1、Designation: C1332 01 (Reapproved 2013)Standard Test Method forMeasurement of Ultrasonic Attenuation Coefficients ofAdvanced Ceramics by Pulse-Echo Contact Technique1This standard is issued under the fixed designation C1332; the number immediately following the designation indicates the year oforigi
2、nal adoption or, in 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 describes a procedure for measurementof ultraso
3、nic attenuation coefficients for advanced structuralceramic materials. The procedure is based on a broadbandbuffered piezoelectric probe used in the pulse-echo contactmode and emitting either longitudinal or shear waves. Theprimary objective of this test method is materials characteriza-tion.1.2 The
4、 procedure requires coupling an ultrasonic probe tothe surface of a plate-like sample and the recovery of succes-sive front surface and back surface echoes. Power spectra ofthe echoes are used to calculate the attenuation spectrum(attenuation coefficient as a function of ultrasonic frequency)for the
5、 sample material. The transducer bandwidth and spectralresponse are selected to cover a range of frequencies andcorresponding wavelengths that interact with microstructuralfeatures of interest in solid test samples.1.3 The purpose of this test method is to establish funda-mental procedures for measu
6、rement of ultrasonic attenuationcoefficients. These measurements should distinguish and quan-tify microstructural differences among solid samples andtherefore help establish a reference database for comparingmaterials and calibrating ultrasonic attenuation measurementequipment.1.4 This test method a
7、pplies to monolithic ceramics and alsopolycrystalline metals. This test method may be applied towhisker reinforced ceramics, particulate toughened ceramics,and ceramic composites provided that similar constraints onsample size, shape, and finish are met as described herein formonolithic ceramics.1.5
8、 This test method sets forth the constraints on samplesize, shape, and finish that will assure valid attenuationcoefficient measurements. This test method also describes theinstrumentation, methods, and data processing procedures foraccomplishing the measurements.1.6 This test method is not recommen
9、ded for highly attenu-ating materials such as very thick, very porous, rough-surfacedmonolithics or composites. This test method is not recom-mended for highly nonuniform, heterogeneous, cracked,defective, or otherwise flaw-ridden samples that are unrepre-sentative of the nature or inherent characte
10、ristics of thematerial under examination.1.7 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
11、 limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C1331 Test Method for Measuring Ultrasonic Velocity inAdvanced Ceramics with Broadband Pulse-Echo Cross-Correlation MethodE664 Practice for the Measurement of the Apparent Attenu-ation of Longitudinal Ultrasonic Waves by ImmersionM
12、ethodE1316 Terminology for Nondestructive ExaminationsE1495 Guide for Acousto-Ultrasonic Assessment ofComposites, Laminates, and Bonded Joints2.2 ASNT Document:Recommended Practice SNT-TC-1A for NondestructiveTesting Personnel Qualification and Certification32.3 Military Standard:MIL-STD-410 Nondest
13、ructive Testing Personnel Qualifica-tion and Certification41This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.03 onPhysical Properties and Non-Destructive Evaluation.Current edition approved Feb. 1, 2013. Publish
14、ed April 2013. Originallyapproved in 1996. Last previous edition approved in 2007 as C133201(2007). DOI:10.1520/C1332-01R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
15、efer 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, http:/www.asnt.org.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbin
16、s Ave., Philadelphia, PA 19111-5098, http:/www.dodssp.daps.mil.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.4 Additional references are cited in the text and at end ofthis test method.3. Terminology3.1 Definitions of Terms Specif
17、ic to This Standard:3.1.1 acoustic impedance (Z)a property (1)5defined by amaterials density, p, and the velocity of sound within it, v,where Z = v.3.1.2 attenuation coeffcient ()decrease in ultrasoundintensity with distance expressed in nepers (Np) per unitlength, herein, = ln(I0/I)/d, where is att
18、enuationcoefficient, d is path length or distance, I0is original intensityand I is attenuated intensity (2).3.1.3 attenuation spectrumthe attenuation coefficient, ,expressed as a function of ultrasonic frequency, f, or plotted as versus f, over a range of ultrasonic frequencies within thebandwidth o
19、f the transducer and associated pulser-receiverinstrumentation.3.1.4 back surfacethe surface of a test sample which isopposite to the front surface and from which back surfaceechoes are returned at normal incidence directly to the trans-ducer.3.1.5 bandwidththe frequency range of an ultrasonicprobe,
20、 defined by convention as the difference between thelower and upper frequencies at which the signal amplitude is 6dB down from the frequency at which maximum signalamplitude occurs. The frequency at which the maximumoccurs is termed the center frequency of the probe or trans-ducer.3.1.6 broadband tr
21、ansduceran ultrasonic transducer ca-pable of sending and receiving undistorted signals over a broadbandwidth, consisting of thin damped piezoelectric crystal in abuffered probe (search unit).3.1.7 buffered probean ultrasonic search unit as defined inTerminology E1316 but containing a delay line or b
22、uffer rod towhich the piezoelement, that is, transducer consisting of apiezoelectric crystal, is affixed. The buffer rod separates thepiezoelement from the test sample (see Fig. 1).3.1.8 buffer rodan integral part of a buffered probe orsearch unit, usually a quartz or fused silica cylinder thatprovi
23、des a time delay between the excitation pulse from thepiezoelement and echoes returning from a sample coupled tothe free end of the buffer rod.3.1.9 free surfacethe back surface of a solid test sampleinterfaced with a very low density medium, usually air or othergas, to assure that the back surface
24、reflection coefficient equals1 to a high degree of precision.3.1.10 frequency (f)number of oscillations per second ofultrasonic waves, measured in megahertz, MHz, herein.3.1.11 front surfacethe surface of a test sample to whichthe buffer rod is coupled at normal incidence (designated as testsurface
25、in Terminology E1316).3.1.12 inherent attenuationultrasound energy loss in asolid as a result of scattering, diffusion, and absorption. Thisstandard assumes that the dominant inherent losses are due toRayleigh and stochastic scattering (2) by the materialmicrostructure, for example, by grains, grain
26、 boundaries, andmicropores. Measured ultrasound energy loss which, if notcorrected, may include losses due to diffraction, individualmacroflaws, surface roughness, couplant variations, and trans-ducer defects.3.1.13 reflection coeffcient (R)measure of relative inten-sity of sound waves reflected bac
27、k into a material at aninterface, defined in terms of the acoustic impedance of thematerial in which the sound wave originates (Z0) and theacoustic impedance of the material interfaced with it (Zi),where R =(Zi Z0)/(Zi+ Z0)2.3.1.14 test sample a solid coupon or material part thatmeets the constraint
28、s needed to make the attenuation coeffi-cient measurements described herein, that is, a test sample orpart having flat, parallel, smooth, preferably ground/polishedopposing (front and back) surfaces and having no discreteflaws or anomalies that are unrepresentative of the inherentproperties of the m
29、aterial.3.1.15 transmission coeffcient (T)measure of relative in-tensity of sound waves transmitted through an interface,defined in terms of the acoustic impedance of the material inwhich the sound wave originates (Z0) and the acoustic imped-ance of the material interfaced with it (Zi), where T =(4Z
30、iZ0)/(Zi+ Z0)2so that R + T =1.3.1.16 wavelength ()distance that sound (of a particularfrequency) travels during one period (during one oscillation), = v/f, where v is the velocity of sound in the material andwhere velocity is measured in cm/s, and wavelength in cm,herein.3.2 Other terms used in thi
31、s test method are defined inTerminology E1316.4. Summary of Test Method4.1 This test method describes a procedure for determininga materials inherent attenuation coefficient and attenuationspectrum by means of a buffered broadband probe operating inthe pulse-echo contact mode on a solid sample that
32、has smooth,flat, parallel surfaces.4.2 The procedure described in this test method involvesdigital acquisition and computer processing of ultrasonic echowaveforms returned by the test sample. Test sample5The boldface numbers in parentheses refer to a list of references at the end ofthis standard.FIG
33、. 1 Cross Section of Buffered Broadband Ultrasonic ProbeC1332 01 (2013)2constraints, probing methods, data validity criteria, and mea-surement corrections are prescribed herein.5. Significance and Use5.1 This test method is useful for characterizing materialmicrostructure or measuring variations in
34、microstructure thatoccur because of material processing conditions and thermal,mechanical, or chemical exposure (3). When applied to mono-lithic or composite ceramics, the procedure should revealmicrostructural gradients due to density, porosity, and grainvariations. This test method may also be app
35、lied to polycrys-talline metals to assess variations in grain size, porosity, andmultiphase constituents.5.2 This test method is useful for measuring and comparingmicrostructural variations among different samples of the samematerial or for sensing and measuring subtle microstructuralvariations with
36、in a given sample.5.3 This test method is useful for mapping variations in theattenuation coefficient and the attenuation spectrum as theypertain to variations in the microstructure and associatedproperties of monolithic ceramics, ceramic composites andmetals.5.4 This test method is useful for estab
37、lishing a referencedatabase for comparing materials and for calibrating ultrasonicattenuation measurement equipment.5.5 This test method is not recommended for highly attenu-ating monolithics or composites that are thick, highly porous,or that have rough or highly textured surfaces. For thesemateria
38、ls Practice E664 may be appropriate. Guide E1495 isrecommended for assessing attenuation differences amongcomposite plates and laminates that may exhibit, for example,pervasive matrix porosity or matrix crazing in addition tohaving complex fiber architectures or thermomechanical deg-radation (3). Th
39、e proposed ASTM Standard Test Method forMeasuring Ultrasonic Velocity inAdvanced Ceramics (C1331)is recommended for characterizing monolithic ceramics withsignificant porosity or porosity variations (4).6. Personnel Qualifications6.1 It is recommended that nondestructive evaluation/examination perso
40、nnel applying this test method be qualified inaccordance with a nationally recognized personnel qualifica-tion practice or standard such asASNT SNT-TC-1A, MILSTD410, or a similar document. The qualification practice orstandard used and its applicable revision(s) should be specifiedin a contractual a
41、greement.6.2 Knowledge of the principles of ultrasonic testing isrequired. Personnel applying this test method shall be experi-enced practitioners of ultrasonic examinations and associatedmethods for signal acquisition, processing, and interpretation.6.3 Personnel shall have proficiency in computer
42、program-ming and signal processing using digital methods for time andfrequency domain signal analysis. Familiarity with the Fouriertransform and associated spectrum analysis methods for ultra-sonic signals is required.7. Apparatus7.1 The instrumentation and apparatus for pulse-echo con-tact ultrason
43、ic attenuation coefficient measurement shouldinclude the following (see Fig. 2). Appropriate equipment canbe assembled from any of several suppliers.7.1.1 Buffered Probe, meeting the following requirements:7.1.1.1 The probe should have a center frequency thatcorresponds to an ultrasonic wavelength t
44、hat is less than onefifth of the thickness, d, of the test sample.7.1.1.2 The probe bandwidth should match the bandwidth ofreceived echoes. This may require transducer bandwidths offrom 50 to 200 MHz.7.1.1.3 The probe should be well constructed, carefullyselected, and shown to be free of internal de
45、fects and structuralanomalies that distort received echoes.7.1.1.4 The frequency spectra of the first two echoes re-turned by the free end of the buffer should be essentiallygaussian (bell shaped).FIG. 2 Block Diagram of Computer System for Ultrasonic Signal Acquisition and Processing for Pulse-Echo
46、 Attenuation MeasurementC1332 01 (2013)37.1.2 Buffer Rod, with length that results in a time delay 3times the interval between two successive echoes from theback surface of the test sample. This imposes a limit on the testsample thickness if the buffer rod length is fixed or predeter-mined by design
47、.7.1.3 Couplant, meeting the following requirements:7.1.3.1 The couplant should be a fluid such as glycerine oran ultrasonic gel that will not corrode, damage, or be absorbedby the test sample or part being examined.7.1.3.2 The couplant film or couplant layer thickness shouldbe much less than the ul
48、trasound wavelength in the couplant atthe probes center frequency.7.1.3.3 Ideally, to avoid echo distortions, the acoustic im-pedance of the couplant should be between that of the bufferrod material and test sample (5). With fluid couplants, justreducing the couplant layer thickness is usually more
49、practicalthan impedance matching by changing the fluid. For example,if glycerine is used between a fused quartz buffer and a steelsample, the couplant layer thickness should be less than 1 m.7.1.3.4 Dry coupling, for example, with an elastomer or thindeformable polymer film, may be used provided that echodistortions or phase inversions are avoided by acoustic imped-ance matching (5) and by substantially reducing the couplantlayer thickness.7.1.4 Pulser-Receiver, having a bandwidth exceeding that ofthe probe by a factor of 1.5 to 2 and inclu
