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Abstract A nondestructive evaluation (NDE) technique based on highly nonlinear solitary waves (HNSWs) has been developed recently by a few groups worldwide. The technique is based on the propagation and detection of these waves along a one-dimensional monoperiodic array of spherical particles in which one end of the array is in contact with the material/structure to be inspected, and the particle at the opposite end induces the waves by means of a mechanical impact. Several studies have demonstrated that the dynamic interaction between the waves and the element to be evaluated is dependent on the geometric and mechanical properties of the structure, and such dependency can be monitored by sensing the waves reflected at the interface between the array and the structure. This NDE technique is typically performed by using the so-called HNSW transducer. The term transducer indicates a portable device that consists of a monoperiodic array of particles, a device to trigger the waves, and a sensing element to detect the waves. In the study presented in this article, the long-term performance of three transducers was investigated by placing them above a test object whose mechanical and geometric properties were left constant for a week while the transducers triggered and detected thousands of waves. Any variability of the waves was quantified by extracting simple features such as amplitude, time of flight, and cross-correlation. To investigate the cause of variabilities, 16 measurements were captured with short videos at ∼1000 fps. The results of the study demonstrate that the traveling time of the solitary waves is the most reliable parameter for long-term monitoring with the lowest variability and the least susceptibility to physical changes within the array. In addition, the findings of this study allow the framing of a valid strategy to improve the design of the transducers in order to make the HNSW-based technique suitable for long-term monitoring.
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Magnetospheric Mass Density as Determined by ULF Wave Analysis
The technique to estimate the mass density in the magnetosphere using the physical properties of observed magnetohydrodynamic waves is known as magnetoseismology. This technique is important in magnetospheric research given the difficulty of determining the density using particle experiments. This paper presents a review of magnetoseismic studies based on satellite observations of standing Alfvén waves. The data sources for the studies include AMPTE/CCE, CRRES, GOES, Geotail, THEMIS, Van Allen Probes, and Arase. We describe data analysis and density modeling techniques, major results, and remaining issues in magnetoseismic research.
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- Award ID(s):
- 1840970
- PAR ID:
- 10325906
- Date Published:
- Journal Name:
- Frontiers in Astronomy and Space Sciences
- Volume:
- 8
- ISSN:
- 2296-987X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fspas.2021.708940
