ASTM C1332-01(2013)
(Test Method)Standard Test Method for Measurement of Ultrasonic Attenuation Coefficients of Advanced Ceramics by Pulse-Echo Contact Technique
Standard Test Method for Measurement of Ultrasonic Attenuation Coefficients of Advanced Ceramics by Pulse-Echo Contact Technique
SIGNIFICANCE AND USE
5.1 This test method is useful for characterizing material microstructure or measuring variations in microstructure that occur because of material processing conditions and thermal, mechanical, or chemical exposure (3). When applied to monolithic or composite ceramics, the procedure should reveal microstructural gradients due to density, porosity, and grain variations. This test method may also be applied to polycrystalline metals to assess variations in grain size, porosity, and multiphase constituents.
5.2 This test method is useful for measuring and comparing microstructural variations among different samples of the same material or for sensing and measuring subtle microstructural variations within a given sample.
5.3 This test method is useful for mapping variations in the attenuation coefficient and the attenuation spectrum as they pertain to variations in the microstructure and associated properties of monolithic ceramics, ceramic composites and metals.
5.4 This test method is useful for establishing a reference database for comparing materials and for calibrating ultrasonic attenuation measurement equipment.
5.5 This test method is not recommended for highly attenuating monolithics or composites that are thick, highly porous, or that have rough or highly textured surfaces. For these materials Practice E664 may be appropriate. Guide E1495 is recommended for assessing attenuation differences among composite plates and laminates that may exhibit, for example, pervasive matrix porosity or matrix crazing in addition to having complex fiber architectures or thermomechanical degradation (3). The proposed ASTM Standard Test Method for Measuring Ultrasonic Velocity in Advanced Ceramics (C1331) is recommended for characterizing monolithic ceramics with significant porosity or porosity variations (4).
SCOPE
1.1 This test method describes a procedure for measurement of ultrasonic attenuation coefficients for advanced structural ceramic materials. The procedure is based on a broadband buffered piezoelectric probe used in the pulse-echo contact mode and emitting either longitudinal or shear waves. The primary objective of this test method is materials characterization.
1.2 The procedure requires coupling an ultrasonic probe to the surface of a plate-like sample and the recovery of successive front surface and back surface echoes. Power spectra of the echoes are used to calculate the attenuation spectrum (attenuation coefficient as a function of ultrasonic frequency) for the sample material. The transducer bandwidth and spectral response are selected to cover a range of frequencies and corresponding wavelengths that interact with microstructural features of interest in solid test samples.
1.3 The purpose of this test method is to establish fundamental procedures for measurement of ultrasonic attenuation coefficients. These measurements should distinguish and quantify microstructural differences among solid samples and therefore help establish a reference database for comparing materials and calibrating ultrasonic attenuation measurement equipment.
1.4 This test method applies to monolithic ceramics and also polycrystalline metals. This test method may be applied to whisker reinforced ceramics, particulate toughened ceramics, and ceramic composites provided that similar constraints on sample size, shape, and finish are met as described herein for monolithic ceramics.
1.5 This test method sets forth the constraints on sample size, shape, and finish that will assure valid attenuation coefficient measurements. This test method also describes the instrumentation, methods, and data processing procedures for accomplishing the measurements.
1.6 This test method is not recommended for highly attenuating materials such as very thick, very porous, rough-surfaced monolithics or composites. This test method is not recommended for highly nonuniform, heterogeneous, cracked, defe...
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Designation: C1332 − 01 (Reapproved 2013)
Standard Test Method for
Measurement of Ultrasonic Attenuation Coefficients of
Advanced Ceramics by Pulse-Echo Contact Technique
This standard is issued under the fixed designation C1332; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 This test method is not recommended for highly attenu-
atingmaterialssuchasverythick,veryporous,rough-surfaced
1.1 Thistestmethoddescribesaprocedureformeasurement
monolithics or composites. This test method is not recom-
of ultrasonic attenuation coefficients for advanced structural
mended for highly nonuniform, heterogeneous, cracked,
ceramic materials. The procedure is based on a broadband
defective, or otherwise flaw-ridden samples that are unrepre-
buffered piezoelectric probe used in the pulse-echo contact
sentative of the nature or inherent characteristics of the
mode and emitting either longitudinal or shear waves. The
material under examination.
primary objective of this test method is materials characteriza-
tion.
1.7 This standard does not purport to address all of the
1.2 The procedure requires coupling an ultrasonic probe to safety concerns, if any, associated with its use. It is the
the surface of a plate-like sample and the recovery of succes-
responsibility of the user of this standard to establish appro-
sive front surface and back surface echoes. Power spectra of
priate safety and health practices and determine the applica-
the echoes are used to calculate the attenuation spectrum
bility of regulatory limitations prior to use.
(attenuation coefficient as a function of ultrasonic frequency)
1.8 This international standard was developed in accor-
forthesamplematerial.Thetransducerbandwidthandspectral
dance with internationally recognized principles on standard-
response are selected to cover a range of frequencies and
ization established in the Decision on Principles for the
corresponding wavelengths that interact with microstructural
Development of International Standards, Guides and Recom-
features of interest in solid test samples.
mendations issued by the World Trade Organization Technical
1.3 The purpose of this test method is to establish funda-
Barriers to Trade (TBT) Committee.
mental procedures for measurement of ultrasonic attenuation
coefficients.Thesemeasurementsshoulddistinguishandquan-
2. Referenced Documents
tify microstructural differences among solid samples and
2.1 ASTM Standards:
therefore help establish a reference database for comparing
C1331Test Method for Measuring Ultrasonic Velocity in
materials and calibrating ultrasonic attenuation measurement
Advanced Ceramics with Broadband Pulse-Echo Cross-
equipment.
Correlation Method
1.4 Thistestmethodappliestomonolithicceramicsandalso
E664Practice for the Measurement of theApparentAttenu-
polycrystalline metals. This test method may be applied to
ation of Longitudinal Ultrasonic Waves by Immersion
whisker reinforced ceramics, particulate toughened ceramics,
Method
and ceramic composites provided that similar constraints on
E1316Terminology for Nondestructive Examinations
sample size, shape, and finish are met as described herein for
E1495 Guide for Acousto-Ultrasonic Assessment of
monolithic ceramics.
Composites, Laminates, and Bonded Joints
1.5 This test method sets forth the constraints on sample
2.2 ASNT Document:
size, shape, and finish that will assure valid attenuation
Recommended Practice SNT-TC-1A for Nondestructive
coefficient measurements. This test method also describes the
Testing Personnel Qualification and Certification
instrumentation, methods, and data processing procedures for
accomplishing the measurements.
1 2
This test method is under the jurisdiction of ASTM Committee E07 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Nondestructive Testing and is the direct responsibility of Subcommittee E07.06 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Ultrasonic Method. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2013. Published April 2013. Originally the ASTM website.
approved in 1996. Last previous edition approved in 2007 as C1332– 01 (2007). AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
DOI: 10.1520/C1332-01R13. 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1332 − 01 (2013)
piezoelectric crystal, is affixed. The buffer rod separates the
piezoelement from the test sample (see Fig. 1).
3.1.8 buffer rod—an integral part of a buffered probe or
search unit, usually a quartz or fused silica cylinder that
provides a time delay between the excitation pulse from the
piezoelement and echoes returning from a sample coupled to
the free end of the buffer rod.
3.1.9 free surface—the back surface of a solid test sample
interfacedwithaverylowdensitymedium,usuallyairorother
gas, to assure that the back surface reflection coefficient equals
FIG. 1 Cross Section of Buffered Broadband Ultrasonic Probe
1 to a high degree of precision.
3.1.10 frequency (f)—number of oscillations per second of
2.3 Military Standard:
ultrasonic waves, measured in megahertz, MHz, herein.
MIL-STD-410 Nondestructive Testing Personnel Qualifica-
3.1.11 front surface—the surface of a test sample to which
tion and Certification
thebufferrodiscoupledatnormalincidence(designatedastest
2.4 Additional references are cited in the text and at end of
surface in Terminology E1316).
this test method.
3.1.12 inherent attenuation—ultrasound energy loss in a
3. Terminology
solid as a result of scattering, diffusion, and absorption. This
3.1 Definitions of Terms Specific to This Standard: standard assumes that the dominant inherent losses are due to
3.1.1 acoustic impedance (Z)—a property (1) defined by a Rayleigh and stochastic scattering (2) by the material
material’s density, p, and the velocity of sound within it, v, microstructure, for example, by grains, grain boundaries, and
where Z = ρv. micropores. Measured ultrasound energy loss which, if not
corrected, may include losses due to diffraction, individual
3.1.2 attenuation coeffıcient (α)—decrease in ultrasound
macroflaws, surface roughness, couplant variations, and trans-
intensity with distance expressed in nepers (Np) per unit
ducer defects.
length, herein, α = [ln(I /I)]/d, where α is attenuation
coefficient, d is path length or distance, I is original intensity
3.1.13 reflection coeffıcient (R)—measure of relative inten-
and I is attenuated intensity (2). sity of sound waves reflected back into a material at an
interface, defined in terms of the acoustic impedance of the
3.1.3 attenuation spectrum—the attenuation coefficient, α,
material in which the sound wave originates (Z ) and the
expressed as a function of ultrasonic frequency, f, or plotted as 0
acoustic impedance of the material interfaced with it (Z),
α versus f, over a range of ultrasonic frequencies within the i
where R=[(Z − Z )/(Z + Z )] .
bandwidth of the transducer and associated pulser-receiver i 0 i 0
instrumentation.
3.1.14 test sample—a solid coupon or material part that
meets the constraints needed to make the attenuation coeffi-
3.1.4 back surface—the surface of a test sample which is
cient measurements described herein, that is, a test sample or
opposite to the front surface and from which back surface
part having flat, parallel, smooth, preferably ground/polished
echoes are returned at normal incidence directly to the trans-
opposing (front and back) surfaces and having no discrete
ducer.
flaws or anomalies that are unrepresentative of the inherent
3.1.5 bandwidth—the frequency range of an ultrasonic
properties of the material.
probe, defined by convention as the difference between the
lower and upper frequencies at which the signal amplitude is 6 3.1.15 transmission coeffıcient (T)—measure of relative in-
tensity of sound waves transmitted through an interface,
dB down from the frequency at which maximum signal
amplitude occurs. The frequency at which the maximum defined in terms of the acoustic impedance of the material in
which the sound wave originates (Z ) and the acoustic imped-
occurs is termed the center frequency of the probe or trans-
ducer. ance of the material interfaced with it (Z), where T =
i
(4ZZ )/(Z + Z ) so that R + T=1.
i 0 i 0
3.1.6 broadband transducer—an ultrasonic transducer ca-
pableofsendingandreceivingundistortedsignalsoverabroad 3.1.16 wavelength (λ)—distance that sound (of a particular
bandwidth, consisting of thin damped piezoelectric crystal in a frequency)travelsduringoneperiod(duringoneoscillation),λ
buffered probe (search unit). = v/f, where v is the velocity of sound in the material and
where velocity is measured in cm/µs, and wavelength in cm,
3.1.7 buffered probe—anultrasonicsearchunitasdefinedin
herein.
TerminologyE1316butcontainingadelaylineorbufferrodto
which the piezoelement, that is, transducer consisting of a
3.2 Other terms used in this test method are defined in
Terminology E1316.
Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
4. Summary of Test Method
Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://
www.dodssp.daps.mil.
4.1 This test method describes a procedure for determining
The boldface numbers in parentheses refer to a list of references at the end of
this standard. a material’s inherent attenuation coefficient and attenuation
C1332 − 01 (2013)
spectrum by meansofabufferedbroadbandprobeoperatingin composite plates and laminates that may exhibit, for example,
thepulse-echocontactmodeonasolidsamplethathassmooth, pervasive matrix porosity or matrix crazing in addition to
flat, parallel surfaces.
having complex fiber architectures or thermomechanical deg-
radation (3). The proposed ASTM Standard Test Method for
4.2 The procedure described in this test method involves
Measuring UltrasonicVelocity inAdvanced Ceramics (C1331)
digital acquisition and computer processing of ultrasonic echo
is recommended for characterizing monolithic ceramics with
waveforms returned by the test sample. Test sample
significant porosity or porosity variations (4).
constraints, probing methods, data validity criteria, and mea-
surement corrections are prescribed herein.
6. Personnel Qualifications
5. Significance and Use
6.1 It is recommended that nondestructive evaluation/
5.1 This test method is useful for characterizing material
examinationpersonnelapplyingthistestmethodbequalifiedin
microstructure or measuring variations in microstructure that
accordance with a nationally recognized personnel qualifica-
occur because of material processing conditions and thermal,
tionpracticeorstandardsuchasASNTSNT-TC-1A,MILSTD
mechanical, or chemical exposure (3). When applied to mono-
410, or a similar document. The qualification practice or
lithic or composite ceramics, the procedure should reveal
standardusedanditsapplicablerevision(s)shouldbespecified
microstructural gradients due to density, porosity, and grain
in a contractual agreement.
variations. This test method may also be applied to polycrys-
6.2 Knowledge of the principles of ultrasonic testing is
talline metals to assess variations in grain size, porosity, and
required. Personnel applying this test method shall be experi-
multiphase constituents.
enced practitioners of ultrasonic examinations and associated
5.2 This test method is useful for measuring and comparing
methods for signal acquisition, processing, and interpretation.
microstructuralvariationsamongdifferentsamplesofthesame
material or for sensing and measuring subtle microstructural 6.3 Personnel shall have proficiency in computer program-
variations within a given sample. ming and signal processing using digital methods for time and
frequency domain signal analysis. Familiarity with the Fourier
5.3 This test method is useful for mapping variations in the
transform and associated spectrum analysis methods for ultra-
attenuation coefficient and the attenuation spectrum as they
sonic signals is required.
pertain to variations in the microstructure and associated
properties of monolithic ceramics, ceramic composites and
7. Apparatus
metals.
5.4 This test method is useful for establishing a reference 7.1 The instrumentation and apparatus for pulse-echo con-
tact ultrasonic attenuation coefficient measurement should
database for comparing materials and for calibrating ultrasonic
attenuation measurement equipment. include the following (see Fig. 2).Appropriate equipment can
be assembled from any of several suppliers.
5.5 This test method is not recommended for highly attenu-
7.1.1 Buffered Probe, meeting the following requirements:
ating monolithics or composites that are thick, highly porous,
or that have rough or highly textured surfaces. For these 7.1.1.1 The probe should have a center frequency that
materials Practice E664 may be appropriate. Guide E1495 is corresponds to an ultrasonic wavelength that is less than one
recommended for assessing attenuation differences among fifth of the thickness, d, of the test sample.
FIG. 2 Block Diagram of Computer System for Ultrasonic Signal Acquisition and Processing for Pulse-Echo Attenuation Measurement
C1332 − 01 (2013)
7.1.1.2 Theprobebandwidthshouldmatchthebandwidthof 7.1.7 Oscilloscope Time Base, preferably a programmable
received echoes. This may require transducer bandwidths of timebasemoduleusingageneralpurposeinterfacebus(GPIB)
from 50 to 200 MHz. witharesolutionofatleast5nsandselectablerangesincluding
a fundamental time base of 200 ns.
7.1.1.3 The probe should be well constructed, carefully
7.1.8 Digital Time Synthesizer, bus programmable module,
selected,andshowntobefreeofinternaldefectsandstructural
to introduce a known time delay between the start of three
anomalies that distort received echoes.
separate time gates in the oscilloscope time base. Each time
7.1.1.4 The frequency spectra of the first two echoes re-
gate must generate a “window” to exclusively contain one of
turned by the free end of the buffer should be essentially
the echoes of interest, that is, front surface and two successive
gaussian (bell shaped).
back surface echoes. The gate, that is, window start times,
7.1.2 Buffer Rod, with length that results in a time delay ≥3
should be program controlled and
...
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