1、Designation: E 494 05Standard Practice forMeasuring Ultrasonic Velocity in Materials1This standard is issued under the fixed designation E 494; 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
2、parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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. Scope1.1 This practice covers a test procedure for measuringultraso
3、nic 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 materi
4、al 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 smoothe
5、r.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 in
6、 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 sev
7、eral 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 obtain
8、ed 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,an
9、d 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 This standard does not purport to address all of thes
10、afety 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. Referenced Documents2.1 ASTM Standards:2C 597 Test Method for Pulse V
11、elocity Through ConcreteE 317 Practice for Evaluating Performance Characteristicsof Ultrasonic Pulse-Echo Examination Instruments andSystems Without the Use of Electronic MeasurementInstrumentsE 543 Practice for Evaluating Agencies Performing Nonde-structive TestingE 797 Practice for Measuring Thick
12、ness by Manual Ultra-sonic Pulse-Echo Contact MethodE 1316 Terminology for Nondestructive Testing2.2 ASNT Documents:3SNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and CertificationASNI/ASNT-CP-189 Standard for Qualification and Certi-fication of Nondestructive Test
13、ing Personnel2.3 AIA Document:4NAS-410 Certification and Qualification of NondestructiveTesting Personnel1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.06 onUltrasonic Method.Current edition approved Dec.
14、 1, 2005. Published December 2005. Originallyapproved in 1973. Last previous edition approved in 2001 as E 494 - 95(2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, ref
15、er to the standards Document Summary page onthe ASTM website.3Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.4Available from Aerospace Industries Association of America, Inc. (AIA), 1250Eye St., NW, Washington, DC 20005.1C
16、opyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, see Terminology E 1316.4. Summary of Practice4.1 Several possible modes of vibration can propagate insolids.
17、This procedure is concerned with two velocities ofpropagation, namely those associated with longitudinal (vl) andtransverse (vt) waves. The longitudinal velocity is independentof sample geometry when the dimensions at right angles to thebeam are very large compared with beam area and wave length.The
18、 transverse velocity is little affected by physical dimensionsof the sample.The procedure described in Section 7 is, as notedin the scope, for use with conventional pulse echo flawdetection equipment only.5. Basis of Application5.1 The following items are subject to contractual agree-ment between th
19、e parties using or referencing this practice:5.2 Personnel QualificationIf specified in the contractualagreement, personnel performing to this practice shall bequalified in accordance with a nationally or internationallyrecognized NDT personnel qualification practice or standardsuch as ASNI/ASNT-CP-
20、189, SNT-TC-1A, NAS-410,orasimilar document and certified by the employer or certifyingagency, as applicable. The practice or standard used and itsapplicable revision shall be identified in the contractual agree-ment between the using parties.5.3 Qualification of Nondestructive AgenciesIf specifiedi
21、n the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E 543. The applicableedition of Practice E 543 shall be specified in the contractualagreement.6. Apparatus6.1 The ultrasonic testing system to be used in this practiceshall include the following:6.1.1
22、Test InstrumentAny ultrasonic instrument compris-ing a time base, transmitter (pulser), receiver (echo amplifier),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 7.
23、1.4 and7.2.4), along the A-scan base line within 60.5 mm 0.020 in.For maximum accuracy, the highest possible frequency thatwill present at least two easily distinguishable back echoes, andpreferably five, shall be used.6.1.2 Search UnitThe search unit containing a search unitthat generates and recei
24、ves ultrasonic waves of an appropriatesize, type and frequency, designed for tests by the contactmethod shall be used. Contact straight beam longitudinal modeshall be used for longitudinal velocity measurements, andcontact straight beam shear mode for transverse velocitymeasurements.6.1.3 CouplantFo
25、r longitudinal velocity measurements,the couplant should be the material used in practice, forexample, 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 mate
26、rials have been used effectively. Mostliquids will not support transverse waves. In porous materialsspecial nonliquid couplants are required. The couplant mustnot be deleterious to the material.6.1.4 Standard Reference Blocks:6.1.4.1 Velocity StandardAny material of known velocity,that can be penetr
27、ated by the acoustical wave, and that has anappropriate surface roughness, shape, thickness, 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 refere
28、nce block should have an attenuationsimilar to that of the test material.6.1.4.2 For horizontal linearity check, see Practice E 317.7. Procedure7.1 Longitudinal Wave VelocityDetermine bulk, longitu-dinal wave velocity (vl) by comparing the transit time of alongitudinal wave in the unknown material t
29、o the transit timeof ultrasound in a velocity standard (vk).7.1.1 Select samples of each with flat parallel surfaces andmeasure the thickness of each to an accuracy of 60.02 mm0.001 in. or 0.1 %, whichever is greater.7.1.2 Align the search unit over each sample and obtain anominal signal pattern (se
30、e Fig. 1) of as many back echoes asare clearly defined. The time base (sweep control) must be setthe same for both measurements.7.1.3 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 clearl
31、y defined onthe known and unknown sample. For better accuracy, adjust theamplitude of the last back echo by means of the gain control toapproximately the same height as the first back echo, after theposition of the leading edge of the first back echo has beenfixed. This allows more accurate time or
32、distance measure-ments. The position of the leading 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 ro
33、und trips between Echo 1 andEcho 7. Count the 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
34、not be the same.7.1.4 Calculate the value of the unknown velocity as fol-lows:v15 Aknltlvk!/Alnktk! (1)FIG. 1 Initial Pulse and 7 Back EchoesE494052where: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,
35、unknown material,tl= thickness of unknown material, m in.,vk= velocity in known material, 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 mate
36、rial, m in.NOTE 3The units used in measurement are not significant as long asthe system is consistent.7.2 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 veloc
37、ity (vt).7.2.1 Select samples of each with flat parallel surfaces andmeasure the thickness of each to an accuracy of 60.02 mm0.001 in. or 0.1 %, whichever is greater.7.2.2 Align the search unit (see Fig. 1) over each sample andobtain an optimum signal pattern of as many back echoes as areclearly def
38、ined. The time base (sweep control) must be thesame for both measurements.7.2.3 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 a
39、ccuracy, adjust theamplitude of the last back echo by means of the gain control 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 determ
40、ine the position of theleading edge of the last back echo. Count the number of 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 b
41、ack echo measured neednot be the same.7.2.4 Calculate the value of the unknown 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= th
42、ickness of unknown material, m in.,vt= velocity of transverse wave in known material, m/sin./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 materia
43、l, m in. (See Note 3).8. Report8.1 The following are data which should be included in areport on velocity measurements:8.1.1 Longitudinal Wave:8.1.1.1 Ak= _m in.8.1.1.2 nl= _8.1.1.3 tl= _m in.8.1.1.4 vk= _m/s in./s8.1.1.5 Al= _m in.8.1.1.6 nk= _8.1.1.7 tk= _m in.8.1.1.8 vl(using Eq 1) = _m/s in./s8.
44、1.2 Transverse Wave:8.1.2.1 At= _m in.8.1.2.2 ns= _8.1.2.3 ts= _m in.8.1.2.4 vt= _m/s in./s8.1.2.5 As= _m in.8.1.2.6 nt= _8.1.2.7 tt= _m in.8.1.2.8 vs(using Eq 2) = _m/s in./s8.1.3 Horizontal linearity8.1.4 Test frequency8.1.5 Couplant8.1.6 Search unit:8.1.6.1 Frequency8.1.6.2 Size8.1.6.3 Shape8.1.6
45、.4 Type8.1.6.5 Serial number8.1.7 Sample geometry8.1.8 Instrument:8.1.8.1 Name8.1.8.2 Model number8.1.8.3 Serial number8.1.8.4 Pertinent control settings9. Keywords9.1 measure of ultrasonic velocity; nondestructive testing;ultrasonic properties of materials; ultrasonic thickness gages;ultrasonic vel
46、ocityE494053APPENDIXES(Nonmandatory Information)X1. FORMULASX1.1 Using the technique of this practice will give resultsin some instances which are only approximate calculations.The determination of longitudinal and transverse velocity ofsound in a material makes it possible to approximately calcu-la
47、te the elastic constants, Poissons ratio, elastic moduli,acoustic impedance, reflection coefficient, and transmissioncoefficient. In thisAppendix, the formulas for calculating someof these factors are as follows (see Note X1.1):X1.1.1 Poissons Ratio:s51 2 2vs/vl!2#/21 2 vs/vl!2#where:s = Poissons ra
48、tio,vs= ultrasonic transverse velocity, m/s or in./s, andvl= ultrasonic longitudinal velocity, m/s or in./s.X1.1.2 Youngs Modulus of Elasticity:E 5 rvs23vl22 4vs2!#/vl22 vs2!where:r = density, kg/m3or lb/in.3,vl= longitudinal velocity, m/s or in./s,vs= transverse velocity, m/s or in./s, andE = Young
49、s modulus of elasticity, N/m2or lb/in.2 (seeNotes X1.2 and X1.3).X1.1.3 Acoustic Impedance (see Note X1.3):z 5rvlwhere:z = acoustic impedance (kg/m2 s or lb/in.2 s).X1.1.4 Shear Modulus (see Note X1.3):G 5rvs2X1.1.5 Bulk Modulus (see Note X1.3):K 5rvl22 4/3!vs2#X1.1.6 Reflection Coeffcient for Energy (R):R 5 Z22 Z1!2/Z21 Z1!2where:Z1= acoustic impedance in Medi
