Wear-fatigue test methods and their significance
The unified methods of wear-fatigue tests of models of active systems, which are based on a combination of the known mechanical fatigue, friction and wear test methods, are offered. A bending fatigue test method for a uniform cylindrical specimen with a test portion diameter of 10 mm is adopted as a...
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Bahdanovich, A.V. Tyurin, S.A. Andriyashin, V.A. Elavyi, A.M. 2013-08-20T03:37:50Z 2013-08-20T03:37:50Z 2009 Wear-fatigue test methods and their significance / A.V. Bahdanovich, S.A. Tyurin, V.A. Andriyashin, A.M. Elavyi // Проблемы прочности. — 2009. — № 1. — С. 121-128. — Бібліогр.: 5 назв. — англ. 0556-171X https://nasplib.isofts.kiev.ua/handle/123456789/48467 539.4 The unified methods of wear-fatigue tests of models of active systems, which are based on a combination of the known mechanical fatigue, friction and wear test methods, are offered. A bending fatigue test method for a uniform cylindrical specimen with a test portion diameter of 10 mm is adopted as a basic one. Предложены единые методики износоусталостных испытаний моделей активных систем, основанные на известных методах испытания материалов на механическую усталость, трение и износ. В качестве базовой предложена методика испытания на циклический изгиб гладкого цилиндрического образца с рабочей частью диаметром 10 мм. en Інститут проблем міцності ім. Г.С. Писаренко НАН України Проблемы прочности Научно-технический раздел Wear-fatigue test methods and their significance Методики износоусталостных испытаний и их значимость Article published earlier |
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Wear-fatigue test methods and their significance |
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Wear-fatigue test methods and their significance Bahdanovich, A.V. Tyurin, S.A. Andriyashin, V.A. Elavyi, A.M. Научно-технический раздел |
| title_short |
Wear-fatigue test methods and their significance |
| title_full |
Wear-fatigue test methods and their significance |
| title_fullStr |
Wear-fatigue test methods and their significance |
| title_full_unstemmed |
Wear-fatigue test methods and their significance |
| title_sort |
wear-fatigue test methods and their significance |
| author |
Bahdanovich, A.V. Tyurin, S.A. Andriyashin, V.A. Elavyi, A.M. |
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Bahdanovich, A.V. Tyurin, S.A. Andriyashin, V.A. Elavyi, A.M. |
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Научно-технический раздел |
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2009 |
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English |
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Проблемы прочности |
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Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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Article |
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Методики износоусталостных испытаний и их значимость |
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The unified methods of wear-fatigue tests of models of active systems, which are based on a combination of the known mechanical fatigue, friction and wear test methods, are offered. A bending fatigue test method for a uniform cylindrical specimen with a test portion diameter of 10 mm is adopted as a basic one.
Предложены единые методики износоусталостных испытаний моделей активных систем, основанные на известных методах испытания материалов на механическую усталость, трение и износ. В качестве базовой предложена методика испытания на циклический изгиб гладкого цилиндрического образца с рабочей частью диаметром 10 мм.
|
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0556-171X |
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https://nasplib.isofts.kiev.ua/handle/123456789/48467 |
| citation_txt |
Wear-fatigue test methods and their significance / A.V. Bahdanovich, S.A. Tyurin, V.A. Andriyashin, A.M. Elavyi // Проблемы прочности. — 2009. — № 1. — С. 121-128. — Бібліогр.: 5 назв. — англ. |
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UDC 539.4
Wear-Fatigue Test Methods and Their Significance
A. V. B ahdanovich ,a S. A. T y u rin ,b V. A. A n d riy ash in ,b and A. M . E lavyib
a Yanka Kupala State University of Grodno, Grodno, Belarus
b The Joint Institute of Mechanical Engineering, National Academy of Sciences of
Belarus, Minsk, Belarus
The unified methods o f wear-fatigue tests o f models o f active systems, which are based on a
combination o f the known mechanical fatigue, friction and wear test methods, are offered. A
bending fatigue test method fo r a uniform cylindrical specimen with a test portion diameter o f 10 mm
is adopted as a basic one.
K e y w o r d s : fatigue, friction, wear-fatigue tests, specimen, counterspecimen.
In tro d u c tio n . Special wear-fatigue test methods have been elaborated for
experimental assessment o f mutual and jo in t influence o f friction and fatigue
processes on the working capacity o f materials and models o f active systems
under complex loading conditions [1-5].
Under laboratory conditions the wear-fatigue damage resistance is usually
studied by testing small models o f active systems. The tests are perform ed on
special wear-fatigue test machines o f a SI series [5-6].
One o f the ways o f developing complex wear-fatigue test methods is to
combine the known m echanical fatigue test methods with the friction and wear
test methods. Figure 1 illustrates, as an example, the principle o f such combination
whereby a basic fatigue test m ethod incorporates bending w ith rotation. Note that
rotary m otion is m ost typical o f m odern machines; therefore, the methods as
shown in Fig. 1 are o f practical importance.
A similar approach enables the m achines intended for wear-fatigue tests to
be used for conventional tests or m echanical fatigue tests or for friction and wear
testing under preset conditions.
The Basic Test Schem es. A test object for m echanical fatigue tests is a
structural element, for example, a cylindrical one o f a given geom etry (Fig. 2c). If
the tests are perform ed in the sliding or rolling friction modes, the test object is a
friction pair (Fig. 2b, c) consisting o f specimen 1 and counterspecimen 2; they are
also called the body and the counterbody. N ote that here the specimen is always
referred to as the cylindrical structural element and the counterspecimen (counter
body) as the bushing or the roller. Finally, in wear-fatigue tests the test objects are
the models o f active systems o f two elements - 1 and 2 (Fig. 2a, d).
It should be mentioned that all the methods o f wear-fatigue testing (Fig. 2)
im plemented on SI series machines are based on using a uniform smooth
cylindrical specimen with a test portion diameter d = 2 r = 10 mm. It is identical
to a standard fatigue test specimen. This provides both the consistency o f tests as
well as comparability o f test results.
L et’s address the m echano-sliding fatigue test scheme (Fig. 2e). The
cylindrical specimen 1 is fixed in a spindle 2 and rotates with angular speed « 1.
© A. V. BAHDANOVICH, S. A. TYURIN, V. A. ANDRIYASHIN, A. M. ELAVYI, 2009
ISSN 0556-171X. Проблемы прочности, 2009, № 1 121
A. V. Bahdanovich, S. A. Tyurin, V. A. Andriyashin, and A. M. Elavyi
Friction and wear
tests methods
Fig. 1. Development of wear-fatigue test methods: MRF - mechano-rolling fatigue, MSF -
mechano-sliding fatigue, FF - fretting fatigue.
A vertical bending load Q (upwards or downwards) is applied to its free end.
Also, a nonrotating counterspecimen 3, for example, a plate or a partial bushing,
is in contact w ith the specimen test portion zone o f diam eter d = 10 m m under a
contact load F N . Thus, the m aximum contact and bending stresses arise
sim ultaneously in the specimen test portion zone.
Im plementation o f the test scheme as shown in Fig. 2e makes it possible to
perform the following tests:
- wear-fatigue tests for m echano-sliding fatigue (Fig. 2e) w ith variables F N ,
Q , and w 1;
- m echanical fatigue tests in bending w ith rotation (Fig. 2c) w ith variables
Q and w 1. In this case, the counterspecimen 3 is removed, so F N = 0;
- sliding friction and w ear tests (Fig. 2c) with variables F n and m. In this
case, no bending loading is applied (Q = 0), and specimen 1 is made shorter for
the sake o f m aterial saving.
In m echanical fatigue tests (Fig. 2c) the bending load Q can be constant
(invariable in time t), but the operating norm al stresses at every point o f the
working section o f specimen 1 change during a symmetric cycle (Fig. 3) with
period T due to rotation o f the specimen.
I f the greatest bending m om ent in the specimen working section is M = Q l,
where l is the distance from the w eakest section to a load action line Q; the
highest norm al stresses in the same section are given by
a = M / W , (1)
where W is the m om ent o f resistance.
In sliding friction tests (Fig. 2d), the contact load F n can be static, i.e.,
constant, but the operating contact stresses are cyclic too. Therefore, these tests
are essentially the sliding fatigue tests (under asymmetric tension-compression
conditions).
M echanical fatigue
tests methods
122 ISSN 0556-171X. npoôneMbi npoHHoemu, 2009, № 1
Wear-Fatigue Test Methods and Their Significance
Fig. 2. Typical wear-fatigue test methods: 1, 1a, 1b - specimens; 2 - test apparatus spindle; 3, 4 -
counterspecimena; Q is bending load, FN is contact load, and and w2 are rotational speeds of
a specimen and counterspecimen, respectively.
The conditions whereby sliding fatigue is realized can be described integrally
by either contact loading F N or an average (nominal) contact pressure (2), or a
specific sliding friction force called also the frictional stresses (3):
P a = F N / A a > (2)
r Ws = f sP a = F s / A a = f s F N / A a , (3)
where A a is the nominal area o f contact, F s is the sliding friction force, and f s
is the coefficient o f sliding friction.
ISSN 0556-171X. npoôëeMbi nponnocmu, 2009, № 1 123
A. V. Bahdanovich, S. A. Tyurin, V. A. Andriyashin, and A. M. Elavyi
Let us consider the m echano-rolling fatigue test scheme (Fig. 2a). It differs
from the mechano-sliding fatigue test scheme (Fig. 2e) in that the fixed bushing is
replaced w ith a rotating roller 3. Thus, the specimen and the roller can rotate
generally w ith different angular speeds W j and m 2 and in different directions.
Realization o f the test scheme as shown Fig. 2a enables one to carry out the
following tests:
- wear-fatigue tests for m echano-rolling fatigue (Fig. 2a) w ith variables F N ,
Q , W j, and m2 ;
- m echanical fatigue tests in bending w ith rotation (Fig. 2c) w ith variables
Q and m j . In this case, roller 3 is removed, so F N = 0 and m2 = 0;
- tests in rolling friction or sliding-and-rolling friction (Fig. 2b) with
variables F N , m 1, and m2. In this case, no bending load is applied (Q = 0), and
specimen 1 is made shorter for the purpose o f m aterial saving.
The conditions whereby rolling friction is realized (see Fig. 2b) can be
described by either a contact load F n , or the highest pressure in the center o f a
contact area (4) which is defined by the Hertz formula (for a case o f elastic
deformation), or a specific rolling friction force (5) called also the frictional stress
'Wr
p 0 n p F N / A p ,
= f r P 0 = F r l A a = f r F N / A a
(4)
(5)
where A p is the area o f contact (A p = a for a circular contact area o f radius a,
A p = lb for a band-shaped contact zone m easuring l X b , and A p = a b for an
elliptic contact area o f dimensions a X b), n p is the factor (n p = 0.478 for
circular and elliptic contact areas and n p = 0.637 for a band-shaped contact
zone), F r is the rolling friction force, and f r is the coefficient o f rolling
friction.
Fig. 3 Fig. 4
Fig. 3. A symmetrical stress cycle in mechanical fatigue tests.
Fig. 4. Cycle of stresses in rolling fatigue tests.
In rolling friction tests (see Fig. 2b) the contact load F n , as in sliding
friction, can be static, i.e., constant in time, but the operating contact pressure (for
example, p 0 = a zmax) is cyclic (Fig. 4). Thus, the rolling friction tests by the
scheme in Fig. 2, are essentially the rolling fatigue tests o f m aterial surface layer.
124 ISSN 0556-171X. npoôëeMbi npounocmu, 2009, N9 1
Wear-Fatigue Test Methods and Their Significance
The fretting fatigue test scheme is shown in Fig. 5a. In this case, two
counterspecimens 3 called the fretting bridges are pressed w ith a contact load F N
to a test portion o f the rotating cylindrical specimen 1 subjected to a bending load
Q. It can be given circumferential (with a speed v j) or axial (with a speed v 2)
oscillatory m ovem ent o f small amplitude or to raise both simultaneously to the
last.
a
b
c
Fig. 5. Test schemes for fretting fatigue (a), mechanical fatigue (b), and fretting (c).
Implementation o f the test scheme as shown in Fig. 5 permits the following
types o f tests:
- wear-fatigue tests for fretting fatigue (see Fig. 5a) w ith variables F n , Q,
w, v and v 2;
- m echanical bending fatigue tests with rotation (see Fig. 5b) with variables
Q and w. In this case, no fretting bridges are used, so F N = 0, v 2 = v 2 = 0;
- fretting tests with axial and/or circumferential sliding (see Fig. 5c) with
variables F N , v and v 2 . In this case, no bending load is applied (Q = 0), and
specimen 1 is m ade shorter for the purpose o f m aterial saving.
The conditions o f force interaction between the specimen and the counter
specimen in fretting fatigue can be represented by cyclic stresses (1), frictional
stresses (3) or nominal contact pressure,
q = f n / a o , (6)
where A 0 is the initial (nominal) area o f contact.
ISSN 0556-171X. Проблемы прочности, 2009, № 1 125
A. V. Bahdanovich, S. A. Tyurin, V. A. Andriyashin, and A. M. Elavyi
T he Basic C harac te ris tic s o f R esistance to W ear-Fatigue D am ages. The
basic characteristics o f resistance to wear-fatigue damages are determined by
wear-fatigue testing o f appropriate objects.
The basic quantitative characteristics o f fracture strength are assessed by test
results and by plotting a corresponding fatigue curve.
By w ay o f example, Fig. 6 shows four experimental fatigue curves: a
m echanical fatigue curve N ( a a ) plotted by test results for a specimen o f 0.45%
carbon steel (normalized); a rolling fatigue curve N ( p 0 ) constructed by the
rolling friction tests results for the pair o f 0.45 carbon steel specimen/25KhGT
steel roller (after improvement), and two m echano-rolling fatigue curves plotted
by wear-fatigue test results for the active system o f 0.45% carbon steel/25KhGT
steel.
Steel 45 specimen.
Curve of mechanical fatigue N (oa )
Steel 45/steel 25KhGT friction pair.
Curve of rolling fatigue N (p0)
Mechano-rolling fatigue curves
Direct effect N (aa , p0 = const) Inverse effect N (p0, a a = const)
Fig. 6. For determination of basic characteristics of wear-fatigue damages (the point number
indicates the sequence of tests).
In the m echanical fatigue tests, disintegration o f a specimen serves as a limit
state criterion. In rolling fatigue tests, a critical density o f pittings on a specim en’s
test surface is taken as a limit state criterion. The limit states based on damage
126 ISSN 0556-171X. npoôneMu npounocmu, 2009, № 1
Wear-Fatigue Test Methods and Their Significance
and fracture criteria for m echanical and rolling fatigue tests take place in tests for
mechano-rolling fatigue.
In all o f the four cases, the fatigue limits ( o _ 1, p j , o _ 1p , p f o ), parameters
o f slope o f the left-hand branch o f fatigue curves (mo , M p , m op , Mpa ), and the
abscissas o f critical points o f fatigue curves ( N Ga, N Gp , N Gop , N Gp a ) are
determined. Note that the fatigue limits at m echanical ( o _ 1) and rolling fatigue
( p f ) are unequivocal and unique characteristics o f the test objects, while those in
mechano-rolling fatigue tests ( o _ p , p f o ) are not. Similar fatigue curves to be
plotted can be as m any as the num ber o f preset values o f parameters p 0 = const
or o a = const in wear-fatigue tests when the mechanisms o f direct and back
effects are studied.
The influence o f friction and w ear processes on the variation o f mechanical
fatigue resistance characteristics can be represented by the direct effect
K D = ° _ 1 p / ° _ 1 . (7)
In this case, the K d index is a characteristic o f strength. For the conditions
for which the results are given in Fig. 6 we have K d = 256/165 = 1.62.
The influence o f m echanical fatigue processes on the variation of
characteristics o f a friction and w ear process can be represented by the back effect
index
K b = p fo I p f ■ (8)
In this case, the K b index is a tribological characteristic. For the conditions
for w hich the test results are presented in Fig. 6 we have K b = 2200/1760 = 1.25.
Table 1 provides notations and summarizes num erical values o f all the
parameters determined by fatigue curves as shown in Fig. 6. A study o f these
experimental data enables us to make the following conclusions:
(i) the lim it stresses in m echano-rolling fatigue are essentially higher than
those in m echanical and rolling fatigue ( K d > 1, K b > 1);
(ii) the fatigue curve exponent increases in passing from the mechanical
fatigue curve to the corresponding m echano-rolling fatigue curve (m 0p > > m o )
and from the rolling fatigue curve to the corresponding m echano-rolling fatigue
curve (m po > > mp ).
T a b l e 1
System of Notation and Numerical Values of Basic Characteristics
Characteristics Mechanical
fatigue curves
Rolling
fatigue curves
Mechano-rolling fatigue curves
N (a a ) N (?0) N (aa , p0 = const) N (p0, oa = const)
Fatigue limit, MPa 56w_1a p f = 1760 a_1 p = 256 pfo = 2200
Abscissas of critical
points of fatigue curves,
cycles
N g q = 9-106 Nap = 2.6 • 107 N gqp = 5 • 106 Napo = 2 • 107
Fatigue curve exponent ma w 7.5 mp = 14.5 map w 11.6 mpo = 24-6
ISSN 0556-171X. Проблемы прочности, 2009, № 1 127
A. V. Bahdanovich, S. A. Tyurin, V. A. Andriyashin, and A. M. Elavyi
Differently, under the given experim ental conditions the wear-fatigue
resistance to damage has turned out to be higher than the m echanical or rolling
fatigue resistance.
C o n c l u s i o n s
1. Unified methods for complex wear-fatigue testing o f models o f active
systems have been developed, which can be im plemented using m odern machines
o f a SI series and ensure assessment o f fracture strength under preset conditions.
2. N ew characteristics o f resistance to wear-fatigue damages, w hich are
determined from mechano-sliding, m echano-rolling fatigue, and fretting fatigue
tests, are proposed.
1. L. A. Sosnovskii, “The m ethod o f wear fatigue tests o f power systems and
their m odels,” In t. J . F r ic t . W ear , 14, No. 5, 937-952 (1993).
2. K. V. Frolov and N. A. M akhutov, “N ew test machines and m ethods,”
Z a v o d . L a b ., No. 5, 32-33 (1995).
3. M. S. Vysotskii, N. A M akhutov, V. N. Koreshkov, et al., “On development
o f standard methods for wear-fatigue tests,” I b id , 35-38 (1995).
4. N. A. Mahutov, A. V. Bogdanovich, P. V. Andronov, et al., “M ethods of
wear-fatigue tests and their realisation on the SI m achines,” Ib id , No. 6,
17-42 (1995).
5. “SI series machines for wear-fatigue tests,” in: L. A. Sosnovskii and M. S.
Vysotskii (Eds.), T r ib o -F a tig u e -9 5 : A n n u a l [in Russian], Tribo-Fatigue Ltd.,
Gomel (1996).
Received 11. 06. 2008
128 ISSN 0556-171X. Проблемы прочности, 2009, № 1
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