ASTM E2789-10
(Guide)Standard Guide for Fretting Fatigue Testing
Standard Guide for Fretting Fatigue Testing
SIGNIFICANCE AND USE
Fretting fatigue tests are used to determine the effects of several fretting parameters on the fatigue lives of metallic materials. Some of these parameters include differing materials, relative displacement amplitudes, normal force at the fretting contact, alternating tangential force, the contact geometry, surface integrity parameters such as finish, and the environment. Comparative tests are used to determine the effectiveness of palliatives on the fatigue life of specimens with well-controlled boundary conditions so that the mechanics of the fretting fatigue test can be modeled. Generally, it is useful to compare the fretting fatigue response to plain fatigue to obtain knockdown or reduction factors from fretting fatigue. The results may be used as a guide in selecting material combinations, design stress levels, lubricants, and coatings to alleviate or eliminate fretting fatigue concerns in new or existing designs. However, due to the synergisms of fatigue, wear, and corrosion on the fretting fatigue parameters, extreme care should be exercised in the judgment to determine if the test conditions meet the design or system conditions.
For data to be comparable, reproducible, and correlated amongst laboratories and relevant to mimic fretting in an application, all parameters critical to the fretting fatigue life of the material in question will need to be replicated. Because alterations in environment, metallurgical properties, fretting loading (controlled forces and displacements), compliance of the test system, etc. can affect the response, no general guidelines exist to quantitatively ascertain what the effect will be on the specimen fretting fatigue life if a single parameter is varied. To assure test results can be correlated and reproduced, all material variables, testing information, physical procedures, and analytical procedures should be reported in a manner that is consistent with good current test practices.
Because of the wear phenomenon involved i...
SCOPE
1.1 This guide defines terminology and covers general requirements for conducting fretting fatigue tests and reporting the results. It describes the general types of fretting fatigue tests and provides some suggestions on developing and conducting fretting fatigue test programs.
1.2 Fretting fatigue tests are designed to determine the effects of mechanical and environmental parameters on the fretting fatigue behavior of metallic materials. This guide is not intended to establish preference of one apparatus or specimen design over others, but will establish guidelines for adherence in the design, calibration, and use of fretting fatigue apparatus and recommend the means to collect, record, and reporting of the data.
1.3 The number of cycles to form a fretting fatigue crack is dependent on both the material of the fatigue specimen and fretting pad, the geometry of contact between the two, and the method by which the loading and displacement are imposed. Similar to wear behavior of materials, it is important to consider fretting fatigue as a system response, instead of a material response. Because of this dependency on the configuration of the system, quantifiable comparisons of various material combinations should be based on tests using similar fretting fatigue configurations and material couples.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: E2789 − 10
StandardGuide for
Fretting Fatigue Testing
This standard is issued under the fixed designation E2789; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E466 Practice for Conducting Force Controlled Constant
Amplitude Axial Fatigue Tests of Metallic Materials
1.1 This guide defines terminology and covers general
E467 Practice for Verification of Constant Amplitude Dy-
requirements for conducting fretting fatigue tests and reporting
namic Forces in an Axial Fatigue Testing System
the results. It describes the general types of fretting fatigue
E468 Practice for Presentation of Constant Amplitude Fa-
tests and provides some suggestions on developing and con-
tigue Test Results for Metallic Materials
ducting fretting fatigue test programs.
E1012 Practice for Verification of Testing Frame and Speci-
1.2 Fretting fatigue tests are designed to determine the
men Alignment Under Tensile and Compressive Axial
effects of mechanical and environmental parameters on the
Force Application
frettingfatiguebehaviorofmetallicmaterials.Thisguideisnot
E1823 TerminologyRelatingtoFatigueandFractureTesting
intended to establish preference of one apparatus or specimen
E1942 Guide for Evaluating DataAcquisition Systems Used
design over others, but will establish guidelines for adherence
in Cyclic Fatigue and Fracture Mechanics Testing
in the design, calibration, and use of fretting fatigue apparatus
G15 Terminology Relating to Corrosion and CorrosionTest-
and recommend the means to collect, record, and reporting of
ing (Withdrawn 2010)
the data.
G40 Terminology Relating to Wear and Erosion
G190 GuideforDevelopingandSelectingWearTests(With-
1.3 The number of cycles to form a fretting fatigue crack is
dependent on both the material of the fatigue specimen and drawn 2015)
fretting pad, the geometry of contact between the two, and the
3. Terminology
method by which the loading and displacement are imposed.
Similar to wear behavior of materials, it is important to
3.1 Definitions and symbols used in this guide are in
consider fretting fatigue as a system response, instead of a
accordance with Terminology E1823. Relevant definitions
material response. Because of this dependency on the configu-
from Terminology G15 or G40 are provided in 3.2.Additional
ration of the system, quantifiable comparisons of various
definitions specific to this guide are provided in 3.3.
material combinations should be based on tests using similar
3.2 Definitions:
fretting fatigue configurations and material couples.
3.2.1 Terms from Terminologies G15 and G40.
1.4 This standard does not purport to address all of the
3.2.2 coeffıcient of friction (COF)—The dimensionless ratio
safety concerns, if any, associated with its use. It is the
of the tangential force, Q, between two bodies to the normal
responsibility of the user of this standard to establish appro-
force,P,pressingthesebodiestogetherwhenthetwobodiesare
priate safety and health practices and determine the applica-
slipping with respect to each other, µ=Q/P.
bility of regulatory limitations prior to use.
3.2.2.1 Discussion—Under partial slip conditions, the ratio
of the tangential force to the normal force is less than the COF.
2. Referenced Documents
In addition, when COF is defined as the ratio of Q to P, the
2.1 ASTM Standards:
measured COF is an average along the interface. In reality, the
E3 Guide for Preparation of Metallographic Specimens
COF can vary along the interface. Hence, a local definition is
E4 Practices for Force Verification of Testing Machines
often used, given by µ(x,y)=q(x,y)/p(x,y) where q(x,y) is the
shear traction distribution along the interface and p(x,y) is the
normal pressure distribution. The COF is often greater in the
This guide is under the jurisdiction of ASTM Committee E08 on Fatigue and
slip regions of a partial slip interface compared to the stick
Fracture and is the direct responsibility of Subcommittee E08.05 on Cyclic
Deformation and Fatigue Crack Formation. regions due to the disruptions in the surface caused by fretting.
Current edition approved Nov. 1, 2010. Published January 2011. DOI: 10.1520/
G40
E2789.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
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E2789 − 10
3.2.3 fretting—Small amplitude oscillatory motion, usually level (maximum stress or stress amplitude for a given mean
tangential, between two solid surfaces in contact. stressorstressratio)forfailureatacertainnumberofcyclesor
3.2.3.1 Discussion—The term fretting refers only to the the stress level at which a percentage of the population would
nature of the motion without reference to the wear, corrosion, survive a certain number of cycles.
fatigue, or other damage that may occur. It is discouraged to
3.3.5 fretting fatigue limit—The limiting value of the
use the term fretting to denote fretting corrosion or other forms
median fatigue strength when fretting is present as the fatigue
of fretting wear due to the ambiguity that may arise. As the
life becomes very large.
amplitude of fretting increases, the condition eventually be-
3.3.5.1 Discussion—The fretting fatigue limit strongly de-
comes reciprocating sliding and the interaction should no
pends on the fretting conditions.
longer be referred to as fretting.
3.3.6 fretting fatigue reduction factor—The reduction in
3.2.4 fretting corrosion—The deterioration at the interface
fatigue strength due to the presence of fretting, defined as the
between contacting surfaces as the result of corrosion and
ratio of the fretting fatigue limit and fatigue limit.
slight oscillatory slip between the two surfaces. G15
3.3.6.1 Discussion—This reduction factor may also be
basedonthefrettingfatiguestrengthdefinedeitherasthestress
3.2.5 fretting wear—Wear that occurs as the result of
level (maximum stress or stress amplitude for a given mean
fretting action. G40
stressorstressratio)forfailureatacertainnumberofcyclesor
3.3 Definitions of Terms Specific to This Standard:
the stress level at which a percentage of the population would
3.3.1 displacement amplitude—The peak-to-peak relative
survive a certain number of cycles.
displacement divided by two or total cycle displacement
3.3.7 fretting fatigue damage threshold—The combination
divided by four.
of fretting fatigue loading conditions and number of fretting
3.3.1.1 Discussion—The displacement amplitude is typi-
cycles that can be sustained before degradation of fatigue life
cally based on a remote reference location. Note that the
is observed.
definition of displacement amplitude in the context of fretting
3.3.7.1 Discussion—The fretting fatigue loading conditions
wear and tribosystems testing sometimes refers to the full
may include combinations of the normal force, the displace-
peak-to-peak relative displacement, rather than the definition
ment amplitude, the tangential force amplitude, and the bulk
given here, which is consistent with the use of the term
fatigue loading. The concept of a fretting fatigue damage
amplitude in Terminology E1823. Hence, whenever the term
threshold is related to the development of an initial crack
displacement amplitude is used, it should be clearly defined or
characterizedwithamaximumandrangeinstressintensitythat
a reference made to this guide.
exceeds the threshold value for crack growth. Generally, after
3.3.2 fretting damage—The pits, scarring, disruptions and
the fretting fatigue damage threshold has been reached, remov-
material transfer on the surface due to fretting.
ing the source of fretting, while maintaining the fatigue
3.3.2.1 Discussion—Cracks may be associated with the
loading, in configurations where they can be separated, has
fretting damage, though in many cases they may not be present
minimal effect on the remaining life.
or be sufficiently small, such that the fatigue life is not
3.3.8 gross slip—The condition for which all points in
significantly degraded. Hence, the disturbed appearance and
contact experience relative slip over a complete cycle, as
level of roughness of the fretting damage cannot be reliably
illustrated in Fig. 1.
used to determine whether the fatigue life is reduced. In some
cases the directionality of roughness, also called the surface 3.3.9 normal force—Force normal to the contact interface.
texture, can be determined via profilometry methods. This
3.3.9.1 Discussion—Due to the accumulation of debris
texture may be correlated to the directionality of fretting and in within the contact or wear in the slip regions, this force may
some cases the characteristics of the texture can provide a
not remain constant but change during the test.
useful screening metric for fretting damage.
3.3.10 normal pressure—Resultant of the normal force di-
3.3.3 fretting fatigue—The process of crack formation at a
vided by the contact area.
fretting damage site, progressive crack growth, possibly cul- 3.3.10.1 Discussion—Tobeconsideredanaverageonly.The
minating in complete fracture, occurring in a material sub-
true distribution of pressure within the contact area depends on
jected to concomitantly fretting and fluctuating stresses and the exact profile and roughness of the contacting surfaces.
strains.
Analyticalorcomputationalmethodsmaybeusedtodetermine
3.3.3.1 Discussion—Fretting fatigue is generally character- this pressure; for example, see Ref. (1) . Wear will cause the
ized by a sharp decrease in the fatigue life at the same stress
profiles of the contacting bodies to change during the test. If
levelofastandardspecimen,attributedtotheshortenedtimeto wear occurs, the size of the non-conforming contacts (for
formacrackandtheaccelerationofthecrackgrowthunderthe
example, flat on cylindrical, cylindrical on cylindrical, sphere
coupling of the fretting and bulk cyclic stresses and strains. on flat, and so on) will typically increase.
3.3.4 fretting fatigue knockdown factor—The reduction in
3.3.11 partial slip—The condition for which only a portion
fatigue strength due to the presence of fretting, defined as the oftheinterfaceofthecontactingbodiesexperiencerelativeslip
difference in the fatigue limit and fretting fatigue limit divided over a complete cycle, as illustrated in Fig. 1.
by the fatigue limit.
3.3.4.1 Discussion—This knockdown factor may also be
The boldface numbers in parentheses refer to a list of references at the end of
basedonthefrettingfatiguestrengthdefinedeitherasthestress this standard.
E2789 − 10
FIG. 1 Illustration of the Meanings of Slip and Reciprocating Sliding
3.3.12 plain fatigue—Often used to describe fatigue without existing designs. However, due to the synergisms of fatigue,
presence of fretting. wear, and corrosion on the fretting fatigue parameters, extreme
care should be exercised in the judgment to determine if the
3.3.13 reciprocating sliding—The condition when the con-
test conditions meet the design or system conditions.
tact area at the two extremes of the cycle do not overlap, as
illustrated in Fig. 1.
4.2 For data to be comparable, reproducible, and correlated
3.3.13.1 Discussion—Under fretting conditions, at least a
amongst laboratories and relevant to mimic fretting in an
portion of the contact areas always overlap at the extremes of
application, all parameters critical to the fretting fatigue life of
the cycle.
the material in question will need to be replicated. Because
alterations in environment, metallurgical properties, fretting
3.3.14 relative slip—The amount of tangential displacement
loading (controlled forces and displacements), compliance of
between a point on the interface of one body and a point on the
the test system, etc. can affect the response, no general
surface of the second body.
guidelines exist to quantitatively ascertain what the effect will
3.3.14.1 Discussion—The point on one of the bodies serves
be on the specimen fretting fatigue life if a single parameter is
as a reference, which is often defined as the location when the
varied. To assure test results can be correlated and reproduced,
two bodies first come into contact under application of the
all material variables, testing information, physical procedures,
normal pressure at the interface. The relative slip may be
and analytical procedures should be reported in a manner that
defined as a local or remote reference. Fundamentally, a local
is consistent with good current test practices.
measureisdesired,however,experimentallyaremotedisplace-
ment is measured and in many times controlled.
4.3 Because of the wear phenomenon involved in fretting,
idealized contact conditions from which the fretting contact
3.3.15 slip—Local movement of surfaces in contact.
area and pressure may be calculated exist only at the onset of
3.3.16 tangential force—Force acting parallel to the contact
the test. Although it is still possible to calculate an average
interface.
fretting pressure using the initial contact area, the pressure
within the contact area may vary considerably.
4. Significance and Use
4.1 Fretting fatigue tests are used to determine the effects of 4.4 Results of the fretting fatigue tests may be suitable for
application to design when the test conditions adequately
several fretting parameters on the fatigue lives of metallic
materials. Some of these parameters include differing mimic the design service conditions.
materials,relativedisplacementamplitudes,normalforceatthe
5. Background
fretting contact, alternating tangential force, the contact
geometry, surface integrity parameters such as finish, and the 5.1 Interfacial Conditions:
environment. Comparative tests are used to determine the When designing a test program to mimic the design service
effectivenessofpalliativesonthefatiguelifeofspecimenswith conditions, one must first identify whether the interface con-
well-controlled boundary conditions so that the mechanics of ditions are partial slip or gross slip. This will help determine
the fretting fatigue test can be modeled. Generally, it is useful whichtypeoffrettingfatiguetestmaybemorerelevant.InFig.
to compare the fretting fatigue response to plain fatigue to 2, a running condition fretting map is shown (2). Two primary
obtain knockd
...
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