1、Designation: E494 10Standard Practice forMeasuring Ultrasonic Velocity in Materials1This standard is issued under the fixed designation E494; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pa
2、rentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This specification has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This practice covers a test procedure for measuringultrasoni
3、c velocities in materials with conventional ultrasonicpulse echo flaw detection equipment in which results aredisplayed in an A-scan display. This practice describes amethod whereby unknown ultrasonic velocities in a materialsample are determined by comparative measurements using areference material
4、 whose ultrasonic velocities are accuratelyknown.1.2 This procedure is intended for solid materials 5 mm (0.2in.) thick or greater. The surfaces normal to the direction ofenergy propagation shall be parallel to at least 63. Surfacefinish for velocity measurements shall be 3.2 m (125 in.) rmsor smoot
5、her.NOTE 1Sound wave velocities are cited in this practice using thefundamental units of metres per second, with inches per second suppliedfor reference in many cases. For some calculations, it is convenient tothink of velocities in units of millimetres per microsecond. While theseunits work nicely
6、in the calculations, the more natural units were chosenfor use in the tables in this practice. The values can be simply convertedfrom m/s to mm/s by moving the decimal point three places to the left,that is, 3500 m/s becomes 3.5 mm/s.1.3 Ultrasonic velocity measurements are useful for deter-mining s
7、everal important material properties.Youngs modulusof elasticity, Poissons ratio, acoustic impedance, and severalother useful properties and coefficients can be calculated forsolid materials with the ultrasonic velocities if the density isknown (see Appendix X1).1.4 More accurate results can be obta
8、ined with more spe-cialized ultrasonic equipment, auxiliary equipment, and spe-cialized techniques. Some of the supplemental techniques aredescribed in Appendix X2. (Material contained in AppendixX2 is for informational purposes only.)NOTE 2Factors including techniques, equipment, types of material,
9、and operator variables will result in variations in absolute velocityreadings, sometimes by as much as 5 %. Relative results with a singlecombination of the above factors can be expected to be much moreaccurate (probably within a 1 % tolerance).1.5 The values stated in SI units are to be regarded as
10、standard.1.6 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 regulatory limitations prior to use.2. Ref
11、erenced Documents2.1 ASTM Standards:2C597 Test Method for Pulse Velocity Through ConcreteE317 Practice for Evaluating Performance Characteristicsof Ultrasonic Pulse-Echo Testing Instruments and Systemswithout the Use of Electronic Measurement InstrumentsE543 Specification for Agencies Performing Non
12、destruc-tive TestingE797 Practice for Measuring Thickness by Manual Ultra-sonic Pulse-Echo Contact MethodE1316 Terminology for Nondestructive Examinations2.2 ASNT Documents:3SNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and CertificationASNI/ASNT-CP-189 Standard fo
13、r Qualification and Certi-fication of Nondestructive Testing Personnel2.3 AIA Document:4NAS-410 Certification and Qualification of NondestructiveTesting Personnel3. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, see Terminology E1316.1This practice is under the jurisdicti
14、on of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.06 onUltrasonic Method.Current edition approved Sept. 1, 2010. Published October 2010. Originallyapproved in 1973. Last previous edition approved in 2001 as E494 - 05. DOI:10.1520/E0494-10.2For r
15、eferenced 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.3Available fromAmerican Society for Nondestructive Testing (ASNT),
16、P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1250Eye St., NW, Washington, DC 20005.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harb
17、or Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Practice4.1 Several possible modes of vibration can propagate insolids. This procedure is concerned with two velocities ofpropagation, namely those associated with longitudinal (vl) andtransverse (vt) waves. The lon
18、gitudinal velocity is independentof sample geometry when the dimensions at right angles to thebeam are very large compared with beam area and wave length.The transverse velocity is little affected by physical dimensionsof the sample.The procedure described in Section 8 is, as notedin the scope, for
19、use with conventional pulse echo flawdetection equipment only.5. Significance and Use5.1 This practice describes a test procedure for the applica-tion of conventional ultrasonic methods to determine velocityin materials wherein unknown ultrasonic velocities in a mate-rial sample are determined by co
20、mparative measurementsusing a reference material whose ultrasonic velocities areaccurately known.5.2 Although not all methods described in this practice areapplied equally or universally to all velocity measurements indifferent materials, it does provide flexibility and a basis forestablishing contr
21、actual criteria between users, and may beused as a general guideline for preparing a detailed procedureor specification for a particular application.5.3 This practice is directed towards the determination oflongitudinal and shear wave velocities using the appropriatesound wave form. This practice al
22、so outlines methods todetermine elastic modulus and can be applied in both contactand immersion mode.6. Basis of Application6.1 The following items are subject to contractual agree-ment between the parties using or referencing this practice:6.2 Personnel QualificationIf specified in the contractuala
23、greement, personnel performing to this practice shall bequalified in accordance with a nationally or internationallyrecognized NDT personnel qualification practice or standardsuch as ASNI/ASNT-CP-189, SNT-TC-1A, NAS-410,orasimilar document and certified by the employer or certifyingagency, as applic
24、able. The practice or standard used and itsapplicable revision shall be identified in the contractual agree-ment between the using parties.6.3 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E543.
25、 The applicableedition of Practice E543 shall be specified in the contractualagreement.7. Apparatus7.1 The ultrasonic testing system to be used in this practiceshall include the following:7.1.1 Test InstrumentAny ultrasonic instrument compris-ing a time base, transmitter (pulser), receiver (echo amp
26、lifier),and anA-scan indicator circuit to generate, receive, and displayelectrical signals related to ultrasonic waves. Equipment shallallow reading the positions of Ak, As, At, Al(defined in 8.1.4 and8.2.4), along the A-scan base line within 60.5 mm (0.020 in.).For maximum accuracy, the highest pos
27、sible frequency thatwill present at least two easily distinguishable back echoreflections, and preferably five, shall be used.7.1.2 Search UnitThe search unit containing a search unitthat generates and receives ultrasonic waves of an appropriatesize, type and frequency, designed for tests by the con
28、tactmethod shall be used. Contact straight beam longitudinal modeshall be used for longitudinal velocity measurements, andcontact straight beam shear mode for transverse velocitymeasurements.7.1.3 CouplantFor longitudinal velocity measurements,the couplant should be the material used in practice, fo
29、rexample, clean light-grade oil. For transverse velocity mea-surements, a high viscosity material such as resin or solid bondshall be used. In some materials isopolybutene, honey, or otherhigh-viscosity materials have been used effectively. Mostliquids will not support transverse waves. In porous ma
30、terialsspecial nonliquid couplants are required. The couplant mustnot be deleterious to the material.7.1.4 Standard Reference Blocks:7.1.4.1 Velocity StandardAny material of known velocity,that can be penetrated by the acoustical wave, and that has anappropriate surface roughness, shape, thickness,
31、and parallel-ism. The velocity of the standard should be determined bysome other technique of higher accuracy, or by comparisonwith water velocity that is known (see Appendix X2.5 andAppendix X4). The reference block should have an attenuationsimilar to that of the test material.7.1.4.2 For horizont
32、al linearity check, see Practice E317.8. Procedure8.1 Longitudinal Wave VelocityDetermine bulk, longitu-dinal wave velocity (vl) by comparing the transit time of alongitudinal wave in the unknown material to the transit timeof ultrasound in a velocity standard (vk).8.1.1 Select samples of each with
33、flat parallel surfaces andmeasure the thickness of each to an accuracy of 60.02 mm(0.001 in.) or 0.1 %, whichever is greater.8.1.2 Align the search unit over each sample and obtain anominal signal pattern (see Fig. 1) of as many back echoes asare clearly defined. The time base (sweep control) must b
34、e setthe same for both measurements.8.1.3 Using a scale or caliper measure the distance at thebase line between the leading edge of the first back echo andthe leading edge of the last back echo that is clearly defined onthe known and unknown sample. For better accuracy, adjust theamplitude of the la
35、st back echo by means of the gain control toapproximately the same height as the first back echo, after theFIG. 1 Initial Pulse and 7 Back EchoesE494 102position of the leading edge of the first back echo has beenfixed. This allows more accurate time or distance measure-ments. The position of the le
36、ading edge of the last back echo isthen determined. The signal has traversed a distance twice thethickness of the specimen between each back echo. The signaltraversing the specimen and returning is called a round trip. InFig. 1 the signal has made six round trips between Echo 1 andEcho 7. Count the
37、number of round trips from first echo usedto the last echo measured on both samples. This number will beone less than the number of echoes used. Note that the samplethickness, number of round trips, and distance from front to lastback echo measured need not be the same.8.1.4 Calculate the value of t
38、he unknown velocity as fol-lows:v15 Aknltlvk!/Alnktk! (1)where:Ak= distance from first to Nth back echo on the knownmaterial, m (in.), measured along the baseline of theA-scan display,nl= number of round trips, unknown material,tl= thickness of unknown material, m (in.),vk= velocity in known materia
39、l, m/s (in./s),Al= distance from the first to the Nth back echo on theunknown material, m (in.), measured along thebaseline of the A-scan display,nk= number of round trips, known material, andtk= thickness, known material, m (in.).NOTE 3The units used in measurement are not significant as long asthe
40、 system is consistent.8.2 Transverse VelocityDetermine transverse velocity (vs)by comparing the transit time of a transverse wave in anunknown material to the transit time of a transverse wave in amaterial of known velocity (vt).8.2.1 Select samples of each with flat parallel surfaces andmeasure the
41、 thickness of each to an accuracy of 60.02 mm(0.001 in.) or 0.1 %, whichever is greater.8.2.2 Align the search unit (see Fig. 1) over each sample andobtain an optimum signal pattern of as many back echoes as areclearly defined. The time base (sweep control) must be thesame for both measurements.8.2.
42、3 Using a scale or caliper measure the distance at thebase line between the leading edge of the first back echo andthe leading edge of the last back echo that is clearly defined onthe known and unknown sample. For better accuracy, adjust theamplitude of the last back echo by means of the gain contro
43、l toapproximately the same height as the first back echo, after theposition of the leading edge of the first back echo has beenfixed. This adds high-frequency components of the signalwhich have been attenuated. Then determine the position of theleading edge of the last back echo. Count the number of
44、 roundtrips from first echo used to the last echo measured on bothsamples. This number will be one less than the number ofechoes used. Note that the sample thickness, number of roundtrips, and distance from first to last back echo measured neednot be the same.8.2.4 Calculate the value of the unknown
45、 velocity as fol-lows:vs5 Atnstsvt!/Asnttt! (2)where:At= distance from first to Nth back echo on the knownmaterial, m (in.), measured along the baseline of theA-scan display,ns= number of round trips, unknown material,ts= thickness of unknown material, m (in.),vt= velocity of transverse wave in know
46、n material, m/s(in./s),As= distance from the first to the Nth back echo on theunknown material, m (in.), measured along the base-line of the A-scan display,nt= number of round trips, known material, andtt= thickness, known material, m (in.). (See Note 3).9. Report9.1 The following are data which sho
47、uld be included in areport on velocity measurements:9.1.1 Longitudinal Wave:9.1.1.1 Ak= _m (in.)9.1.1.2 nl= _9.1.1.3 tl= _m (in.)9.1.1.4 vk= _m/s (in./s)9.1.1.5 Al= _m (in.)9.1.1.6 nk= _9.1.1.7 tk= _m (in.)9.1.1.8 vl(using Eq 1) = _m/s (in./s)9.1.2 Transverse Wave:9.1.2.1 At= _m (in.)9.1.2.2 ns= _9.
48、1.2.3 ts= _m (in.)9.1.2.4 vt= _m/s (in./s)9.1.2.5 As= _m (in.)9.1.2.6 nt= _9.1.2.7 tt= _m (in.)9.1.2.8 vs(using Eq 2) = _m/s (in./s)9.1.3 Horizontal linearity9.1.4 Test frequency9.1.5 Couplant9.1.6 Search unit:9.1.6.1 Frequency9.1.6.2 Size9.1.6.3 Shape9.1.6.4 Type9.1.6.5 Serial number9.1.7 Sample ge
49、ometry9.1.8 Instrument:9.1.8.1 Name9.1.8.2 Model number9.1.8.3 Serial number9.1.8.4 Pertinent control settings10. Keywords10.1 measure of ultrasonic velocity; nondestructive testing;ultrasonic properties of materials; ultrasonic thickness gages;ultrasonic velocityE494 103APPENDIXES(Nonmandatory Information)X1. FORMULASX1.1 Using the technique of this practice will give resultsin some instances which are only approximate calculations.The determin
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