Advanced Materials Research
ISSN: 1662-8985, Vols. 189-193, pp 4087-4091
doi:10.4028/www.scientific.net/AMR.189-193.4087
© 2011 Trans Tech Publications, Switzerland
Online: 2011-02-21
Cutting mechanism and model for cutting Al/SiCp composites
Kuai Ji Cai1,a , Zhang Fei Hu2,b
1
School of Mechanical and Powel Engineering, Henan Polytechnic University, Jiaozuo, Henan,
454000, China;
2
College of Mechanical Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001,
China
a
b
[email protected], [email protected]
Keywords: Al/Sicp; Interrupted Cutting; Tool Wear; Nanostructured Materials; Cemented Carbide
Abstract. Al/SiCp composite material is rapidly advanced due to its applications to weapon, military,
aeronautics and astronautics. In some cases, fields of research are stagnating for its difficulty in
material processing. In this study, we are particularly concerned about the cutting mechanism of
Al/SiCp through modeling and simulations on wear rate of the tools. These simulations of tool wear
rate and cutting mechanism of Al/SiCp are proved by cutting tests on Al/SiCp with nanocemented
carbide tool WC-7Co and common cemented carbide tool YG8. A detailed investigation suggests that
the cutting instinct of Al/SiCp is of interrupted cutting process. And the grain loss, less tipping and
blade fracture during tool wear results from high frequency intermittent shock by SiC grain. The wear
behavior on the tool flank is mainly of grain loss. However, the wear behavior of the rake face is not
only of grain loss, but also abrasive wear of WC grain by SiC grain. It is conclusively demonstrated
that the model of tool wear rate is sufficient for revolution characterization of tool wear rate on grain
size, volume fraction of reinforcement, and also significantly important to prove the interrupted
cutting process mechanism of Al/SiCp.
Introduction
SiCp/Al composites are characterized by its excellent physical and mechanical properties such as high
strength, high stiffness, wear resistance, antifatigue, high fracture toughness, good heat stability and
low coefficient of linear expansion, so these materials have found extensive applications in aviation,
aerospace and other industries [1].
Because of the reinforcement of SiC particles, SiCp/Al composites are very difficult to process,
and related processing mechanism and processing models are presented as research frontiers. In 2005,
Kishawy, H. A. studied the wear mechanism of SiCp/Al composites and built a tool wear model. In
his study, it is believed that the tool wear mechanism is the two-body abrasive wear and three-body
abrasive wear behavior which is induced by the SiC particles in the matrix, and the effects of the
volume fraction of particles, the radius of the cutting edge and the cutting speed on the wearing of the
tool flank could be well predicted with the built model [2]; Dabade, Uday A. built a cutting-force
predicting model based on the two-body abrasive wear and three-body abrasive wear of tools [3];
Kannan, S. studied the effects of the size and volume fraction of SiC particles on the tool wear [4];
Dazhen, W built a tool-chip fraction model of SiCp/Al composites in cutting and verified the
correctness of the model through tests [5]; N. Muthukrishnan built a neural network model of SiCp/Al
in cutting and he well predicted the quality and specific energy of the cutting face and the tool wear
through that model [6]. The above cutting models well reflected the particle wear behavior caused by
the scoring on the tool flank by the SiC particles in the matrix. Some researchers pointed out that an
economic machining speed in cutting practice required cutting SiCp/Al composites in low speed
[7,8], but few reports have concerned the mechanism of low-speed cutting and the law of tool
wearing. Therefore, the study on the low-speed cutting mechanism of SiCp/Al composites and
corresponding tool wear models is of considerable practical significance.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
Tech Publications, www.ttp.net. (ID: 130.203.136.75, Pennsylvania State University, University Park, USA-06/03/16,05:48:40)
4088
Manufacturing Process Technology
In this paper, attempts are made to interpret the low-speed interrupted cutting mechanism of
SiCp/Al composites using the theory of fatigue fraction mechanics. Besides, a model for tool wear
calculation is built and simulation and tests on the model are conducted.
Model for calculating interrupted cutting of SiCp/Al and simulation
Model proposition. Suppose: SiC particles are distributed uniformly in the matrix. The particles are
spherical with identical sizes. The intensity of each action on the cutting edge is the same, and each
SiC particle may fall off or be broken or extruded in the matrix once being shocked. It is clear that
such circumstances are the best in respect to the cutting mechanism of SiCp/Al composites. However,
the cutting processing is very complicated, and factors that affect the tool wearing are not limited to
the impact of SiC particles but include built-up edge and the diffusion and oxidation of chemical
elements at high temperature, etc.
It is showed by tests that the impact-fatigue cycle life of common cemented carbide is about
105~107 [9]. After 105~107 times of impact, impacted grains fractured and fell off to form pits. Thus,
low-stiffness and less wear-resistant binder phases are revealed and scraped off by harder SiC
particles, so hard phases are revealed. With the above course repeated, the interrupted cutting is
formed, so the tool wore quickly. Based on the above discussions and laboratory observation, it is
presumed that a plurality of WC grains, which served as friction points, fell off and formed worn
particles after a cycle of interrupted cutting from the beginning of the cutting. In this case, it is
equivalent to that each WC grain that served as a friction point would peel off a △h –thick surface
layer under each impact of SiC particles. Suppose the mean grain size of WC is φ, then:
∆h =
φ
N
(1)
Whereφ is the mean grain size (mm) of WC, N is the cycle index (times) of the critical stress for
the peel-off of WC grains under given cutting conditions.
Since the binder phase is very thin and can be scraped off easily, its effect is presented in the form
of a coefficient. Therefore, with only the wear of hard phases under the limitation of cycling in fatigue
being taken into account and with the width VB of the wear land on the tool flank as the indicators, the
tool wear of SiCp/Al composites can be described as follows:
φ
（2）
dt
N
Where dVB is the width of the wear land on the tool flank (mm), dt is the cutting time (min) and
dt=dl/nf, where dl is the cutting length, n is the workpiece rotation speed (r/min), and f is the feeding
speed (mm/r), Cg is the cobalt-phase influence coefficient, Ca is the coefficient of area and Ca＝Ar/An,
where Ar is the actual area of contact and An is the nominal area of contact, ζ is the number of SiC
particles per unit area (number/mm2), D is the workpiece diameter (mm), aw is the cutting width (mm),
N is the cycle index of the critical stress when breakage occurs (times).
Thus, the wear rate of a tool can be expressed as:
dVB
φ
（3）
∝ Cg Ca nζπ Daw
dt
N
Under given cutting conditions, the parameters in formula (3) are all settled or can be calculated
according to the cutting conditions. When other cutting conditions are fixed, the wear rate of the tool
flank is proportional to the grain sizeφ of WC. According to the model, the wearing rate of a tool
made of nano-metric cemented carbide should be lower owing to its fine grains, large surface area,
high cohesive strength and good impact resistance.
According to formula (3), the wear rate increases with the increase of the SiC volume fraction of
the wild phase in composites; with the increase in the cutting speed and the cutting depth, the tool
wear rate increases. When the grain sizeφ of WC is given, the wear extent in general wearing stages
dVB ∝ C g Ca nζπ Daw
Advanced Materials Research Vols. 189-193
4089
exhibits a linear relationship with the cutting time t; when the grain sizeφ of WC increases, the slope
of the VB-t curve increases proportionally. A number of wear curves have validated the above rule
[9, 10]. According to (3), VB∝φt, or t∝VB/φ. Theoretically, the service life T of a tool is in inverse
proportion to the grain size φ of WC under the same wear standard. With dt=dl/nf being introduced
in (2), it could be seen that VB∝1/f, i.e., the wear extent of the tool decreases with the increase of the
feeding speed, which is a cutting regulation existing exclusively in cutting SiCp/Al composites.
R.D. Han also obtained similar laboratory results [11]. Therefore, this model well reflected the cutting
mechanism and cutting regulation of SiCp/Al composites theoretically from the new perspective of
interrupted cutting.
Calculation model simulation. The parameters in (2) are determined as shown in Table 1.
Tab.1 Parameters for compution model of tool wear
Cg
1.
1
Ca
0.
9
n
(r/min)
48,75,96
ζ
/mm
2
1711
D
/m
m
ap
/mm
φ/µm
N
/time
115
0.1-0.3
0.2-1
18538
Through the regression analysis on the laboratory data from SiCp/Al cutting, the cycle index N of
the critical stress of nano-metric cemented carbide is illustrated in Table 1. From the parameters in
Table 1, the following items could be calculated: the law of the tool wear rate in the model varying
with the grain size of the tool, the SiC volume fraction of the wild phase in composites as well as the
cutting speed and the cutting depth, which are shown in Fig. 3~Fig. 5.
Fig.3 Wear rate of tool change with grain size
Fig.4 Wear rate of tool change with volume fraction of SiC
4090
Manufacturing Process Technology
Fig.5 Wear rate change with cutting depth and speed
Figure 3 showed the variation of the tool wearing rate versus the grain size of the tool, from which
it could be seen that there are tool wearing rates increasing with the grain size at all cutting depths;
Fig. 4 showed the variation of the tool wearing rate versus the SiC volume fraction, and there is a law
that the tool wearing rate increased with the volume fraction when the SiC volume fraction varied
from 10% to 50%; Fig. 5 showed the variation of the tool wearing rate versus the cutting speed and the
cutting depth. The results of simulation suggested that the tool wearing rate increased in proportion to
the increase of the cutting speed and the cutting depth. The simulation results accorded with the
results of theoretical analysis.
Cutting test on paniculate-reinforced aluminum matrix composites
SiCp/Al6061 is employed for the cutting test in order to verify the theory and the results of simulation
analysis on the model for the tool wear rate.
Test equipment: CA6140 engine lathe; cutting tools: common cemented carbide YG8 with the
grain size of 1~5µm and nano-metric cemented carbide WC-7Co with the grain size of 0.2µm; cutting
material: SiCp/Al6061.
In SiCp/Al6061, the size of SiC particles is 20µm, the volume fraction is 30%, the workpiece
diameter is 115mm, and the width is 40mm. The material properties are shown in Table 2. The
orthogonal experimental method is adopted. A L9(34) orthogonal experimental table is employed. The
factors and level parameters are shown in Table 3.
Tab.2 Performance of Al/SiCp particulate reinforced
Density
(g/cm3)
2.9
Hardness
HB(MPa)
723
Tensile
strength (MPa)
362
Fracture toughness
(MPam1/2)
14.8
Elastic
modulus (GPa)
116
Tab.3 Orthogonal experimental factor
Level
A cutting speed
Vs(rpm)
48
75
96
1
2
3
factor
B cutting depth
ap(mm)
0.1
0.2
0.3
C feed rates
f(mm/r)
0.1
0.2
0.3
D null
Table 4 L9 (34) orthogonal experimental results
number
A
B
C
D
1
2
3
4
5
6
7
8
9
1
1
1
2
2
2
3
3
3
1
2
3
1
2
3
1
2
3
1
2
3
2
3
1
3
1
2
1
2
3
3
1
2
2
3
1
Tool wear
WC-7Co
0.45
0.35
0.2
0.25
0.15
0.4
0.1
0.5
0.25
YG8
0.6
0.45
0.3
0.35
0.25
0.45
0.2
0.55
0.35
Cutting time
t
6.25
3.125
2.083
2
1.33
4
1.041
3.125
2.082
Wear rate
WC-7Co
0.072
0.112
0.096
0.125
0.113
0.1
0.096
0.16
0.12
YG8
0.096
0.144
0.144
0.175
0.187
0.1125
0.192
0.176
0.168
The test results are shown in Table 4: the wearing values of the flanks at the noses of the tools made
of nano-metric cemented carbide and common cemented carbide are consistent with the variation
trend in the results of model analysis. According to Table 4, the grain size of the nano-metric
cemented carbide WC-7Co is 0.2µm which is much less than that of common cemented carbide YG8
(1-5µm). Therefore, a tool made of nano-metric cemented carbide WC-7Co had better wear resistance
Advanced Materials Research Vols. 189-193
4091
and a lower wear rate. The test results accords with the variation trends in the theoretical analysis and
simulation of model. It is suggested by tests that the model well reflects the actual law of tool wearing
under given laboratory conditions and could perform rather accurate analysis on the tool wear rate in
interrupted cutting.
Conclusions
In this study, the interrupted cutting mechanism of SiCp/Al composites with nano-metric cemented
carbide tool and corresponding model on tool wear are investigated. The following conclusions are
drawn: 1) The cutting mechanism in the low-speed cutting of SiCp/Al composites using tools made of
nano-metric cemented carbide is basically the interrupted cutting; 2) A model for calculating the tool
wear rate, which characterizes the interrupted cutting performance of SiCp/Al composites, is
presented. The results of calculation based on this model approaches test results and reflects the
cutting mechanism of SiCp/Al composites and tool wearing laws. Therefore, this model had
considerable theoretical significance and practical values.
References
[1] R.J. Arsenault, S. Fishman, M. Taya: Progress in Materials Science.Vol.38 (1994), p. 1
[2] H.A. Kishawy, S. Kannan, M. Balazinski: CIRP Annals - Manufacturing Technology. Vol.54
(2005), p.55
[3] U.A. Dabade, D. Dapkekar, S.S. Joshi: International Journal of Machine Tools and Manufacture.
Vol.49 (2009), p.690
[4] S. Kannan, H.A. Kishawy, I.M. Deiab et al.: Journal of Manufacturing Processes. Vol.8 (2006),
p.67
[5] Dazhen Wang, Huaming Liu, Rongdi Han et al.: Tribology. Vol.20 (2000), p. 85(In Chinese)
[6] N. Muthukrishnan, in: ASME International Mechanical Engineering Congress & Exposition,
American Society of Mechanical Engineers publishers(2009)
[7] Wenfeng Zhang, Xiaonan Pan: Journal of Materials Engineering. (1999), p. 14(In Chinese)
[8] N. muthukrishnan, J.P. Davim: Journal of Materials Processing Technology. Vol.209 (2009),
p.225
[9] Shigang Xiao: Cutting tool materials and it's reasonable selection (China Machine Press, Beijing
1990)( In Chinese)
[10] RiyaoChen: Metal-cutting principles (China Machine Press, Beijing 1998)( In Chinese)
[11] Rongdi Han, Hongquan Yao, Chunhua Yan et al: Acta Materiea compositae Sinica. Vol.14
(1997), p. 71(In Chinese)
Manufacturing Process Technology
10.4028/www.scientific.net/AMR.189-193
Cutting Mechanism and Model for Cutting Al/SiCp Composites
10.4028/www.scientific.net/AMR.189-193.4087
DOI References
[1] R.J. Arsenault, S. Fishman, M. Taya: Progress in Materials Science.Vol.38 (1994), p. 1
10.1016/1044-5803(94)90103-1
[3] U.A. Dabade, D. Dapkekar, S.S. Joshi: International Journal of Machine Tools and Manufacture. Vol.49
(2009), p.690
10.1016/j.ijmachtools.2009.03.003
[4] S. Kannan, H.A. Kishawy, I.M. Deiab et al.: Journal of Manufacturing Processes. Vol.8 (2006), p.67
10.1016/j.ijmachtools.2006.01.003
[7] Wenfeng Zhang, Xiaonan Pan: Journal of Materials Engineering. (1999), p. 14(In Chinese)
10.1007/BF03183562
[8] N. muthukrishnan, J.P. Davim: Journal of Materials Processing Technology. Vol.209 (2009), p.225
10.1016/j.ijrmhm.2008.10.018