ASTM C1361-10(2015)
(Practice)Standard Practice for Constant-Amplitude, Axial, Tension-Tension Cyclic Fatigue of Advanced Ceramics at Ambient Temperatures
Standard Practice for Constant-Amplitude, Axial, Tension-Tension Cyclic Fatigue of Advanced Ceramics at Ambient Temperatures
SIGNIFICANCE AND USE
4.1 This practice may be used for material development, material comparison, quality assurance, characterization, reliability assessment, and design data generation.
4.2 High-strength, monolithic advanced ceramic materials are generally characterized by small grain sizes (
4.3 Cyclic fatigue by its nature is a probabilistic phenomenon as discussed in STP 91A and STP 588.(1,2)4 In addition, the strengths of advanced ceramics are probabilistic in nature. Therefore, a sufficient number of test specimens at each testing condition is required for statistical analysis and design, with guidelines for sufficient numbers provided in STP 91A, (1) STP 588, (2) and Practice E739. The many different tensile specimen geometries available for cyclic fatigue testing may result in variations in the measured cyclic fatigue behavior of a particular material due to differences in the volume or surface area of material in the gage section of the test specimens.
4.4 Tensile cyclic fatigue tests provide information on the material response under fluctuating uniaxial tensile stresses. Uniform stress states are required to effectively evaluate any non-linear stress-strain behavior which may develop as the result of cumulative damage processes (for example, microcracking, cyclic fatigue crack growth, etc.).
4.5 Cumulative damage processes due to cyclic fatigue may be influenced by testing mode, testing rate (related to frequency), differences between maximum and minimum force (R or Α), effects of processing or combinations of constituent materials, or environmental influences, or both. Other factors that influence cyclic fatigue behaviour are: void or porosity content, methods of test specimen preparation or fabrication,test specimen conditioning, test environment, force or strain limits during cycling, wave shapes (that is, sinusoidal, trapezoidal, etc.), and failure mode. Some of these effects may be consequences of stress corrosion or sub critical (slow) crack growth which can...
SCOPE
1.1 This practice covers the determination of constant-amplitude, axial tension-tension cyclic fatigue behavior and performance of advanced ceramics at ambient temperatures to establish “baseline” cyclic fatigue performance. This practice builds on experience and existing standards in tensile testing advanced ceramics at ambient temperatures and addresses various suggested test specimen geometries, test specimen fabrication methods, testing modes (force, displacement, or strain control), testing rates and frequencies, allowable bending, and procedures for data collection and reporting. This practice does not apply to axial cyclic fatigue tests of components or parts (that is, machine elements with non uniform or multiaxial stress states).
1.2 This practice applies primarily to advanced ceramics that macroscopically exhibit isotropic, homogeneous, continuous behaviour. While this practice applies primarily to monolithic advanced ceramics, certain whisker- or particle-reinforced composite ceramics as well as certain discontinuous fibre-reinforced composite ceramics may also meet these macroscopic behaviour assumptions. Generally, continuous fibre-reinforced ceramic composites (CFCCs) do not macroscopically exhibit isotropic, homogeneous, continuous behaviour and application of this practice to these materials is not recommended.
1.3 The values stated in SI units are to be regarded as the standard and are in accordance with IEEE/ASTM SI 10.
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. Refer to Section 7 for specific precautions.
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Designation: C1361 − 10 (Reapproved 2015)
Standard Practice for
Constant-Amplitude, Axial, Tension-Tension Cyclic Fatigue
of Advanced Ceramics at Ambient Temperatures
This standard is issued under the fixed designation C1361; 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* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice covers the determination of constant-
C1145 Terminology of Advanced Ceramics
amplitude, axial tension-tension cyclic fatigue behavior and
C1273 Test Method for Tensile Strength of Monolithic
performance of advanced ceramics at ambient temperatures to
Advanced Ceramics at Ambient Temperatures
establish “baseline” cyclic fatigue performance. This practice
C1322 Practice for Fractography and Characterization of
builds on experience and existing standards in tensile testing
Fracture Origins in Advanced Ceramics
advanced ceramics at ambient temperatures and addresses
E4 Practices for Force Verification of Testing Machines
various suggested test specimen geometries, test specimen
E6 Terminology Relating to Methods of Mechanical Testing
fabrication methods, testing modes (force, displacement, or
E83 Practice for Verification and Classification of Exten-
strain control), testing rates and frequencies, allowable
someter Systems
bending, and procedures for data collection and reporting.This
E337 Test Method for Measuring Humidity with a Psy-
practice does not apply to axial cyclic fatigue tests of compo-
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
nents or parts (that is, machine elements with non uniform or
peratures)
multiaxial stress states).
E467 Practice for Verification of Constant Amplitude Dy-
1.2 This practice applies primarily to advanced ceramics namic Forces in an Axial Fatigue Testing System
that macroscopically exhibit isotropic, homogeneous, continu- E468 Practice for Presentation of Constant Amplitude Fa-
tigue Test Results for Metallic Materials
ous behaviour. While this practice applies primarily to mono-
lithic advanced ceramics, certain whisker- or particle- E739 PracticeforStatisticalAnalysisofLinearorLinearized
Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
reinforced composite ceramics as well as certain discontinuous
E1012 Practice for Verification of Testing Frame and Speci-
fibre-reinforced composite ceramics may also meet these
men Alignment Under Tensile and Compressive Axial
macroscopic behaviour assumptions. Generally, continuous
Force Application
fibre-reinforced ceramic composites (CFCCs) do not macro-
E1823 TerminologyRelatingtoFatigueandFractureTesting
scopically exhibit isotropic, homogeneous, continuous behav-
IEEE/ASTM SI 10 Standard for Use of the International
iour and application of this practice to these materials is not
System of Units (SI) (The Modern Metric System)
recommended.
2.2 Military Handbook:
1.3 The values stated in SI units are to be regarded as the
MIL-HDBK-790 Fractography and Characterization of
standard and are in accordance with IEEE/ASTM SI 10. 3
Fracture Origins in Advanced Structural Ceramics
1.4 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
3.1 Definitions—Definitions of terms relating to advanced
responsibility of the user of this standard to establish appro-
ceramics, cyclic fatigue, and tensile testing as they appear in
priate safety and health practices and determine the applica-
Terminology C1145, Terminology E1823, and Terminology
bility of regulatory limitations prior to use. Refer to Section 7
E6, respectively, apply to the terms used in this practice.
for specific precautions.
Selected terms with definitions non-specific to this practice
1 2
This practice is under the jurisdiction of ASTM Committee C28 on Advanced For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Ceramics and is the direct responsibility of Subcommittee C28.01 on Mechanical contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Properties and Performance. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved July 1, 2015. Published September 2015. Originally the ASTM website.
approved in 1996. Last previous edition approved in 2010 as C1361 – 10. DOI: Available from Army Research Laboratory-Materials Directorate, Aberdeen
10.1520/C1361-10R15. Proving Ground, MD 21005.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1361 − 10 (2015)
3.2.7.1 Discussion—Certain materials and environments
preclude the attainment of a cyclic fatigue limit. Values
tabulated as cyclic fatigue limits in the literature are frequently
(but not always) values of S at 50 % survival at N cycles of
f f
stress in which the mean stress, S , equals zero.
m
–2
3.2.8 cyclic fatigue strength S , [FL ], n—the limiting
N
valueofthemediancyclicfatiguestrengthataparticularcyclic
fatigue life, N. (See Terminology E1823.)
f
3.2.9 gage length, [L], n—the original length of that portion
of the test specimen over which strain or change of length is
determined. (See Terminology E6.)
3.2.10 load ratio, n—in cyclic fatigue loading, the algebraic
ratio of the two loading parameters of a cycle; the most widely
used ratios (see Terminology E1823):
FIG. 1 Cyclic Fatigue Nomenclature and Wave Forms
minimum force valley force
R 5 or R 5
maximumforce peakforce
and:
follow in 3.2 with the appropriate source given in parenthesis.
force amplitude ~maximum force 2 minimum force!
Α 5 orΑ 5
Terms specific to this practice are defined in 3.3.
mean force maximum force1minimum force
~ !
–2
3.2 Definitions of Terms Non Specific to This Standard:
3.2.11 modulus of elasticity [FL ], n—the ratio of stress to
3.2.1 advanced ceramic, n—a highly engineered, high per-
corresponding strain below the proportional limit. (See Termi-
formance predominately non-metallic, inorganic, ceramic ma-
nology E6.)
terial having specific functional attributes. (See Terminology
3.2.12 percent bending, n—the bending strain times 100
C1145.)
divided by the axial strain. (See Practice E1012.)
–1
3.2.2 axial strain [LL ], n—theaveragelongitudinalstrains
3.2.13 S-N diagram, n—aplotofstressversusthenumberof
measured at the surface on opposite sides of the longitudinal
cycles to failure. The stress can be maximum stress, S ,
max
axis of symmetry of the test specimen by two strain-sensing
minimum stress, S , stress range, ∆S or S , or stress
devices located at the mid length of the reduced section. (See min r
amplitude, S . The diagram indicates the S-N relationship for a
a
Practice E1012.)
specified value of S , Α, R and a specified probability of
–1 m
3.2.3 bending strain [LL ], n—the difference between the
survival. For N, a log scale is almost always used, although a
strainatthesurfaceandtheaxialstrain.Ingeneral,thebending
linear scale may also be used. For S, a linear scale is usually
strain varies from point to point around and along the reduced
used, although a log scale may also be used. (See Terminology
section of the test specimen. (See Practice E1012.)
E1823 and Practice E468.)
3.2.4 constant amplitude loading, n—in cyclic fatigue
3.2.14 slow crack growth, n—sub-critical crack growth
loading, a loading in which all peak loads are equal and all of
(extension) that may result from, but is not restricted to, such
the valley forces are equal. (See Terminology E1823.)
mechanisms as environmentally-assisted stress corrosion or
3.2.5 cyclic fatigue, n—the process of progressive localized
diffusive crack growth.
permanent structural change occurring in a material subjected
–2
3.2.15 tensile strength [FL ], n—the maximum tensile
to conditions that produce fluctuating stresses and strains at
stress which a material is capable of sustaining. Tensile
some point or points and that may culminate in cracks or
strengthiscalculatedfromthemaximumforceduringatension
completefractureafterasufficientnumberoffluctuations.(See
test carried to rupture and the original cross-sectional area of
Terminology E1823.) See Fig. 1 for nomenclature relevant to
the test specimen. (See Terminology E6.)
cyclic fatigue testing.
3.2.5.1 Discussion—In glass technology static tests of con- 3.3 Definitions of Terms Specific to This Standard:
–2
siderable duration are called static fatigue tests, a type of test
3.3.1 maximum stress, S [FL ], n—the maximum ap-
max
generally designated as stress-rupture.
plied stress during cyclic fatigue.
3.2.5.2 Discussion—Fluctuations may occur both in load
–2
3.3.2 mean stress, S [FL ], n—the average applied
max
and with time (frequency) as in the case of random vibration.
stress during cyclic fatigue such that
3.2.6 cyclic fatigue life, N—thenumberofloadingcyclesof
f
S 1S
max min
a specified character that a given test specimen sustains before
S 5 (1)
m
failure of a specified nature occurs. (See Terminology E1823.)
–2
–2 3.3.3 minimum stress, S [FL ], n—the minimum applied
min
3.2.7 cyclic fatigue limit, S, [FL ], n—thelimitingvalueof
f
stress during cyclic fatigue.
the median cyclic fatigue strength as the cyclic fatigue life,N,
f
6 7 –2
becomes very large. (for example, N>10 -10 ). (See Terminol- 3.3.4 stress amplitude, S [FL ], n—the difference between
a
ogy E1823) the mean stress and the maximum or minimum stress such that
C1361 − 10 (2015)
S 2 S growth which can be difficult to quantify. In addition, surface
max min
S 5 5 S 2 S 5 S 2 S (2)
a max m m min
2 or near-surface flaws introduced by the test specimen fabrica-
–2
tion process (machining) may or may not be quantifiable by
3.3.5 stress range, ∆SorS [FL ], n—the difference
r
conventional measurements of surface texture. Therefore, sur-
between the maximum stress and the minimum stress such that
face effects (for example, as reflected in cyclic fatigue reduc-
∆S = S = S – S
r max min
tion factors as classified by Marin (3)) must be inferred from
3.3.6 time to cyclic fatigue failure, tf [t], n—total elapsed
the results of numerous cyclic fatigue tests performed with test
timefromtestinitiationtotestterminationrequiredtoreachthe
specimens having identical fabrication histories.
number of cycles to failure.
4.6 The results of cyclic fatigue tests of specimens fabri-
4. Significance and Use cated to standardized dimensions from a particular material or
selected portions of a part, or both, may not totally represent
4.1 This practice may be used for material development,
the cyclic fatigue behavior of the entire, full-size end product
material comparison, quality assurance, characterization, reli-
or its in-service behavior in different environments.
ability assessment, and design data generation.
4.7 However, for quality control purposes, results derived
4.2 High-strength, monolithic advanced ceramic materials
from standardized tensile test specimens may be considered
are generally characterized by small grain sizes (<50 µm) and
indicativeoftheresponseofthematerialfromwhichtheywere
bulk densities near the theoretical density. These materials are
taken for given primary processing conditions and post-
candidates for load-bearing structural applications requiring
processing heat treatments.
high degrees of wear and corrosion resistance, and high-
temperature strength. Although flexural test methods are com- 4.8 The cyclic fatigue behavior of an advanced ceramic is
monly used to evaluate strength of advanced ceramics, the non dependent on its inherent resistance to fracture, the presence of
uniform stress distribution in a flexure specimen limits the flaws, or damage accumulation processes, or both. There can
volume of material subjected to the maximum applied stress at
be significant damage in the test specimen without any visual
fracture. Uniaxially-loaded tensile strength tests may provide evidence such as the occurrence of a macroscopic crack. This
information on strength-limiting flaws from a greater volume
can result in a specific loss of stiffness and retained strength.
of uniformly stressed material. Depending on the purpose for which the test is being
conducted, rather than final fracture, a specific loss in stiffness
4.3 Cyclic fatigue by its nature is a probabilistic phenom-
4 or retained strength may constitute failure. In cases where
enon as discussed in STP 91Aand STP 588.(1,2) In addition,
fracture occurs, analysis of fracture surfaces and fractography,
the strengths of advanced ceramics are probabilistic in nature.
though beyond the scope of this practice, are recommended.
Therefore, a sufficient number of test specimens at each testing
condition is required for statistical analysis and design, with
5. Interferences
guidelines for sufficient numbers provided in STP 91A, (1)
STP 588, (2) and Practice E739. The many different tensile
5.1 Test environment (vacuum, inert gas, ambient air, etc.)
specimen geometries available for cyclic fatigue testing may including moisture content (for example, relative humidity)
result in variations in the measured cyclic fatigue behavior of
mayhaveaninfluenceonthemeasuredcyclicfatiguebehavior.
aparticularmaterialduetodifferencesinthevolumeorsurface In particular, the behavior of materials susceptible to slow
area of material in the gage section of the test specimens.
crack growth fracture will be strongly influenced by test
environment and testing rate. Conduct tests to evaluate the
4.4 Tensile cyclic fatigue tests provide information on the
mechanical cyclic fatigue behaviour of a material in inert
material response under fluctuating uniaxial tensile stresses.
environments to minimize slow crack growth effects.
Uniform stress states are required to effectively evaluate any
Conversely, conduct tests in environments or at test modes and
non-linear stress-strain behavior which may develop as the
rates representative of service conditions to evaluate material
result of cumulative damage processes (for example,
performance under use conditions, or both. Regardless of
microcracking, cyclic fatigue crack growth, etc.).
whether testing is conducted in uncontrolled ambient air or
4.5 Cumulative damage processes due to cyclic fatigue may
controlled environments, monitor and report relative humidity
be influenced by testing mode, testing rate (related to
andtemperatureataminimumatthebeginningandendofeach
frequency), differences between maximum and minimum force
test, and hourly if the test duration is greater than 1 h. Testing
(R or Α)
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C1361 − 10 C1361 − 10 (Reapproved 2015)
Standard Practice for
Constant-Amplitude, Axial, Tension-Tension Cyclic Fatigue
of Advanced Ceramics at Ambient Temperatures
This standard is issued under the fixed designation C1361; 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*
1.1 This practice covers the determination of constant-amplitude, axial tension-tension cyclic fatigue behavior and performance
of advanced ceramics at ambient temperatures to establish “baseline” cyclic fatigue performance. This practice builds on
experience and existing standards in tensile testing advanced ceramics at ambient temperatures and addresses various suggested
test specimen geometries, test specimen fabrication methods, testing modes (force, displacement, or strain control), testing rates
and frequencies, allowable bending, and procedures for data collection and reporting. This practice does not apply to axial cyclic
fatigue tests of components or parts (that is, machine elements with non uniform or multiaxial stress states).
1.2 This practice applies primarily to advanced ceramics that macroscopically exhibit isotropic, homogeneous, continuous
behaviour. While this practice applies primarily to monolithic advanced ceramics, certain whisker- or particle-reinforced composite
ceramics as well as certain discontinuous fibre-reinforced composite ceramics may also meet these macroscopic behaviour
assumptions. Generally, continuous fibre-reinforced ceramic composites (CFCCs) do not macroscopically exhibit isotropic,
homogeneous, continuous behaviour and application of this practice to these materials is not recommended.
1.3 The values stated in SI units are to be regarded as the standard and are in accordance with IEEE/ASTM SI 10.
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. Refer to Section 7 for specific precautions.
2. Referenced Documents
2.1 ASTM Standards:
C1145 Terminology of Advanced Ceramics
C1273 Test Method for Tensile Strength of Monolithic Advanced Ceramics at Ambient Temperatures
C1322 Practice for Fractography and Characterization of Fracture Origins in Advanced Ceramics
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E83 Practice for Verification and Classification of Extensometer Systems
E337 Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
E467 Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System
E468 Practice for Presentation of Constant Amplitude Fatigue Test Results for Metallic Materials
E739 Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
E1012 Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial Force
Application
E1823 Terminology Relating to Fatigue and Fracture Testing
IEEE/ASTM SI 10 Standard for Use of the International System of Units (SI) (The Modern Metric System)
2.2 Military Handbook:
MIL-HDBK-790 Fractography and Characterization of Fracture Origins in Advanced Structural Ceramics
This practice is under the jurisdiction of ASTM Committee C28 on Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on Mechanical Properties
and Performance.
Current edition approved July 15, 2010July 1, 2015. Published August 2010September 2015. Originally approved in 1996. Last previous edition approved in 20072010
as C1361 – 01C1361 – 10. (2007). DOI: 10.1520/C1361-10.10.1520/C1361-10R15.
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 ASTM website.
Available from Army Research Laboratory-Materials Directorate, Aberdeen Proving Ground, MD 21005.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1361 − 10 (2015)
FIG. 1 Cyclic Fatigue Nomenclature and Wave Forms
3. Terminology
3.1 Definitions—Definitions of terms relating to advanced ceramics, cyclic fatigue, and tensile testing as they appear in
Terminology C1145, Terminology E1823, and Terminology E6, respectively, apply to the terms used in this practice. Selected
terms with definitions non-specific to this practice follow in 3.2 with the appropriate source given in parenthesis. Terms specific
to this practice are defined in 3.3.
3.2 Definitions of Terms Non Specific to This Standard:
3.2.1 advanced ceramic, n—a highly engineered, high performance predominately non-metallic, inorganic, ceramic material
having specific functional attributes. (See Terminology C1145.)
–1
3.2.2 axial strain [LL ], n—the average longitudinal strains measured at the surface on opposite sides of the longitudinal axis
of symmetry of the test specimen by two strain-sensing devices located at the mid length of the reduced section. (See Practice
E1012.)
–1
3.2.3 bending strain [LL ], n—the difference between the strain at the surface and the axial strain. In general, the bending strain
varies from point to point around and along the reduced section of the test specimen. (See Practice E1012.)
3.2.4 constant amplitude loading, n—in cyclic fatigue loading, a loading in which all peak loads are equal and all of the valley
forces are equal. (See Terminology E1823.)
3.2.5 cyclic fatigue, n—the process of progressive localized permanent structural change occurring in a material subjected to
conditions that produce fluctuating stresses and strains at some point or points and that may culminate in cracks or complete
fracture after a sufficient number of fluctuations. (See Terminology E1823.) See Fig. 1 for nomenclature relevant to cyclic fatigue
testing.
3.2.5.1 Discussion—
In glass technology static tests of considerable duration are called static fatigue tests, a type of test generally designated as
stress-rupture.
3.2.5.2 Discussion—
Fluctuations may occur both in load and with time (frequency) as in the case of random vibration.
3.2.6 cyclic fatigue life, N —the number of loading cycles of a specified character that a given test specimen sustains before
f
failure of a specified nature occurs. (See Terminology E1823.)
–2
3.2.7 cyclic fatigue limit, S , [FL ], n—the limiting value of the median cyclic fatigue strength as the cyclic fatigue life,N ,
f f
6 7
becomes very large. (for example, N>10 -10 ). (See Terminology E1823)
3.2.7.1 Discussion—
Certain materials and environments preclude the attainment of a cyclic fatigue limit. Values tabulated as cyclic fatigue limits in
the literature are frequently (but not always) values of S at 50 % survival at N cycles of stress in which the mean stress, S , equals
f f m
zero.
C1361 − 10 (2015)
–2
3.2.8 cyclic fatigue strength S , [FL ], n—the limiting value of the median cyclic fatigue strength at a particular cyclic fatigue
N
life, N . (See Terminology E1823.)
f
3.2.9 gage length, [L], n—the original length of that portion of the test specimen over which strain or change of length is
determined. (See Terminology E6.)
3.2.10 load ratio, n—in cyclic fatigue loading, the algebraic ratio of the two loading parameters of a cycle; the most widely used
ratios (see Terminology E1823):
minimum force valley force
R 5 or R 5
maximum force peak force
and:
force amplitude ~maximum force 2 minimum force!
Α5 or Α5
mean force maximum force1minimum force
~ !
–2
3.2.11 modulus of elasticity [FL ], n—the ratio of stress to corresponding strain below the proportional limit. (See Terminology
E6.)
3.2.12 percent bending, n—the bending strain times 100 divided by the axial strain. (See Practice E1012.)
3.2.13 S-N diagram, n—a plot of stress versus the number of cycles to failure. The stress can be maximum stress, S ,
max
minimum stress, S , stress range, ΔS or S , or stress amplitude, S . The diagram indicates the S-N relationship for a specified value
min r a
of S , Α, R and a specified probability of survival. For N, a log scale is almost always used, although a linear scale may also be
m
used. For S, a linear scale is usually used, although a log scale may also be used. (See Terminology E1823 and Practice E468.)
3.2.14 slow crack growth, n—sub-critical crack growth (extension) that may result from, but is not restricted to, such
mechanisms as environmentally-assisted stress corrosion or diffusive crack growth.
–2
3.2.15 tensile strength [FL ], n—the maximum tensile stress which a material is capable of sustaining. Tensile strength is
calculated from the maximum force during a tension test carried to rupture and the original cross-sectional area of the test
specimen. (See Terminology E6.)
3.3 Definitions of Terms Specific to This Standard:
–2
3.3.1 maximum stress, S [FL ], n—the maximum applied stress during cyclic fatigue.
max
–2
3.3.2 mean stress, S [FL ], n—the average applied stress during cyclic fatigue such that
max
S 1S
max min
S 5 (1)
m
–2
3.3.3 minimum stress, S [FL ], n—the minimum applied stress during cyclic fatigue.
min
–2
3.3.4 stress amplitude, S [FL ], n—the difference between the mean stress and the maximum or minimum stress such that
a
S 2 S
max min
S 5 5 S 2 S 5 S 2 S (2)
a max m m min
–2
3.3.5 stress range, ΔS or S [FL ], n—the difference between the maximum stress and the minimum stress such that ΔS = S
r r
= S – S
max min
3.3.6 time to cyclic fatigue failure, tf [t], n—total elapsed time from test initiation to test termination required to reach the
number of cycles to failure.
4. Significance and Use
4.1 This practice may be used for material development, material comparison, quality assurance, characterization, reliability
assessment, and design data generation.
4.2 High-strength, monolithic advanced ceramic materials are generally characterized by small grain sizes (<50 μm) and bulk
densities near the theoretical density. These materials are candidates for load-bearing structural applications requiring high degrees
of wear and corrosion resistance, and high-temperature strength. Although flexural test methods are commonly used to evaluate
strength of advanced ceramics, the non uniform stress distribution in a flexure specimen limits the volume of material subjected
to the maximum applied stress at fracture. Uniaxially-loaded tensile strength tests may provide information on strength-limiting
flaws from a greater volume of uniformly stressed material.
4.3 Cyclic fatigue by its nature is a probabilistic phenomenon as discussed in STP 91A and STP 588.(1,2) In addition, the
strengths of advanced ceramics are probabilistic in nature. Therefore, a sufficient number of test specimens at each testing condition
is required for statistical analysis and design, with guidelines for sufficient numbers provided in STP 91A, (1) STP 588, (2) and
The boldface numbers in parentheses refer to the list of references at the end of this standard.
C1361 − 10 (2015)
Practice E739. The many different tensile specimen geometries available for cyclic fatigue testing may result in variations in the
measured cyclic fatigue behavior of a particular material due to differences in the volume or surface area of material in the gage
section of the test specimens.
4.4 Tensile cyclic fatigue tests provide information on the material response under fluctuating uniaxial tensile stresses. Uniform
stress states are required to effectively evaluate any non-linear stress-strain behavior which may develop as the result of cumulative
damage processes (for example, microcracking, cyclic fatigue crack growth, etc.).
4.5 Cumulative damage processes due to cyclic fatigue may be influenced by testing mode, testing rate (related to frequency),
differences between maximum and minimum force (R or Α), effects of processing or combinations of constituent materials, or
environmental influences, or both. Other factors that influence cyclic fatigue behaviour are: void or porosity content, methods of
test specimen preparation or fabrication,test specimen conditioning, test environment, force or strain limits during cycling, wave
shapes (that is, sinusoidal, trapezoidal, etc.), and failure mode. Some of these effects may be consequences of stress corrosion or
sub critical (slow) crack growth which can be difficult to quantify. In addition, surface or near-surface flaws introduced by the test
specimen fabrication process (machining) may or may not be quantifiable by conventional measurements of surface texture.
Therefore, surface effects (for example, as reflected in cyclic fatigue reduction factors as classified by Marin (3)) must be inferred
from the results of numerous cyclic fatigue tests performed with test specimens having identical fabrication histories.
4.6 The results of cyclic fatigue tests of specimens fabricated to standardized dimensions from a particular material or selected
portions of a part, or both, may not totally represent the cyclic fatigue behavior of the entire, full-size end product or its in-service
behavior in different environments.
4.7 However, for quality control purposes, results derived from standardized tensile test specimens may be considered indicative
of the response of the material from which they were taken for given primary processing conditions and post-processing heat
treatments.
4.8 The cyclic fatigue behavior of an advanced ceramic is dependent on its inherent resistance to fracture, the presence of flaws,
or damage accumulation processes, or both. There can be significant damage in the test specimen without any visual evidence such
as the occurrence of a macroscopic crack. This can result in a specific loss of stiffness and retained strength. Depending on the
purpose for which the test is being conducted, rather than final fracture, a specific loss in stiffness or retained str
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