1、Designation: E3039 16Standard Test Method forDetermination of Crack-Tip-Opening Angle of Pipe SteelsUsing DWTT Specimens1This standard is issued under the fixed designation E3039; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of fracturepropagation toughness in terms of the steady-state crack
3、-tip-opening angle (CTOA) using the drop-weight tear test (DWTT)specimen. The method is applicable to pipe steels that exhibitpredominantly ductile fracture with at least 85% shear areameasured according to Test Method E436 - Standard TestMethod for Drop-Weight Tear Tests of Ferritic Steels. This te
4、stmethod applies to steel pipes with wall thicknesses between 6mm and 20 mm.1.2 In terms of apparatus, specimen design, and testmethodology, this test method draws from Test Method E436and API 5L3 - Recommended Practice for Conducting Drop-Weight Tear Tests on Line Pipe.1.3 The development of this t
5、est method has been driven bythe need to design for fast ductile fracture arrest of axialrunning cracks in steel high-pressure gas pipelines (1).2Thepurpose has been to develop a test to characterize fracturepropagation resistance in a form suitable for use as a pipe milltest (2). The traditional Ch
6、arpy test has been shown to beinadequate for modern high toughness pipe steels (1). This testmethod measures fracture propagation resistance in terms ofcrack-tip opening angle, and is used to characterize pipe steels.1.4 The values stated in SI units are to be regarded as thestandard values; those g
7、iven in parentheses are for informationonly.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulat
8、ory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE436 Test Method for Drop-Weight Tear Tests of FerriticSteelsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Meth
9、odE1823 Terminology Relating to Fatigue and Fracture TestingE1942 Guide for Evaluating Data Acquisition Systems Usedin Cyclic Fatigue and Fracture Mechanics TestingE2298 Test Method for Instrumented Impact Testing ofMetallic MaterialsE2472 Test Method for Determination of Resistance toStable Crack E
10、xtension under Low-Constraint Conditions2.2 ISO Standards:4ISO 22889 Metallic materials Method of Test for theDetermination of Resistance to Stable Crack ExtensionUsing Specimens of Low ConstraintISO 14456 Steel Charpy V-notch Pendulum Impact Test Instrumented Test Method2.3 API Recommended Practice
11、:5API Recommended Practice 5L3 Drop-Weight Tear Tests onLine Pipe3. Terminology3.1 Symbols:a = crack size, mman= initial notch depth, mmb = specimen ligament size (b=W-a),mmb0= initial ligament size (b0=W-an),mmCv= full-size Charpy V-notch absorbed energy, JB = specimen thickness, mm1This test metho
12、d is under the jurisdiction of ASTM Committee E08 on Fatigueand Fracture and is the direct responsibility of Subcommittee E08.07 on FractureMechanics.Current edition approved May 1, 2016. Published June 2016. DOI: 10.1520/E3039162The boldface numbers in parentheses refer to a list of references at t
13、he end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from International Organiza
14、tion for Standardization (ISO), ISOCentral Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http:/www.iso.org.5Available from American Petroleum Institute (API), 1220 L. St., NW,Washington, DC 20005-4070, http:/www.api.org.Copyright ASTM International, 100 Barr
15、 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1L = specimen length, mmM = total mass of the moving striker (hammer), kgP = force, kNPm= maximum force applied by the hammer during the test,kNrp= plastic rotation factorS = specimen span between anvil contact points (S = 25
16、4mm for standard DWTT tests), mmt0= time at the beginning of specimen deformation, sv0= initial striker impact velocity, m/sW = specimen width, mmy= yield strength, MPa = load-line displacement (LLD), mmm= load-line displacement (LLD) at maximum force, mm = absolute value of slope of the ln(P/Pm) ve
17、rsus (-m)/Scurve as specified in Section 8.3.2 Acronyms:CTOA = crack-tip opening angle, degreeCTOAB/2= critical crack-tip opening angle in the steady-state stage as determined by this test method,degreeDWTT = drop-weight tear testSE(B) = single-edge bend specimenS-SSM = simplified single-specimen CT
18、OA test method3.3 Definitions:3.3.1 crack-tip opening angle (CTOA), deg, nangleformed between the fractured surfaces measured at the cracktip.3.3.2 critical crack-tip-opening angle (CTOAB/2), deg,nsteady-state value of CTOA as measured by this testmethod, intended to approximate the CTOA on the mid-
19、thickness plane as the angle between the crack flanks. Thecrack flanks extend from the crack tip to one-half of the DWTTspecimen thickness (B/2) behind the crack tip (see Fig. 1)during steady-state propagation.3.3.2.1 DiscussionThe shape of the tearing crack is ini-tially dominated by a flat tunneli
20、ng region that often transitionsfrom flat to slant fracture, and tends to approach a constanttunneling shape after a crack extension of approximately onespecimen thickness. The CTOA tends to approach a constant,steady-state value (CTOAB/2) during propagation through themid-portion of the original li
21、gament. It must be recognized thatthe CTOA often depends on where it is measured, that is, atwhat distance behind the crack tip, and the measurement iscomplicated by tunneling. In this test method, CTOAB/2isdefined as the angle between the crack flanks extending fromthe crack tip to a distance B/2 a
22、long the crack surface. Thisparameter may be compared with optical measurements made,for example, using pictures of the specimen surface taken witha high-speed camera. Discussion of the optical method isincluded in Test Method E2472.3.3.2.2 DiscussionThis procedure uses CTOAB/2for thecritical crack-
23、tip-opening angle to distinguish it from theCTOAcin Test Method E2472 and ISO 22889, in which CTOAis measured or calculated at 1 mm behind the current crack tip.4. Summary and Significance4.1 The objective of this test method is to use measurementsof force (P) versus load-line displacement () to der
24、ive thecritical steady-state crack-tip opening angle (CTOAB/2) basedon the simplified single-specimen method (S-SSM) (2). TheS-SSM is a further development of the previous two-specimenCTOA method (3) and simplification of a single-specimenCTOA method (4). In addition, the calculation of CTOArequires
25、 a value for the plastic rotation factor (rp). For typicalpipe steels, values of rphave been estimated experimentally(5), and will be discussed in Section 8.4.2 The CTOAB/2value derived according to this testmethod is close to the value in the high-constraint mid-thickness region of the DWTT specime
26、ns, and is significantlylower than the surface CTOA values measured optically (5, 6).This reflects the effects of through-thickness constraint and theresulting crack-tip tunneling.4.3 Steady-state ductile crack propagation velocities rangebetween 12-20 m/s in DWTT specimens impacted with ahammer vel
27、ocity of 5 m/s. The crack velocity decreases astoughness increases (6). DWTT specimens of steels tested atroom temperature usually exhibit shear fracture under impactloading; that is, the flat (tunnelling) morphology at crackinitiation usually transitions to a near-45 slant fracture that isconsidere
28、d to be a shear morphology. For pipe steels, thismimics the fracture mode observed in full-scale pipe bursttests.4.4 The apparatus, specimen dimensions and testing proce-dure in this test method are the same as those described in TestMethod E436 or API RP 5L3 and Test Method E2298, seeSection 2. The
29、 intent is to adopt the standardized DWTT testprocedures, machines (for example, hammer and anvilsupports), and instrumentation requirements to the maximumFIG. 1 Measurement point for CTOAB/2and location of mid-thickness planeE3039 162extent possible. The following sections provide specificrequireme
30、nts, procedures and calculations for determiningCTOA.5. Apparatus5.1 The test shall be conducted using a test machine that hassufficient energy to completely break the specimen in oneimpact. The key dimensions, shown in Fig. 2, are: distancebetween supports (span) S = 254 mm (10 in.), radius of impa
31、cthammer striking edge = 25.4 mm (1 in.), and radius of fixedsupport anvils = 19 mm (0.75 in.). Drawings of the test fixtureand specimen can also be found in Test Method E436 or APIRP 5L3.5.2 The initial velocity v0 of the hammer at impact shall be5 m/s v0 10 m/s and shall be known within 6 5%, asdi
32、scussed below.5.3 For force measurement and displacement determination,the provisions of Test Method E2298 shall apply. Instrumen-tation 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 electronicsensor (piezoelectr
33、ic load cell, strain gauge load cell or a forcemeasurement derived from an accelerometer).5.4.2 The force measuring system (including strain gauges,wiring, and amplifier) shall have a bandwidth of at least 100kHz as discussed in Guide E1942.5.4.3 The signal shall be recorded without filtering. Post-
34、testfiltering, however, is allowed as detailed in Test MethodE2298, 7.2 but efforts should be taken to avoid introducingerrors through filtering, as discussed in Guide E1942.5.4.4 Calibration of the recorder and measurement systemmay be performed statically in accordance with the accuracyrequirement
35、s given in 5.4.4.1. For pendulum machines, it isrecommended that the force calibration be performed with thestriker attached to the pendulum assembly. The strain gaugesignal conditioning equipment, cables, and recording deviceshall be used in the calibration. In most cases, a computer isused for dat
36、a acquisition and the calibration shall be performedwith the voltage read from the computer. The intent is tocalibrate with the electronics and cables which are used duringactual testing.5.4.4.1 The static linearity and hysteresis error including allparts of the force measurement system up to the re
37、cordingapparatus shall be within 6 2 % of the recorded force, between50 % and 100 % of the nominal force range, and within 6 1%of the full scale force value between 10 % and 50 % of thenominal force range as detailed in Test Method E2298, 7.2.4.1.NOTE 1For testing in accordance with this test method
38、, it isrecommended to calibrate the instrumented striker up to 500 kN.5.4.5 Recalibration shall be performed if the instrumentedstriker has undergone dismantling or repair, unless it can beshown that removal of the striker from the test machine andsubsequent re-attachment to the machine does not aff
39、ect thecalibration.5.5 Displacement Determination:5.5.1 Displacement shall be measured using a non-contacting transducer according to 5.5.4 or calculated usingforce-time measurements with Newtons equations of motionas outlined in 5.5.2.5.5.2 Assuming a rigid striker of mass m with an initialvelocity
40、 v0the velocity v(t) at the contact point as a function ofelapsed time is calculated as:vt! 5 v021m*t0tPt!dt (1)If the specimen is assumed not to lift off at the anvils thebending displacement (t) is evaluated from:FIG. 2 Dimensions (in mm) of the machine-notched specimen (top) and supporting anvils
41、 (bottom). The anvils are fixed in position.E3039 163t! 5 *t0tvt!dt (2)5.5.3 For drop weight and pendulum machines, the initialimpact velocity needed to perform the above integrations iscalculated from:v05 =2gh0(3)where:g = local acceleration due to gravity, andh0= height of striker from point of re
42、lease to point of initialimpact.5.5.3.1 Alternatively, for drop weight and pendulummachines, it is acceptable to use for v0the optically measuredvelocity registered when the pendulum passes through itslowest position and strikes the specimen.5.5.4 Displacement can also be determined by non-contactin
43、g measurement of the displacement of the strikerrelative to the anvil using optical, inductive, or capacitivemethods. The signal transfer characteristics of the displace-ment measurement system shall correspond to that of the forcemeasuring system in order to minimize phase difference anddata skew e
44、rrors, as discussed in Guide E1942. The displace-ment measuring system shall be designed for maximumnominal values of 40 mm. Linearity errors in the measuringsystem shall yield measured values to within 6 2 % over arange of 1 mm to 40 mm. Measurements up to 1 mm may notbe sufficiently accurate to de
45、termine the displacement within 62 %. In this case, the displacement of the specimen shall bedetermined from the time measurement and the striker impactvelocity as indicated in Eq 1 and Eq 2.5.6 The recording apparatus (that is, high-speed data acqui-sition system and instrumented striker) shall com
46、ply with TestMethod E2298 Section 7. Data acquisition systems that arecommercially available for instrumented Charpy tests areacceptable if they meet the accuracy requirements defined herefor this test. Force-time data acquisition at a rate of 106/s (1MHz) or greater is required (5,6).6. Specimen6.1
47、 For seamless pipes, the specimen can be removed at anylocation, but for welded pipes the specimen shall be taken froma location approximately 90 from the weld (7). The specimensshall be oriented in C-L orientation according to TerminologyE1823-13. Other orientations and locations may be usedprovide
48、d they are agreed upon between the testing facility andthe client and reported with the test results. The specimenwidth and length shall be W = 76 mm and L = 305 mm (Fig.2).6.2 Specimens shall have full pipe thickness to avoid anyeffect that a reduction in thickness might have on CTOA.6.3 The specim
49、ens shall be flattened to remove the pipecurvature from the test specimen according to Test MethodE436 or API RP 5L3.6.4 Acceptable notches are a pressed notch with depth 5 mm6 0.5 mm as per Test Method E436 or API RP 5L3, or astraight machined notch with depth 10 mm 6 0.5 mm as shownin Fig. 2. It has been shown that pressed notches and straightnotches produce equivalent CTOAB/2values, that is, the type ofnotch does not strongly influence fracture propagation tough-ness or the slope of the force versus deflection curve beyondthe maximum force (8,
