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Inspection Principles and Techniques
Published in Don E. Bray, Roderic K. Stanley, Nondestructive Evaluation, 2018
Don E. Bray, Roderic K. Stanley
Surface waves possess unique characteristics that make them useful for some very specialized inspection problems. As previously discussed, surface waves are generated when energy is excited at a surface, typically with either a longitudinal wave probe placed on the surface with no couplant, or, with a 90° surface wave probe, as shown in Fig. 8-29. Rayleigh waves are best excited with a shear wave, angle beam probe where the incident angle is just past the second critical angle (Fig. 5-13). With the concentration of energy at the surface, these waves are obviously quite sensitive to surface defects. Also, they will travel long distances, following either straight or curved paths. Because of the surface concentration, they are also quite sensitive to any sort of surface anomaly,, such as pitting, oil droplets, or other reflector.
Waves propagation for magneto-thermoelastic medium during the two-temperature theory with the gravitational field
Published in Waves in Random and Complex Media, 2022
A surface wave is one of two types of waves that travel across the surface of a medium as opposed to through it. Surface waves usually have larger amplitudes and longer wavelengths than body waves, and they travel more slowly than body waves. Love waves and Rayleigh waves are two types of surface waves. In physics, a surface wave is a mechanical wave that propagates along the interface between differing media. A surface wave can also be an electromagnetic wave guided by a refractive index gradient. In radio transmission, a ground wave is a surface wave that propagates close to the surface of the earth [19–26].
Bleustein–Gulyaev wave in a nonlocal piezoelectric layered structure
Published in Mechanics of Advanced Materials and Structures, 2020
Surface waves have numerous applications in many technological fields, such as nondestructive testing (NDT) technique, filters, resonators, sensors etc. Surface acoustic wave propagation in piezoelectric composites has drawn attention of many researchers due to their diverse applications in many engineering fields like mechanical, electrical, petroleum and forensic engineering. One type of shear horizontal electro-acoustic surface wave in which the direction of material particle motion is perpendicular to the propagating direction and parallel to the surface of half-space, which can propagate in a class of transversely isotropic piezoelectric media, is commonly known as Bleustein–Gulyaev (BG) wave or electro-acoustic wave [19, 20]. These waves were simultaneously observed by Bleustein and Gulyaev. These waves can propagate in highly symmetric piezoelectric materials because they have no elastic counterparts in purely elastic homogeneous materials [21, 22]. Studies indicate that BG wave can propagate in the structure comprising of thin film/substrate layered structures made of the same piezoelectric material but opposite poling directions, and its penetration depth is in the same order as the wavelength [23]. In the absence of piezoelectric effect, BG wave degenerates to the shear bulk wave. Thorough investigations of propagation characteristics of BG wave have been done by many researchers to successfully apply it to surface acoustic wave (SAW) devices [24–26]. Bleustein–Gulyaev wave is a promising candidate over other surface waves to be employed for sensores and acoustic devices [27, 28]. Using BG surface wave, [29] a new ultrasonic method i.e., the Bleustein–Gulyaev wave method which is superior to the existing ultrasonic methods, is used for measuring the viscosity of liquids at high pressure. Due to the high sensitivity, BG waves are widely used for liquid sensing applications [30, 31].