ASTM C1332-18(2023)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1332 − 18 (Reapproved 2023)
Standard Practice 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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope monolithics or composites. This practice is not recommended
for highly nonuniform, heterogeneous, cracked, defective, or
1.1 This practice describes a procedure for measurement of
otherwise flaw-ridden samples that are unrepresentative of the
ultrasonic attenuation coefficients for advanced structural ce-
nature or inherent characteristics of the material under exami-
ramic materials. The procedure is based on a broadband
nation.
buffered piezoelectric probe used in the pulse-echo contact
1.7 This standard does not purport to address all of the
mode and emitting either longitudinal or shear waves. The
safety concerns, if any, associated with its use. It is the
primary objective of this practice is materials characterization.
responsibility of the user of this standard to establish appro-
1.2 The procedure requires coupling an ultrasonic probe to
priate safety, health, and environmental practices and deter-
the surface of a plate-like sample and the recovery of succes-
mine the applicability of regulatory limitations prior to use.
sive front surface and back surface echoes (refer to Fig. 3).
1.8 This international standard was developed in accor-
Power spectra of the echoes are used to calculate the attenua-
dance with internationally recognized principles on standard-
tion spectrum (attenuation coefficient as a function of ultra-
ization established in the Decision on Principles for the
sonic frequency) for the sample material. The transducer
Development of International Standards, Guides and Recom-
bandwidth and spectral response are selected to cover a range
mendations issued by the World Trade Organization Technical
of frequencies and corresponding wavelengths that interact
Barriers to Trade (TBT) Committee.
with microstructural features of interest in solid test samples.
1.3 The purpose of this practice is to establish fundamental
2. Referenced Documents
procedures for measurement of ultrasonic attenuation coeffi-
2.1 ASTM Standards:
cients. These measurements should distinguish and quantify
C1331 Practice for Measuring Ultrasonic Velocity in Ad-
microstructural differences among solid samples and therefore
vanced Ceramics with Broadband Pulse-Echo Cross-
help establish a reference database for comparing materials and
Correlation Method
calibrating ultrasonic attenuation measurement equipment.
E543 Specification for Agencies Performing Nondestructive
1.4 This practice applies to monolithic ceramics and also
Testing
polycrystalline metals. This practice may be applied to whisker
E664/E664M Practice for the Measurement of the Apparent
reinforced ceramics, particulate toughened ceramics, and ce-
Attenuation of Longitudinal Ultrasonic Waves by Immer-
ramic composites provided that similar constraints on sample
sion Method
size, shape, and finish are met as described herein for mono-
E1316 Terminology for Nondestructive Examinations
lithic ceramics.
E1495/E1495M Guide for Acousto-Ultrasonic Assessment
of Composites, Laminates, and Bonded Joints
1.5 This practice sets forth the constraints on sample size,
shape, and finish that will assure valid attenuation coefficient
2.2 ASNT Documents:
measurements. This practice also describes the instrumentat-
Recommended Practice SNT-TC-1A for Nondestructive
ion, methods, and data processing procedures for accomplish-
Testing Personnel Qualification and Certification
ing the measurements.
ANSI/ASNT CP-189 Standard for Qualification and Certifi-
cation of Nondestructive Testing Personnel
1.6 This practice is not recommended for highly attenuating
materials such as very thick, very porous, rough-surfaced
1 2
This practice is under the jurisdiction of ASTM Committee E07 on Nonde- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
structive 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 Dec. 1, 2023. Published December 2023. Originally the ASTM website.
approved in 1996. Last previous edition approved in 2018 as C1332 – 18. DOI: Available from American Society for Nondestructive Testing (ASNT), P.O. Box
10.1520/C1332-18R23. 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 − 18 (2023)
3.1.6 broadband transducer—an ultrasonic transducer ca-
pable of sending and receiving undistorted signals over a broad
bandwidth, consisting of thin damped piezoelectric crystal in a
buffered probe (search unit).
3.1.7 buffered probe—an ultrasonic search unit as defined in
Terminology E1316 but containing a delay line or buffer rod to
which the piezoelement, that is, transducer consisting of a
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
FIG. 1 Cross Section of Buffered Broadband Ultrasonic Probe
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.
2.3 ISO Standard:
3.1.9 free surface—the back surface of a solid test sample
ISO 9712 Non-destructive Testing – Qualification and Cer-
interfaced with a very low density medium, usually air or other
tification of NDT Personnel
gas, to assure that the back surface reflection coefficient equals
2.4 Aerospace Industries Association Document:
1 to a high degree of precision.
NAS 410 Certification and Qualification of Nondestructive
3.1.10 frequency (f)—number of oscillations per second of
Testing Personnel
ultrasonic waves, measured in megahertz, MHz, herein.
2.5 Additional references are cited in the text and at end of
3.1.11 front surface—the surface of a test sample to which
this practice.
the buffer rod is coupled at normal incidence (designated as test
surface in Terminology E1316).
3. Terminology
3.1.12 inherent attenuation—ultrasound energy loss in a
3.1 Definitions of Terms Specific to This Standard:
solid as a result of scattering, diffusion, and absorption. This
3.1.1 acoustic impedance (Z)—a property (1) defined by a
standard assumes that the dominant inherent losses are due to
material’s density, p, and the velocity of sound within it, v,
Rayleigh and stochastic scattering (2) by the material
where Z = ρv.
microstructure, for example, by grains, grain boundaries, and
3.1.2 attenuation coeffıcient (α)—decrease in ultrasound
micropores. Measured ultrasound energy loss which, if not
intensity with distance expressed in nepers (Np) per unit
corrected, may include losses due to diffraction, individual
length, herein, α = [ln(I /I)]/d, where α is attenuation
macroflaws, surface roughness, couplant variations, and trans-
coefficient, d is path length or distance, I is original intensity,
ducer defects.
and I is attenuated intensity (2).
3.1.13 reflection coeffıcient (R)—measure of relative inten-
3.1.3 attenuation spectrum—the attenuation coefficient, α,
sity of sound waves reflected back into a material at an
expressed as a function of ultrasonic frequency, f, or plotted as
interface, defined in terms of the acoustic impedance of the
α versus f, over a range of ultrasonic frequencies within the
material in which the sound wave originates (Z ) and the
bandwidth of the transducer and associated pulser-receiver
acoustic impedance of the material interfaced with it (Z ),
i
instrumentation.
where R = [(Z − Z )/(Z + Z )] .
i 0 i 0
3.1.4 back surface—the surface of a test sample which is
3.1.14 test sample—a solid coupon or material part that
opposite to the front surface and from which back surface
meets the constraints needed to make the attenuation coeffi-
echoes are returned at normal incidence directly to the trans-
cient measurements described herein, that is, a test sample or
ducer.
part having flat, parallel, smooth, preferably ground/polished
3.1.5 bandwidth—the frequency range of an ultrasonic
opposing (front and back) surfaces and having no discrete
probe, defined by convention as the difference between the
flaws or anomalies that are unrepresentative of the inherent
lower and upper frequencies at which the signal amplitude is
properties of the material.
6 dB down from the frequency at which maximum signal
3.1.15 transmission coeffıcient (T)—measure of relative in-
amplitude occurs. The frequency at which the maximum
tensity of sound waves transmitted through an interface,
occurs is termed the center frequency of the probe or trans-
defined in terms of the acoustic impedance of the material in
ducer.
which the sound wave originates (Z ) and the acoustic imped-
ance of the material interfaced with it (Z ), where T =
i
(4Z Z )/(Z + Z ) so that R + T = 1.
i 0 i 0
Available from International Organization for Standardization (ISO), ISO
3.1.16 wavelength (λ)—distance that sound (of a particular
Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
Geneva, Switzerland, http://www.iso.org.
frequency) travels during one period (during one oscillation), λ
Available from Aerospace Industries Association of America, Inc., 1250 Eye St.
= v/f, where v is the velocity of sound in the material and
NW, Washington, DC, 20005.
where velocity is measured in cm/μs, and wavelength in cm,
The boldface numbers in parentheses refer to a list of references at the end of
this standard. herein.
C1332 − 18 (2023)
FIG. 2 Block Diagram of Computer System for Ultrasonic Signal Acquisition and Processing for Pulse-Echo Attenuation Measurement
occur because of material processing conditions and thermal,
mechanical, or chemical exposure (3). When applied to mono-
lithic or composite ceramics, the procedure should reveal
microstructural gradients due to density, porosity, and grain
variations. This practice may also be applied to polycrystalline
metals to assess variations in grain size, porosity, and multi-
phase constituents.
5.2 This practice 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 practice 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.
FIG. 3 Schematic of Signal Acquisition and Data-Processing
Stages for Determining Frequency Dependence of Attenuation
5.4 This practice is useful for establishing a reference
Coefficient by Using Broadband Ultrasonic Pulse-Echo Method
database for comparing materials and for calibrating ultrasonic
attenuation measurement equipment.
3.2 Other terms used in this practice are defined in Termi-
5.5 This practice is not recommended for highly attenuating
nology E1316.
monolithics or composites that are thick, highly porous, or that
have rough or highly textured surfaces. For these materials
4. Summary of Practice
Practice E664/E664M may be appropriate. Guide E1495/
4.1 This practice describes a procedure for determining a
E1495M is recommended for assessing attenuation differences
material’s inherent attenuation coefficient and attenuation spec-
among composite plates and laminates that may exhibit, for
trum by means of a buffered broadband probe operating in the
example, pervasive matrix porosity or matrix crazing in addi-
pulse-echo contact mode on a solid sample that has smooth,
tion to having complex fiber architectures or thermomechanical
flat, parallel surfaces.
degradation (3). The proposed ASTM Standard Practice for
Measuring Ultrasonic Velocity in Advanced Ceramics (C1331)
4.2 The procedure described in this practice involves digital
is recommended for characterizing monolithic ceramics with
acquisition and computer processing of ultrasonic echo wave-
significant porosity or porosity variations (4).
forms returned by the test sample. Test sample constraints,
probing methods, data validity criteria, and measurement
6. Personnel Qualifications
corrections are prescribed herein.
6.1 If specified in the contractual agreement, personnel
5. Significance and Use
performing examinations to this practice shall be qualified in
5.1 This practice is useful for characterizing material mi- accordance with a nationally or internationally recognized
crostructure or measuring variations in microstructure that NDT personnel qualification practice or standard such as
C1332 − 18 (2023)
ANSI/ASNT CP-189, SNT-TC-1A, NAS 410, ISO 9712, or a 8.1.3.4 Dry coupling, for example, with an elastomer or thin
similar document and certified by the employer or certifying deformable polymer film, may be used provided that echo
agency, as applicable. The practice or standard used and its distortions or phase inversions are avoided by acoustic imped-
applicable revision shall be identified in the contractual agree- ance matching (5) and by substantially reducing the couplant
ment between the using parties. layer thickness.
8.1.4 Pulser-Receiver, having a bandwidth exceeding that of
6.2 Knowledge of the principles of ultrasonic testing is
the probe by a factor of 1.5 to 2 and including the probe/
required. Personnel applying this practice shall be experienced
transducer bandwidth to avoid significant distortions of the
practitioners of ultrasonic examinations and associated meth-
received signals. The pulser-receiver should have controls for
ods for signal acquisition, processing, and interpretation.
pulse voltage level, pulse duration, pulse repetition rate, pulse
6.3 Personnel shall have proficiency in computer program-
damping, gain (signal amplification steps), and received signal
ming and signal processing using digital methods for time and
and synchro
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