AMERICAN JOURNAL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
© 2011, Science Huβ, http://www.scihub.org/AJSIR
ISSN: 2153-649X doi:10.5251/ajsir.2011.2.99.106
Effect of loads, sliding speeds and times on the wear rate
for different materials
Hani Aziz Ameen1, Khairia Salman Hassan2 and Ethar Mohamed Mhdi Mubarak3
1
2
3
Technical College – Baghdad - Iraq .
E-mail:haniazizameen@yahoo.com
Institute of Technology – Baghdad / Mechanical Dept.-Iraq.
E-mail:almaden20002000@yahoo.com
Institute of Technology – Baghdad / Mechanical Dept.-Iraq.
E-mail:etharmubark@yahoo.com
ABSTRACT
A study has been made on the wear rate for different materials (Steel, Aluminum and brass)
under the effect of sliding speed, time and different loads, where the apparatus pin on disc has
been used to study the specification of the adhesion wear. The experiments has been performed
on a group of specimens under different cases of times (5 to 30) minutes, and under different
loads (0.5 to 2) Kg, and different speeds (2.5 to 9) m/sec. A mathematical model has been made
for all cases that were studied depending on the method of least squares which helps in
foretelling about the wear rate through the knowledge of time limits as a variable with fixing the
other variables; also building a model with the same method by which foretelling the rate of
adhesive wear through knowing the sliding speed as a variable after fixing the other variables,
also making another model foretelling the rate of adhesive wear through knowing the variable
loads. A study was made for the damaged surface from wearing for the aluminum alloy as a
sample to illustrate the wear lines to the direction of the formation of wear; and from the results, it
was clear that the cracks which are vertical on the direction of sliding and will meet together with
the lines of weariness, and the results will show that the rate of adhesion wear will be direct
proportional with (time, sliding speed and load) , and the low carbon steel has less wear rate than
the other materials.
Keywords: Wear, Steel, Aluminum alloy 2017, Low carbon steel, Brass, Sliding speed
INTRODUCTION
The adhesive wear occurs when two surfaces are
moving relatively one over the other, and this relative
movement is in one direction or a successive
movement under the effect of the load so that the
pressure on the adjacent projections is big enough to
make a load plastic deformation and adhesion. This
adhesion will be at a high grade of efficiency and
capability in relative to the clean surfaces, and
adhesion will take place between a number of these
projections whose sizes will be bigger and the area
will be increased during movement (Eyre 1976,
Halling 1976). At the end there will be some relative
wear in the superficial tissues in the weak points of
the noticeable places as shown in Fig.(1) bellows :
Fig.1 The mechanism illustration of adhesion wear (Buckley,1981)
Am. J. Sci. Ind. Res., 2011, 2(1): 99-106
This adhesion wear is proportional directly to the load
applied and the sliding distance and indirectly with
the hardness of the metal. The adhesion wear is one
of the most prevailing wears, it forms 15% of the
industrial wear (Daries 1980 , Scott 1979) , which
happens when the surfaces are sliding one over the
other, so that the pressure between the adjacent
projections is enough to produce some local
formation adhesion and plastic (Eyre 1976). The
mechanism of the formation of the adhesion wear
could be explained as follows:
Every surface, however, smoothly appears, it will be
rough in the microscopic scale and contains a range
of tops and lows, and when two surfaces meet then
this contact takes place at these projections which
are little and relatively isolated; thus when applying a
load on these surfaces, then locally there will be a
high pressure and heat which will cause overtaking
the elastic limits of one surface or both surfaces and
the deformation of the projections in a plastic way, so
that, the real contacting areas are increased to a limit
to support the applied load. The contacting areas are
inclined to be damaged under the effect of the
relative movements between the two surfaces. The
weariness occurs usually at one surface, because of
the resistance of the in between surface to breaking
and weariness due to the reaction of strain hardness
during the adhesion of projections (Yust 1985,
Grainger 1994, Askwith 1980). The removed
substance (due to the shearing of projections) will
take the shape of small foils which is usually
transferred to the opposite surface or it is found
separately between the two surfaces. Fabijanic et al.
2005, studied the resistance of wear and corrosion
for the carbonic tool steel formed by hot forming
through the couple surface heat treatments followed
by heat treatments at low temperatures aiming not to
precipitate the carbides at the core and retaining a
structure similar to the original metal. Galvanetto et
al. 2006, studied the improvement of wear and
corrosion resistance of RPS Ti-TiN coating by mean
of thermal oxidation, and they found that the wear
and its rate will be less in the specimens which were
painted and oxidized and this will increase in the
metals already coated without its oxidization also with
the chemical corrosion. In the current research the
effect of loads, sliding speeds and times on the wear
rate for different materials are investigated.
Wear Theories
There are several theories which were found to
explain the phenomenon of adhesion wear, and from
that the simple adhesion wear theory. Archard
(Smart,1979) assumed that the contact occurs
between a number of projections of diameter (d) and
the contact area will be (
, thus this area will
bear a load of (
where (
) is the yield
stress of the material during the sliding where it will
pass through a sliding of length (2ro). Archard also
assumed that the fragments resulted will be of
hemispherical shape, and the volume will be (
)
. Thus the volume of the weariness (Q) for the whole
distance of sliding can be determined by the equation
:-
…………… (1)
Where no is the number of point of contact.
As at every point of contact, the projection is carrying
a load of (
will be
, then the total applied load
……………………..………..(2)
Also the amount of volume of the weariness will be
………………………….(3)
This equation is depending on the theory that all the
projections were contact by the load which will
produce fragments. It was proved that a percentage
of these contacts will result particles of weariness
(Sam Sonov, 1984) . Thus the equation becomes
…………………………………. (4)
Where is the possibility of producing these particles
at the projections contacts, this equation is known a
Archard Equation (Halling, 1979).
Rowe (Smart,1979) was able to modify the simple
adhesion wear theory to represent the surface films
after reconsideration Archart equation by adding
some new variations on it which is (
a
coefficient which represents the particulars of the
sliding metals upon each other and does not depent
on the particulars of the lubricant, also (B) is the
coefficient that represents the lubricant or the surface
films, and the equation which expresses the volume
(Q) of weariness becomes as follows
…………………………………(5)
And this equation expresses " Rowe Modified
Adhesion Theory" .
Wear Apparatus: The rate of wear will be relatively
small in most of the machinery and engineering tool,
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Am. J. Sci. Ind. Res., 2011, 2(1): 99-106
and mostly the value of the change in dimensions is
only few microns every year (Halling, 1976), and for
measuring wear they are using some apparatuses
and instruments which give results about the rate of
wear happening in the tools and machinery. From
these apparatus which is used in high pressure
contact tests where it is able to get very quick results
by applying loads on very small areas of contact and
to achieve this test there are some different
engineering arrangement as shown in Fig.(2), and for
each of these tests , the part (A) is the metal
subjected to wear, then the measurement of wear will
be known by one of the measurement methods. In
the current study the apparatus pin on disc has been
used to study the specification of the adhesion wear.
Fig.2 Three common methods to test wear (Halling, 1976)
Measurement Methods of wear: The widely known
methods in studying wear, depend on choosing the
sliding surfaces, and then measuring, before testing
the removal material, and after that, and any change
taking place, will be attributed to the resulted wear
(Rabinowicz,1965). There are several methods to
specify wear such as:
5- Methods for the measurement wear using radio
tracers techniques (measurement of non adherent
debris method)
In the current research the weighting method is used,
that is considered from the easiest methods followed
to fix and measure the wear. This method is
summarized in weighting the sample before the test
and after that, then the rate of wear will be calculated
from the lost weight.
Experimental
Metal Selection: Three different materials (Steel,
Aluminum and brass) are selected. The chemical
composition is get by ARL Spectrometer apparatus.
i- Steel with low carbon 1020 according to AISI was
chosen, the chemical composition shown in Table(1).
1-Weighting method
2- Mechanical gauging method
3- Optical method
4- Methods for the measurement wear using radio
tracers techniques (measurement of radioactive pickup method).
Table 1 Chemical composition of Low carbon steel 1020 (AISI)
Element%
V
Cu
Mo
Cr
Ni
Actual Value
0.002
0.022
0.054
0.024
0.004
Si
0.019
S
0.014
P
-
Mn
0.65
C
0.169
Standard
0.05
0.40.14Value
0.65
0.22
ii- Aluminum 2017 according to DIN 1725/1 was chosen. The chemical composition is given in table(2).
Table 2 Chemical composition of aluminum 2017
Element%
Si
Mg
Fe
Actual Value
0.1
0.301
0.675
Standard
0.2-0.8
0.4
Value
Cu
3.606
3.5-4.5
Zn
0.153
Pb
0.0756
-
iii- Brass according to DIN 17660 was chosen. The chemical composition is given in table(3).
101
Mn
0.215
0.4
Am. J. Sci. Ind. Res., 2011, 2(1): 99-106
Table 3 Chemical composition of brass
Element%
Actual Value
Fe
0.062
Zn
8.201
Pb
0.0474
0.02
Mn
0.045
0.1
Sn
0.039
Standard
Value
0.05
8.1
0.05
0.02
0.05
0.2
0.05
Fabrication of Specimens: Cylindrical specimens
for the adhesion wear tests were fabricated with
dimensions (10x20mm) according to ASTM
specifications for all metals used.
Al
Ni
1- Weighing the specimen before test by digital
sensitive balance, with accuracy 0.0001g of
type XB 220 A Precisa , as shown in Fig.(4).
Table 4 classification of the specimens
Classification of Specimens: After completing the
fabrication of specimens, these specimens were
classified and sorted into groups as shown in
table(4).
Adhesion Wear Tests
Adhesion wear test is done by the weighing
difference method on the specimens in table(4) on
the apparatus of wear test shown in Fig.(3).
And the wear rate is get according to the following
steps:
State of specimens
Fabricated specimens of Aluminum
Fabricated specimens of Brass
Fabricated specimens of Steel
Fig.3 Apparatus of adhesive wear test
102
Specimen
symbol
A
B
C
Am. J. Sci. Ind. Res., 2011, 2(1): 99-106
Fig.4Apparatus of the digital sensitive balance
2- Specify the variables which want to know its
effect on the wear rate like time and fixing
other variables (load , sliding speed).
3- Specify the hardness of the steel disc and it
was found, HRC=68 RC
4- Fixing the specimen by the bearer in vertical
position on disc.
5- Fitting the operation time.
6- Checking the cleanness of the disc before
the test start .
7- Operate the apparatus with select specified
times with fixing other variables.
8- Stopping the operation and weighing the
specimen.
9- Repeat the process with fixing time and
changing other variables.
where
is the sliding distance (cm) ,
and n= 940 rpm
RESULTS AND DISCUSSION
The tests on the adhesion wear has been done on
the groups of specimens given in table(4) as follows:
A- Variable time
Variable times 5 , 10 , 15, 20 and 30 minutes, with
fixed load 1 Kg and fixed distance 5 cm. Results are
shown in table (5).
B-Variable loads
Variables of loads (0.5 , 1 , 1.5 and 2 ) Kg with fixing
the time at 10 min. and the distance for 5 cm. Results
are shown in table (6).
C- Variable sliding speed
Variable sliding speed (2.5, 5, 7, 8 and 9) m/sec with
fixing the time 10 minutes and the load 1Kg. Results
are shown in table (7).
The wear rate is calculated from the following
equation:
……………………………………..(6)
Table 5 Wear rate for variable time
Time (min.)
5
10
15
20
30
Aluminum
1.1 E–7
4.5 E–7
4 E–7
3.6 E–7
Wear rate (g/cm)
Brass
1.5 E–8
2 E–8
8 E–8
Steel
0.029 E–6
0.035 E–6
0.043 E–6
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Table 6. Wear rate for variable loads
load (Kg)
Wear rate (g/cm)
Brass
0.5 E–8
1.5 E–8
5.4 E–8
Aluminum
0
0
6 E–7
1.1 E–6
0.5
1
1.5
2
2.5
Steel
0.023 E–6
0.025 E–6
0.0256 E–6
Table 7. Wear rate for variable sliding speed
Sliding speed (m/s)
Wear rate (g/cm)
Brass
Aluminum
Steel
2.5
0.09 E–6
5
1 E–7
2.5 E–8
0.068 E–6
7
9 E–7
1.1 E–7
0.05 E–6
8
0.046 E–6
9
0
1.5 E–7
Aluminum specimen was taken as a sample to study the topography of the surface, as shown in Fig.(5).
5 min.
10 min.
15 min.
20 min.
Time
0.5 Kg
1 Kg
1.5 Kg
2 Kg
Load
Fig.5 Topography of the aluminum specimen surface
It has been studied, the damaged surface due to the
adhesion wear for the various loads of aluminum
specimens and photos taken by the light microscope
which can show that the lines in the direction of
weariness is in the same direction with the fragment
left from weariness. Also it was found that the cracks
are vertical on the direction of sliding and their
meeting together with the lines of weariness cause
the separation and dislocation of slight layers from
the surface of the specimen, forming by that the
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Am. J. Sci. Ind. Res., 2011, 2(1): 99-106
damage of weariness as shown in Fig.(5) which
shows the distortion took place in the surface of the
specimen.
………………………………(14)
…………………………………..(15)
In the similar way the relationships of wear rate with
sliding speed and variables load are derived. Thus
the mathematical model of wear rate will be as
follows:
Variable Speed
Wr= 5.08*10–7 – 0.25 *10–7 V
for
Aluminum
Wr= –1.22*10–7 + 0.31 *10–7 V
for
Brass
Wr= 0.1176*10–6 – 0.01 *10–6 V
for
Steel
Variable Time
Wr= 1.55*10–7 + 0.14 *10–7 t
for
Aluminum
Wr= –2.667*10–8 +0.65 *10–8 t
for
Brass
Wr= 0.0217*10–6 – 0.0007 *10–6 t
for
Steel
Variable Load
Wr= 0.2575*10–6 + 0.134 *10–6 F
for
Aluminum
Wr= –2.433*10–8 + 4.9 *10–8 F
for
Brass
Wr= 0.022*10–6 + 0.0015 *10–6 F
for
Steel
Mathematical Model: After completion of the
adhesion wear tests and taking into consideration
that the sliding speed is variables which will be
effected with other variables like loads and time
which were fixed in finding the model which was
found after relying on the method of the simplest
linear deviation to show the relation between the
basic variables to test wear. The model included the
following steps:1- Writing the general formula for extracting the
rate of wear from the Eq.(6).
2- The Ordinary Least Square (OLS) method is
applied in estimating the Eq.(6) through
minimizing the total value of the total error
squares and the error is the difference
between the actual value and the estimated
value according to the steps, where it was
built a model the simplest linear deviation
representing the relation between the
dependent variable (wear rate) Wr and the
independent variable (time) t.
whereas :
……………………… (7)
following is summarize of OLS steps which basically
depend on minimizing the total errors.
……………………….(8)
where V, t, and F are the sliding speed , time and
load respectively.
……………..(9)
CONCLUSIONS
In this research it was intended to study the rate of
adhesion wear for different metals under the
influence of different cases (time, loads and sliding
speed); also to make a mathematical model which
can tell the rate of adhesion wear through the
knowledge of the time period, sliding speed and
loads , these models are for experiments and
applications.
Then derive Eq.(9) with respect to
…………..(10)
……… (11)
After that the derived equation is equalized to zero,
the estimated values
follows:
It was concluded that the cracks which are vertical on
the direction of sliding and will meet together with the
lines of weariness, and the results will show that the
rate of adhesion wear will be direct proportional with
(time, sliding speed and load) , and the low carbon
steel has less wear rate than the other materials.
are determined as
………………….(12)
………………………………(13)
where
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Am. J. Sci. Ind. Res., 2011, 2(1): 99-106
Askwith T.C. " Surface Journal " , Vol.11, P.2, 1980.
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