ASTM E2374-04
(Guide)Standard Guide for Acoustic Emission System Performance Verification
Standard Guide for Acoustic Emission System Performance Verification
SCOPE
1.1 System performance verification methods stimulate 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.
General Information
Relations
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: E2374 – 04
Standard Guide for
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 E1781 Practice for Secondary Calibration of Acoustic
Emission Sensors
1.1 System performance verification methods stimulate the
examination article on which the sensor is mounted. The
3. Terminology
resulting stress wave travels in the examination article and is
3.1 examination article—the item which is being examined
detected by the sensor(s) in a manner similar to acoustic
with AE and to which AE sensors are attached.
emission.
3.2 velocity—the measured velocity of a stress wave, trav-
1.2 This guide describes methods which can be used to
eling in the examination article, using specified AE system
verify the response of an Acoustic Emission system including
parameters and components. Velocity is often used in triangu-
sensors, couplant, sensor mounting devices, cables and system
lation calculations to determine the position of the AE source.
electronic components.
3.3 auto sensor test (AST)—an electronic means by which a
1.3 Acoustic emission system performance characteristics,
sensor can be fed an electronic pulse to excite the examination
which may be evaluated using this document, include some
article.The resulting stress wave in the examination article can
waveform parameters, and source location accuracy.
be measured by the same sensor or by other sensors that are on
1.4 Performance verification is usually conducted prior to
the same examination article. See 3.4 and 3.5.
beginning the examination.
3.4 auto sensor test-self test mode—a means by which an
1.5 Performance verification can be conducted during the
AST sensor may be used to check its own performance.
examination if there is any suspicion that the system perfor-
3.5 auto sensor test-near neighbor mode—a means by
mance may have changed.
which anAST sensor may be used to determine the sensitivity
1.6 Performance verification may be conducted after the
of one or more neighboring sensors on the same examination
examination has been completed.
article.
2. Referenced Documents
4. Significance and Use
2.1 ASTM Standards:
4.1 Acoustic Emission data acquisition can be affected by
E750 Practice for CharacterizingAcoustic Emission Instru-
numerous factors associated with the electronic instrumenta-
mentation
tion, cables, sensors, sensor holders, couplant, the examination
E976 Guide for Determining the Reproducibility of Acous-
article on which the sensor is mounted, background noise, and
tic Emission Sensor Response
the user’s settings of the acquisition parameters (for example,
E1316 Terminology for Nondestructive Examinations
threshold).
E1419 Practice for Examination of Seamless, Gas-Filled,
4.2 This guide is not intended to replace annual (or semi-
Pressure Vessels Using Acoustic Emission
annual) instrumentation calibration (see Practice E750)or
sensor recertification (see Practice E1781).
4.3 This guide is not intended to replace routine electronic
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc-
evaluation of AE instrumentation or routine sensitivity verifi-
tive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic
cation of AE sensors (see Guide E976).
Emission Method.
4.4 This guide is not intended to verify the maximum
Current edition approved May 1, 2004. Published June 2004. DOI: 10.1520/
E2374-04.
processing capacity or speed of an AE system.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.5 This guide does not purport to address all of the safety
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
concerns, if any associated with its use. It is the responsibility
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. of the user of this guide to establish appropriate safety and
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2374 – 04
health practices and determine the applicability of regulatory situation the independent pulser is left in place and used
limitations prior to use. periodically to assure system performance.
5.1.3 AST Capable Integrated Pulser/Sensor—An AE sen-
5. Apparatus
sor that has been designed to accept an electronic signal/pulse
into its crystal. The mechanical displacement of the crystal
5.1 To determine system performance a sensor must be
excites the examination article. The stress wave generated in
subjected to a stress wave traveling in the examination article.
Transient stress waves are launched by mechanical or electro- the examination article can be detected by other sensors on the
mechanical devices that produce a waveform with fast rise- same examination article. With certain realizations of theAST
time, short duration and repeatable peak amplitude. Steady function (self test mode), it can also be detected by the exciting
state (continuous) stress waves are launched by mechanical or
sensor.
electromechanical devices that produce a waveform with long
5.1.3.1 Auto Sensor Test: Near Neighbor Mode—An inte-
duration constant amplitude.
grated pulser/sensor can be used to measure sensitivity and
5.1.1 Pencil Lead Break (PLB)—Amechanical pencil tech-
time-of-flight (that is, the time required for a stress wave to
nique whereby lead is pushed against the examination article’s
travel the sensor-spacing distance) for neighboring sensors on
surface with sufficient force to break the lead. When the lead
the same examination article. The time-of-flight can be used to
breaks, there is a sudden release of stress on the surface. (See
calculate the apparent velocity of the stress wave (apparent
Guide E976, paragraph 4.3.3 and Fig. 4.)
velocity = sensor spacing/time-of-flight).
5.1.1.1 The distance between the PLB and the sensor must
5.1.3.2 Auto Sensor Test: Self Test Mode—An integrated
be specified.
pulser/sensor can be used to verify the performance of the
5.1.1.2 The “Hsu pencil source” uses a mechanical pencil
sensor coupling and the sensor and channel electronics to
with a 2.5 mm lead extension, 2H hardness and 0.3 mm or 0.5
which it is attached by establishing a baseline duration (or
mm diameter (0.3 mm is preferred).
energy) measured from the AST pulse using a sensor that is
5.1.1.3 The “Nielsen shoe” can aid in breaking the lead
known to be operating properly and mounted optimally on the
consistently.
examination article. The baseline duration number (for ex-
5.1.1.4 The pencil should be held at an angle of 30 degrees
ample, 10 000 µs) can then be compared with theASTduration
to the surface.
measurements from each channel on the examination article.
5.1.1.5 Three to five lead breaks are generally conducted to
Channels, which produceAST duration measurements that are
show a consistent result.
low compared to the baseline, should be recoupled, repaired or
5.1.1.6 Application standards (for example, Test Method
replaced as necessary.
E1419) specify the minimum signal amplitude that must be
5.1.4 Spring Loaded Center Punch—Aspringloadeddevice
measured by the AE instrumentation.
that imparts a mechanical impact force, creating a very large
5.1.1.7 Channels which are found to have unacceptably low
stress wave on the examination article. The spring assures a
or high sensitivity can be recoupled (that is, replace couplant),
consistent and repeatable force.
repaired (that is, replace sensor, or cable, or both), or replaced
5.1.4.1 The spring-loaded center punch is of particular
(that is, exchanged for another channel), or both.
advantagewhenAEsensorsaredistributedoverlargedistances
5.1.1.8 PLB can be used to determine the apparent velocity
on an examination article, as the imparted force is so strong it
in the examination article (apparent velocity = sensor spacing/
can be detected easily.
time-of-flight).“Time-of-flight”isthetimerequiredforastress
wave to travel the sensor-spacing distance
5.1.4.2 The spring-loaded center punch is readily available
5.1.2 Independent Piezoelectric Pulser—An electrome-
and easy to apply anywhere on the examination article, at any
chanicaldeviceheldagainsttheexaminationarticleandusedin
time.
conjunction with an electronic signal or pulse generator. The
5.1.4.3 To avoid damage to the surface, it is desirable to
electrical signal from the signal/pulse generator is converted
apply the center punch through an intermediate interface such
into a mechanical displacement by the transducer’s crystal.
as a thin sheet of metal or coin.
(See Guide E976, paragraph 4.3.1.) One significant advantage
5.1.5 Projectile—An object which is launched or projected
ofthistechniqueisthattheoutputoftheelectronicsignal/pulse
to impact the surface of the examination article. Examples
generator can be adjusted in numerous ways (for example,
include a steel ball dropped onto the surface, a BB gun fired at
amplitude and repetition rate).
the surface or a mass at the end of a pendulum. In most cases
5.1.2.1 The independent pulser can be used to excite the
the energy being imparted onto the surface can be determined.
receivingAE sensor before, during and after an examination as
5.1.6 Gas Jet—A gas jet forces a gas through a nozzle at
verification that there were no changes in coupling or sensor
high pressure onto the surface of the examination article being
response. The independent pulser technique is particularly
instrumented. The gas jet is controlled by an electronic valve
useful when there is limited access to the examination article
with the ability of being turned on momentarily to create a
thatwouldprecludetheuseofmanualtechniques(forexample,
transientsurfacewaveorkeptontocreateacontinuoussurface
PLB).
wave.
5.1.2.2 The independent pulser
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.