ASTM E3039-20

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of the standard as published by ASTM is to be considered the official document.
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Designation: E3039 − 18 E3039 − 20
Standard Test Method for
Determination of Crack-Tip-Opening Angle of PipeFerritic
Steels Using DWTT-Type Specimens
This standard is issued under the fixed designation E3039; 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.
ε NOTE—Fig 6. was editorially corrected in September 2019.
1. Scope
1.1 This test method covers the determination of fracture propagation toughness in terms of the steady-state crack-tip-opening
angle (CTOA) using the drop-weight tear test (DWTT)-type specimen. The method is applicable to pipeferritic steels that exhibit
predominantly ductile fracture with at least 85%85 % shear area measured according to Test Method E436 - Standard Test Method
for Drop-Weight Tear Tests of Ferritic Steels. This test method applies to steel pipesferritic steels with wall thicknesses between
6 mm and 20 mm. Annex A1 describes the method to test pipeferritic steels with wall thickness thicknesses between 20 mm to
32 mm.
1.2 In terms of apparatus, specimen design, and test methodology, this test method draws from Test Method E436 and API 5L3
- Recommended Practice for Conducting Drop-Weight Tear Tests on Line Pipe.
1.3 The development of this test method has been driven by the need to design for fast ductile fracture arrest of axial running
cracks in steel high-pressure gas pipelines (1). The purpose has been to develop a test to characterize fracture propagation
resistance in a form suitable for use as a pipe mill test (2). The traditional Charpy test has been shown to be inadequate for modern
high toughness pipe steels (1). This test method measures fracture propagation resistance in terms of crack-tip opening angle, and
is used to characterize pipeferritic steels.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
This test method is under the jurisdiction of ASTM Committee E08 on Fatigue and Fracture and is the direct responsibility of Subcommittee E08.07 on Fracture
Mechanics.
Current edition approved Nov. 1, 2018Sept. 1, 2020. Published January 2019September 2020. Originally approved in 2016. Last previous edition approved in 20162018
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as E3039–16.–18 . DOI: 10.1520/E3039–18E0110.1520/E3039–20.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3039 − 20
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E436 Test Method for Drop-Weight Tear Tests of Ferritic Steels
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1823 Terminology Relating to Fatigue and Fracture Testing
E1942 Guide for Evaluating Data Acquisition Systems Used in Cyclic Fatigue and Fracture Mechanics Testing
E2298 Test Method for Instrumented Impact Testing of Metallic Materials
E2472 Test Method for Determination of Resistance to Stable Crack Extension under Low-Constraint Conditions
2.2 ISO Standards:
ISO 22889 Metallic materials — Method of Test for the Determination of Resistance to Stable Crack Extension Using
Specimens of Low Constraint
ISO 14456 Steel — Charpy V-notch Pendulum Impact Test — Instrumented Test Method
2.3 API Recommended Practice:
API Recommended Practice 5L3 Drop-Weight Tear Tests on Line Pipe
3. Terminology
3.1 Symbols:
a = crack size, mm
a = initial notch depth, mm
n
b = specimen ligament size (b=W-a), mm
b = initial ligament size (b =W-a ), mm
0 0 n
C = full-size Charpy V-notch absorbed energy, J
v
B = specimen thickness, mm
L = specimen length, mm
M = total mass of the moving striker (hammer), kg
P = force, kN
P = maximum force applied by the hammer during the test, kN
m
r = plastic rotation factor
p
S = specimen span between anvil contact points (S = 254 mm for standard DWTT-type tests), mm
t = time at the beginning of specimen deformation, s
v = initial striker impact velocity, m/s
W = specimen width, mm
σ = yield strength, MPa
y
Δ = load-line displacement (LLD), mm
Δ = load-line displacement (LLD) at maximum force, mm
m
ξ = absolute value of slope of the ln(P/P ) versus (Δ-Δ )/S curve as specified in Section 8.
m m
3.2 Acronyms:
CTOA = crack-tip opening angle, degree
CTOA = critical crack-tip opening angle in the steady-state stage as determined by this test method, degree
B/2
DWTT = drop-weight tear test
SE(B) = single-edge bend specimen
S-SSM = simplified single-specimen CTOA test method
3.3 Definitions:
3.3.1 crack-tip opening angle (CTOA), [deg], n—angle formed between the fractured surfaces measured at the crack tip.
3.3.2 critical crack-tip-opening angle (CTOA ), [deg], n—steady-state value of CTOA as measured by this test method, intended
B/2
to approximate the CTOA on the mid-thickness plane as the angle between the crack flanks. The crack flanks extend from the crack
tip to one-half of the DWTT-type specimen thickness (B/2) behind the crack tip (see Fig. 1) during steady-state propagation.
3.3.2.1 Discussion—
The shape of the tearing crack is initially dominated by a flat tunneling region that often transitions from flat to slant fracture, and
tends to approach a constant tunneling shape after a crack extension of approximately one specimen thickness. The CTOA tends
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
Available from American Petroleum Institute (API), 1220 L. St., NW, Washington, DC 20005-4070, http://www.api.org.
E3039 − 20
FIG. 1 Measurement point for CTOA and location of mid-thickness plane
B/2
to approach a constant, steady-state value (CTOA ) during propagation through the mid-portion of the original ligament. It must
B/2
be recognized that the CTOA often depends on where it is measured, that is, at what distance behind the crack tip, and the
measurement is complicated by tunneling. In this test method, CTOA is defined as the angle between the crack flanks extending
B/2
from the crack tip to a distance B/2 along the crack surface. This parameter may be compared with optical measurements made,
for example, using pictures of the specimen surface taken with a high-speed camera. Discussion of the optical method is included
in Test Method E2472.
3.3.2.2 Discussion—
This procedure uses CTOA for the critical crack-tip-opening angle to distinguish it from the CTOA in Test Method E2472 and
B/2 c
ISO 22889, in which CTOA is measured or calculated at 1 mm behind the current crack tip.
4. Summary and Significance
4.1 The objective of this test method is to use measurements of force (P) versus load-line displacement (Δ) to derive the critical
steady-state crack-tip opening angle (CTOA ) based on the simplified single-specimen method (S-SSM) (2). The S-SSM is a
B/2
further development of the previous two-specimen CTOA method (3) and simplification of a single-specimen CTOA method (4).
In addition, the calculation of CTOA requires a value for the plastic rotation factor (r ). For typical pipeferritic steels, values of
p
r have been estimated experimentally (5), and will be discussed in Section 8.
p
4.2 The CTOA value derived according to this test method is close to the value in the high-constraint mid-thickness region of
B/2
the DWTT-type specimens, and is significantly lower than the surface CTOA values measured optically (5, 6). This reflects the
effects of through-thickness constraint and the resulting crack-tip tunneling.
4.3 Steady-state ductile crack propagation velocities range between 12-20 m/s in DWTT-type specimens impacted with a hammer
velocity of 5 m/s. The crack velocity decreases as toughness increases (6). DWTT-type specimens of steels tested at room
temperature usually exhibit shear fracture under impact loading; that is, the flat (tunnelling) morphology at crack initiation usually
transitions to a near-45° slant fracture that is considered to be a shear morphology. For pipe steels, this mimics the fracture mode
observed in full-scale pipe burst tests.
4.4 The apparatus, specimen dimensions and testing procedure in this test method are the same as those described in Test Method
E436 or API RP 5L3 and Test Method E2298, see Section 2. The intent is to adopt the standardized DWTT test procedures,
machines (for example, hammer and anvil supports), and instrumentation requirements to the maximum extent possible. The
following sections provide specific requirements, procedures and calculations for determining CTOA.
5. Apparatus
5.1 The test shall be conducted using a test machine that has sufficient energy to completely break the specimen in one impact.
The key dimensions, shown in Fig. 2, are: distance between supports (span) S = 254 mm (10 in.), radius of impact hammer striking
edge = 25.4 mm (1 in.), and radius of fixed support anvils = 19 mm (0.75 in.). Drawings of the test fixture and specimen can also
be found in Test Method E436 or API RP 5L3.
5.2 The initial velocity v0v of the hammer at impact shall be 5 m/s ≤ v ≤ 10 m/s and shall be known within 6 5%, as discussed
0 0
below.
E3039 − 20
FIG. 2 Dimensions (in mm) of the machine-notched specimen (top) and supporting anvils (bottom). The anvils are fixed in position.
5.3 For force measurement and displacement determination, the provisions of Test Method E2298 shall apply. Instrumentation
shall be used to determine force-time or force-displacement curves.
5.4 Force Measurement:
5.4.1 Force shall be measured by means of an electronic sensor (piezoelectric load cell, strain gauge load cell or a force
measurement derived from an accelerometer).
5.4.2 The force measuring system (including strain gauges, wiring, and amplifier) shall have a bandwidth of at least 100 kHz as
discussed in Guide E1942.
5.4.3 The signal shall be recorded without filtering. Post-test filtering, however, is allowed as detailed in Test Method E2298, 7.2
but efforts should be taken to avoid introducing errors through filtering, as discussed in Guide E1942.
5.4.4 Calibration of the recorder and measurement system may be performed statically in accordance with the accuracy
requirements given in 5.4.4.1. For pendulum machines, it is recommended that the force calibration be performed with the striker
attached to the pendulum assembly. The strain gauge signal conditioning equipment, cables, and recording device shall be used
in the calibration. In most cases, a computer is used for data acquisition and the calibration shall be performed with the voltage
read from the computer. The intent is to calibrate with the electronics and cables which are used during actual testing.
5.4.4.1 The static linearity and hysteresis error including all parts of the force measurement system up to the recording apparatus
shall be within 6 2 % of the recorded force, between 50 % and 100 % of the nominal force range, and within 6 1 % of the full
scale force value between 10 % and 50 % of the nominal force range as detailed in Test Method E2298, 7.2.4.1.
NOTE 1—For testing in accordance with this test method, it is recommended to calibrate the instrumented striker up to 500 kN.
5.4.5 Recalibration shall be performed if the instrumented striker has undergone dismantling or repair, unless it can be shown that
removal of the striker from the test machine and subsequent re-attachment to the machine does not affect the calibration.
5.5 Displacement Determination:
E3039 − 20
5.5.1 Displacement shall be measured using a non-contacting transducer according to 5.5.4 or calculated using force-time
measurements with Newton’s equations of motion as outlined in 5.5.2.
5.5.2 Assuming a rigid striker of mass m with an initial velocity v the velocity v(t) at the contact point as a function of elapsed
time is calculated as:
1 t
v~t! 5 v 2 * P~t!dt (1)
t
m
If the specimen is assumed not to lift off at the anvils the bending displacement Δ(t) is evaluated from:
t
Δ t 5 v t dt (2)
~ ! * ~ !
t
5.5.3 For drop weight and pendulum machines, the initial impact velocity needed to perform the above integrations is calculated
from:
v 5=2gh (3)
0 0
where:
g = local acceleration due to gravity, and
h = height of striker from point of release to point of initial impact.
5.5.3.1 Alternatively, for drop weight and pendulum machines, it is acceptable to use for v the optically measured velocity
registered when the pendulum passes through its lowest position and strikes the specimen.
5.5.4 Displacement can also be determined by non-contacting measurement of the displacement of the striker relative to the anvil
using optical, inductive, or capacitive methods. The signal transfer characteristics of the displacement measurement system shall
correspond to that of the force measuring system in order to minimize phase difference and data skew errors, as discussed in Guide
E1942. The displacement measuring system shall be designed for maximum nominal values of 40 mm. Linearity errors in the
measuring system shall yield measured values to within 6 2 % over a range of 1 mm to 40 mm. Measurements up to 1 mm may
not be sufficiently accurate to determine the displacement within 6 2 %. In this case, the displacement of the specimen shall be
determined from the time measurement and the striker impact velocity as indicated in Eq 1 and Eq 2.
5.6 The recording apparatus (that is, high-speed data acquisition system and instrumented striker) shall comply with Test Method
E2298 Section 7. Data acquisition systems that are commercially available for instrumented Charpy tests are acceptable if they
meet the accuracy requirements defined here for this test. Force-time data acquisition at a rate of 10 /s (1 MHz) or greater is
required (5,6).
6. Specimen
6.1 The specimen width and length shall be W = 76 mm and L = 305 mm (Fig. 2). Any orientations and locations may be used
provided they are a
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