ASTM E647-95

ASTM E647 95
0759530 0559533 047
Designation: E 647 - 95
4Tb
Standard Test Method for
Measurement of Fatigue Crack Growth Rates'
This standard is issued under the fixed designation E 647; 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 (e) indicates an editorial change since the last revision or reapproval.
E 337 Test Method for Measuring Humidity with a
1. Scope
Psychrometer (the Measurement of Wet- and Dry-Bulb
1. i This test method2 covers the determination of steady-
tempe rature^)^
state fatigue crack growth rates from near-threshold to K,,,
E 338 Test Method for Sharp-Notch Tension Testing of
controlled instability using either compact tension, C(T),
High-Strength Sheet Materials3
(Fig. 1) or middle-tension, M(T), (Fig. 2) specimens. Results
E 399 Test Method for Plane-Strain Fracture Toughness
are expressed in terms of the crack-tip stress-intensity factor
of Metallic Materials3
range (Am, defined by the theory of linear elasticity.
E 467 Practice for Verification of Constant Amplitude
1.2 Several different test procedures are provided, the
Dynamic Loads on Displacements in an Axial Load
optimum test procedure being primarily dependent on the
Fatigue Testing System3
magnitude of the fatigue crack growth rate to be measured.
E 56 1 Practice for R-Curve Determination3
1.3 Materials that can be tested by this test method are not
E 6 16 Terminology Relating to Fracture Testing3
limited by thicknesses or by strength so long as specimens are
E 813 Test Method for Jlo A Measure of Fracture
of sufficient thickness to preclude buckling and of sufficient
Toughness3
planar size to remain predominantly elastic during testing.
E 1 150 Definitions of Terms Relating to Fatigue3
1.4 A range of specimen sizes with proportional planar
dimensions is provided, but size is variable to be adjusted for
yield strength and applied load. Specimen thickness may be
3. Terminology
varied independent of planar size.
1.5 Specimen configurations other than those contained 3.1 The terms used in this test method are given in
in this method may be used provided that well-established Terminology E 6, Definitions E 1150, and Terminology
stress-intensity factor calibrations are available and that
E 616. Wherever these terms are not in agreement with one
specimens are of sufficient planar size to remain predomi-
another, use the definitions given in Terminology E 6 i6
nantly elastic during testing.
which are applicable to this test method.
1.6 Residual stress/crack closure may significantly influ-
3.2 Definitions:
ence the fatigue crack growth rate data, particularly at low
3.2.1 crack length, a[L], n-See crack size.
stress-intensity factors and low stress ratios, although such
3.2.2 crack size, a[L], n-a linear measure of a principal
variables are not incorporated into the computation of AK.
planar dimension of a crack. This measure is commonly
1.7 Values stated in SI units are to be regarded as the
used in the calculation of quantities descriptive of the stress
standard. Values given in parentheses are for information only.
and displacement fields and is often also termed crack length
1.8 This standard does not purport to address all of the
or depth.
safety concerns, if any, associated with its use. It is the
Discussion-In the C(T) specimen, a is measured from the
responsibility of the user of this standard to establish appro-
line connecting the bearing points of load application; in the
priate safety and health practices and determine the applica-
M(T) specimen, a is measured from the perpendicular
bility of regulatory limitations prior to use.
bisector of the central crack.
Discussion-In fatigue testing, crack length is the physical
crack size. See physical crack size in Terminology E 6 16.
2. Referenced Documents
3.2.3 cycle-in fatigue, under constant amplitude loading,
2.1 ASTM Standards:
the load variation from the minimum to the maximum and
E 4 Practices for Force Verification of Testing Machines3
then to the minimum load.
E 6 Terminology Relating to Methods of Mechanical
Discussion-In spectrum loading, the definition of cycle
Testing3
vanes with the counting method used.
E 8 Test Methods for Tension Testing of Metallic
Discussion-In this test method, the symbol N is used to
Materials3
represent the number of cycles.
3.2.4 -tätigue-crack-growth rate, da/dN, [LI-crack exten-
sion per cycle of loading.
I This test method is under the jurisdiction of ASTM Committee E-8 on
3.2.5 fatigue cycle-See cycle.
Fatigue and Fracture and is the direct responsibility of Subcommittee E08.06 on
Crack Growth Behavior.
3.2.6 load cycle-See cycle.
Current edition approved Apr. 15, 1995. Published June 1995. Originally
3.2.7 load range, A P [q-in fatigue, the algebraic
publi
...