ASTM F2516-2018 Standard Test Method for Tension Testing of Nickel-Titanium Superelastic Materials.pdf

1、Designation: F2516 14F2516 18Standard Test Method forTension Testing of Nickel-Titanium Superelastic Materials1This standard is issued under the fixed designation F2516; 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 tension testing of superelastic nickel-titanium (nitinol) materials, specifically the metho

3、ds fordetermination of upper plateau strength, lower plateau strength, residual elongation, tensile strength, and elongation.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all

4、 of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.4 This international standard was d

5、eveloped in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Doc

6、uments2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical TestingE8E8/E8M Test Methods for Tension Testing of Metallic Materials Metric E0008_E0008ME83 Practice for Verification and Classification of Extensometer SystemsE111 Test Method for Youngs Modulus, Tangent Modulus, and Chord

7、 ModulusE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE1876 Test Method for Dynamic Youngs Modulus, Shear Modulus, and Poissons Ratio by Impulse Excitation of VibrationE3098 T

8、est Method for Mechanical Uniaxial Pre-strain and Thermal Free Recovery of Shape Memory AlloysF2004 Test Method for Transformation Temperature of Nickel-Titanium Alloys by Thermal AnalysisF2005 Terminology for Nickel-Titanium Shape Memory AlloysF2082/F2082M Test Method for Determination of Transform

9、ation Temperature of Nickel-Titanium Shape Memory Alloys byBend and Free Recovery3. Terminology3.1 The definitions of terms relating to tension testing appearing in Terminology E6 and the terms relating to nickel-titaniumshape memory alloys appearing in Terminology F2005 shall be considered as apply

10、ing to the terms used in this test method.Engineering stress and strain are assumed unless otherwise noted. Additional terms being defined are as follows (see Fig. 1):3.2 Definitions:3.2.1 alignment stress, nstress (not to exceed 7 MPa) applied to the specimen after it is installed in the grips to e

11、nsure thatthe specimen is straight and aligned to the grips.3.2.2 elongation at fracture (ElF), nelongation measured just prior to the sudden decrease in force associated with fracture.See Fig. 1 and X1.2. E63.2.2.1 Discussion1 This test method is under the jurisdiction of ASTM Committee F04 on Medi

12、cal and Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved Oct. 1, 2014Oct. 1, 2018. Published February 2015October 2018. Originally approved in 2005. Last previous edition approved in 20072014 asF2516 07F2516 14.2.

13、 DOI: 10.1520/F2516-14.10.1520/F2516-18.2 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.This document is not

14、an ASTM standard and is intended only to provide the user of an ASTM standard 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.

15、 In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Elongation at fracture results may be very sensitive to test variable

16、s such as test speed, specimen geometry, heat dissipation, surfacefinish, and alignment. See Test Methods E8/E8M.3.2.2.2 DiscussionCorrections for non-uniform strains between the extensometer attachments, including in the necked region, are beyond the scopeof this standard. See Test Methods E8/E8M.3

17、.2.3 fracture ductility (f), ntrue plastic strain at fracture. See X1.2. E63.2.3.1 DiscussionFor prismatic specimens, the fracture ductility is calculated as follows:f 5lnSAOAfD 5lnS 112RA%100D (1)where:AO = original cross-sectional area,Af = area at fracture of its smallest cross section after test

18、ing, andRA% = reduction of area, %. See Terminology E6.3.2.4 lower plateau strength (LPS)(LPS), nthe stress at 2.5 % strain during unloading of the sample, after loading to 6 %strain. See Fig. 1. E63.2.5 reduction of area percent (RA%), npercent difference between the original cross-sectional area o

19、f a tension test specimenand the area of its smallest cross section after fracture.3.2.5.1 DiscussionWhen the specimen necks prior to fracture, reduction in area provides a measure of the material ductility. The reduction of areaof a prismatic specimen is calculated using the difference in the origi

20、nal cross-sectional area, AO, of a specimen and the area atfracture of its smallest cross section, Af, after testing as follows:RA%5100%AO 2AfAO(2)FIG. 1 Terms Illustrated on Typical Stress-Strain Diagram of Superelastic NitinolF2516 1823.2.5.2 DiscussionFor measuring a specimens Af with an original

21、 circular or rectangular cross sections, see Test Methods E8/E8M, Section 7.12.3.2.6 residual elongation, Elrf% , %the difference between the strain at a stress of 7.0set stress at or between the alignmentstress and a maximum of 7 MPa during unloading and the strain at a stress of 7.0 MPa during loa

22、ding. that same set stress duringthe initial loading. See Fig. 1 and X1.4.3.2.7 uniform elongation, Elu%, %the elongation determined at the maximum force sustained by the test piece just priorto necking, or fracture, or both. See Fig. 1.3.2.7.1 DiscussionUniform elongation is not an accurate measure

23、 of ductility. See X1.2.3.2.8 upper plateau strength (UPS)the stress at 3 % strain during loading of the sample. See Fig. 1. E64. Summary of Test Method4.1 Using conventional tensile testing apparatus, the material is pulled to 6 % strain, then unloaded to less than 7 MPa, thenpulled to failure.5. S

24、ignificance and Use5.1 Tension tests provide information on the strength and ductility the elastic and plastic properties of materials under uniaxialtensile stresses.5.2 Tension tests, as described in this test method, also provide information on the superelasticity, as defined in TerminologyF2005,

25、of the material at the test temperature.6. Apparatus6.1 Apparatus is as described in Test Methods E8E8/E8M.7. Test Specimen7.1 Test specimens are as described in Test Methods E8E8/E8M.8. Procedure8.1 Procedure shall be per Test Methods E8E8/E8M with the following additions:8.1.1 Unless otherwise spe

26、cified, the temperature of the test shall be 22.0 6 2.0C. It is recommended that the material Thematerial should be tested at a temperature that is a minimum of 5C above the austenitic finish transformation temperature (Af) inorder to prevent testing of a partially transformed material. The temperat

27、ure of the test should be 22.0 6 2.0C or 37 6 2.0C,unless otherwise specified. See Terminology F2005 for the definition of Af. See Test Methods F2004, F2082/F2082M, and E3098to determine Af.8.1.2 The free-running crosshead speed shall be limited per Table 1. See X1.3.8.1.3 The test shall consist of

28、zeroing the force transducer, test machine per Test Method E8/E8M, gripping the specimen,loading the specimen to the alignment stress, pulling the specimen to 6 % strain, reversing the motion to unload the specimen toless than 7 MPa, the alignment stress, and then pulling the specimen to failure. Se

29、e X1.4.TABLE 1 Crosshead Speed Limitsd, diameter orthickness (mm)AMaximum crosshead speed in mm/min per mmof initial length of reduced section (or initialdistance between grips for specimens nothaving reduced sections)First Cycle(load to 6 % strainand unload)Second Cycle(load to failure)d # 0.2 0.08

30、 0.80.2 2.5 0.01 0.1A For tubing, use d that gives an equivalent surface area to diameter ratio; forround tubing, d = (outer diameter) (inner diameter).F2516 1838.1.4 For materials with diameter greater than 0.2 mm, strain shall be determined by use of a calibrated extensometer of classC or better (

31、see Practice E83). For materials with diameter less than or equal to 0.2 mm, strain may be determined by use of anextensometer or by crosshead motion. When using crosshead motion to calculate strain, the length between the grips must be shallbe a minimum of 150 mm. See X1.5.NOTE 1It is recommended t

32、hat strain Strain should be measured using extensometer versus crosshead displacement as this will result in a moreaccurate measurement of strain.8.1.4.1 When using a clip-on extensometer with small-diameter wire, care mustshall be taken not to bend or distort the wirewhen attaching the extensometer

33、.8.1.5 Upper plateau strength shall be determined as the value of the stress at a strain of 3.0 % during the initial loading of thespecimen.8.1.6 Lower plateau strength shall be determined as the value of the stress at a strain of 2.5 % during the unloading of thespecimen.8.1.7 Residual elongation s

34、hall be determined by the difference between the strain at a stress of 7.0set stress at or between thealignment stress and a maximum of 7 MPa during unloading and the strain at a stress of 7.0 MPa during that same set stress duringthe initial loading.8.1.8 The uniform elongation shall be determined

35、by elongation when the maximum force is reached just prior to necking orfracture, or both.8.1.9 The elongation at fracture shall be determined by elongation measured just prior to the sudden decrease in force associatedwith fracture.9. Report9.1 The report shall include the following information, un

36、less otherwise specified:9.1.1 Material and sample identification,9.1.2 Specimen type,9.1.3 Upper plateau strength,9.1.4 Lower plateau strength,9.1.5 Residual elongation,9.1.6 Tensile strength,9.1.7 Uniform elongation, if required,9.1.8 Elongation at fracture,9.1.9 Test temperature,9.1.10 Strain det

37、ermination method (extensometer or crosshead),9.1.11 Crosshead speed, and9.1.12 Gage length (length of reduced section or distance between grips for specimens not having reduced sections).10. Precision and Bias310.1 An interlaboratory study was conducted in accordance with Practice E691 using three

38、different diameters of superelasticwire. For wire diameters of 0.2 and 0.5 mm, eleven laboratories participated in the study with each laboratory obtaining threeresults for each diameter. For the 2.5 mm diameter wire, eight laboratories participated in the study with each laboratory obtainingthree r

39、esults. The details are given in ASTM Research Report RR:F04-1010.310.2 The results are summarized in Tables 2-6 for each tensile parameter. The terms repeatability limit and reproducibility limitare used as specified in Practice E177.10.3 No measurement of bias is possible with this test method sin

40、ce there is presently no accepted reference material.11. Keywords11.1 lower plateau strength; nickel titanium; nitinol; residual elongation; shape memory; superelasticity; upper plateau strength3 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Res

41、earch Report RR:F04-1010.TABLE 2 Precision of Upper Plateau Strength (MPa)Diameter (mm) Grand Mean RepeatabilityStandard DeviationReproducibilityStandard DeviationRepeatabilityLimitReproducibilityLimit0.2 499 13 55 36 1540.5 492 11 35 30 982.5 500 13 25 35 71F2516 184APPENDIXES(Nonmandatory Informat

42、ion)X1. RATIONALEX1.1 During tensile testing of superelastic nitinol material, heat is given off during the austenite-to-martensite transformation.Strain rate is limited to allow the heat to transfer out of the specimen. Otherwise the increase in specimen temperature willinfluence the stress-strain

43、response.4X1.1 Measurement of modulus of elasticity requires very precise measurements beyond the scope of this standard. test method.Test Methods E111and E1876 address determination of modulus of elasticity. For superelastic nitinol, the dynamic method (TestMethod E1876) is preferred. Note that the

44、 modulus of elasticity exhibits large variation with the martensitic transformation.trans-formation (1).4X1.2 Tensile loading of nickel-titanium superelastic materials to fracture will generally encompass elastic strains, phasetransformation strains, martensite reorientation strains (twinning) and p

45、lastic strains (2). Tensile loading following plastic yieldingand the accompanying drop in tangent modulus, usually results in an instability that localizes the highest stress into a narrowedneck region and ends in fracture. The Uniform Elongation measurement, which is determined at the onset of nec

46、king, is not anaccurate measure of ductility. However, Uniform Elongation can be useful as a process control measure. Elongation at Fractureprovides an overall elongation value that includes elongation between the extensometer attachment points, including the neckingelongation, but is dependent on t

47、he gage length and underestimates the strain in the necked fracture region. Conventionally,Reduction of Area and Fracture Ductility are used to estimate the high strains in the necked region. They are interpreted asmeasures of material ductility, the ability of a material to deform plastically befor

48、e fracturing (see Terminology E6). In addition,4 Shaw, J. A. and Kyriakides, S., “On the Nucleation and Propagation of Phase Transformation Fronts in a NiTi Alloy”, Acta Mater, Vol 45, No. 2, 1997, pp. 683700.4 Spinner, S. and Rozner,A. G., “Elastic Properties of NiTi as a Function of Temperature”,

49、The Journal ofAcoustical Society ofAmerica,boldface numbers in parenthesesrefer to a list of references at the end of this Vol. 40, No. 5, 1966, pp. 10091015.standard.TABLE 3 Precision of Lower Plateau Strength (MPa)Diameter (mm) Grand Mean RepeatabilityStandard DeviationReproducibilityStandard DeviationRepeatabilityLimitReproducibilityLimit0.2 196 10 35 27 970.5 146 9 27 26 752.5 138 13 19 36 52TABLE 4 Precision of Residual Elongation (%)Diameter (mm) Grand Mean RepeatabilityStandard DeviationReproducibilityStandard DeviationRepeatabi