ASTM B771-11(2017) Standard Test Method for Short Rod Fracture Toughness of Cemented Carbides.pdf
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1、Designation: B771 11 (Reapproved 2017)Standard Test Method forShort Rod Fracture Toughness of Cemented Carbides1This standard is issued under the fixed designation B771; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 the fracturetoughness of cemented carbides (KIcSR) by testing slotted shor
3、trod or short bar specimens.1.2 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.3 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 s
4、tandard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles
5、for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic Materials3. Termin
6、ology Definitions3.1 stress intensity factor, Kl,(dimensional units FL3/2)the magnitude of the ideal-crack-tip stress field for mode 1 ina linear-elastic body.NOTE 1Values of K for mode l are given by:Kl5 limit y=2r# (1)r0where:r = distance directly forward from the crack tip to alocation where the
7、significant stress yis calculated,andy= principal stress normal to the crack plane.3.2 Abbreviations: fracture toughness of cemented carbide,KIcSR,(dimensional units FL3/2)the material-toughnessproperty measured in terms of the stress-intensity factor Klbythe operational procedure specified in this
8、test method.4. Summary of Test Method4.1 This test method involves the application of an openingload to the mouth of the short rod or short bar specimen whichcontains a chevron-shaped slot. Load versus displacementacross the slot at the specimen mouth is recorded autographi-cally. As the load is inc
9、reased, a crack initiates at the point ofthe chevron slot and slowly advances longitudinally, tending tosplit the specimen in half. The load goes through a smoothmaximum when the width of the crack front is about one thirdof the specimen diameter (short rod) or breadth (short bar).Thereafter, the lo
10、ad decreases with further crack growth. Twounloading-reloading cycles are performed during the test tomeasure the effects of any macroscopic residual stresses in thespecimen. The fracture toughness is calculated from themaximum load in the test and a residual stress parameter whichis evaluated from
11、the unloading-reloading cycles on the testrecord.5. Significance and Use5.1 The property KIcSRdetermined by this test method isbelieved to characterize the resistance of a cemented carbide tofracture in a neutral environment in the presence of a sharpcrack under severe tensile constraint, such that
12、the state ofstress near the crack front approaches tri-tensile plane strain,and the crack-tip plastic region is small compared with thecrack size and specimen dimensions in the constraint direction.AKIcSRvalue is believed to represent a lower limiting value offracture toughness. This value may be us
13、ed to estimate therelation between failure stress and defect size when theconditions of high constraint described above would be ex-pected. Background information concerning the basis for1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and i
14、s the direct responsibility of Subcom-mittee B09.06 on Cemented Carbides.Current edition approved April 1, 2017. Published April 2017. Originallyapproved in 1987. Last previous edition approved in 2011 as B771 111. DOI:10.1520/B0771-11E01R17.2For referenced ASTM standards, visit the ASTM website, ww
15、w.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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis i
16、nternational standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT)
17、 Committee.1development of this test method in terms of linear elasticfracture mechanics may be found in Refs (1-7).35.2 This test method can serve the following purposes:5.2.1 To establish, in quantitative terms significant to ser-vice performance, the effects of fabrication variables on thefractur
18、e toughness of new or existing materials, and5.2.2 To establish the suitability of a material for a specificapplication for which the stress conditions are prescribed andfor which maximum flaw sizes can be established withconfidence.6. Specimen Configuration, Dimensions, and Preparation6.1 Both the
19、round short rod specimen and the rectangularshaped short bar specimen are equally acceptable and havebeen found to have the same calibration (5). The short roddimensions are given in Fig. 1; the short bar in Fig. 2.6.2 Grip SlotDepending on the apparatus used to test thespecimen, a grip slot may be
20、required in the specimen frontface, as shown in Fig. 3. The surfaces in the grip slot shall havea smooth ground finish so that the contact with each grip willbe along an essentially continuous line along the entire gripslot, rather than at a few isolated points or along a shortsegment within the gri
21、p slot.6.3 Crack-Guiding SlotsThese may be ground using adiamond abrasive wheel of approximately 124 6 3 mm (4.9 60.1 in.) diameter, with a thickness of 0.36 6 0.01 mm (0.01406 0.0005 in.). The resulting slots in the specimen are slightly3The boldface numbers in parentheses refer to the list of refe
22、rences at the end ofthis standard.Standard DimensionsShort Rod(mm) (in.)B = 12.700 0.025 0.500 0.001W = 19.050 0.075 0.750 0.003 = 0.381 0.025 0.015 0.001For Curved Slot Optionao= 6.350 0.075 0.250 0.003 = 58.0 0.5R = 62.23 1.27 02.45 0.05For Straight Slot Optionao= 6.744 0.075 0.266 0.003 = 55.2 0.
23、5R=FIG. 1 Short Rod SpecimenStandard DimensionsShort Bar(mm) (in.)B = 12.700 0.025 0.500 0.001H = 11.050 0.025 0.435 0.001W = 19.050 0.075 0.750 0.003 = 0.381 0.025 0.015 0.001For Curved Slot Optionao= 6.350 0.075 0.250 0.003 = 58.0 0.5R = 62.23 1.27 2.45 0.05For Straight Slot Optionao= 6.744 0.075
24、0.266 0.003 = 55.2 0.5R=FIG. 2 Short Bar SpecimenNOTE 1The dashed lines show the front face profile of Figs. 1 and 2without grip slot.FIG. 3 Short Rod and Short Bar Grip Slot in Specimen Front FaceB771 11 (2017)2thicker than the diamond wheel (0.38 6 0.02 mm, or 0.015 60.001 in.). A diamond concentr
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