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ASTM E2374-16(2021)

(Guide)

Standard Guide for Acoustic Emission System Performance Verification

Standard Guide for Acoustic Emission System Performance Verification

SIGNIFICANCE AND USE
4.1 Acoustic Emission data acquisition can be affected by numerous factors associated with the electronic instrumentation, cables, sensors, sensor holders, couplant, the examination article on which the sensor is mounted, background noise, and the user's settings of the acquisition parameters (for example, threshold).  
4.2 This guide is not intended to replace annual (or semi-annual) instrumentation calibration (see Practice E750) or sensor recertification (see Practice E1781).  
4.3 This guide is not intended to replace routine electronic evaluation of AE instrumentation or routine reproducibility verification of AE sensors (see Guide E976).  
4.4 This guide is not intended to verify the maximum processing capacity or speed of an AE system.  
4.5 This guide 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 guide to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
SCOPE
1.1 System performance verification methods launch stress waves into the examination article on which the sensor is mounted. The resulting stress wave travels in the examination article and is detected by the sensor(s) in a manner similar to acoustic emission.  
1.2 This guide describes methods which can be used to verify the response of an Acoustic Emission system including sensors, couplant, sensor mounting devices, cables and system electronic components.  
1.3 Acoustic emission system performance characteristics, which may be evaluated using this document, include some waveform parameters, and source location accuracy.  
1.4 Performance verification is usually conducted prior to beginning the examination.  
1.5 Performance verification can be conducted during the examination if there is any suspicion that the system performance may have changed.  
1.6 Performance verification may be conducted after the examination has been completed.  
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.8 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.9 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.

General Information

Status
Published
Publication Date
31-Oct-2021
ICS
17.140.01 - Acoustic measurements and noise abatement in general
Technical Committee
E07 - Nondestructive Testing
Drafting Committee
E07.04 - Acoustic Emission Method
Current Stage
Ref Project

Relations

Refers
ASTM E750-15(2020) - Standard Practice for Characterizing Acoustic Emission Instrumentation
Effective Date
01-Jun-2020

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ASTM E2374-16(2021) - Standard Guide for Acoustic Emission System Performance VerificationASTM E2374-16(2021) - Standard Guide for Acoustic Emission System Performance Verification
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ASTM E2374-16(2021) - Standard Guide for Acoustic Emission System Performance Verification
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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: E2374 −16 (Reapproved 2021)
Standard Guide for
1
Acoustic Emission System Performance Verification
This standard is issued under the fixed designation E2374; 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* 2. Referenced Documents
2
1.1 System performance verification methods launch stress 2.1 ASTM Standards:
waves into the examination article on which the sensor is
E750 Practice for Characterizing Acoustic Emission Instru-
mounted. The resulting stress wave travels in the examination mentation
article and is detected by the sensor(s) in a manner similar to
E976 GuideforDeterminingtheReproducibilityofAcoustic
acoustic emission. Emission Sensor Response
E1316 Terminology for Nondestructive Examinations
1.2 This guide describes methods which can be used to
E1419 Practice for Examination of Seamless, Gas-Filled,
verify the response of an Acoustic Emission system including
Pressure Vessels Using Acoustic Emission
sensors, couplant, sensor mounting devices, cables and system
E1781 Practice for Secondary Calibration ofAcoustic Emis-
electronic components.
sion Sensors
1.3 Acoustic emission system performance characteristics,
which may be evaluated using this document, include some
3. Terminology
waveform parameters, and source location accuracy.
3.1 Definitions of Terms Specific to This Standard:
1.4 Performance verification is usually conducted prior to
3.1.1 examination article—the item which is being exam-
beginning the examination.
ined with AE and to which AE sensors are attached.
1.5 Performance verification can be conducted during the
3.1.2 velocity—the measured velocity of a stress wave,
examination if there is any suspicion that the system perfor-
traveling in the examination article, using specifiedAE system
mance may have changed.
parameters and components. Velocity is often used in triangu-
lation calculations to determine the position of the AE source.
1.6 Performance verification may be conducted after the
examination has been completed.
3.1.3 auto sensor test (AST)—an electronic means by which
a sensor can be fed an electronic pulse to excite the examina-
1.7 The values stated in SI units are to be regarded as
tionarticle.Theresultingstresswaveintheexaminationarticle
standard. No other units of measurement are included in this
canbemeasuredbythesamesensororbyothersensorsthatare
standard.
on the same examination article. See 3.1.4 and 3.1.5.
1.8 This standard does not purport to address all of the
3.1.4 auto sensor test-self test mode—a means by which an
safety concerns, if any, associated with its use. It is the
AST sensor may be used to check its own performance.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.1.5 auto sensor test-near neighbor mode—a means by
mine the applicability of regulatory limitations prior to use.
which anAST sensor may be used to determine the sensitivity
1.9 This international standard was developed in accor-
of one or more neighboring sensors on the same examination
dance with internationally recognized principles on standard-
article.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4. Significance and Use
mendations issued by the World Trade Organization Technical
4.1 Acoustic Emission data acquisition can be affected by
Barriers to Trade (TBT) Committee.
numerous factors associated with the electronic
instrumentation, cables, sensors, sensor holders, couplant, the
1
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc-
tive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic
2
Emission Method. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2021. Published November 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2004. Last previous edition approved in 2016 as E2374 - 16. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2374-16R21. the ASTM website.
*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
1

---------------------- Page: 1 ----------------------
E2374 − 16 (2021)
examination article on which the sensor is moun
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4.1 IEM Applications and Capabilities—IEM has been successfully applied to a wide range of NDT applications in the manufacture, maintenance, and repair of metallic and non-metallic parts. Examples of anomalies detected are discussed in 1.1 and 6.2. IEM has been proven to provide fast, cost-effective, and accurate NDT solutions in nearly all manufacturing, maintenance, or repair modalities. Examples of the successful application focuses include, but are not limited to: sintered powder metals, castings, forgings, stampings, ceramics, glass, wood, weldments, heat treatment, composites, additive manufacturing, machined products, and brazed products.  
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4.2.1 IEM systems are comprised of hardware and software capable of inducing vibrations, recording the component response to the induced vibrations, and executing analysis of the data collected.  
4.2.2 Hardware Requirements—Examples of a tabletop impact excitation system and a production-grade drop excitation system are shown in Fig. 1 and Fig. 2, respectively. IEM systems include: an excitation device (for example, modal hammer / impact device / dropping system) providing an impulse excitation to the object, a vibration detector (for example., microphone), a signal amplifier, an Analog-to-Digital Converter (ADC), an embedded logic, and a data User Interface (UI). Tested parts can typically be on any surface type, but they can also be supported (for example, foam support, held with an elastic) in consideration of possible damping influences. The following schematics show the basic parts for an impact excitation approach (Fig. 3) and a drop excitation approach (Fig. 4).
FIG. 1 IEM Tabletop Testing System Using a Non-Instrumented Impactor
FIG. 2 Production-Grade Drop Excitation System
FIG. 3 Schematic of Impact Excitation Approach
FIG. 4 Schematic of Drop Excitation Approach  
4.3 Constraints and Limitations:  
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1.1 This practice covers a general procedure for using the Impulse Excitation Method (IEM) to facilitate natural frequency measurement and detection of defects and material variations in metallic and non-metallic parts. This test method is also known as Impulse Excitation Technique (IET), Acoustic Resonance Testing (ART), ping testing, tap testing, and other names. IEM is listed as a Resonance Ultrasound Spectroscopy (RUS) method. The method applies an impulse load to excite and then record resonance frequencies of a part. These recorded resonance frequencies are compared to a reference population or within subgroups/families of examples of the same part, or modeled frequencies, or both.  
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Standard Guide for Acoustic Emission Examination of Small Parts

SIGNIFICANCE AND USE
4.1 The purpose of the AE examination is to analyze how an examination object is withstanding the applied load, or if it is suffering from some latent damage. Consequently the emission activity must be evaluated in relation to the applied load.  
4.2 The applied load (on the examination object) may include mechanical forces (tension, compression or torsional), internal pressure and thermal gradients. It may be short to long, random or cyclic. The applied load may be controlled by the examiner or may already exist as part of the process. In either case the applied load is measured along with the AE activity.  
4.3 Possible applications include the determination of part integrity, quality control assessment of production processes on a sampled or 100 % inspection basis, in-process examination during a period of applied load of a fabrication process (for example, spot welding, bonding, soldering, pressing, etc.), proof-testing after fabrication, monitoring a “region of interest” (or concern) of a structure (for example, bridge joint or repair, vessel, pipe), and re–examination after intervals of service.
SCOPE
1.1 This guide covers techniques for conducting acoustic emission (AE) examinations of small parts. It is confined to examination objects (or defined regions of larger objects) where there is low AE signal attenuation throughout the examination region. This eliminates the consideration of complex attenuation factor corrections and multiple sensor and array placements based on overcoming signal losses over distances.  
1.2 The guide assumes a typical AE examination as one where there is a controlled or measured stress acting upon the part being monitored by AE. Particular emphasis is placed on sensor and system selection, sensor placements, stressing considerations, noise reduction/rejection techniques, spatial filtering, location determination, use of guard sensors, collection of AE data, AE data analysis and report. The purpose of the AE examination is to analyze how an object under evaluation is withstanding the applied load.  
1.3 Possible applications of this guide includes materials characterization, quality control of production processes, proof testing after fabrication, evaluating regions of interest of larger structures and retesting after intervals of service. The applied load may include mechanical forces (tension, compression or torsional) internal pressure and thermal gradients.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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.

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ASTM E976-15(2021)(Guide)
Standard Guide for Determining the Reproducibility of Acoustic Emission Sensor Response

SIGNIFICANCE AND USE
3.1 Acoustic emission data is affected by several characteristics of the instrumentation. The most obvious of these is the system sensitivity. Of all the parameters and components contributing to the sensitivity, the acoustic emission sensor is the one most subject to variation. This variation can be a result of damage or aging, or there can be variations between nominally identical sensors. To detect such variations, it is desirable to have a method for measuring the response of a sensor to an acoustic wave. Specific purposes for checking sensors include: (1) checking the stability of its response with time; (2) checking the sensor for possible damage after accident or abuse; (3) comparing a number of sensors for use in a multichannel system to ensure that their responses are adequately matched; and (4) checking the response after thermal cycling or exposure to a hostile environment. It is very important that the sensor characteristics be always measured with the same sensor cable length and impedance as well as the same preamplifier or equivalent. This guide presents several procedures for measuring sensor response. Some of these procedures require a minimum of special equipment.  
3.2 It is not the intent of this guide to evaluate AE system performance. Refer to Practice E750 for characterizing acoustic instrumentation and refer to Guide E2374 for AE system performance verification.  
3.3 The procedures given in this guide are designed to measure the response of an acoustic emission sensor to an arbitrary but repeatable acoustic wave. These procedures in no way constitute a calibration of the sensor. The absolute calibration of a sensor requires a complete knowledge of the characteristics of the acoustic wave exciting the sensor or a previously calibrated reference sensor. In either case, such a calibration is beyond the scope of this guide.  
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SCOPE
1.1 This guide defines simple economical procedures for testing or comparing the performance of acoustic emission sensors. These procedures allow the user to check for degradation of a sensor or to select sets of sensors with nearly identical performances. The procedures are not capable of providing an absolute calibration of the sensor nor do they assure transferability of data sets between organizations.  
1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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.

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ASTM E1106-12(2021)(Test Method)
Standard Test Method for Primary Calibration of Acoustic Emission Sensors

SIGNIFICANCE AND USE
4.1 Transfer Standards—One purpose of this test method is for the direct calibration of displacement transducers for use as secondary standards for the calibration of AE sensors for use in nondestructive evaluation. For this purpose, the transfer standard should be high fidelity and very well behaved and understood. If this can be established, the stated accuracy should apply over the full frequency range up to 1 MHz.
Note 1: The stated accuracy applies only if the transfer standard returns to quiescence, following the transient input, before any wave reflected from the boundary of the calibration block returns to the transfer standard (∼100 μs). For low frequencies with periods on the order of the time window, this condition is problematical to prove.  
4.2 Applications Sensors—This test method may also be used for the calibration of AE sensors for use in nondestructive evaluation. Some of these sensors are less well behaved than devices suitable for a transfer standard. The stated accuracy for such devices applies in the range of 100 kHz to 1 MHz and with less accuracy below 100 kHz.
SCOPE
1.1 This test method covers the requirements for the absolute calibration of acoustic emission (AE) sensors. The calibration yields the frequency response of a transducer to waves, at a surface, of the type normally encountered in acoustic emission work. The transducer voltage response is determined at discrete frequency intervals of approximately 10 kHz up to 1 MHz. The input is a given well-established dynamic displacement normal to the mounting surface. The units of the calibration are output voltage per unit mechanical input (displacement, velocity, or acceleration).  
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Standard Practice for the Measurement of the Apparent Attenuation of Longitudinal Ultrasonic Waves by Immersion Method

SIGNIFICANCE AND USE
5.1 The measurement of apparent attenuation in materials is useful in applications such as the comparison of heat treatments of different lots of material or the assessment of the degradation of materials due to environment.  
5.2 Several different modes of wave vibration can be propagated in solids. This practice is concerned with the attenuation associated with longitudinal waves introduced into the specimen by the immersion method.  
5.3 This practice allows for the comparison of the apparent attenuations of geometrically similar specimens.  
5.4 For the determination of apparent attenuation, the procedures described herein are valid only for measurements in the far field of the ultrasonic beam.
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1.1 This practice describes a procedure for measuring the apparent attenuation of ultrasound in materials or components with flat, parallel surfaces using conventional pulse-echo ultrasonic flaw detection equipment in which reflected indications are displayed in an A-scan presentation.  
1.2 The measurement procedure is readily adaptable for the determination of relative attenuation between materials. For absolute (true) attenuation measurements, indicative of the intrinsic nature of the material, it is necessary to correct for specimen geometry, sound beam divergence, instrumentation, and procedural effects. These results can be obtained with more specialized ultrasonic equipment and techniques.  
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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.

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ASTM E1781/E1781M-20(Practice)
Standard Practice for Secondary Calibration of Acoustic Emission Sensors

SIGNIFICANCE AND USE
4.1 The purpose of this practice is to enable the transfer of calibration from sensors that have been calibrated by primary calibration to other sensors.
SCOPE
1.1 This practice covers requirements for the secondary calibration of acoustic emission (AE) sensors. The secondary calibration yields the frequency response of a sensor to waves of the type normally encountered in acoustic emission work. The source producing the signal used for the calibration is mounted on the same surface of the test block as the sensor under testing (SUT). Rayleigh waves are dominant under these conditions; the calibration results represent primarily the sensor's sensitivity to Rayleigh waves. The sensitivity of the sensor is determined for excitation within the range of 100 kHz to 1 MHz. Sensitivity values are usually determined at frequencies approximately 10 kHz apart. The units of the calibration are volts per unit of mechanical input (displacement, velocity, or acceleration).  
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Standard Practice for Evaluating Characteristics of Ultrasonic Search Units

SIGNIFICANCE AND USE
5.1 This practice is intended to provide standardized procedures for evaluating ultrasonic search units. It is not intended to define performance and acceptance criteria, but rather to provide data from which such criteria may be established.  
5.2 These procedures are intended to evaluate the characteristics of single-element piezoelectric search units.  
5.3 Implementation may require more detailed procedural instructions in a format of the using facility.  
5.4 The measurement data obtained may be employed by users of this practice to specify, describe, or provide a performance criteria for procurement and quality assurance, or service evaluation of the operating characteristics of ultrasonic search units. All or portions of the practice may be used as determined by the user.  
5.5 The measurements are made primarily under pulse-echo conditions. To determine the relative performance of a search unit as either a transmitter or a receiver may require additional tests.  
5.6 While these procedures relate to many of the significant parameters, others that may be important in specific applications may not be treated. These might include power handling capability, breakdown voltage, wear properties of contact units, radio-frequency interference, and the like.  
5.7 Care must be taken to ensure that comparable measurements are made and that users of the practice follow similar procedures. The conditions specified or selected (if optional) may affect the test results and lead to apparent differences.  
5.8 Interpretation of some test results, such as the shape of the frequency response curve, may be subjective. Small irregularities may be significant. Interpretation of the test results is beyond the scope of this practice.  
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SCOPE
1.1 This practice covers measurement procedures for evaluating certain characteristics of ultrasonic search units (also known as “probes”) that are used with ultrasonic testing instrumentation. This practice describes means for obtaining performance data that may be used to define the acoustic and electric responses of ultrasonic search units.  
1.2 The procedures are designed to measure search units as individual components (separate from the ultrasonic test instrument) using commercial search unit characterization systems or using laboratory instruments such as signal generators, pulsers, amplifiers, digitizers, oscilloscopes, and waveform analyzers.  
1.3 The procedures are applicable to manufacturing acceptance and incoming inspection of new search units or to periodic performance evaluation of search units throughout their service life.  
1.4 The procedures in Annex A1 – Annex A6 are generally applicable to ultrasonic search units operating within the 0.4 to 10 MHz range. Annex A7 is applicable to higher frequency immersion search unit evaluation. Annex A8 describes a practice for measuring sound beam profiles in metals from contact straight-beam search units. Additional Annexes, such as sound beam profiling for angle-beam search units in metal and alternate means for search unit characterization, will be added when developed.  
1.5 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
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Standard Practice for Resonance Testing Using the Impulse Excitation Method

SIGNIFICANCE AND USE
4.1 IEM Applications and Capabilities—IEM has been successfully applied to a wide range of NDT applications in the manufacture, maintenance, and repair of metallic and non-metallic parts. Examples of anomalies detected are discussed in 1.1 and 6.2. IEM has been proven to provide fast, cost-effective, and accurate NDT solutions in nearly all manufacturing, maintenance, or repair modalities. Examples of the successful application focuses include, but are not limited to: sintered powder metals, castings, forgings, stampings, ceramics, glass, wood, weldments, heat treatment, composites, additive manufacturing, machined products, and brazed products.  
4.2 General Approach and Equipment Requirements for IEM:  
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FIG. 1 IEM Tabletop Testing System Using a Non-Instrumented Impactor
FIG. 2 Production-Grade Drop Excitation System
FIG. 3 Schematic of Impact Excitation Approach
FIG. 4 Schematic of Drop Excitation Approach  
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ASTM F2174-02(2023)(Practice)
Standard Practice for Verifying Acoustic Emission Sensor Response

SIGNIFICANCE AND USE
3.1 Degradation in sensor performance can occur due to dropping, mechanical shock while mounted on the test structure, temperature cycles, and so forth. It is necessary and desirable to have a simple measurement procedure that will check the consistency of sensor response, while holding all other variables constant.  
3.2 While test blocks of many different kinds have been used for this purpose for many years, an acrylic polymer rod offers the best all-around combination of suitable acoustic properties, practical convenience, ease of procurement, and low cost.  
3.3 Because the acoustic properties of the acrylic rod are known to depend on temperature, this practice requires that the rod, sensors, and couplant be stabilized at the same working temperature, prior to application of the practice.  
3.4 Attention should be paid to storage conditions for the acrylic polymer rod. For example, it should not be left in a freezing or hot environment overnight, unless it is given time for temperature stabilization before use.  
3.5 Properly applied and with proper record keeping, this practice can be used in many ways, such as:  
3.5.1 To determine when a sensor is no longer suitable for use.  
3.5.2 To check sensors that have been exposed to high-risk conditions such as dropping, overheating, and so forth.  
3.5.3 To get an early warning of sensor degradation over time.  
3.5.4 To obtain matched sets of sensors and preamplifiers.  
3.5.5 To verify sensors quickly but accurately in the field, and to assist troubleshooting when a channel does not pass a performance check.
SCOPE
1.1 This practice is used for routinely checking the sensitivity of acoustic emission (AE) sensors. It is intended to provide a reliable, precisely specified way of comparing a set of sensors or telling whether an individual sensor's sensitivity has degraded during its service life, or both.  
1.2 The procedure in this practice is not a “calibration” and does not give frequency-response information.  
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.4 This practice does not purport to recommend one sensor manufacturer over another nor does it imply that one type of sensor will react differently from another when using this procedure.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 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.

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ASTM
ASTM E1932-12(2022)(Guide)
Standard Guide for Acoustic Emission Examination of Small Parts

SIGNIFICANCE AND USE
4.1 The purpose of the AE examination is to analyze how an examination object is withstanding the applied load, or if it is suffering from some latent damage. Consequently the emission activity must be evaluated in relation to the applied load.  
4.2 The applied load (on the examination object) may include mechanical forces (tension, compression or torsional), internal pressure and thermal gradients. It may be short to long, random or cyclic. The applied load may be controlled by the examiner or may already exist as part of the process. In either case the applied load is measured along with the AE activity.  
4.3 Possible applications include the determination of part integrity, quality control assessment of production processes on a sampled or 100 % inspection basis, in-process examination during a period of applied load of a fabrication process (for example, spot welding, bonding, soldering, pressing, etc.), proof-testing after fabrication, monitoring a “region of interest” (or concern) of a structure (for example, bridge joint or repair, vessel, pipe), and re–examination after intervals of service.
SCOPE
1.1 This guide covers techniques for conducting acoustic emission (AE) examinations of small parts. It is confined to examination objects (or defined regions of larger objects) where there is low AE signal attenuation throughout the examination region. This eliminates the consideration of complex attenuation factor corrections and multiple sensor and array placements based on overcoming signal losses over distances.  
1.2 The guide assumes a typical AE examination as one where there is a controlled or measured stress acting upon the part being monitored by AE. Particular emphasis is placed on sensor and system selection, sensor placements, stressing considerations, noise reduction/rejection techniques, spatial filtering, location determination, use of guard sensors, collection of AE data, AE data analysis and report. The purpose of the AE examination is to analyze how an object under evaluation is withstanding the applied load.  
1.3 Possible applications of this guide includes materials characterization, quality control of production processes, proof testing after fabrication, evaluating regions of interest of larger structures and retesting after intervals of service. The applied load may include mechanical forces (tension, compression or torsional) internal pressure and thermal gradients.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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.

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