1、Designation: D7006 03 (Reapproved 2013)Standard Practice forUltrasonic Testing of Geomembranes1This standard is issued under the fixed designation D7006; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides a summary of equipment andprocedures for ultrasonic testing of geomembranes using thepulse echo method.1.2 Ultra
3、sonic wave propagation in solid materials is corre-lated to physical and mechanical properties and condition ofthe materials. In ultrasonic testing, two wave propagationcharacteristics are commonly determined: velocity (based onwave travel time measurements) and attenuation (based onwave amplitude m
4、easurements). Velocity of wave propagationis used to determine thickness, density, and elastic properties ofmaterials. Attenuation of waves in solid materials is used todetermine microstructural properties of the materials. Inaddition, frequency characteristics of waves are analyzed toinvestigate th
5、e properties of a test material. Travel time,amplitude, and frequency distribution measurements are usedto assess the condition of materials to identify damage anddefects in solid materials. Ultrasonic measurements are used todetermine the nature of materials/media in contact with a testspecimen as
6、well. Measurements are conducted in the time-domain (time versus amplitude) or frequency-domain (fre-quency versus amplitude).1.3 Measurements of one or more ultrasonic wave transmis-sion characteristics are made based on the requirements of thespecific testing program.1.4 The values stated in SI un
7、its are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health pra
8、ctices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4437 Practice for Non-destructive Testing (NDT) for De-termining the Integrity of Seams Used in Joining FlexiblePolymeric Sheet GeomembranesD4545 Practice for Determining the In
9、tegrity of FactorySeams Used in Joining Manufactured Flexible SheetGeomembranes (Withdrawn 2008)3D4883 Test Method for Density of Polyethylene by theUltrasound TechniqueE1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions:3.1.1 atmosphere for testing geomembranes, nair main
10、-tained at a relative humidity of 50 to 70 % and a temperatureof 21 6 1C.3.1.2 geomembrane, nan essentially impermeable geosyn-thetic composed of one or more synthetic sheets.3.1.3 For definitions of terms related to ultrasonic testing,refer to Terminology E1316.4. Summary of Practice4.1 Mechanical
11、waves are introduced to a geomembranefrom a surface of the material using an ultrasonic transducer.Transmission characteristics of the waves in the geomembraneare determined. The measured characteristics are used toevaluate certain properties and condition of geomembranes.5. Significance and Use5.1
12、This practice covers test arrangements, measurementtechniques, sampling methods, and calculations to be used fornondestructive evaluation of geomembranes using ultrasonictesting.1This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-thetics and is the direct responsibility of Subco
13、mmittee D35.10 on Geomembranes.Current edition approved May 1, 2013. Published May 2013. Originallyapproved in 2003. Last previous edition approved in 2008 as D700603(2008).DOI: 10.1520/D7006-03R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service
14、at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho
15、cken, PA 19428-2959. United States15.2 Wave velocity may be established for particulargeomembranes (for specific polymer type, specificformulation, specific density). Relationships may be estab-lished between velocity and both density and tensile propertiesof geomembranes. An example of the use of u
16、ltrasound fordetermining density of polyethylene is presented in TestMethod D4883. Velocity measurements may be used to deter-mine thickness of geomembranes (1, 2).4Travel time andamplitude of transmitted waves may be used to assess thecondition of geomembranes and to identify defects in geomem-bran
17、es including surface defects (for example, scratches, cuts),inner defects (for example, discontinuities withingeomembranes), and defects that penetrate the entire thicknessof geomembranes (for example, pinholes) (3, 4). Bondingbetween geomembrane sheets can be evaluated using traveltime, velocity, o
18、r impedance measurements for seam assess-ment (5-10). Examples of the use of ultrasonic testing fordetermining the integrity of field and factory seams throughtravel time and velocity measurements (resulting in thicknessmeasurements) are presented in Practices D4437 and D4545,respectively. An ultras
19、onic testing device is routinely used forevaluating seams in prefabricated bituminous geomembranesin the field (11). Integrity of geomembranes may be monitoredin time using ultrasonic measurements.NOTE 1Differences may exist between ultrasonic measurements andmeasurements made using other methods du
20、e to differences in testconditions such as pressure applied and probe dimensions. An example isultrasonic and mechanical thickness measurements.5.3 The method is applicable to testing both in the labora-tory and in the field for parent material and seams. The testdurations are very short as wave tra
21、nsmission throughgeomembranes occurs within microseconds.6. Apparatus6.1 The test equipment consists of a single transducer (bothtransmitter and receiver); a pulse generator; a pulse receiver(includes amplifier and filters for noise reduction); electroniccircuits to measure and record waveforms, to
22、measure wavetravel time, to measure wave amplitudes, and to displayreceived signals; electronic circuitry to time and synchronizeall instrument functions; and connecting cables. The testapparatus is shown in Fig. 1.6.2 Piezoelectric transducers are effective for wave trans-mission. Compressional wav
23、es (P-waves, longitudinal waves)shall be used for ultrasonic testing of geomembranes. A spacershall be used to obtain good near surface resolution and toeliminate near field effects for accurate measurement of ultra-sonic wave propagation characteristics in geomembranes. Aplastic spacer has been fou
24、nd to be effective for geomem-branes. The thickness of the spacer shall be at least twice thethickness of the test specimen. The thickness of the spacer shallbe less than 5 to 10 times the thickness of the test geomem-brane. For testing geomembranes with various thicknesses, usethe material with the
25、 largest thickness for selection of the4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.FIG. 1 Test ApparatusD7006 03 (2013)2thickness of the spacer. The spacer shall be sufficiently large tocover the active surface area of the transducer to ensure that
26、 thewaveform generated is fully transmitted to the test specimenthrough the spacer. The center frequency of the transducer shallbe between 1 and 20 MHz (a 10 MHz transducer has beenfound to be effective). Focused transducers shall be used fortextured geomembranes to ensure measurements are made over
27、essentially a “point” on the test material. Other means may alsobe used if high frequency mechanical waves can be generatedwith these devices.6.3 Pulse generator shall generate pulses of electrical energythat activate the transducer. Pulsers that generate spike orsquare wave type voltage pulses have
28、 been found to beeffective for testing geomembranes.6.4 The receiver shall amplify and filter the signal receivedby the transducer after the waves have been transmittedthrough a test sample.6.5 Electronic circuitry shall be used to measure travel timeof waves in a test sample. The circuitry shall al
29、low fordetermination of travel times with a precision equal to or betterthan 0.1 s. If attenuation and amplitude measurements aredesired, instrumentation shall be used to record the waveformsreceived from a test material. The circuitry shall allow fordetermination of amplitudes with a precision equa
30、l to or betterthan 1 mV. Electronic circuitry may also be used to displayreceived signals. Analog to digital converters and computer-ized signal acquisition and analysis setups have been found tobe effective for testing geomembranes.6.6 Electronic circuitry shall be used to time and synchro-nize all
31、 instrument functions to eliminate uncertainty in thedetermination of wave transit times.NOTE 2The apparatus listed here has been found to be effective fortesting geomembranes. Ultrasonic testing of materials is a well establishedfield and other types of devices may also be used for testing geomem-b
32、ranes. Details for various test arrangements and examples of devicesproduced by various manufacturers are available in (12). Effectiveness ofalternative devices shall be demonstrated prior to their routine use forgeomembranes.7. Materials7.1 A coupling agent shall be used to ensure good contactbetwe
33、en the transducer and test specimen. Coupling agentsinclude water, commercial ultrasonic couplants, oil, petroleumjelly, grease, glycerin, propylene glycol, or other viscous fluids.Water has been used effectively on flat surfaces. More viscousmaterials may be used on inclined surfaces.8. Sampling an
34、d Test Specimens8.1 Test specimens shall be cut such that a distance greaterthan 10 times the thickness of the specimen shall be leftbetween the transducer and the edges of the specimen in everydirection.8.2 In field testing, measurements shall be taken at locationsthat are at a distance greater tha
35、n 10 times the thickness of thespecimen from the edges of the geomembrane sheet in anydirection.NOTE 3Seam inspection tests may be conducted at locations closer tothe edge of geomembranes than specified in 8.2. Effectiveness of the nearedge measurements shall be demonstrated prior to their routine u
36、se toensure that potential edge reflections do not interfere with measurementsthrough the thickness of geomembranes.9. Calibration9.1 The electronic equipment shall be calibrated to ensureaccurate determination of the transit time. Calibration bars orblocks with known thicknesses and wave transmissi
37、on veloci-ties shall be used for calibration procedures.10. Conditioning10.1 For baseline measurements (for example, measure-ments used to establish baseline ultrasonic properties for aparticular geomembrane), specimens shall be exposed to thestandard atmosphere for testing geomembranes for a period
38、sufficient to reach moisture and temperature equilibrium.Exposure for 24 h has been found to be effective for reachingequilibrium.10.2 Tests can be conducted at conditions outside the rangefor standard atmosphere conditions for various applicationssuch as field measurements. For these measurements,
39、speci-mens shall be in moisture and temperature equilibrium withtheir surrounding environment.NOTE 4Correction factors shall be used if comparisons are to be madebetween standard and nonstandard testing conditions. Correction factorsare determined by taking measurements at nonstandard conditions and
40、normalizing these by the measurements conducted at standard conditions.10.3 Surface PreparationThe surface of the test geomem-brane shall be free of excessive dust, particles, and any othermaterials that may interfere with wave transmission. Thesurface of geomembranes may be cleaned with a damp clot
41、h toensure a clean measurement surface prior to testing.11. Procedure11.1 Ultrasonic measurements in geomembranes shall beconducted using the pulse echo test method. In this method,ultrasonic waves are sent and received from one surface of atest specimen using one or two transducers.Asingle transduc
42、ershall be used in the measurements of geomembranes.11.2 Ultrasonic measurements on geomembranes may betaken using two test arrangements. In both arrangements, thetransducer shall be orthogonal to the test geomembrane.11.2.1 Arrangement AIn this arrangement the transducerassembly is placed over the
43、test geomembrane. The transducerassembly consists of the ultrasonic transducer and the spacer.Apply a small amount of couplant between the transducer andthe spacer to ensure that the two units are in good contact withno air gaps. Then, apply a small amount of couplant on thesurface of the geomembran
44、e at the measurement location.Place the transducer assembly on the geomembrane leaving athin film of couplant between the assembly and the geomem-brane. Ensure that the transducer assembly is in good contact(for example, no air gaps) with the geomembrane.Asmall loadmay be permanently attached on top
45、 of the transducer toprovide good contact with the geomembrane and ensure thatthe transducer is perfectly orthogonal to the test specimen. Thisarrangement is presented in Fig. 2a.11.2.2 Arrangement BIn this arrangement the transducerassembly is placed below the test geomembrane.Apply a smallD7006 03
46、 (2013)3amount of couplant between the transducer and the spacer toensure that the two units are in good contact with no air gaps.Then, apply a small amount of couplant on the top surface ofthe spacer. Place the geomembrane over the spacer leaving athin film of couplant between the spacer and the ge
47、omembrane.Ensure that the geomembrane is in good contact (for example,no air gaps) with the transducer assembly. This arrangement ispresented in Fig. 2b. In this arrangement, no pressure is appliedto the geomembrane. Pressure can affect the thickness of thegeomembrane, which can affect the travel ti
48、me in the geomem-brane. This arrangement is applicable when the underside of ageomembrane is accessible.NOTE 5Commercially available “delay line” transducers can be usedin Test Arrangement A. These transducers have plastic spacers attached tothe ultrasonic units. Use of these types of transducers ha
49、s been found to beeffective for testing geomembranes. Commercially available immersiontransducer setups can be used in Test Arrangement B. In these setups awater resistant transducer is placed at a certain depth in a water bath. Thespecimen is placed directly on the surface of water at a fixed distanceaway from the transducer. The water between the specimen and thetransducer acts as the spacer. These systems are particularly effective forfocused transducers. Care must be taken not to leave the test specimen incontact with water for extended periods of time when using th
