Topic
Acoustic emission
About: Acoustic emission is a research topic. Over the lifetime, 16293 publications have been published within this topic receiving 211456 citations.
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TL;DR: In this paper, the authors described and evaluated acoustic waveguides for diagnostics of partial discharge (PD) in electrical insulation and dielectrics, and showed how the use of acoustic waveguide can improve diagnostic PD measurements in hostile and inaccessible locations.
Abstract: Acoustical waves travel by molecular interaction, and as a consequence, wave attenuation and transit time can be extremely sensitive to changes in the media in which they propagate. With careful acoustic measurements, a wide variety of media properties can be monitored. These range from variations in gas mixtures and pressure, to changes in material density, porosity, and crystal size and orientation. Acoustical technology can also be applied in the listening mode to sense the tiny acoustic emissions from partial discharges in dielectrics, and from stress, strain, and other events. Many of these acoustic techniques are ideal for applying to the science of electrical insulation and dielectrics, and in this paper these different methods are described and evaluated. The subject is introduced with an outline of ultrasonic partial discharge (PD) diagnostics and nondestructive evaluation, with emphasis on acoustic factors which affect accuracy. It is then shown how the use of acoustic waveguides can improve diagnostic PD measurements in hostile and inaccessible locations. In a completely different application, a technique is described in which sound velocity measurements in gas mixtures are used for predicting electrical strength. Other valuable acoustical applications which are outlined are the monitoring of sounds from bouncing particles on metal surfaces and from gas bubbles generated in liquid dielectrics. From this latter phenomenon the temperature of a hot metal surface in a liquid can be estimated. A related subject which is also discussed is the attenuation of sound waves by gas bubbles in a liquid dielectric.
59 citations
TL;DR: Moevus et al. as mentioned in this paper analyzed two SiC/[Si-B-C] composites exhibiting different mechanical behaviours under tensile testing: low strain to failure for the one, high strain-to-failure for the other with similar ultimate strength.
59 citations
TL;DR: In this paper, a simple point probe was used to measure the electrical potential associated with an acoustic surface wave in a piezoelectric medium by using a LiNbO3 delay line.
Abstract: Data are presented which indicate that detection of the rf electrical potential associated with an acoustic surface wave in a piezoelectric medium by a simple point probe can yield extensive information about the propagation characteristics of such waves. Such a probe, in mechanical contact with the propagating surface of a 107‐MHz LiNbO3 delay line, has been used to measure the diffraction pattern of the acoustic energy, spreading of the acoustic beam, insertion loss due to misalignment of the transducer axis with the crystal symmetry axis, and the amplitude and phase variations of the acoustic wave near the output transducer.
59 citations
TL;DR: In this article, a test equipment was designed to study thermal shock and thermal fatigue of ceramic materials subjected to fast heating (ascending) by heating one surface of it by an oxy-hydrogen flame while cooling the opposite surface.
59 citations