High-frequency description of truncated-Floquet-waves and guided-waves for a semi-infinite array of line sources on a grounded dielectric slab

<p>Fitting subduction zone guided waves with synthetics is an ideal choice for studying the velocity structure of the oceanic crust. After an earthquake occurs in subduction zones, seismic waves can be trapped in the low-velocity oceanic crust and propagated as guided waves. The arrival time and frequency characteristics of the guided waves can be used to image the velocity structure of the oceanic crust. The analysis and modeling based on guided wave observations provide a rare opportunity to understand the velocity structure of the oceanic crust and the variations in oceanic crustal materials during the subduction process.</p><p>High-frequency guided waves have been observed in the subduction zone of eastern Alaska. On several sections, observed seismograms recorded by seismic stations show low-frequency (<2Hz) onsets ahead of the main high-frequency (>2Hz) guided waves. Differences in the arrival times and dispersion characteristics of seismic phases are related to the velocity structure of the oceanic crust, and the characteristics of coda waves are related to the distribution of elongated scatters in the oceanic crust. Through fitting the observed broadband waveforms and synthetics modeled with the 2-D FDM (Finite Difference Method), we obtain the preferred oceanic crustal velocity models for several sections in the subduction zone of eastern Alaska. The preferred models can explain the seismic phase arrival times, dispersions, and coda characteristics in the observed waveforms. With the obtained P- and S- wave models of velocity structures on several sections, the material compositions they represent are deduced, and the variations of oceanic crustal materials during subducting can be understood. This provides new evidence for studying the details of the subduction process in the subduction zone of eastern Alaska.</p>

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High frequency radiation from truncated arrays of filamentary sources on a dielectric slab

Proceedings of IEEE Antennas and Propagation Society International Symposium and URSI National Radio Science Meeting ◽

10.1109/aps.1994.408208 ◽

2002 ◽

Cited By ~ 1

Author(s):

L. Carin ◽

L.B. Felsen ◽

Teng-Tai Hsu

Keyword(s):

High Frequency ◽

Dielectric Slab ◽

Frequency Radiation ◽

High Frequency Radiation

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Advanced debonding detection technique for aerospace composite structures

Aircraft Engineering and Aerospace Technology ◽

10.1108/aeat-10-2020-0222 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Assunta Sorrentino ◽

Fulvio Romano ◽

Angelo De Fenza

Keyword(s):

High Frequency ◽

Composite Structures ◽

Guided Waves ◽

Plastic Material ◽

Impact Damage ◽

Small Scale ◽

Content Type ◽

Stiffened Panels ◽

Reinforced Plastic ◽

Debonding Detection

Purpose The purpose of this paper is to introduce a methodology aimed to detect debonding induced by low impacts energies in typical aeronautical structures. The methodology is based on high frequency sensors/actuators system simulation and the application of elliptical triangulation (ET) and probability ellipse (PE) methods as damage detector. Numerical and experimental results on small-scale stiffened panels made of carbon fiber-reinforced plastic material are discussed. Design/methodology/approach The damage detection methodology is based on high frequency sensors/actuators piezoceramics system enabling the ET and the PE methods. The approach is based on ultrasonic guided waves propagation measurement and simulation within the structure and perturbations induced by debonding or impact damage that affect the signal characteristics. Findings The work is focused on debonding detection via test and simulations and calculation of damage indexes (DIs). The ET and PE methodologies have demonstrated the link between the DIs and debonding enabling the identification of position and growth of the damage. Originality/value The debonding between two structural elements caused in manufacturing or in-service is very difficult to detect, especially when the components are in low accessibility areas. This criticality, together with the uncertainty of long-term adhesive performance and the inability to continuously assess the debonding condition, induces the aircrafts’ manufacturers to pursuit ultraconservative design approach, with in turn an increment in final weight of these parts. The aim of this research’s activity is to demonstrate the effectiveness of the proposed methodology and the robustness of the structural health monitoring system to detect debonding in a typical aeronautical structural joint.

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Experimental Study of High Frequency Guided Wave Inspection of Anchored Bolts

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.117-119.962 ◽

2011 ◽

Vol 117-119 ◽

pp. 962-966 ◽

Cited By ~ 1

Author(s):

Wen He ◽

Xiao Jiang Luo ◽

Kui Zhao ◽

Wang Cheng ◽

Chun Hui Zhong

Keyword(s):

Spectral Density ◽

Power Spectral Density ◽

High Frequency ◽

Guided Waves ◽

Broad Band ◽

Frequency Component ◽

Guided Wave ◽

Reflected Waves ◽

Power Spectral ◽

Density Values

High frequency longitudinal guided waves were used to inspect the anchored rock bolts. Experiments were conducted to find the optimal frequencies for the bolt testing. A broad-band signal was excited at the top end of the bolt, and the power spectral density(PSD) analysis of the bolt end reflected waves was made. Base on that the frequency component of the bolt end reflected waves could be obtain, and the frequencies with higher power spectral density values are the optimal ones. At optimal frequencies, the guided wave attenuates more slightly than it is at other frequencies and the bolt end reflected waves can be clearly acquisitioned. Experimental results show that the optimal frequencies of guided wave in a free bolt and in an anchored bolt are quite the same, and they are mainly affected by the bolt instead of the anchor media. Conclusions can be drawn that the propagation velocities of guided wave at optimal frequencies in a free bolt are close to those in the embedded section of the bolt. As a result, the bolt length and the position of flaw in the anchored bolt can be determined by the guided wave velocity in a free bolt and the reflected wave from the bolt end and from the flaw, respectively.

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