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Significance and Use
5.2 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 D4883. Velocity measurements may be used to determine thickness of geomembranes (1, 2).4 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 D4437 and D4545, 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.
5.3 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 occurs within microseconds.
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).
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D4437 Practice for Non-destructive Testing (NDT) for Determining the Integrity of Seams Used in Joining Flexible Polymeric Sheet Geomembranes
D4545 Practice for Determining the Integrity of Factory Seams Used in Joining Manufactured Flexible Sheet Geomembranes
D4883 Test Method for Density of Polyethylene by the Ultrasound Technique
E1316 Terminology for Nondestructive Examinations
ICS Number Code 59.080.70 (Geotextiles)
UNSPSC Code 30121701(Geomesh); 41111804(Ultrasonic examination equipment)