1、Designation: E1921 16E1921 17Standard Test Method forDetermination of Reference Temperature, To, for FerriticSteels in the Transition Range1This standard is issued under the fixed designation E1921; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of revision, the 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 a reference temperature, To, which characteri
3、zes the fracture toughness offerritic steels that experience onset of cleavage cracking at elastic, or elastic-plastic KJc instabilities, or both. The specific typesof ferritic steels (3.2.1) covered are those with yield strengths ranging from 275 to 825 MPa (40 to 120 ksi) and weld metals, afterstr
4、ess-relief annealing, that have 10 % or less strength mismatch relative to that of the base metal.1.2 The specimens covered are fatigue precracked single-edge notched bend bars, SE(B), and standard or disk-shaped compacttension specimens, C(T) or DC(T). A range of specimen sizes with proportional di
5、mensions is recommended. The dimension onwhich the proportionality is based is specimen thickness.1.3 Median KJc values tend to vary with the specimen type at a given test temperature, presumably due to constraint differencesamong the allowable test specimens in 1.2. The degree of KJc variability am
6、ong specimen types is analytically predicted to be afunction of the material flow properties (1)2 and decreases with increasing strain hardening capacity for a given yield strengthmaterial. This KJc dependency ultimately leads to discrepancies in calculated To values as a function of specimen type f
7、or the samematerial. To values obtained from C(T) specimens are expected to be higher than To values obtained from SE(B) specimens. Bestestimate comparisons of several materials indicate that the average difference between C(T) and SE(B)-derived To values isapproximately 10C (2). C(T) and SE(B) To d
8、ifferences up to 15C have also been recorded (3). However, comparisons ofindividual, small datasets may not necessarily reveal this average trend. Datasets which contain both C(T) and SE(B) specimensmay generate To results which fall between the To values calculated using solely C(T) or SE(B) specim
9、ens. It is therefore stronglyrecommended that the specimen type be reported along with the derived To value in all reporting, analysis, and discussion ofresults. This recommended reporting is in addition to the requirements in 11.1.1.1.4 Requirements are set on specimen size and the number of replic
10、ate tests that are needed to establish acceptablecharacterization of KJc data populations.1.5 To is dependent on loading rate. To is evaluated for a quasi-static loading rate range with 0.1 2 MPam/s) in Annex A1.1.6 The statistical effects of specimen size on KJc in the transition range are treated
11、using the weakest-link theory (4) appliedto a three-parameter Weibull distribution of fracture toughness values. A limit on KJc values, relative to the specimen size, isspecified to ensure high constraint conditions along the crack front at fracture. For some materials, particularly those with lowst
12、rain hardening, this limit may not be sufficient to ensure that a single-parameter (KJc) adequately describes the crack-frontdeformation state (5).1.7 Statistical methods are employed to predict the transition toughness curve and specified tolerance bounds for 1T specimensof the material tested. The
13、 standard deviation of the data distribution is a function of Weibull slope and median KJc. The procedurefor applying this information to the establishment of transition temperature shift determinations and the establishment of tolerancelimits is prescribed.1.8 This test method assumes that the test
14、 material is macroscopically homogeneous such that the materials have uniform tensileand toughness properties. The fracture toughness evaluation of nonuniform materials is not amenable to the statistical analysismethods employed in the main body of this test method. Application of the analysis of th
15、is test method to an inhomogeneous1 This test method is under the jurisdiction of ASTM Committee E08 on Fatigue and Fracture and is the direct responsibility of E08.07 on Fracture Mechanics.Current edition approved May 15, 2016Jan. 1, 2017. Published August 2016May 2017. Originally approved in 1997.
16、 Last previous edition approved in 20152016 asE1921 15aE1921 16.1. DOI: 10.1520/E1921-16.10.1520/E1921-17.2 The boldface numbers in parentheses refer to the list of references at the end of this standard.This document is not an ASTM standard and is intended only to provide the user of an ASTM standa
17、rd an indication of what changes have been made to the previous version. Becauseit 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 versionof the standard as published by ASTM
18、is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1material will result in an inaccurate estimate of the transition reference value To and non-conservative confidence bounds. Forexample, multipas
19、s weldments can create heat-affected and brittle zones with localized properties that are quite different fromeither the bulk material or weld. Thick section steels also often exhibit some variation in properties near the surfaces.Metallography and initial screening may be necessary to verify the ap
20、plicability of these and similarly graded materials. Anappendix to analyze the cleavage toughness properties of nonuniform or inhomogeneous materials is currently being prepared. Inthe interim, users are referred to (6-8) for procedures to analyze inhomogeneous materials.1.9 This standard does not p
21、urport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E4
22、 Practices for Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing of Metallic MaterialsE23 Test Methods for Notched Bar Impact Testing of Metallic MaterialsE74 Practice of Calibration of Force-Measuring Instruments for Verifying the Force Indication of Testing MachinesE111
23、 Test Method for Youngs Modulus, Tangent Modulus, and Chord ModulusE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE208 Test Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic SteelsE399 Test Method for Linear-Elastic Plan-S
24、train Fracture Toughness KIc of Metallic MaterialsE436 Test Method for Drop-Weight Tear Tests of Ferritic SteelsE561 Test Method for KR Curve DeterminationE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE1820 Test Method for Measurement of Fracture To
25、ughnessE1823 Terminology Relating to Fatigue and Fracture Testing2.2 ASME Standards:4ASME Boiler and Pressure Vessel Code, Section II, Part D3. Terminology3.1 Terminology given in Terminology E1823 is applicable to this test method.3.2 Definitions:3.2.1 ferritic steelstypically carbon, low-alloy, an
26、d higher alloy grades. Typical microstructures are bainite, tempered bainite,tempered martensite, and ferrite and pearlite. All ferritic steels have body centered cubic crystal structures that displayductile-to-cleavage transition temperature fracture toughness characteristics. See also Test Methods
27、 E23, E208 and E436.3.2.1.1 DiscussionThis definition is not intended to imply that all of the many possible types of ferritic steels have been verified as being amenableto analysis by this test method.3.2.2 stress-intensity factor, K FL 3/2the magnitude of the mathematically ideal crack-tip stress
28、field coefficient (stress fieldsingularity) for a particular mode of crack-tip region deformation in a homogeneous body.3.2.2.1 DiscussionIn this test method, Mode I is assumed. See Terminology E1823 for further discussion.3.2.3 J-integral, J FL1a mathematical expression; a line or surface integral
29、that encloses the crack front from one cracksurface to the other; used to characterize the local stress-strain field around the crack front (9). See Terminology E1823 for furtherdiscussion.3.3 Definitions of Terms Specific to This Standard:3.3.1 control force, Pm Fa calculated value of maximum force
30、, used in 7.8.1 to stipulate allowable precracking limits.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 A
31、vailable from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Two Park Ave., New York, NY 10016-5990, http:/www.asme.org.E1921 1723.3.2 crack initiationdescribes the onset of crack propagation from a preexisting macroscopic crack created in the specimenby a stipulat
32、ed procedure.3.3.3 effective modulus, Eeff FL2an elastic modulus that allows a theoretical (modulus normalized) compliance to match anexperimentally measured compliance for an actual initial crack size, ao.3.3.4 effective yield strength, Y FL-2, an assumed value of uniaxial yield strength that repre
33、sents the influence of plasticyielding upon fracture test parameters.3.3.4.1 DiscussionIt is calculated as the average of the 0.2 % offset yield strength YS, and the ultimate tensile strength, TS as follows:Y 5YS1TS23.3.5 elastic modulus, E FL2a linear-elastic factor relating stress to strain, the v
34、alue of which is dependent on the degreeof constraint. For plane stress, E = E is used, and for plane strain, E/(1 v2) is used, with E being Youngs modulus and v beingPoissons ratio.3.3.6 elastic plastic Jc FL1J-integral at the onset of cleavage fracture.3.3.7 elastic-plastic KJ FL3/2 An elastic-pla
35、stic equivalent stress intensity factor derived from the J-integral.3.3.7.1 DiscussionIn this test method, KJ also implies a stress intensity factor determined at the test termination point under conditions that requirecensoring the data by 8.9.2.3.3.8 elastic-plastic KJc FL3/2an elastic-plastic equ
36、ivalent stress intensity factor derived from the J-integral at the point ofonset of cleavage fracture, Jc.3.3.9 equivalent value of median toughness, K Jcmed!eqFL-3/2an equivalent value of the median toughness for a multi-temperature data set.3.3.10 Eta ()a dimensionless parameter that relates plast
37、ic work done on a specimen to crack growth resistance defined interms of deformation theory J-integral (10).3.3.11 failure probability, pfthe probability that a single selected specimen chosen at random from a population of specimenswill fail at or before reaching the KJc value of interest.3.3.12 in
38、itial ligament length, bo L the distance from the initial crack tip, ao, to the back face of a specimen.3.3.13 load-line displacement rate,LLLT-1rate of increase of specimen load-line displacement.3.3.14 pop-ina discontinuity in a force versus displacement test record (11).3.3.14.1 DiscussionA pop-i
39、n event is usually audible, and is a sudden cleavage crack initiation event followed by crack arrest. The test record willshow increased displacement and drop in applied force if the test frame is stiff. Subsequently, the test record may continue on tohigher forces and increased displacements.3.3.15
40、 precracked Charpy, PCC, specimenSE(B) specimen with W = B = 10 mm (0.394 in.).3.3.16 provisional reference temperature, (ToQ) CInterim To value calculated using the standard test method describedherein. ToQ is validated as To in 10.5.3.3.17 reference temperature, To CThe test temperature at which t
41、he median of the KJc distribution from 1T size specimenswill equal 100 MPam (91.0 ksiin.).3.3.18 SE(B) specimen span, S Lthe distance between specimen supports (See Test Method E1820 Fig. 3).3.3.19 specimen thickness, B Lthe distance between the parallel sides of a test specimen as depicted in Fig.
42、13.3.3.19.1 DiscussionIn the case of side-grooved specimens, the net thickness, BN, is the distance between the roots of the side-groove notches.3.3.20 specimen size, nTa code used to define specimen dimensions, where n is expressed in multiples of 1 in.E1921 1733.3.20.1 DiscussionIn this method, sp
43、ecimen proportionality is required. For compact specimens and bend bars, specimen thickness B = n inches.3.3.21 temperature, TQ CFor KJc values that are developed using specimens or test practices, or both, that do not conformto the requirements of this test method, a temperature at which KJc (med)
44、= 100 MPam is defined as TQ. TQ is not a provisionalvalue of To.3.3.22 time to control force, tm T,time to Pm.3.3.23 Weibull fitting parameter, K0a scale parameter located at the 63.2 % cumulative failure probability level (12).KJc = K0when pf = 0.632.3.3.24 Weibull slope, bwith pf and KJc data pair
45、s plotted in linearized Weibull coordinates obtainable by rearranging Eq 17,b is the slope of a line that defines the characteristics of the typical scatter of KJc data.3.3.24.1 DiscussionA Weibull slope of 4 is used exclusively in this method.3.3.25 yield strength, YS FL2the stress at which a mater
46、ial exhibits a specific limiting deviation from the proportionalityof stress to strain at the test temperature. This deviation is expressed in terms of strain.3.3.25.1 DiscussionIt is customary to determine yield strength by either (1) Offset Method (usually a strain of 0.2 % is specified) or (2)Tot
47、al-Extension-Under-Force Method (usually a strain of 0.5 % is specified although other values of strain may be used).3.3.25.2 DiscussionWhenever yield strength is specified, the method of test must be stated along with the percent offset or total strain under force.The values obtained by the two met
48、hods may differ.4. Summary of Test Method4.1 This test method involves the testing of notched and fatigue precracked bend or compact specimens in a temperature rangewhere either cleavage cracking or crack pop-in develop during the loading of specimens. Crack aspect ratio, a/W, is nominally 0.5.Speci
49、men width in compact specimens is two times the thickness. In bend bars, specimen width can be either one or two timesthe thickness.4.2 Force versus displacement across the notch at a specified location is recorded by autographic recorder or computer dataacquisition, or both. Fracture toughness is calculated at a defined condition of crack instability. The J-integral value at instability,Jc, is calculated and converted into its equivalent in units of stress intens
