1、Designation:E122106 Designation: E1221 10Standard Test Method forDetermining Plane-Strain Crack-Arrest Fracture Toughness,KIa, of Ferritic Steels1This standard is issued under the fixed designation E1221; the number immediately following the designation indicates the year oforiginal adoption or, in
2、the case 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 employs a side-grooved, crack-line-wedge-loaded specimen to obtain
3、a rapid run-arrest segment offlat-tensile separation with a nearly straight crack front. This test method provides a static analysis determination of the stressintensity factor at a short time after crack arrest. The estimate is denoted Ka. When certain size requirements are met, the test resultprov
4、ides an estimate, termed KIa, of the plane-strain crack-arrest toughness of the material.1.2 The specimen size requirements, discussed later, provide for in-plane dimensions large enough to allow the specimen to bemodeled by linear elastic analysis. For conditions of plane-strain, a minimum specimen
5、 thickness is also required. Bothrequirements depend upon the crack arrest toughness and the yield strength of the material. A range of specimen sizes maytherefore be needed, as specified in this test method.1.3 If the specimen does not exhibit rapid crack propagation and arrest, Kacannot be determi
6、ned.1.4 The values stated in SI units are to be regarded as the standards. The values given in parentheses are provided forinformation only.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard
7、to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E8 Test Methods for Tension Testing of Metallic MaterialsE23 Test Methods for Notched Bar Impact Testing of Metallic MaterialsE208 Tes
8、t Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic SteelsE399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness KIcof Metallic MaterialsE616 Terminology Relating to Fracture Testing (Discontinued 1996)E1304 Test Method for Plane-Strain
9、 (Chevron-Notch) Fracture Toughness of Metallic MaterialsE1823 Terminology Relating to Fatigue and Fracture Testing3. Terminology3.1 Definitions:3.1.1 Definitions in Terminology E1823 are applicable to this test method.3.2 Definitions of Terms Specific to This Standard:3.2.1 conditional value of the
10、 plane-strain crack-arrest fracture toughness, KQa(FL3/2) the conditional value of KIacalculated from the test results and subject to the validity criteria specified in this test method.3.2.1.1 DiscussionIn this test method, side-grooved specimens are used. The calculation of KQais based upon measur
11、ementsof both the arrested crack size and of the crack-mouth opening displacement prior to initiation of a fast-running crack and shortlyafter crack arrest.3.2.2 crack-arrest fracture toughness, KA(FL3/2)the value of the stress intensity factor shortly after crack arrest asdetermined from dynamic me
12、thods of analysis.1This test method is under the jurisdiction of ASTM Committee E08 on Fracture TestingFatigue and Fracture and is the direct responsibility of Subcommittee E08.07 onLinear-Elastic Fracture.Current edition approved Jan. 15, 2006. Published February 2006. Originally approved in 1988.
13、Last previous edition approved in 2002 as E122196 (2002). DOI:10.1520/E1221-06.on Fracture Mechanics.Current edition approved Nov. 1, 2010. Published March 2011. Originally approved in 1988. Last previous edition approved in 2006 as E1221 06. DOI:10.1520/E1221-10.2For referencedASTM standards, visit
14、 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.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standar
15、d 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 i
16、s to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.2.1 DiscussionThe in-plane specimen dimensions must be large enough for adequate enclosure of the crack-tip plasticzone by a linear-elastic s
17、tress field.3.2.3 crack-arrest fracture toughness, Ka(FL3/2)the value of the stress intensity factor shortly after crack arrest, asdetermined from static methods of analysis.3.2.3.1 DiscussionThe in-plane specimen dimensions must be large enough for adequate enclosure of the crack-tip plasticzone by
18、 a linear-elastic stress field.3.2.4 plane-strain crack-arrest fracture toughness, KIa(FL3/2)the value of crack-arrest fracture toughness, Ka, for a crackthat arrests under conditions of crack-front plane-strain.3.2.4.1 DiscussionThe requirements for attaining conditions of crack-front plane-strain
19、are specified in the procedures of thistest method.3.2.5 stress intensity factor at crack initiation, Ko(FL3/2)the value of K at the onset of rapid fracturing.3.2.5.1 DiscussionIn this test method, only a nominal estimate of the initial driving force is needed. For this reason, Koiscalculated on the
20、 basis of the original (machined) crack (or notch) size and the crack-mouth opening displacement at the initiationof a fast-running crack.4. Summary of Test Method4.1 This test method estimates the value of the stress intensity factor, K, at which a fast running crack will arrest. This testmethod is
21、 made by forcing a wedge into a split-pin, which applies an opening force across the crack starter notch in a modifiedcompact specimen, causing a run-arrest segment of crack extension. The rapid run-arrest event suggests need for a dynamicanalysis of test results. However, experimental observations
22、(1, 2)3indicate that, for this test method, an adjusted static analysisof test results provides a useful estimate of the value of the stress intensity factor at the time of crack arrest.4.2 Calculation of a nominal stress intensity at initiation, Ko, is based on measurements of the machined notch si
23、ze and thecrack-mouth opening displacement at initiation. The value of Kais based on measurements of the arrested crack size and thecrack-mouth opening displacements prior to initiation and shortly after crack arrest.5. Significance and Use5.1 In structures containing gradients in either toughness o
24、r stress, a crack may initiate in a region of either low toughness orhigh stress, or both, and arrest in another region of either higher toughness or lower stress, or both. The value of the stress intensityfactor during the short time interval in which a fast-running crack arrests is a measure of th
25、e ability of the material to arrest sucha crack. Values of the stress intensity factor of this kind, which are determined using dynamic methods of analysis, provide a valuefor the crack-arrest fracture toughness which will be termed KAin this discussion. Static methods of analysis, which are much le
26、sscomplex, can often be used to determine K at a short time (1 to 2 ms) after crack arrest. The estimate of the crack-arrest fracturetoughness obtained in this fashion is termed Ka. When macroscopic dynamic effects are relatively small, the difference betweenKAand Kais also small (1-4). For cracks p
27、ropagating under conditions of crack-front plane-strain, in situations where the dynamiceffects are also known to be small, KIadeterminations using laboratory-sized specimens have been used successfully to estimatewhether, and at what point, a crack will arrest in a structure (5, 6). Depending upon
28、component design, loading compliance, andthe crack jump length, a dynamic analysis of a fast-running crack propagation event may be necessary in order to predict whethercrack arrest will occur and the arrest position. In such cases, values of KIadetermined by this test method can be used to identify
29、those values of K below which the crack speed is zero. More details on the use of dynamic analyses can be found in Ref (4).5.2 This test method can serve at least the following additional purposes:5.2.1 In materials research and development, to establish in quantitative terms significant to service
30、performance, the effects ofmetallurgical variables (such as composition or heat treatment) or fabrication operations (such as welding or forming) on the abilityof a new or existing material to arrest running cracks.5.2.2 In design, to assist in selection of materials for, and determine locations and
31、 sizes of, stiffeners and arrestor plates.6. Apparatus6.1 The procedure involves testing of modified compact specimens that have been notched by machining. To minimize theintroduction of additional energy into the specimen during the run-arrest event, the loading system must have a low compliancecom
32、pared with the test specimen. For this reason a wedge and split-pin assembly is used to apply a force on the crack line. Thisloading arrangement does not permit easy measurement of opening forces. Consequently, opening displacement measurements inconjunction with crack size and compliance calibratio
33、ns are used for calculating Koand Ka.6.2 Loading Arrangement:6.2.1 A typical loading arrangement is shown in Fig. 1. The specimen is placed on a support block whose thickness should beadequate to allow completion of the test without interference between the wedge and the lower crosshead of the testi
34、ng machine.The support block should contain a hole that is aligned with the specimen hole, and whose diameter should be between 1.05 and1.15 times the diameter of the hole in the specimen. The force that pushes the wedge into the split-pin is transmitted through aforce transducer.3The boldface numbe
35、rs in parentheses refer to the list of references at the end of this test method.E1221 1026.2.1.1 The surfaces of the wedge, split-pin, support block, and specimen hole should be lubricated. Lubricant in the form ofthin (0.13 mm or 0.005 in.) strips of TFE-fluorocarbon is preferred. Molybdenum disul
36、fide (both dry and in a grease vehicle) andhigh-temperature lubricants can also be used.6.2.1.2 A low-taper-angle wedge and split-pin arrangement is used. If grease or dry lubricants are used, a matte finish (gritblasted) on the sliding surfaces may be helpful in avoiding galling. The split-pin must
37、 be long enough to contact the full specimenthickness, and the radius must be large enough to avoid plastic indentations of the test specimen. In all cases it is recommendedthat the diameter of the split-pin should be 0.13 mm (0.005in.) less than the diameter of the specimen hole. The wedge must bel
38、ong enough to develop the maximum expected opening displacement. Any air or oil hardening tool steel is suitable for makingthe wedge and split-pins. A hardness in the range from RC45 to RC55 has been used successfully. With the recommended wedgeangle and proper lubrication, a loading machine produci
39、ng15 to110 the expected maximum opening force is adequate. Thedimensions of a wedge and split-pin assembly suitable for use with a 25.4-mm (1.0-in.) diameter loading hole are shown in Fig.2. The dimensions should be scaled when other hole diameters are used. A hole diameter of 1.0 in. has been found
40、 satisfactory forspecimens having 125 W 170 mm (5 W 6.7 in.).NOTE 1Specimens tested with the arrangement shown in Fig. 1 may not exhibit an adequate segment of run-arrest fracturing, for example, at testingtemperatures well above the NDT temperature. In these circumstances, the use of the loading ar
41、rangement shown in Fig. 3 has been found to be helpful(2, 7) and may be employed.6.3 Displacement GagesDisplacement gages are used to measure the crack-mouth opening displacement at 0.25W from theload-line.Accuracy within 2 % over the working range is required. Either the gage recommended in Test Me
42、thod E399 or a similargage modified to accommodate conical seats is satisfactory. It is necessary to attach the gage in a fashion such that seating contactwith the specimen is not altered by the jump of the crack. Two methods that have proven satisfactory for doing this are shown inFig. 4. Other gag
43、es can be used so long as their accuracy is within 2 %.7. Specimen Configuration, Dimensions, and Preparation7.1 Standard Specimen:7.1.1 The configuration of a compact-crack-arrest (CCA) specimen that is satisfactory for low- and intermediatestrength steelsFIG. 1 Schematic Pictorial and Sectional Vi
44、ews Showing theStandard Arrangement of the Wedge and Split-Pin Assembly, theTest Specimen, and the Support BlockE1221 103is shown in Fig. 5. (In this context, an intermediate-strength steel is considered to be one whose static yield stress, sYS,isoftheorder of 700 MPa (100 ksi) or less.)7.1.1.1 The
45、thickness, B, shall be either full product plate thickness or a thickness sufficient to produce a condition ofplane-strain, as specified in 9.3.3.7.1.1.2 Side grooves of depth B/8 per side shall be used. For alloys that require notch-tip embrittlement (see 7.1.3.2) the sidegrooves should be introduc
46、ed after deposition of the brittle weld.7.1.1.3 The specimen width, W, shall be within the range 2B # W # 8B.7.1.1.4 The displacement gage shall measure opening displacements at an offset from the load line of 0.25W, away from thecrack tip.7.1.2 Specimen Dimensions:7.1.2.1 In order to limit the exte
47、nt of plastic deformation in the specimen prior to crack initiation, certain size requirements mustbe met. These requirements depend upon the material yield strength. They also depend upon Ka, and therefore the Koneeded toachieve an appropriate run-arrest event.7.1.2.2 The in-plane specimen dimensio
48、ns must be large enough to allow for the linear elastic analysis employed by this testmethod. These requirements are given in 9.3.2 and 9.3.4, in terms of allowable crack jump lengths.mm in.A 203 8.00B 8.4 0.33D 25.1 0.99E 25.4 1.00F 57.2 2.25G 50.8 2.00H 1.50 38.1NOTE 1The dimensions given are suit
49、able for use with a 25.4 mm (1.0 in.) diameter loading hole in a 50.8 mm (2.0 in.) thick test specimen. Thesedimensions should be scaled appropriately when other hole diameters and specimen thicknesses are used.FIG. 2 Suggested Geometry and Dimensions of a Wedge and Split-Pin AssemblyFIG. 3 Sectional View of a Loading Arrangement That May BeHelpful When Testing Specimens at Higher TemperaturesE1221 1047.1.2.3 For a test result to be termed plane-strain (KIa) by this test method, the specimen thickness, B, should meet therequirement given in 9.3.3.7.1.3 Star
