with inelastic deformation by the shear
action and that in granite or sandstone is characterized by brittle fracture [7]. Zeuch (1985)
indicated that fractures are nucleated in the rock in advance of the cutter tip and all of the large
chips had an apparently crushed, powdered region at the trailing edge of the fragment which might
represent the region of intense triaxial compression [8]. Some researchers consider that the crushed
zone, under the load of an indenter, forms before the formation of the cone crack and its formation
results from the accumulation of crushed rock between the tool and the loaded rock; others suppose
that the formation of cone cracks precedes the formation of the zone of the crushed rock [3].
Kesteren (1993) hypothesized that the size of the crushed zone is determined by bifurcation of a
shear crack into a tensile crack under mixed mode loading conditions, which was verified by using
numerical tools [9]. The crushed zone is an energy intensive zone and transfers the cutting load. So,
its size determines the cutting forces and geometry of the chip.
The formation of cracks or chipping and crushed zone depends on the properties of rocks. Some
physical mechanisms applied to plastic or porous rocks can’t be used to describe the cutting process
of brittle hard rocks. Here we review a number of our investigations in the cutting processes of
diabase and granite. The objective is to propose the mechanisms of cracks formation and
propagation and the characters of the crushed zone based on experimental observation and
47
48
49
50
51
52
53
theoretical considerations. The cutting processes of diabase and granite under different cutting
conditions were observed by a workshop microscope, and the cutting experiments of granite were
carried out and observed under a polarization microscope as well to obtain detailed information on
the formation and development of microcracks. The stress fields of the rocks in cutting processes
were measured by laser speckle interferometry method. The fracture mechanism under the cutting
action was also analyzed by comparing the topographies of the chips with the rock fractographies of
tensile test and shear test samples.
54
Experiment
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
The experiments were conducted to observe and analyze the cutting processes of diabase and
granite under different cutting conditions, respectively.
The diabase with shore hardness of 79, compress strength of 0.25 GPa and doleritic texture was
cut by carbide K20 cutting tools with rake angle of –10°, 0° and 10°, and clearance angle of 6°. The
cutting processes were observed with a microscope from the side view of the workpieces. The
cutting parameters used in cutting the diabase included: the depth of cut 0.08mm, 0.2mm, 0.4mm,
0.8mm, 1.2mm; cut width 7.5mm, manual feed.
The cutting processes of granite were conducted in the following two ways. The macro cutting
processes on a planner by carbide tools were observed with a workshop microscope. The depth of
cut of 0.08mm, 0.4mm and 0.8mm, and cutting width of 0.6mm were used. The cutting tools have a
rake angle of -10°, 10° and clearance angle of 6°.
The cutting processes of granite were also observed with a polarization microscope on a
micro-feed cutting device by PDC cutters to assess the micro-process in cutting granite, especially
the effects of mineral properties on granite cutting mechanism. The cutting parameters include: rake
angle -10°, -5° and 5°; a clearance angle 8°; and the depth of cut 0.05mm ~0.1mm, manual feed.
Five kinds of granite with different mineral composition and grain size were studied. The granites
consist mainly of the minerals of feldspar, quartz, plagioclase and metabiolite.
72
Results and Discussion
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
Cutting Processes of Diabase.
Features of the Cutting Process of Diabase. The typical cutting process of diabase includes the
following three stages. (1) When the cutting tool contacts the diabase, powder chips form and some
small lateral cracks occur, leading to the crater in the contact zone around the tool tip, as shown in
Fig.1 (a). The powder chips flow away from the contact zone with some small chippings as the
cutting tool being fed. (2) The diabase in the contact zone near the tool tip becomes compact under
the press of the cutting tool. Simultaneously, the rock in the zone is crushed and accumulated (see
Fig.1 (b)). (3) The size of the crushed zone increases and transfers the cutting force from the cutting
tool. The dominating crack, initiating from the contact zone above the tool tip, propagates along the
upper boundary of the crushed zone and then towards the free surface of the workpiece, which leads
to chipping, as shown in Fig.1 (c) and Fig.1 (d). The actual depth of cut in this case is larger than
the mean depth of cut. The crushed zone has the shape of a wedge.
The features of the cutting process described above are more apparently when cutting at larger
depth of cut or negative rake angle [10, 11, 13].
Crushed Zone in Diabase Cutting Process. It can be concluded, based on the experimental
observation of the diabase cutting process, that the crushed zone forms after the lateral crack
initiating at the contact point with the tool tip intersect with the crack initiated above the tool tip. It
forms and grows repeatedly. The crushed zone transfers the cutting loads acting as a cutting tool
when it becomes large. The real rake angle, therefore, is about 70° for the cutting tool with rake
angle of –10° and 50° ∼ 60° for the other cutting tools. The depth of cut has no effects on the real
angle [10, 11, 13].
Powder chips
Powder chips
Cutting
tool
Cutting
tool
Powder chips
Cutting
tool
ap
Main crack
Crushed zone
Lateral crack
94
95
(a)
Chip
(b)
(a) The formation of powder chips and lateral crack
(b) The formation of crushed zone
(c) The propagation of main crack and chipping
(d) Photography of the cutting process of diabase
(γ0= -10°, α0=8°, ap=8mm)
Main crack
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
(c)
Crushed zone
Cutting
tool
96
97
98
99
100
101
102
103
apover
50µm
(d)
Fig.1 The cutting process of diabase (ap: depth of cut; apover: depth of over cut)
Fig.2 shows SEM observation of the material in the crushed zone. It can be seen that the crushed
zone consists of slice, granular minerals with average diameter < 4.8　m. There are no obvious
boundary cracks in the crushed rock, which means that the crushed rock is compacted.
5 µm
50 µm
50 µm
(a) Topography of crushed zone (b) Fractography of tensile test (c) Fractography of shear test
Fig.2 SEM observation of crushed zone and samples of diabase
The topography of the crushed zone (Fig. 2(a)) shows similar features to the fractography of the
tensile test sample of diabase (Fig.2(b)). This means that the rock in the crushed zone is cracked and
crushed mainly by the action of tensile stress. The crushed rock is compacted under the press action
of the cutting tool due to the existence of mineral defects such as porosity, cleavage plane, etc. in
the diabase. The crushed rock doesn’t adhere to the rake face of the cutting tool.
The size of the crushed zone is affected by the depth of cut and rake angle of the cutting tool.
With the increase of the depth of cut, the contact length between the crushed zone and the rake face
increases. And the real rake angle decreases with the increase of the rake angle.
The Formation and Propagation of Cracks in Diabase Cutting Processes. (1)Mechanism of
the Formation and Propagation of Cracks. The typical formation and propagation of the cracks
in cutting diabase can be described as follows (See Fig.1) [10,13].
The dominating crack generates above the tool tip. Continuous feed of the cutting tool causes it
to propagate along the upper boundary of the crushed zone to the point lower than the depth of cut
resulting in over cut. Then the crack propagates again towards the free surface, which causes the
formation of chipping and crater on the surface of the workpiece. The crack trajectory takes
generally on an arc contour. Some new microcracks may occur and develop at the direction parallel
to the surface. These cracks may stop propagating or change their direction if they meet some initial
defects in the rock.
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
The cutting strain fields of the diabase were measured by means of laser speckle interferometry
to understand the reasons causing the fracture of the rock in cutting processes [10,12].
As shown in Fig.3, a high tensile strain concentration zone and high shear strain concentration
occur above the cutting tool tip respectively. It can be concluded that the initial crack is caused
mainly by the tensile stress because the maximum normal strain is larger than the maximum shear
strain and the tensile strength of the rock is much less than the shear strength. It conforms to some
researchers’ results of theoretical analysis about indentation processes theory of brittle materials that
high compressive strain zone occurs near the cutting tool tip.
In spite of some errors on the measurements of the rock displacement and on the calculation of
the strain field, the maximum gradient direction of normal strain conforms to the crack trajectory. It
is proved by the measured results of strain field that the cracks form mainly by the action of tensile
stress and propagate along the maximal gradient direction of the normal strain. The reasons causing
the fracture of the rock in cutting diabase can be further verified by comparing the topographies of
cutting chips with the fractographies of the tensile and shear test samples.
33
Tool
29 23
20
Fx
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
19
Fy
16
15
13
-7
28 15
5
8
10
12
6
9 14 18
36
40
-9.6
12
-5
-3
-8.6
-5.6
-7.6
-6
-6
36
9
34
23
25
20
15
30
12
20
20
16
12
16
10
11
17
13
7
24
15
23
23
13
17
19
(a)
(b)
(c)
(d)
Fig.3 Cutting strain field of diabase (+: tensile strain; -: compressive strain)
(a) Main strain field ε1(Fx=740N, Fy=252N)
(b) Main strain field ε1(Fx=1.04kN, Fy=390N )
(c) Main strain field ε2(Fx=1.04kN, Fy=390N) (d)Max. shear strain field ε1(Fx=1.04kN, Fy=390N )
The main mineral of the diabase is pyroxene with cleavage plane {110}. The aggregate shows
half-idiomorphic and xenomorcleaphic granular. Other minerals of the diabase include column or
granular epidote with cleavage plane {110} and scale-like chlorite aggregate with cleavage plane
{001}. As shown in Fig.2 (b), the tensile test sample is observed mainly with cleavage fracture and
grain breakage. The cracks form often along the mineral crystalline cleavage. Because of defects,
the fracture develops not only along one but several parallel cleavage planes in different height,
which causes the fractography to show river pattern and step pattern. The grain breakage pattern
observed may occur along the crystalline boundary or/and within a grain. The cracks propagating
along the crystalline boundary may cause the whole grains to be dislodged. If the strength of
crystalline grain is less than that of the crystalline boundary, the grain will is broken locally.
The shear test samples are shown mainly the topographies with flat pattern and striation pattern,
as shown in Fig.2 (c).
Fig.4 shows the typical cutting chips of the diabase, which are divided into three segments. The
first segment, the formation and initial propagation of the crack, and the third segment, the final
propagating stage toward the free surface, reveal the same characters with the fractographies of the
tensile test samples. On the other hand, in the second segment, the chip was found with the features
not only of tensile fractography but also of shear fractography. It means that the crack forms and
then propagates by tensile stress, in its following process, the mixed action of tensile and shear
stress causes the crack to develop [10,13]. It is the tensile crack propagation again to cause the
chipping of the crack finally. This conclusion conforms to that by the cutting strain field in Fig.3.
(2) The Factors Affecting the Formation and Propagation of Cracks in Diabase Cutting
Process. The formation and propagation of cracks in the cutting process of diabase are influenced
by the cutting condition and workpiece property. When increasing the depth of cut ap, the depth the
crack propagates down into the interior of the workpiece increases, resulting in an increase in the
depth of over cut apover. apover is almost proportional to ap in the case where the rake angle is
-10°.When ap is small, apover under positive rake angle is larger than that under negative or 0° rake
angle. On the contrary, apover under positive rake angle are smaller than that under negative or 0°
172
173
174
175
176
rake angle when ap is large. The formation and development of cracks are affected by the defects in
the diabase as well.
50µm
50µm
(a)
50µm
50µm
(b)
(c)
Cutting direction
I
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
II
(a) Topography of segment I
(b) Topography of segment II
(c) Topography of segment III
(d) outline of cutting chip
III
(d)
Fig.4
Fracture features of diabase chip
Cutting Processes of Granite.
The Characteristics of Granite Cutting Processes. Fig.5 and Fig.6 show the cutting processes of
granites observed by means of a microscope and a polarization microscope, respectively.
When the cutting tool tip contacts and presses the rock, the rock is crushed and compacted at
once within a small area in front of the tool tip, as shown in Fig.5and Fig.6 (a). Some of fine
powder chips may be dislodged and erupt from the contact area at the same time. As the process
advances, the crushed zone becomes large, and one or two cracks and lots of microcracks form,
which initiate from the boundary of the crushed zone (See Fig. 6(b)). Continuous application of the
cutting force causes the cracks and microcracks to propagate. One of the cracks develops toward the
free surface, resulting in chipping and a crater on the surface of the workpiece, as shown in Fig.6(c).
The other cracks and mincrocracks stop developing. The similar process has been found for all the
granites under different cutting conditions [10, 11,13-17].
Fig.5 Cutting granite observed with workshop microscope
(Fine grain granite, γo= 10°, αo=8°)
Regarding to the cutting processes of fine grain granite, the chip pattern changes usually from
powder chip to granular and fracture chip as the depth of cut increases. The effects of cutting speed
on the cutting process can be neglected. The cutting processes of coarse grain granite are more
remarkably affected by the mineral properties. The fracture chips are formed easier in cutting coarse
grain granite than fine grain granites.
0.2mm
0.2mm
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
0.2mm
(a)
(b)
(c)
Fig.6 The cutting process of granite observed with polarization microscope
( Fine grain granite, ap=0.1mm, γo= -5°, αo=6°, cutting direction“ ←”)
The Properties of the Crushed Zone. The crushed zone is formed by the press of the cutting
tool rake face and tip. Its shape and size are determined greatly by the properties of mineral material
being cut such as grain size, composition, the direction of cleavage plane and boundary, etc. The
crushed zone causes granular chips generally. The crystalline grain can be seen in a SEM
topography, as shown in Fig.7. Many thinner pieces, parted and micro-cavities are found as well in
the crushed zone. The crushed zone is formed under the action of the tensile stress. There are some
differences between the crushed zones formed in cutting diabase and granite. It has no regular shape
and size because the granites are very brittle and hard.
Once the crushed zone forms, it transfers the cutting force by means of the force balance
obtained by the friction and insertion between the granular chips. When the elastic energy that is
accumulated in this zone excesses some limits, the balance is broken. This leads to the cracks to
propagate in an instable situation and to the formation of chipping.
0.5mm
Fig.7
Topography of crushed zone in granite
The Formation and Propagation of Cracks and Microcracks. In the cutting processes of
granite, one or two cracks form under the action of tensile stress after the formation of the crushed
zone and lots of microcracks may form somewhere around the crushed zone at the same time.
The cracks and microcracks are very straight with very thin tip. This means that the cracks and
microcracks are formed by the cutting stress. The cracks and microcracks propagate stably with the
progress of cutting, as shown in Fig.6. The main crack that is perpendicular to the largest tensile
stress propagates faster than others. The propagation of cracks and microcracks shows the feature of
a tensile crack.
When large depth of cut is used, the formation and propagation of the crack are dominated by the
cutting stress [10, 16, 17]. Lots of initial defects existing in the rock cause the concentration of
stress and change the stress distribution locally. With a decrease in the depth of cut or a increase in
grain size of the granite, the effects of mineral properties such as composition, grain boundary,
cleavage plane, initiate cracks, etc. on the propagation of cracks and microcracks increase. The
propagating processes of the cracks are dominated by the mineral properties when the depth of cut
is smaller than 0.08mm, as shown in Fig. 8 [16, 17].
Effects of Mineral Properties on the Propagation of Microcracks. The cutting processes
under the condition of small depth of cut ( ≤ 0.1mm) are discussed here to get detailed information
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
on the micro cutting process of granite. In this case, the cutting process progresses within a single
mineral grain normally. The propagation of microcracks and cracks is dominated greatly by the
properties of the mineral grain being cut.
Fig.8 shows the propagating process of cracks and microcracks when a feldspar grain is being
cut. The crushed zone is uneven, or stepped. The microcracks are formed after the formation of the
crushed zone with the grain. The cracks and micrcocracks usually develop along the crystal lattices
of the feldspar grain in two right directions, as shown in Fig.8(c). The crater on the cut surface and
the residual microcracks take the contour of a right triangle.
The cracks and microcracks in a feldspar grain grow easier than those in a plagioclase grain
especially in a microline grain.Fig.9 shows the shape of the crushed zone and the propagation of
microcracks and cracks as a quartz grain being cut. The quartz grain is very hard and has no
cleavage plane. The microcracks and cracks induced by the press of the cutting tool, therefore,
propagate in the path of shell, resulting in a shell-like crater and residual microcracks in the rock, as
shown in Fig.9 (b). Most of quartz grains reveal granular cracks. Besides these cracks and
microcracks, the intergranular crack is often formed along the boundary of the quartz grain when
the depth of cut is large. If a quartz grain locates in front of the mineral grain being cut, an
intergranular crack is usually formed on the boundary. The quartz grain is even dislodged when it is
small or the cutting force is large.
0.2mm
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
0.2mm
0.2mm
(a)
(b)
(c )
Fig.8 The propagation of crack5 in a feldspar grain
( Middle size granite, ap=0.07mm, γo= -5°, αo=6°, cutting direction“ ←”)
0.2mm
0.2mm
(a)
(b)
Fig.9 The propagation of crack in a quartz grain
( Middle size granite, ap=0.08mm, γo= -5°, αo=6°, cutting direction“ ←”)
When the cleavage plane of a metabiolite grain is almost perpendicular to the cutting direction,
the grain will be compacted after distorting, which leads to a formation of crushed zone and cracks
in two directions, that is, the direction parallel to and perpendicular to the cleavage plane, as shown
in Fig. 10(a). The cracks and microcracks propagate along cleavage plane and its perpendicular
plane alternatively, resulting in uneven fracture chips and cracks, as shown in Fig.10 (b). The crack
in the metabiolite grain being cut propagates quickly along its cleavage plane if its cleavage plane is
about 45° or small, causing the fracture chip to curl over. The metabiolite is much softer than other
mineral grains in granite. If a metabiolite grain is adjacent to a quartz or feldspar grain being cut,
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
the crack right to the metabiolite cleavage plane will propagate cross metabiolite grain while some
cleavage microcracks occur. This pattern of crack development is caused by the instability due to
kinking in the metabiolite grain [15, 6].
If the cutting process of granite is assisted by low-pressure water jet, the action of wedging,
washing will change the fracture mechanism noticeably [18-20]. When water is jetted into the
cutting zone, it flushes away the rock fractured by the action of the cutting tool, causing the crushed
zone difficult to form. Further more, the granite strength decreases because of the pressure wedge
into the cutting zone, which leads to microcracks generating and developing easily.
0.2mm
0.2mm
(a)
(b)
Fig.10 The propagation of crack in a metabiolite grain
( Fine size granite, ap=0.1mm, γo= -5°, αo=6°, cutting direction“ ←”)
Models of Rock Cutting Mechanism. The diabase cutting process is different with that of
granite due to their different material properties and mineral structure. The crushed zone and
fracture chip in diabase cutting have more regular shape than those in granite cutting process. The
cutting process of diabase can be described by means of the model in Fig.11 (a). The crushed zone
with wedge shape, acting as cutting tool, transfers the cutting force and causes fracture chips.
The crushed zone and fracture chip in diabase cutting have more regular shape than those in granite
cutting process. The cutting process of diabase can be described by means of the model in Fig.11 (a).
The crushed zone with wedge shape, acting as cutting tool, transfers the cutting force and causes
fracture chips
Intergranular
crack
Chipping
Cleavage
crack
Fracture
chips
Cutting
tool
Cutting
tool
Main crack
Main crack Crushed zone
Crushed zone
Granite
299
300
301
302
303
304
305
306
307
308
The cutting process of granites includes the following stages (shown in Fig. 11(b)) (1) The
crushed zone forms under formed by the press of the cutting tool; (2) The cracks and microcracks
form and develop by the action of tensile stress. The cracks reach the free surface, leading to
formation of fracture chip, granular chip and powder chip. (3) The formation and propagation of
cracks and microcracks are affected greatly by the depth of cut, the material properties, such as
grain size, mineral composition, cleavage plane, and grain boundary, etc.
309
Conclusions
310
(1) The diabase cutting process is different with that of granite due to their different material
（a）Diabase
Fig.11
(b) Granite
Models of rock cutting mechanism
311
312
313
314
315
316
317
318
319
320
properties and mineral structure.
(2) The crushed zone, cracks and chipping form under the action of tensile stress both in the cutting
processes of diabase and granite. The main crack in diabase may develop under the mixed
action of tensile stress and stress.
(3) The crushed zone and fracture chip when cutting diabase have more regular shape than those
when cutting granite.
(4) The mineral properties have more remarkably influences on the propagation of microcracks and
cracks in granite than in diabase.
(5) The crushed zone is difficult to form but microcracks easily form and propagate in the case the
cutting process is assisted by water jet.
321
References
322
[1] P.A. Linqvrist: Ph.D. thesis, University of Lulea, (1982)
323
[2] Jr L.L Mishnaevsky: Int.J.Rock Mech.Min.Sci Vol. 30 (1993), p. 663
324
[3] Jr L.L Mishnaevsky: Int.J.Rock Mech.Min.Sci Vol. 32(8) (1995), p. 763
325
326
[4] I.Evans: Theoretical aspects of coal plouging Material property of Non-Metallic material
(London Science Publisher, UK 1958).
327
[5] K.E. Gray: Journal of Petroleum Technology Vol. 1(1962), p. 95
328
[6] M. Hood: Int.J.Rock Mech.Min.Sci Vol. 37(2000), p. 297
329
[7] P.A Lindqrist: ibid Vol. 16 (1983), p. 199
330
[8] D.H. Zeuch: SPE14219,(1985)
331
332
333
[9] Kesteren W.G.M. Van: Proceedings of the International Union of Theoretical and Applied
Mechanics(IUTAM) Sysmposium on Fracture of Brittle, Disordered Materials: Concrete, Rock
and Ceramics (The University of Queensland, Australia 1993)
334
335
[10] C.Y. Wang: The study of rock cutting (Ph.D. Dissertation Dalian University of Technology,
China 1989) (in Chinese)
336
337
[11] C.Y. Wang, et al: Chinese Journal of Rock mechanics and Engineering Vol. 9 (1990), p. 209 (in
Chinese)
338
[12] C.Y. Wang, et al: Int. J. Rock Mech. Min. Sci&Geomech Vol. 1 (1990), p. 65
339
340
[13] P.D. Liu, et al: New developments in mechanics of cutting (Press of Dalian University of
Technology, China 1991) (in Chinese)
341
342
[14] C.Y. Wang, et al: Chinese Journal of Rock Mechanics and Engineering Vol. 10 (1991), p. 185
(in Chinese)
343
344
[15] X. Wei, et al: Proceedings of International Conference of Manufacturing Technology, 1993,
p.27
345
[16] X. Wei, et al: Chinese Journal of Rock Mechanics and Engineering 1(1996), p. 71 (in Chinese)
346
[17] X. Wei, et al: Stone Vol. 7(1998), p. 5 (in Chinese)
347
[18] C.Y. Wang, et al: Chinese Journal of Mechanical Engineering Vol. 32 (1996), p.84 (in Chinese)
348
[19] H. Yuan, et al: China Mechanical Engineering Vol. 7 (1996), p. 69 (in Chinese)
349
[20] C.Y. Wang, et al: ICPCG-96 , JSPE (1996), p. 75