ASTM C1332-01(2007)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C1332 − 01(Reapproved 2007)
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-
1.7 This standard does not purport to address all of the
tion.
safety concerns, if any, associated with its use. It is the
1.2 The procedure requires coupling an ultrasonic probe to
responsibility of the user of this standard to establish appro-
the surface of a plate-like sample and the recovery of succes-
priate safety and health practices and determine the applica-
sive front surface and back surface echoes. Power spectra of
bility of regulatory limitations prior to use.
the echoes are used to calculate the attenuation spectrum
(attenuation coefficient as a function of ultrasonic frequency)
2. Referenced Documents
forthesamplematerial.Thetransducerbandwidthandspectral
2.1 ASTM Standards:
response are selected to cover a range of frequencies and
C1331Test Method for Measuring Ultrasonic Velocity in
corresponding wavelengths that interact with microstructural
Advanced Ceramics with Broadband Pulse-Echo Cross-
features of interest in solid test samples.
Correlation Method
1.3 The purpose of this test method is to establish funda-
E664Practice for the Measurement of theApparentAttenu-
mental procedures for measurement of ultrasonic attenuation
ation of Longitudinal Ultrasonic Waves by Immersion
coefficients.Thesemeasurementsshoulddistinguishandquan-
Method
tify microstructural differences among solid samples and
E1316Terminology for Nondestructive Examinations
therefore help establish a reference database for comparing
E1495 Guide for Acousto-Ultrasonic Assessment of
materials and calibrating ultrasonic attenuation measurement
Composites, Laminates, and Bonded Joints
equipment.
2.2 ASNT Document:
1.4 Thistestmethodappliestomonolithicceramicsandalso
Recommended Practice SNT-TC-1A for Nondestructive
polycrystalline metals. This test method may be applied to
Testing Personnel Qualification and Certification
whisker reinforced ceramics, particulate toughened ceramics,
2.3 Military Standard:
and ceramic composites provided that similar constraints on
MIL-STD-410 Nondestructive Testing Personnel Qualifica-
sample size, shape, and finish are met as described herein for 4
tion and Certification
monolithic ceramics.
2.4 Additional references are cited in the text and at end of
1.5 This test method sets forth the constraints on sample
this test method.
size, shape, and finish that will assure valid attenuation
coefficient measurements. This test method also describes the
instrumentation, methods, and data processing procedures for
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
accomplishing the measurements.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This test method is under the jurisdiction of ASTM Committee C28 on the ASTM website.
Advanced Ceramics and is the direct responsibility of Subcommittee C28.03 on AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
Physical Properties and Non-Destructive Evaluation. 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Current edition approved Aug. 1, 2007. Published August 2007. Originally Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
approved in 1996. Last previous edition approved in 2001 as C1332–01. DOI: Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://
10.1520/C1332-01R07. www.dodssp.daps.mil.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1332 − 01 (2007)
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
1 to a high degree of precision.
3.1.10 frequency (f)—number of oscillations per second of
ultrasonic waves, measured in megahertz, MHz, herein.
3.1.11 front surface—the surface of a test sample to which
thebufferrodiscoupledatnormalincidence(designatedastest
surface in Terminology E1316).
FIG. 1 Cross Section of Buffered Broadband Ultrasonic Probe
3.1.12 inherent attenuation—ultrasound energy loss in a
solid as a result of scattering, diffusion, and absorption. This
standard assumes that the dominant inherent losses are due to
Rayleigh and stochastic scattering (2) by the material micro-
3. Terminology
structure, for example, by grains, grain boundaries, and mi-
3.1 Definitions of Terms Specific to This Standard:
cropores. Measured ultrasound energy loss which, if not
3.1.1 acoustic impedance (Z)—a property (1) defined by a
corrected, may include losses due to diffraction, individual
material’s density, p, and the velocity of sound within it, v,
macroflaws, surface roughness, couplant variations, and trans-
where Z = ρv.
ducer defects.
3.1.2 attenuation coeffıcient (α)—decrease in ultrasound
3.1.13 reflection coeffıcient (R)—measure of relative inten-
intensity with distance expressed in nepers (Np) per unit
sity of sound waves reflected back into a material at an
length, herein, α = [ln(I /I)]/d, where α is attenuation coeffi-
interface, defined in terms of the acoustic impedance of the
cient, d is path length or distance, I is original intensity and I
material in which the sound wave originates (Z ) and the
is attenuated intensity (2).
acoustic impedance of the material interfaced with it (Z),
i
3.1.3 attenuation spectrum—the attenuation coefficient, α,
where R=[(Z − Z )/(Z + Z )] .
i 0 i 0
expressed as a function of ultrasonic frequency, f, or plotted as
3.1.14 test sample— a solid coupon or material part that
α versus f, over a range of ultrasonic frequencies within the
meets the constraints needed to make the attenuation coeffi-
bandwidth of the transducer and associated pulser-receiver
cient measurements described herein, that is, a test sample or
instrumentation.
part having flat, parallel, smooth, preferably ground/polished
3.1.4 back surface—the surface of a test sample which is
opposing (front and back) surfaces and having no discrete
opposite to the front surface and from which back surface
flaws or anomalies that are unrepresentative of the inherent
echoes are returned at normal incidence directly to the trans-
properties of the material.
ducer.
3.1.15 transmission coeffıcient (T)—measure of relative in-
3.1.5 bandwidth—the frequency range of an ultrasonic
tensity of sound waves transmitted through an interface,
probe, defined by convention as the difference between the
defined in terms of the acoustic impedance of the material in
lower and upper frequencies at which the signal amplitude is 6
which the sound wave originates (Z ) and the acoustic imped-
dB down from the frequency at which maximum signal
anceofthematerialinterfacedwithit(Z),where T=(4Z Z )/(
i i 0
amplitude occurs. The frequency at which the maximum
Z + Z ) so that R + T=1.
i 0
occurs is termed the center frequency of the probe or trans-
3.1.16 wavelength (λ)—distance that sound (of a particular
ducer.
frequency)travelsduringoneperiod(duringoneoscillation), λ
3.1.6 broadband transducer—an ultrasonic transducer ca-
= v/f, where v is the velocity of sound in the material and
pableofsendingandreceivingundistortedsignalsoverabroad
where velocity is measured in cm/µs, and wavelength in cm,
bandwidth, consisting of thin damped piezoelectric crystal in a
herein.
buffered probe (search unit).
3.2 Other terms used in this test method are defined in
3.1.7 buffered probe—anultrasonicsearchunitasdefinedin
Terminology E1316.
TerminologyE1316butcontainingadelaylineorbufferrodto
which the piezoelement, that is, transducer consisting of a
4. Summary of Test Method
piezoelectric crystal, is affixed. The buffer rod separates the
4.1 This test method describes a procedure for determining
piezoelement from the test sample (see Fig. 1).
a material’s inherent attenuation coefficient and attenuation
3.1.8 buffer rod—an integral part of a buffered probe or
spectrumbymeansofabufferedbroadbandprobeoperatingin
search unit, usually a quartz or fused silica cylinder that
thepulse-echocontactmodeonasolidsamplethathassmooth,
provides a time delay between the excitation pulse from the
flat, parallel surfaces.
piezoelement and echoes returning from a sample coupled to
4.2 The procedure described in this test method involves
the free end of the buffer rod.
digital acquisition and computer processing of ultrasonic echo
waveforms returned by the test sample. Test sample con-
straints, probing methods, data validity criteria, and measure-
The boldface numbers in parentheses refer to a list of references at the end of
this standard. ment corrections are prescribed herein.
C1332 − 01 (2007)
5. Significance and Use accordance with a nationally recognized personnel qualifica-
tionpracticeorstandardsuchasASNTSNT-TC-1A,MILSTD
5.1 This test method is useful for characterizing material
410, or a similar document. The qualification practice or
microstructure or measuring variations in microstructure that
standardusedanditsapplicablerevision(s)shouldbespecified
occur because of material processing conditions and thermal,
in a contractual agreement.
mechanical, or chemical exposure (3) . When applied to
monolithicorcompositeceramics,theprocedureshouldreveal
6.2 Knowledge of the principles of ultrasonic testing is
microstructural gradients due to density, porosity, and grain required. Personnel applying this test method shall be experi-
variations. This test method may also be applied to polycrys-
enced practitioners of ultrasonic examinations and associated
talline metals to assess variations in grain size, porosity, and methods for signal acquisition, processing, and interpretation.
multiphase constituents.
6.3 Personnel shall have proficiency in computer program-
5.2 This test method is useful for measuring and comparing
ming and signal processing using digital methods for time and
microstructuralvariationsamongdifferentsamplesofthesame
frequency domain signal analysis. Familiarity with the Fourier
material or for sensing and measuring subtle microstructural
transform and associated spectrum analysis methods for ultra-
variations within a given sample.
sonic signals is required.
5.3 This test method is useful for mapping variations in the
7. Apparatus
attenuation coefficient and the attenuation spectrum as they
pertain to variations in the microstructure and associated
7.1 The instrumentation and apparatus for pulse-echo con-
properties of monolithic ceramics, ceramic composites and
tact ultrasonic attenuation coefficient measurement should
metals.
include the following (see Fig. 2).Appropriate equipment can
5.4 This test method is useful for establishing a reference be assembled from any of several suppliers.
7.1.1 Buffered Probe, meeting the following requirements:
databaseforcomparingmaterialsandforcalibratingultrasonic
attenuation measurement equipment. 7.1.1.1 The probe should have a center frequency that
corresponds to an ultrasonic wavelength that is less than one
5.5 This test method is not recommended for highly attenu-
fifth of the thickness, d, of the test sample.
ating monolithics or composites that are thick, highly porous,
7.1.1.2 Theprobebandwidthshouldmatchthebandwidthof
or that have rough or highly textured surfaces. For these
received echoes. This may require transducer bandwidths of
materials Practice E664 may be appropriate. Guide E1495 is
from 50 to 200 MHz.
recommended for assessing attenuation differences among
7.1.1.3 The probe should be well constructed, carefully
composite plates and laminates that may exhibit, for example,
selected,andshowntobefreeofinternaldefectsandstructural
pervasive matrix porosity or matrix crazing in addition to
anomalies that distort received echoes.
having complex fiber architectures or thermomechanical deg-
7.1.1.4 The frequency spectra of the first two echoes re-
radation (3). The proposed ASTM Standard Test Method for
turned by the free end of the buffer should be essentially
MeasuringUltrasonicVelocityinAdvancedCeramics(C1331)
gaussian (bell shaped).
is recommended for characterizing monolithic ceramics with
7.1.2 Buffer Rod,withlengththatresultsinatimedelay ≥3
significant porosity or porosity variations (4).
times the interval between two successive echoes from the
6. Personnel Qualifications
backsurfaceofthetestsample.Thisimposesalimitonthetest
6.1 It is recommended that nondestructive evaluation/ sample thickness if the buffer rod length is fixed or predeter-
examinationpersonnelapplyingthistestmethodbequalifiedin mined by design.
FIG. 2 Block Diagram of Computer System for Ultrasonic Signal Acquisition and Processing for Pulse-Echo Attenuation Measurement
C1332 − 01 (2007)
7.1.3 Couplant, meeting the following requirements: 7.1.10 Video Monitors,oneanalog,onedigital(optional)for
real-time visual inspection of echo waveforms and for making
7.1.3.1 The couplant should be a fluid such as glycerine or
interactivemanualadjustmentstothedataacquisitioncontrols.
an ultrasonic gel that will not corrode, damage, or be absorbed
by the test sample or part being examined. These control adjustments may include probe realignment/
repositioning, couplant thickness optimization, and other ad-
7.1.3.2 Thecouplantfilmorcouplantlayerthicknessshould
justments to obtain echo waveforms that meet acceptance
bemuchlessthantheultrasoundwavelengthinthecouplantat
criteria given herein.
the probe’s center frequency.
7.1.11 XYZ-Ax
...