ASTM D7006-03(2008)
(Practice)Standard Practice for Ultrasonic Testing of Geomembranes
Standard Practice for Ultrasonic Testing of Geomembranes
SIGNIFICANCE AND USE
This practice covers test arrangements, measurement techniques, sampling methods, and calculations to be used for nondestructive evaluation of geomembranes using ultrasonic testing.
Wave velocity may be established for particular geomembranes (for specific polymer type, specific formulation, specific density). Relationships may be established between velocity and both density and tensile properties of geomembranes. An example of the use of ultrasound for determining density of polyethylene is presented in Test Method D 4883. Velocity measurements may be used to determine thickness of geomembranes (1, 2). Travel time and amplitude of transmitted waves may be used to assess the condition of geomembranes and to identify defects in geomembranes including surface defects (for example, scratches, cuts), inner defects (for example, discontinuities within geomembranes), and defects that penetrate the entire thickness of geomembranes (for example, pinholes) (3, 4). Bonding between geomembrane sheets can be evaluated using travel time, velocity, or impedance measurements for seam assessment (5-10). Examples of the use of ultrasonic testing for determining the integrity of field and factory seams through travel time and velocity measurements (resulting in thickness measurements) are presented in Practices D 4437 and D 4545, respectively. An ultrasonic testing device is routinely used for evaluating seams in prefabricated bituminous geomembranes in the field (11). Integrity of geomembranes may be monitored in time using ultrasonic measurements.
Note 1—Differences may exist between ultrasonic measurements and measurements made using other methods due to differences in test conditions such as pressure applied and probe dimensions. An example is ultrasonic and mechanical thickness measurements.
The method is applicable to testing both in the laboratory and in the field for parent material and seams. The test durations are very short as wave transmission through geomembranes...
SCOPE
1.1 This practice provides a summary of equipment and procedures for ultrasonic testing of geomembranes using the pulse echo method.
1.2 Ultrasonic wave propagation in solid materials is correlated to physical and mechanical properties and condition of the materials. In ultrasonic testing, two wave propagation characteristics are commonly determined: velocity (based on wave travel time measurements) and attenuation (based on wave amplitude measurements). Velocity of wave propagation is used to determine thickness, density, and elastic properties of materials. Attenuation of waves in solid materials is used to determine microstructural properties of the materials. In addition, frequency characteristics of waves are analyzed to investigate the properties of a test material. Travel time, amplitude, and frequency distribution measurements are used to assess the condition of materials to identify damage and defects in solid materials. Ultrasonic measurements are used to determine the nature of materials/media in contact with a test specimen as well. Measurements are conducted in the time-domain (time versus amplitude) or frequency-domain (frequency versus amplitude).
1.3 Measurements of one or more ultrasonic wave transmission characteristics are made based on the requirements of the specific testing program.
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.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7006 − 03(Reapproved 2008)
Standard Practice for
Ultrasonic Testing of Geomembranes
This standard is issued under the fixed designation D7006; 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 D4437 Practice for Non-destructive Testing (NDT) for De-
termining the Integrity of Seams Used in Joining Flexible
1.1 This practice provides a summary of equipment and
Polymeric Sheet Geomembranes
procedures for ultrasonic testing of geomembranes using the
D4545 Practice for Determining the Integrity of Factory
pulse echo method.
Seams Used in Joining Manufactured Flexible Sheet
1.2 Ultrasonic wave propagation in solid materials is corre-
Geomembranes (Withdrawn 2008)
lated to physical and mechanical properties and condition of
D4883 Test Method for Density of Polyethylene by the
the materials. In ultrasonic testing, two wave propagation
Ultrasound Technique
characteristics are commonly determined: velocity (based on
E1316 Terminology for Nondestructive Examinations
wave travel time measurements) and attenuation (based on
wave amplitude measurements). Velocity of wave propagation
3. Terminology
isusedtodeterminethickness,density,andelasticpropertiesof
3.1 Definitions:
materials. Attenuation of waves in solid materials is used to
3.1.1 geomembrane,n—anessentiallyimpermeablegeosyn-
determine microstructural properties of the materials. In
thetic composed of one or more synthetic sheets.
addition, frequency characteristics of waves are analyzed to
3.1.2 atmosphere for testing geomembranes, n—air main-
investigate the properties of a test material. Travel time,
amplitude, and frequency distribution measurements are used tained at a relative humidity of 50 to 70 % and a temperature
of 21 6 1°C.
to assess the condition of materials to identify damage and
defects in solid materials. Ultrasonic measurements are used to
3.1.3 For definitions of terms related to ultrasonic testing,
determine the nature of materials/media in contact with a test
refer to Terminology E1316.
specimen as well. Measurements are conducted in the time-
domain (time versus amplitude) or frequency-domain (fre-
4. Summary of Practice
quency versus amplitude).
4.1 Mechanical waves are introduced to a geomembrane
1.3 Measurements of one or more ultrasonic wave transmis-
from a surface of the material using an ultrasonic transducer.
sion characteristics are made based on the requirements of the
Transmission characteristics of the waves in the geomembrane
specific testing program.
are determined. The measured characteristics are used to
1.4 This standard does not purport to address all of the
evaluate certain properties and condition of geomembranes.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety and health practices and determine the applica-
5.1 This practice covers test arrangements, measurement
bility of regulatory limitations prior to use.
techniques, sampling methods, and calculations to be used for
nondestructive evaluation of geomembranes using ultrasonic
2. Referenced Documents
testing.
2.1 ASTM Standards:
5.2 Wave velocity may be established for particular
geomembranes (for specific polymer type, specific
formulation, specific density). Relationships may be estab-
This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-
lished between velocity and both density and tensile properties
thetics and is the direct responsibility of Subcommittee D35.10 on Geomembranes.
of geomembranes. An example of the use of ultrasound for
Current edition approved July 1, 2008. Published September 2008. Originally
determining density of polyethylene is presented in Test
approved in 2003. Last previous edition approved in 2003 as D7006–03. DOI:
10.1520/D7006-03R08.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7006 − 03 (2008)
Method D4883. Velocity measurements may be used to deter- 6. Apparatus
mine thickness of geomembranes (1, 2). Travel time and
6.1 The test equipment consists of a single transducer (both
amplitude of transmitted waves may be used to assess the
transmitter and receiver); a pulse generator; a pulse receiver
conditionofgeomembranesandtoidentifydefectsingeomem-
(includes amplifier and filters for noise reduction); electronic
branes including surface defects (for example, scratches, cuts),
circuits to measure and record waveforms, to measure wave
inner defects (for example, discontinuities within geomem-
travel time, to measure wave amplitudes, and to display
branes), and defects that penetrate the entire thickness of
received signals; electronic circuitry to time and synchronize
geomembranes (for example, pinholes) (3, 4). Bonding be-
all instrument functions; and connecting cables. The test
tween geomembrane sheets can be evaluated using travel time,
apparatus is shown in Fig. 1.
velocity, or impedance measurements for seam assessment
(5-10). Examples of the use of ultrasonic testing for determin- 6.2 Piezoelectric transducers are effective for wave trans-
ing the integrity of field and factory seams through travel time mission. Compressional waves (P-waves, longitudinal waves)
and velocity measurements (resulting in thickness measure- shall be used for ultrasonic testing of geomembranes.Aspacer
ments) are presented in Practices D4437 and D4545, respec- shall be used to obtain good near surface resolution and to
tively. An ultrasonic testing device is routinely used for eliminate near field effects for accurate measurement of ultra-
evaluating seams in prefabricated bituminous geomembranes
sonic wave propagation characteristics in geomembranes. A
in the field (11). Integrity of geomembranes may be monitored plastic spacer has been found to be effective for geomem-
in time using ultrasonic measurements.
branes. The thickness of the spacer shall be at least twice the
NOTE 1—Differences may exist between ultrasonic measurements and
thicknessofthetestspecimen.Thethicknessofthespacershall
measurements made using other methods due to differences in test
be less than 5 to 10 times the thickness of the test geomem-
conditions such as pressure applied and probe dimensions.An example is
brane. For testing geomembranes with various thicknesses, use
ultrasonic and mechanical thickness measurements.
the material with the largest thickness for selection of the
5.3 The method is applicable to testing both in the labora-
thickness of the spacer.The spacer shall be sufficiently large to
tory and in the field for parent material and seams. The test
covertheactivesurfaceareaofthetransducertoensurethatthe
durations are very short as wave transmission through
waveform generated is fully transmitted to the test specimen
geomembranes occurs within microseconds.
throughthespacer.Thecenterfrequencyofthetransducershall
be between 1 and 20 MHz (a 10 MHz transducer has been
found to be effective). Focused transducers shall be used for
The boldface numbers in parentheses refer to the list of references at the end of
texturedgeomembranestoensuremeasurementsaremadeover
this standard.
FIG. 1 Test Apparatus
D7006 − 03 (2008)
essentiallya“point”onthetestmaterial.Othermeansmayalso blocks with known thicknesses and wave transmission veloci-
be used if high frequency mechanical waves can be generated ties shall be used for calibration procedures.
with these devices.
10. Conditioning
6.3 Pulsegeneratorshallgeneratepulsesofelectricalenergy
10.1 For baseline measurements (i.e., measurements used to
that activate the transducer. Pulsers that generate spike or
establish baseline ultrasonic properties for a particular
square wave type voltage pulses have been found to be
geomembrane), specimens shall be exposed to the standard
effective for testing geomembranes.
atmosphere for testing geomembranes for a period sufficient to
6.4 The receiver shall amplify and filter the signal received
reach moisture and temperature equilibrium. Exposure for 24 h
by the transducer after the waves have been transmitted
has been found to be effective for reaching equilibrium.
through a test sample.
10.2 Tests can be conducted at conditions outside the range
6.5 Electronic circuitry shall be used to measure travel time
for standard atmosphere conditions for various applications
of waves in a test sample. The circuitry shall allow for
such as field measurements. For these measurements, speci-
determination of travel times with a precision equal to or better
mens shall be in moisture and temperature equilibrium with
than 0.1 µs. If attenuation and amplitude measurements are
their surrounding environment.
desired, instrumentation shall be used to record the waveforms
NOTE4—Correctionfactorsshallbeusedifcomparisonsaretobemade
received from a test material. The circuitry shall allow for
between standard and nonstandard testing conditions. Correction factors
determination of amplitudes with a precision equal to or better
are determined by taking measurements at nonstandard conditions and
than 1 mV. Electronic circuitry may also be used to display normalizing these by the measurements conducted at standard conditions.
received signals. Analog to digital converters and computer-
10.3 Surface Preparation—The surface of the test geomem-
ized signal acquisition and analysis setups have been found to
brane shall be free of excessive dust, particles, and any other
be effective for testing geomembranes.
materials that may interfere with wave transmission. The
surface of geomembranes may be cleaned with a damp cloth to
6.6 Electronic circuitry shall be used to time and synchro-
ensure a clean measurement surface prior to testing.
nize all instrument functions to eliminate uncertainty in the
determination of wave transit times.
11. Procedure
NOTE 2—The apparatus listed here has been found to be effective for
testinggeomembranes.Ultrasonictestingofmaterialsisawellestablished
11.1 Ultrasonic measurements in geomembranes shall be
field and other types of devices may also be used for testing geomem-
conducted using the pulse echo test method. In this method,
branes. Details for various test arrangements and examples of devices
ultrasonic waves are sent and received from one surface of a
produced by various manufacturers are available in (12). Effectiveness of
alternative devices shall be demonstrated prior to their routine use for
testspecimenusingoneortwotransducers.Asingletransducer
geomembranes.
shall be used in the measurements of geomembranes.
11.2 Ultrasonic measurements on geomembranes may be
7. Materials
taken using two test arrangements. In both arrangements, the
7.1 A coupling agent shall be used to ensure good contact
transducer shall be orthogonal to the test geomembrane.
between the transducer and test specimen. Coupling agents
11.2.1 Arrangement A—In this arrangement the transducer
include water, commercial ultrasonic couplants, oil, petroleum
assembly is placed over the test geomembrane. The transducer
jelly,grease,glycerin,propyleneglycol,orotherviscousfluids.
assembly consists of the ultrasonic transducer and the spacer.
Water has been used effectively on flat surfaces. More viscous
Apply a small amount of couplant between the transducer and
materials may be used on inclined surfaces.
the spacer to ensure that the two units are in good contact with
no air gaps. Then, apply a small amount of couplant on the
8. Sampling and Test Specimens
surface of the geomembrane at the measurement location.
Place the transducer assembly on the geomembrane leaving a
8.1 Test specimens shall be cut such that a distance greater
thin film of couplant between the assembly and the geomem-
than 10 times the thickness of the specimen shall be left
brane. Ensure that the transducer assembly is in good contact
between the transducer and the edges of the specimen in every
(i.e., no air gaps) with the geomembrane.Asmall load may be
direction.
permanently attached on top of the transducer to provide good
8.2 Infieldtesting,measurementsshallbetakenatlocations
contactwiththegeomembraneandensurethatthetransduceris
that are at a distance greater than 10 times the thickness of the
perfectly orthogonal to the test specimen. This arrangement is
specimen from the edges of the geomembrane sheet in any
presented in Fig. 2a.
direction.
11.2.2 Arrangement B—In this arrangement the transducer
NOTE 3—Seam inspection tests may be conducted at locations closer to
assemblyisplacedbelowthetestgeomembrane.Applyasmall
the edge of geomembranes than specified in 8.2. Effectiveness of the near
amount of couplant between the transducer and the spacer to
edge measurements shall be demonstrated prior to their routine use to
ensure that potential edge reflections do not interfere with measurements
ensure that the two units are in good contact with no air gaps.
through the thickness of geomembranes.
Then, apply a small amount of couplant on the top surface of
the spacer. Place the geomembrane over the spacer leaving a
9. Calibration
thinfilmofcouplantbetweenthespacerandthegeomembrane.
9.1 The electronic equipment shall be calibrated to ensure Ensure that the geomembrane is in good contact (i.e., no air
accurate determination of the transit time. Calibration bars or gaps) with the transducer assembly. This arrangement is
D7006 − 03 (2008)
FIG. 2 Test Arrangements
focused transducers. Care must be taken not to leave the test specimen in
presentedinFig.2b.Inthisarrangement,nopressureisapplied
contact with water for extended periods of time when using these setups.
to the geomembrane. Pressure can affect the thickness of the
Test specimens shall not be exposed to water for more than 30 min during
geomembrane, which can affect the travel time in the geomem-
a test.
brane. This arrangement is applicable when the underside of a
11.2.3 If comparisons will be made between ultrasonic
geomembrane is accessible.
measurements, similar test arrangements shall be used. In
NOTE 5—Commercially available “delay line” transducers can be used
particular, the pressure applied t
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