ASTM E2478-11(2016)

Standard Practice for Determining Damage-Based Design Stress for Glass Fiber Reinforced Plastic (GFRP) Materials Using Acoustic Emission

SIGNIFICANCE AND USE
5.1 The damage-based design approach will permit an additional method of design for GFRP materials. This is a very useful technique to determine the performance of different types of resins and composition of GFRP materials in order to develop a damage tolerant and reliable design. This AE-based method is not unique, other damage-sensitive evaluation methods can also be used.  
5.2 This practice involves the use of acoustic emission instrumentation and examination techniques as a means of damage detection to support a destructive test, in order to derive the damage-based design stress.  
5.3 This practice is not intended as a definitive predictor of long-term performance of GFRP materials (such as those used in vessels). For this reason, codes and standards require cyclic proof testing of prototypes (for example, vessels) which are not a part of this practice.  
5.4 Other design methods exist and are permitted.
SCOPE
1.1 This practice details procedures for establishing the direct stress and shear stress damage-based design values for use in the damage-based design criterion for materials to be used in GFRP vessels and other GFRP structures. The practice uses data derived from acoustic emission examination of four-point beam bending tests and in-plane shear tests (see ASME Section X, Article RT-8).  
1.2 The onset of lamina damage is indicated by the presence of significant acoustic emission during the reload portion of load/reload cycles. “Significant emission” is defined with historic index.  
1.3 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units which are provided for information only and are not considered standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-May-2016
• ICS: 59.100.10 - Textile glass materials
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.04 - Acoustic Emission Method

Standards Content (Sample)

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: E2478 − 11 (Reapproved 2016)
Standard Practice for
Determining Damage-Based Design Stress for Glass Fiber
Reinforced Plastic (GFRP) Materials Using Acoustic
Emission
This standard is issued under the fixed designation E2478; 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 D3846 Test Method for In-Plane Shear Strength of Rein-
forced Plastics
1.1 This practice details procedures for establishing the
E543 Specification forAgencies Performing Nondestructive
direct stress and shear stress damage-based design values for
Testing
use in the damage-based design criterion for materials to be
E976 GuideforDeterminingtheReproducibilityofAcoustic
used in GFRPvessels and other GFRPstructures. The practice
Emission Sensor Response
uses data derived from acoustic emission examination of
E1316 Terminology for Nondestructive Examinations
four-point beam bending tests and in-plane shear tests (see
E2374 Guide for Acoustic Emission System Performance
ASME Section X, Article RT-8).
Verification
1.2 Theonsetoflaminadamageisindicatedbythepresence
2.2 ASME Documents:
of significant acoustic emission during the reload portion of
ASMESectionX,ArticleRT-8 TestMethodforDetermining
load/reload cycles. “Significant emission” is defined with
Damage-Based Design Criterion
historic index.
ASMESectionV,Article11 AcousticEmissionExamination
1.3 Units—The values stated in inch-pound units are to be
of Fiber-Reinforced Plastic Vessels
regarded as standard. The values given in parentheses are
2.3 Other Standards:
mathematical conversions to SI units which are provided for
ANSI/ASNT-CP-189 Qualification and Certification of
information only and are not considered standard.
Nondestructive Testing Personnel
1.4 This standard does not purport to address all of the
SNT-TC-1A Recommended Practice for Personnel Qualifi-
safety concerns, if any, associated with its use. It is the
cation and Certification in Nondestructive Testing
responsibility of the user of this standard to establish appro-
NAS-410 Certification and Qualification of Nondestructive
priate safety and health practices and determine the applica-
Test Personnel
bility of regulatory limitations prior to use.
3. Terminology
2. Referenced Documents
3.1 Definitions of terms related to conventional acoustic
2.1 ASTM Standards:
emission are in Terminology E1316, Section B.
D790 Test Methods for Flexural Properties of Unreinforced
3.2 Definitions of Terms Specific to This Standard:
and Reinforced Plastics and Electrical Insulating Materi-
3.2.1 historic index—a measure of the change in MARSE
als
(or other AE feature parameter such as AE Signal Strength)
D4255/D4255M Test Method for In-Plane Shear Properties
throughout an examination.
of Polymer Matrix Composite Materials by the Rail Shear
Method
3.2.2 knee in the curve—a dramatic change in the slope of
the cumulative AE (MARSE or Signal Strength) versus time
curve.
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
structive Testing and is the direct responsibility of Subcommittee E07.04 on
Acoustic Emission Method.
Current edition approved June 1, 2016. Published June 2916. Originally Available from American Society of Mechanical Engineers (ASME), ASME
approved in 2006. Last previous edition approved in 2011 as E2478 - 11. DOI: International Headquarters, Three Park Ave., New York, NY 10016-5990, http://
10.1520/E2478-11R16. www.asme.org.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Standards volume information, refer to the standard’s Document Summary page on Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
the ASTM website. WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2478 − 11 (2016)
3.2.3 measured area of the rectified signal envelope 6.1.3 Procedure and Techniques—The procedures and tech-
(MARSE)—a measure of the area under the envelope of the niques to be utilized shall be as specified in the contractual
rectified linear voltage time signal from the sensor. (seeASME agreement.
Section V, Article 11) 6.1.4 Timing of Examination—The timing of examination
shall be in accordance with 12.4 unless otherwise specified.
3.2.4 significant emission—a level of emission that corre-
6.1.5 Extent of Examination—The extent of examination
sponds to the first time during reloading that the historic index
shall be in accordance with Sections 9 and 10 unless otherwise
attains a value of 1.4.
specified.
4. Summary of Practice
6.1.6 Reporting Criteria—Reporting criteria for the exami-
nationresultsshallbeinaccordancewith15.1unlessotherwise
4.1 This practice uses acoustic emission instrumentation
specified.
and examination techniques during load/reloading of materials
being examined, to determine the onset of significant acoustic
7. Apparatus
emission. The onset of significant emission is related to the
6,7
NOTE 1—Refer to Fig. 1 for AE system block diagram showing key
damage-based design stress by the Felicity ratio.
components of the AE system. It is recommended to use two AE sensors
to monitor the specimen, evaluated on a per channel basis.
5. Significance and Use
7.1 AE Sensors
5.1 The damage-based design approach will permit an
7.1.1 AE sensors shall be resonant in a 100 to 300 kHz
additional method of design for GFRPmaterials.This is a very
frequency band.
useful technique to determine the performance of different
7.1.2 Sensors shall have a peak sensitivity greater than –77
types of resins and composition of GFRP materials in order to
dB (referred to 1 volt per microbar, determined by face-to-face
develop a damage tolerant and reliable design. This AE-based
ultrasonic examination) within the frequency range 100 to 300
method is not unique, other damage-sensitive evaluation meth-
kHz.Sensitivitywithinthe100to300kHzrangeshallnotvary
ods can also be used.
more than 3 dB within the temperature range of intended use.
5.2 This practice involves the use of acoustic emission
7.1.3 Sensors shall be shielded against electromagnetic
instrumentation and examination techniques as a means of
interference through proper design practice or differential
damage detection to support a destructive test, in order to
(anti-coincidence) element design, or both.
derive the damage-based design stress.
7.1.4 Sensors shall have omni-directional response, with
5.3 This practice is not intended as a definitive predictor of
variations not exceeding 2 dB from the peak response.
long-term performance of GFRP materials (such as those used
7.2 Couplant
in vessels). For this reason, codes and standards require cyclic
7.2.1 Commercially available couplants for ultrasonic flaw
prooftestingofprototypes(forexample,vessels)whicharenot
detection may be used. Silicone-based high-vacuum grease has
a part of this practice.
been found to be particularly suitable. Adhesives may also be
5.4 Other design methods exist and are permitted.
used.
7.2.2 Couplant selection should be made to minimize
6. Basis of Application
changesincouplingsensitivityduringacompleteexamination.
6.1 The following items are subject to contractual agree-
Consideration should be given to the time duration of the
ment between the parties using or referencing this practice:
examination and maintaining consistency of coupling through-
6.1.1 Personnel Qualification—If specified in the contrac-
out the examination.
tual agreement, personnel performing examinations to this
7.3 Sensor-Preamplifier Cable
practice shall be qualified in accordance with a nationally or
7.3.1 The cable connecting the sensor to the preamplifier
internationally recognized NDT personnel qualification prac-
shall not attenuate the sensor peak voltage in the 100 to 300
tice or standard such as ANSI/ASNT-CP-189, SNT-TC-1A,
kHz frequency range more than 3 dB (6 ft (1.8 m) is a typical
NAS-410, or a similar document and certified by the employer
length). Integral preamplifier sensors meet this requirement.
or certifying agency, as applicable. The practice or standard
They have inherently short, internal, signal cables.
used and its applicable revision shall be identified in the
7.3.2 Thesensor-preamplifiercableshallbeshieldedagainst
contractual agreement between the using parties.
electromagnetic interference. Standard low-noise coaxial cable
6.1.2 Qualification of Nondestructive Agencies—Ifspecified
is generally adequate.
in the contractual agreement, NDT agencies shall be qualified
and evaluated as described in Practice E543. The applicable
7.4 Preamplifier
revision of Practice E543 shall be specified in the contractual
7.4.1 The preamplifier shall have a noise level no greater
agreement.
thanfivemicrovoltsrms(referredtoashortedinput)withinthe
100 to 300 kHz frequency range.
7.4.2 Preamplifier gain shall vary no more than 61dB
Ramirez, G., Ziehl, P., Fowler, T., 2004, “Nondestructive Evaluation of FRP
Design Criteria with Primary Consideration to Fatigue Loading”, ASME Journal of
within the 100 to 300 kHz frequency band and temperature
Pressure Vessel Technology, Vol. 126, pp. 1–13.
range of use.
Ziehl, P. and Fowler, T., 2003, “Fiber Reinforced Polymer Vessel Design with
7.4.3 Preamplifiers shall be shielded from electromagnetic
a Damage Approach”, Journal of Composite Structures, Vol. 61, Issue 4, pp.
395-411. interference.
E2478 − 11 (2016)
FIG. 1 AE System Block Diagram
NOTE 2—Instead of MARSE, other AE feature parameters such as
7.4.4 Preamplifiers of differential design shall have a mini-
“Signal Strength” may be used.
mum of 40 dB common-mode rejection.
7.4.5 Preamplifiers shall include a bandpass filter with a
7.7.5 Amplitude shall be measured in decibels referenced to
minimum bandwidth of 100 kHz to 300 kHz. Note that the
0 dB as 1 microvolt at the preamplifier input. Usable system
crystal resonant characteristics provide additional filtering as
dynamic range shall be a minimum of 60 dB with 1 dB
does the bandpass filter in the signal conditioner.
resolution over the frequency band of 100 to 300 kHz, and the
7.4.6 It is preferred that the preamplifier be mounted inside
temperature range of 40 to 100°F (4 to 38°C). Not more than
the sensor housing.
61 dB variation in peak detection accuracy shall be allowed
over the stated temperature range.
7.5 Power-Signal Cable
7.7.6 Hit duration (AE signal duration) shall be accurate to
7.5.1 The cable and connectors that provide power to
65 µs and is measured from the first threshold crossing to the
preamplifiers, and that conduct amplified signals to the main
last threshold crossing of the AE signal.
processor, shall be shielded against electromagnetic interfer-
7.7.7 Hit arrival time shall be recorded globally for each
ence. Signal loss shall be less than 3 dB over the length of the
channel accurate to within one millisecond, minimum.
cable.
7.7.8 The system deadtime of each channel of the system
7.6 Power Supply
shall be no greater than 200 µs.
7.6.1 Astable,grounded,powersupplythatmeetsthesignal
7.7.9 The hit definition time shall be 400 µs.
processor manufacturer’s specification shall be used.
7.7.10 The examination threshold shall be set at 40 dB
7.7 Main Signal Processor
(depending on background noise of the system setup when
7.7.1 Themainprocessorshallhavecircuitrythroughwhich
subjected to a constant load of 10 % or less of the estimated
sensor data will be processed. It shall be capable of processing
failure load). Threshold should remain constant during the
hits, hit arrival time, duration, counts, peak amplitude, and
entire examination.
MARSE (or similar AE feature parameters such as Signal
Strength) on each channel.
8. Calibration and Verification
7.7.2 Electroniccircuitryshallbestablewithin 61dBinthe
temperature range 40 to 100°F (4 to 38°C). 8.1 Annual calibration and verification of AE sensors,
7.7.3 Threshold shall be accurate within 61 dB. preamplifiers (if applicable), signal processor, and AE elec-
7.7.4 MARSE shall be measured on a per channel basis and tronic waveform generator (or simulator) should be performed.
shall have a resolution of 1 % of the value obtained from a one Equipmentshouldbeadjustedsothatitconformstoequipment
millisecond duration, 150 kHz sine burst having an amplitude manufacturer’s specifications. Instruments used for calibra-
25dBabovethedataanalysisthreshold.Usabledynamicrange tions must have current accuracy certification that is traceable
shall be a minimum of 40 dB. to the National Institute for Standards and Technology (NIST).
E2478 − 11 (2016)
8.2 Routine electronic evaluations must be performed any atedwiththeloadappliedinboththedirectionofthefibersand
time there is concern about signal processor performance. An perpendicular to the fibers.
AEelectronicwaveformgeneratororsimulator,shouldbeused
in making evaluations. Each signal processor channel must 11. Examination Temperature
respond with peak amplitude reading within 62dBofthe
11.1 For applications with a design operating temperature
electronic waveform generator output.
between 0°F (-18°C) and 120°F (49°C), the temperature of the
8.3 A system performance verification must be conducted
examination shall be within the range of 0°F (-18°C) and
immediately before, and immediately after, each examination.
120°F (49°C).
Aperformance verification uses a mechanical device to induce
11.2 For applications with a design operating temperature
stress waves into the material under examination, at a specified
above 120°F (49°C), the temperature of the examination shall
distance from each sensor. Induced stress waves stimulate a
be within the range of 50°F (10°C) and 120°F (49°C).
sensor in the same way as emission from a flaw. Performance
verificationsverifyperformanceoftheentiresystem(including
11.3 Thedesignandexaminationtemperatures(65 %)shall
couplant). (Refer to Guide E2374 for AE system performance
be reported in the test results.
verification techniques).
8.3.1 The preferred technique for conducting a performance
12. Examination Procedure
verification is a pencil lead break (PLB). Lead should be
12.1 The loading procedure for determining the presence of
brokenonthematerialsurfaceataspecifieddistancefromeach
the Felicity effect is import
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2478 − 11 E2478 − 11 (Reapproved 2016)
Standard Practice for
Determining Damage-Based Design Stress for Glass Fiber
Reinforced Plastic (GFRP) Materials Using Acoustic
Emission
This standard is issued under the fixed designation E2478; 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*Scope
1.1 This practice details procedures for establishing the direct stress and shear stress damage-based design values for use in the
damage-based design criterion for materials to be used in GFRP vessels and other GFRP structures. The practice uses data derived
from acoustic emission examination of four-point beam bending tests and in-plane shear tests (see ASME Section X, Article RT-8).
1.2 The onset of lamina damage is indicated by the presence of significant acoustic emission during the reload portion of
load/reload cycles. “Significant emission” is defined with historic index.
1.3 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are
mathematical conversions to SI units which are provided for information only and are not considered standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D790 Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
D4255/D4255M Test Method for In-Plane Shear Properties of Polymer Matrix Composite Materials by the Rail Shear Method
D3846 Test Method for In-Plane Shear Strength of Reinforced Plastics
E543 Specification for Agencies Performing Nondestructive Testing
E976 Guide for Determining the Reproducibility of Acoustic Emission Sensor Response
E1316 Terminology for Nondestructive Examinations
E2374 Guide for Acoustic Emission System Performance Verification
2.2 ASME Documents:
ASME Section X, Article RT-8 Test Method for Determining Damage-Based Design Criterion
ASME Section V, Article 11 Acoustic Emission Examination of Fiber-Reinforced Plastic Vessels
2.3 Other Standards:
ANSI/ASNT-CP-189 Qualification and Certification of Nondestructive Testing Personnel
SNT-TC-1A Recommended Practice for Personnel Qualification and Certification in Nondestructive Testing
NAS-410 Certification and Qualification of Nondestructive Test Personnel
3. Terminology
3.1 Definitions of terms related to conventional acoustic emission are in Terminology E1316, Section B.
3.2 Definitions of Terms Specific to This Standard:
This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic Emission
Method.
Current edition approved Dec. 1, 2011June 1, 2016. Published January 2012June 2916. Originally approved in 2006. Last previous edition approved in 20062011 as
E2478 - 06a.E2478 - 11. DOI: 10.1520/E2478-11.10.1520/E2478-11R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Three Park Ave., New York, NY 10016-5990, http://
www.asme.org.
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http://www.aia-aerospace.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2478 − 11 (2016)
3.2.1 historic index—a measure of the change in MARSE (or other AE feature parameter such as AE Signal Strength)
throughout an examination.
3.2.2 knee in the curve—a dramatic change in the slope of the cumulative AE (MARSE or Signal Strength) versus time curve.
3.2.3 measured area of the rectified signal envelope (MARSE)—a measure of the area under the envelope of the rectified linear
voltage time signal from the sensor. (see ASME Section V, Article 11)
3.2.4 significant emission—a level of emission that corresponds to the first time during reloading that the historic index attains
a value of 1.4.
4. Summary of Practice
4.1 This practice uses acoustic emission instrumentation and examination techniques during load/reloading of materials being
examined, to determine the onset of significant acoustic emission. The onset of significant emission is related to the damage-based
6,7
design stress by the Felicity ratio.
5. Significance and Use
5.1 The damage-based design approach will permit an additional method of design for GFRP materials. This is a very useful
technique to determine the performance of different types of resins and composition of GFRP materials in order to develop a
damage tolerant and reliable design. This AE-based method is not unique, other damage-sensitive evaluation methods can also be
used.
5.2 This practice involves the use of acoustic emission instrumentation and examination techniques as a means of damage
detection to support a destructive test, in order to derive the damage-based design stress.
5.3 This practice is not intended as a definitive predictor of long-term performance of GFRP materials (such as those used in
vessels). For this reason, codes and standards require cyclic proof testing of prototypes (for example, vessels) which are not a part
of this practice.
5.4 Other design methods exist and are permitted.
6. Basis of Application
6.1 The following items are subject to contractual agreement between the parties using or referencing this practice:
6.1.1 Personnel Qualification—If specified in the contractual agreement, personnel performing examinations to this practice
shall be qualified in accordance with a nationally or internationally recognized NDT personnel qualification practice or standard
such as ANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, or a similar document and certified by the employer or certifying agency,
as applicable. The practice or standard used and its applicable revision shall be identified in the contractual agreement between
the using parties.
6.1.2 Qualification of Nondestructive Agencies—If specified in the contractual agreement, NDT agencies shall be qualified and
evaluated as described in Practice E543. The applicable revision of Practice E543 shall be specified in the contractual agreement.
6.1.3 Procedure and Techniques—The procedures and techniques to be utilized shall be as specified in the contractual
agreement.
6.1.4 Timing of Examination—The timing of examination shall be in accordance with 12.4 unless otherwise specified.
6.1.5 Extent of Examination—The extent of examination shall be in accordance with Sections 9 and 10 unless otherwise
specified.
6.1.6 Reporting Criteria—Reporting criteria for the examination results shall be in accordance with 15.1 unless otherwise
specified.
7. Apparatus
NOTE 1—Refer to Fig. 1 for AE system block diagram showing key components of the AE system. It is recommended to use two AE sensors to monitor
the specimen, evaluated on a per channel basis.
7.1 AE Sensors
7.1.1 AE sensors shall be resonant in a 100 to 300 kHz frequency band.
7.1.2 Sensors shall have a peak sensitivity greater than –77 dB (referred to 1 volt per microbar, determined by face-to-face
ultrasonic examination) within the frequency range 100 to 300 kHz. Sensitivity within the 100 to 300 kHz range shall not vary
more than 3 dB within the temperature range of intended use.
7.1.3 Sensors shall be shielded against electromagnetic interference through proper design practice or differential (anti-
coincidence) element design, or both.
7.1.4 Sensors shall have omni-directional response, with variations not exceeding 2 dB from the peak response.
Ramirez, G., Ziehl, P., Fowler, T., 2004, “Nondestructive Evaluation of FRP Design Criteria with Primary Consideration to Fatigue Loading”, ASME Journal of Pressure
Vessel Technology, Vol. 126, pp. 1–13.
Ziehl, P. and Fowler, T., 2003, “Fiber Reinforced Polymer Vessel Design with a Damage Approach”, Journal of Composite Structures, Vol. 61, Issue 4, pp. 395-411.
E2478 − 11 (2016)
FIG. 1 AE System Block Diagram
7.2 Couplant
7.2.1 Commercially available couplants for ultrasonic flaw detection may be used. Silicone-based high-vacuum grease has been
found to be particularly suitable. Adhesives may also be used.
7.2.2 Couplant selection should be made to minimize changes in coupling sensitivity during a complete examination.
Consideration should be given to the time duration of the examination and maintaining consistency of coupling throughout the
examination.
7.3 Sensor-Preamplifier Cable
7.3.1 The cable connecting the sensor to the preamplifier shall not attenuate the sensor peak voltage in the 100 to 300 kHz
frequency range more than 3 dB (6 ft (1.8 m) is a typical length). Integral preamplifier sensors meet this requirement. They have
inherently short, internal, signal cables.
7.3.2 The sensor-preamplifier cable shall be shielded against electromagnetic interference. Standard low-noise coaxial cable is
generally adequate.
7.4 Preamplifier
7.4.1 The preamplifier shall have a noise level no greater than five microvolts rms (referred to a shorted input) within the 100
to 300 kHz frequency range.
7.4.2 Preamplifier gain shall vary no more than 61 dB within the 100 to 300 kHz frequency band and temperature range of use.
7.4.3 Preamplifiers shall be shielded from electromagnetic interference.
7.4.4 Preamplifiers of differential design shall have a minimum of 40 dB common-mode rejection.
7.4.5 Preamplifiers shall include a bandpass filter with a minimum bandwidth of 100 kHz to 300 kHz. Note that the crystal
resonant characteristics provide additional filtering as does the bandpass filter in the signal conditioner.
7.4.6 It is preferred that the preamplifier be mounted inside the sensor housing.
7.5 Power-Signal Cable
7.5.1 The cable and connectors that provide power to preamplifiers, and that conduct amplified signals to the main processor,
shall be shielded against electromagnetic interference. Signal loss shall be less than 3 dB over the length of the cable.
7.6 Power Supply
7.6.1 A stable, grounded, power supply that meets the signal processor manufacturer’s specification shall be used.
7.7 Main Signal Processor
7.7.1 The main processor shall have circuitry through which sensor data will be processed. It shall be capable of processing hits,
hit arrival time, duration, counts, peak amplitude, and MARSE (or similar AE feature parameters such as Signal Strength) on each
channel.
E2478 − 11 (2016)
7.7.2 Electronic circuitry shall be stable within 61 dB in the temperature range 40 to 100°F (4 to 38°C).
7.7.3 Threshold shall be accurate within 61 dB.
7.7.4 MARSE shall be measured on a per channel basis and shall have a resolution of 1 % of the value obtained from a one
millisecond duration, 150 kHz sine burst having an amplitude 25 dB above the data analysis threshold. Usable dynamic range shall
be a minimum of 40 dB.
NOTE 2—Instead of MARSE, other AE feature parameters such as “Signal Strength” may be used.
7.7.5 Amplitude shall be measured in decibels referenced to 0 dB as 1 microvolt at the preamplifier input. Usable system
dynamic range shall be a minimum of 60 dB with 1 dB resolution over the frequency band of 100 to 300 kHz, and the temperature
range of 40 to 100°F (4 to 38°C). Not more than 61 dB variation in peak detection accuracy shall be allowed over the stated
temperature range.
7.7.6 Hit duration (AE signal duration) shall be accurate to 65 μs and is measured from the first threshold crossing to the last
threshold crossing of the AE signal.
7.7.7 Hit arrival time shall be recorded globally for each channel accurate to within one millisecond, minimum.
7.7.8 The system deadtime of each channel of the system shall be no greater than 200 μs.
7.7.9 The hit definition time shall be 400 μs.
7.7.10 The examination threshold shall be set at 40 dB (depending on background noise of the system setup when subjected
to a constant load of 10 % or less of the estimated failure load). Threshold should remain constant during the entire examination.
8. Calibration and Verification
8.1 Annual calibration and verification of AE sensors, preamplifiers (if applicable), signal processor, and AE electronic
waveform generator (or simulator) should be performed. Equipment should be adjusted so that it conforms to equipment
manufacturer’s specifications. Instruments used for calibrations must have current accuracy certification that is traceable to the
National Institute for Standards and Technology (NIST).
8.2 Routine electronic evaluations must be performed any time there is concern about signal processor performance. An AE
electronic waveform generator or simulator, should be used in making evaluations. Each signal processor channel must respond
with peak amplitude reading within 62 dB of the electronic waveform generator output.
8.3 A system performance verification must be conducted immediately before, and immediately after, each examination. A
performance verification uses a mechanical device to induce stress waves into the material under examination, at a specified
distance from each sensor. Induced stress waves stimulate a sensor in the same way as emission from a flaw. Performance
verifications verify performance of the entire system (including couplant). (Refer to Guide E2374 for AE system performance
verification techniques).
8.3.1 The preferred technique for conducting a performance verification is a pencil lead break (PLB). Lead should be broken
on the material surface at a specified distance from each sensor. The 2H lead, 0.012-in. (0.3-mm) diameter, and 0.079–0.118-in.
(2 to 3-mm) long should be used (see Fig
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