ASTM E2491-06
(Guide)Standard Guide for Evaluating Performance Characteristics of Phased-Array Ultrasonic Examination Instruments and Systems
Standard Guide for Evaluating Performance Characteristics of Phased-Array Ultrasonic Examination Instruments and Systems
SIGNIFICANCE AND USE
This guide is intended to evaluate performance assessment of combinations of phased-array probes and instruments. It is not intended to define performance and acceptance criteria, but rather to provide data from which such criteria may be established.
Recommended procedures described in this guide are intended to provide performance-related measurements that can be reproduced under the specified test conditions using simple targets and the phased-array test system itself. It is intended for phased-array flaw detection instruments operating in the nominal frequency range of 1 MHz to 20 MHz, but the procedures are applicable to measurements on instruments utilizing significantly higher frequency components.
This guide is not intended for service calibration, or maintenance of circuitry for which the manufacturer’s instructions are available.
Implementation of specific assessments may require more detailed procedural instructions in a format of the using facility.
The measurement data obtained may be employed by users of this guide to specify, describe, or provide a performance criteria for procurement and quality assurance, or service evaluation of the operating characteristics of phased-array systems.
Not all assessments described in this guide are applicable to all systems. All or portions of the guide may be used as determined by the user.
SCOPE
1.1 This guide describes procedures for evaluating some performance characteristics of phased-array ultrasonic examination instruments and systems.
1.2 Evaluation of these characteristics is intended to be used for comparing instruments and systems or, by periodic repetition, for detecting long-term changes in the characteristics of a given instrument or system that may be indicative of impending failure, and which, if beyond certain limits, will require corrective maintenance. Instrument characteristics measured in accordance with this guide are expressed in terms that relate to their potential usefulness for ultrasonic examinations. Other electronic instrument characteristics in phased-array units are similar to non-phased-array units and may be measured as described in E 1065 or E 1324.
1.3 Ultrasonic examination systems using pulsed-wave trains and A-scan presentation (rf or video) may be evaluated.
1.4 This guide establishes no performance limits for examination systems; if such acceptance criteria are required, these must be specified by the using parties. Where acceptance criteria are implied herein they are for example only and are subject to more or less restrictive limits imposed by customers and end users controlling documents.
1.5 The specific parameters to be evaluated, conditions and frequency of test, and report data required, must also be determined by the user.
1.6 This guide may be used for the evaluation of a complete examination system, including search unit, instrument, interconnections, scanner fixtures and connected alarm and auxiliary devices, primarily in cases where such a system is used repetitively without change or substitution. This guide is not intended to be used as a substitute for calibration or standardization of an instrument or system to inspect any given material.
1.7 Required test apparatus includes selected test blocks and position encoders in addition to the instrument or system to be evaluated.
1.8 Precautions relating to the applicability of the procedures and interpretation of the results are included.
1.9 Alternate procedures, such as examples described in this document, or others, may only be used with customer approval.
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.
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Designation:E2491–06
Standard Guide for
Evaluating Performance Characteristics of Phased-Array
Ultrasonic Examination Instruments and Systems
This standard is issued under the fixed designation E 2491; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.8 Precautions relating to the applicability of the proce-
dures and interpretation of the results are included.
1.1 This guide describes procedures for evaluating some
1.9 Alternateprocedures,suchasexamplesdescribedinthis
performance characteristics of phased-array ultrasonic exami-
document,orothers,mayonlybeusedwithcustomerapproval.
nation instruments and systems.
1.10 This standard does not purport to address all of the
1.2 Evaluationofthesecharacteristicsisintendedtobeused
safety concerns, if any, associated with its use. It is the
for comparing instruments and systems or, by periodic repeti-
responsibility of the user of this standard to establish appro-
tion, for detecting long-term changes in the characteristics of a
priate safety and health practices and determine the applica-
given instrument or system that may be indicative of impend-
bility of regulatory limitations prior to use.
ing failure, and which, if beyond certain limits, will require
corrective maintenance. Instrument characteristics measured in
2. Referenced Documents
accordance with this guide are expressed in terms that relate to
2.1 ASTM Standards:
their potential usefulness for ultrasonic examinations. Other
E 317 Practice for Evaluating Performance Characteristics
electronic instrument characteristics in phased-array units are
of Ultrasonic Pulse-Echo Examination Instruments and
similar to non-phased-array units and may be measured as
Systems without the Use of Electronic Measurement In-
described in E 1065 or E 1324.
struments
1.3 Ultrasonic examination systems using pulsed-wave
E 494 Practice for Measuring Ultrasonic Velocity in Mate-
trains and A-scan presentation (rf or video) may be evaluated.
rials
1.4 This guide establishes no performance limits for exami-
E 1065 Guide for Evaluating Characteristics of Ultrasonic
nation systems; if such acceptance criteria are required, these
Search Units
must be specified by the using parties. Where acceptance
E 1316 Terminology for Nondestructive Examinations
criteria are implied herein they are for example only and are
E 1324 Guide for Measuring Some Electronic Characteris-
subject to more or less restrictive limits imposed by customer’s
tics of Ultrasonic Examination Instruments
and end user’s controlling documents.
1.5 The specific parameters to be evaluated, conditions and
3. Terminology
frequency of test, and report data required, must also be
3.1 Refer to Terminology E 1316 for definitions of terms in
determined by the user.
this guide
1.6 This guide may be used for the evaluation of a complete
3.2 Definitions:
examination system, including search unit, instrument, inter-
3.2.1 angle corrected gain—also called ACG. This is com-
connections, scanner fixtures and connected alarm and auxil-
pensation for the variation in signal amplitudes received from
iary devices, primarily in cases where such a system is used
fixed depth side drilled holes (SDH’s) during S-scan calibra-
repetitively without change or substitution. This guide is not
tion. The compensation is typically performed electronically at
intended to be used as a substitute for calibration or standard-
multiple depths. Note that there are technical limits to ACG,
ization of an instrument or system to inspect any given
that is, beyond a certain angular range, compensation is not
material.
possible.
1.7 Requiredtestapparatusincludesselectedtestblocksand
3.2.2 annular array probes—phased-array probes that have
position encoders in addition to the instrument or system to be
the transducers configured as a set of concentric rings. They
evaluated.
1 2
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tive Testing and is the direct responsibility of Subcommittee E07.06 on Ultrasonic contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Method. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved May 1, 2006. Published June 2006. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2491–06
allow the beam to be focused to different depths along an axis. resonant frequency of the elements, the material into which the
The surface area of the rings is in most cases constant, which beamisdirected,theminimumdelaypossiblebetweenfiringof
implies a different width for each ring. adjacent pulsers and receivers and the pulser voltage charac-
3.2.3 array (phased)—a patterned arrangement of elements. teristics.
Typical arrangements include linear, annular, two dimensional
4.4 Pulser and receiver parameters in phased-array systems
matrix, and “rho-theta”.
are generally computer controlled and the received signals are
3.2.4 electronic scan—also termed an E-scan. The same
typically displayed on computer monitors via computer data
focal law is multiplexed across a group of active elements;
acquisition systems and may be stored to computer files.
electronic raster scanning is performed at a constant angle and
4.5 Although most systems use piezo-electric materials for
along the phased-array probe length. This is equivalent to a
the elements, electro-magnetic acoustic transducer (EMAT)
conventional ultrasonic probe performing a raster scan. Also
devices have also been designed and built using phased-array
called electronic scanning.
instrumentation.
3.2.5 focal law—the entire set of hardware and software
4.6 Most phased array systems can use encoders for auto-
parameters affecting the acoustic sensitivity field of a phased
mated and semi-automated scanning.
array search unit, whether a pulse-echo or a pitch-catch
4.7 Side Drilled Holes used as targets in this document
configuration. Within focal laws, there are included delay laws
should have diameters less than the wavelength of the pulse
in transmitter and delay laws in receiver, as well as apodization
being assessed and long enough to avoid end effects from
laws, and element activation laws.
causinginterferingsignals.Thiswilltypicallybeaccomplished
3.2.6 linear array probes—probes made using a set of
when the hole diameter is between about 1.5 mm and 2.5 mm
elements juxtaposed and aligned along a linear axis. They
and 20 mm to 25 mm in length.
enable a beam to be moved, focused, and deflected along a
single azimuthal plane.
5. Significance and Use
3.2.7 matrix array probes—theseprobeshaveanactivearea
5.1 This guide is intended to evaluate performance assess-
divided in two dimensions in different elements. This division
ment of combinations of phased-array probes and instruments.
can, for example, be in the form of a checkerboard, or sectored
Itisnotintendedtodefineperformanceandacceptancecriteria,
rings. These probes allow the ultrasonic beam steering in more
but rather to provide data from which such criteria may be
than one plane.
established.
3.2.8 sectorial scan—also termed an S-scan or azimuthal
5.2 Recommended procedures described in this guide are
scan. This may refer to either the beam movement or the data
intended to provide performance-related measurements that
display. As a data display it is a 2D view of all A-scans from
can be reproduced under the specified test conditions using
a specific set of elements corrected for delay and refracted
simple targets and the phased-array test system itself. It is
angle.Whenusedtorefertothebeammovementitreferstothe
intended for phased-array flaw detection instruments operating
setoffocallawsthatsweepsadefinedrangeofanglesusingthe
in the nominal frequency range of 1 MHz to 20 MHz, but the
same set of elements.
3.2.9 S-scan— (q.v. sectorial scan) procedures are applicable to measurements on instruments
utilizing significantly higher frequency components.
4. Summary of Guide
5.3 This guide is not intended for service calibration, or
4.1 Phased-array instruments and systems have similar in-
maintenance of circuitry for which the manufacturer’s instruc-
dividual components as are found in traditional ultrasonic
tions are available.
systems that are based on single channel or multiplexed
5.4 Implementation of specific assessments may require
pulse-echo units. These include pulsers, receivers, probes and
more detailed procedural instructions in a format of the using
interconnecting cables. The most significant difference is that
facility.
phased-array systems form the transmitted ultrasonic pulse by
5.5 The measurement data obtained may be employed by
constructive phase interference from the wavelets formed off
users of this guide to specify, describe, or provide a perfor-
the individually pulsed elements of the phased-array probes.
mance criteria for procurement and quality assurance, or
4.2 Eachphased-arrayprobeconsistsofaseriesofindividu-
service evaluation of the operating characteristics of phased-
ally wired elements that are activated separately using a
array systems.
programmable time delay pattern. Varying the number of
5.6 Not all assessments described in this guide are appli-
elements used and the delay time between the pulses to each
cable to all systems. All or portions of the guide may be used
element allows control of the beam. Depending on the probe
as determined by the user.
design, it is possible to electronically vary the angle (incident
or skew), or the focal distance, or the beam dimensions, or a
6. Procedure
combination of the three. In the receiving mode, acoustic
6.1 Procedures for assessment of several parameters in
energy is received by the elements and the signals undergo a
phased-array systems are described in Annexes A1 to A7.
summation process utilizing the same type of time delay
process as was used during transmission. 6.1.1 These include; determination of beam profile, beam
4.3 The degree of beam steering available is dependent on steering capability, element activity, focusing capability, soft-
several parameters including; number of elements, pitch of the ware calculations (controls and display of received signals),
element spacing, element dimensions, element array shape, compensation for wedge attenuation, receiver gain linearity.
E2491–06
7. Keywords
7.1 characterization;focalpoint;phased-array;phased-array
probe; sound beam profile; ultrasound
ANNEXES
(Mandatory Information)
A1. DETERMINATION OF PHASED-ARRAY BEAM PROFILE
A1.1 Introduction A1.2.2 Linear-Array Probes—Linear-array probes have an
active plane and an inactive or passive plane. Assessment of
A1.1.1 This annex describes procedures to determine beam
the beam in the active plane should be made by use of an
profiles of phased-array probes. Either immersion or contact
electronic scan sequence for probes with sufficient number of
probe applications can be addressed using these procedures.
elements to electronically advance the beam past the targets of
However, it should be cautioned that assessments of contact
interest. For phased array probes using a large portion of the
probes may suffer from variability greater than imposed
available elements to form the beam the number of remaining
tolerances if proper precautions are not taken to ensure
elements for the electronic raster may be too small to allow the
constant coupling conditions.
beam to pass over the target. In this case it will be necessary to
A1.2 Test Setup
have encoded mechanical motion and assess each focal law
along the active plane separately.
A1.2.1 For single focal laws where the beam is fixed (that
A1.2.3 Side-drilled holes should be arranged at various
is, not used in an electronic or sectorial scan mode) and the
depths in a flaw-free sample of the test material in which focal
probe is used in an immersion setup, the ball-target or
laws have been programmed for. Using the linear scan feature
hydrophone options described in E 1065 may be used. For
of the phased-array system the beam is passed over the targets
phased array probes used in a dynamic fashion where several
at the various depths of interest. The electronic scan is
focal laws are used to produce sectorial or electronic scanning
illustrated schematically in Fig. A1.1.
itmaybepossibletomakebeam-profileassessmentswithnoor
A1.2.4 Data collection of the entire waveform over the
little mechanical motion. Where mechanical motion is used it
shallbeencodedtorelatesignaltimeandamplitudetodistance range of interest shall be made. The display shall represent
amplitude as a color or grayscale. Time or equivalent distance
moved. Encoder accuracy shall be verified to be within
tolerances appropriate for the measurements made. Descrip- in the test material shall be presented along one axis and
distance displaced along the other axis.This is a typical B-scan
tions made for electronic scan and sectorial scan beam profile
assessments will be made for contact probes; however, when as illustrated in Fig. A1.2.
assessment in water is required the machined targets may be A1.2.5 Data display for an electronic scan using a phased-
replaced with rods or balls as appropriate. array probe mounted on a wedge can be similarly made using
FIG. A1.1 Electronic Scan of Side Drilled Holes
E2491–06
FIG. A1.2 B-Scan Display of Electronic Scan Represented in Fig. A1.1 (Depth is in the vertical axis and electronic-scan distance is
represented along the horizontal axis.)
simple orthogonal representation of time versus displacement A1.2.9 Waveform collection of signals using a combination
or it can be angle corrected as illustrated in Fig. A1.3. of electronic scanning in the active plane and encoded me-
A1.2.6 Resolution along the displacement axis will be a chanical motion in the passive plane provides data that can be
function of the step size of the electronic scan or, if the scan projection-correctedtoprovidebeamdimensionsinthepassive
uses an encoded mechanical fixture the resolution will be plane. Fig. A1.4 illustrates a method for beam assessment in
dependent on the encoder step-size used for sampling. the passive plane. This technique uses a corner reflection from
A1.2.7 Resolution along the beam axis will be a function of an end-drilled hole at depths established by a series of steps.
the intervals between the target
...
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