An Efficient Damage Quantification Method for Cylindrical Structures Enhanced by a Dry-Point-Contact Torsional-Wave Transducer

Quantification of damage sizes in cylindrical structures such as pipes and rods is of paramount importance in various industries. This work proposes an efficient damage quantification method by using a dry-point-contact (DPC) transducer based on the non-dispersive torsional waves in the low-frequency range. Theoretical analyses are first carried out to investigate the torsional wave interaction with different sizes of defects in cylindrical structures. A damage quantification algorithm is designed based on the wave reflections from the defect and end. Capitalizing on multiple excitations at different frequencies, the proposed algorithm constructs a damage image that identifies the geometric parameters of the defects. Numerical simulations are conducted to validate the characteristics of the theoretically-predicted wave-damage interaction analyses as well as the feasibility of the designed damage quantification method. Using the DPC transducer, experiments are efficiently carried out with a simple physical system. The captured responses are first assessed to confirm the capability of the DPC transducer for generating and sensing torsional waves. The sizes of the defects in two representative steel rods are then quantified with the proposed method. Both numerical and experimental results demonstrate the efficacy of the proposed damage quantification method. The understandings of the wave-damage interaction and the concept of the damage quantification algorithm lay out the foundation for engineering applications.

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Strange VLF bursts in northern Scandinavia: case study of the afternoon "mushroom-like" hiss on 8 December 2013

Annales Geophysicae ◽

10.5194/angeo-33-991-2015 ◽

2015 ◽

Vol 33 (8) ◽

pp. 991-995 ◽

Cited By ~ 4

Author(s):

J. Manninen ◽

N. G. Kleimenova ◽

A. Kozlovsky ◽

I. A. Kornilov ◽

L. I. Gromova ◽

...

Keyword(s):

Low Frequency ◽

Mutual Effect ◽

Time History ◽

Lower Ionosphere ◽

Wave Interaction ◽

Recovery Phase ◽

Frequency Wave ◽

Left Hand ◽

Very Low Frequency ◽

The Right

Abstract. We investigate a non-typical very low frequency (VLF) 1–4 kHz hiss representing a sequence of separated noise bursts with a strange "mushroom-like" shape in the frequency–time domain, each one lasting several minutes. These strange afternoon VLF emissions were recorded at Kannuslehto (KAN, &varphi; = 67.74° N, λ = 26.27° E; L ∼ 5.5) in northern Finland during the late recovery phase of the small magnetic storm on 8 December 2013. The left-hand (LH) polarized 2–3 kHz "mushroom caps" were clearly separated from the right-hand (RH) polarized "mushroom stems" at the frequency of about 1.8–1.9 kHz, which could match the lower ionosphere waveguide cutoff (the first transverse resonance of the Earth–ionosphere cavity). We hypothesize that this VLF burst sequence could be a result of the modulation of the VLF hiss electron–cyclotron instability from the strong Pc5 geomagnetic pulsations observed simultaneously at ground-based stations as well as in the inner magnetosphere by the Time History of Events and Macroscale Interactions during Substorms mission probe (THEMIS-E; ThE). This assumption is confirmed by a similar modulation of the intensity of the energetic (1–10 keV) electrons simultaneously observed by the same ThE spacecraft. In addition, the data of the European Incoherent Scatter Scientific Association (EISCAT) radar at Tromsø show a similar quasi-periodicity in the ratio of the Hall-to-Pedersen conductance, which may be used as a proxy for the energetic particle precipitation enhancement. Our findings suggest that this strange mushroom-like shape of the considered VLF hiss could be a combined mutual effect of the magnetospheric ULF–VLF (ultra low frequency–very low frequency) wave interaction and the ionosphere waveguide propagation.

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Low-Frequency Microwave Response of a Quantum Point Contact

JETP Letters ◽

10.1134/s0021364021140101 ◽

2021 ◽

Vol 114 (2) ◽

pp. 110-115

Author(s):

V. A. Tkachenko ◽

A. S. Yaroshevich ◽

Z. D. Kvon ◽

O. A. Tkachenko ◽

E. E. Rodyakina ◽

...

Keyword(s):

Point Contact ◽

Low Frequency ◽

Quantum Point Contact ◽

Microwave Response ◽

Quantum Point

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Detection and monitoring of axial cracks on cylindrical structures using torsional wave generated by piezoelectric macro-fiber composite

10.1117/12.914957 ◽

2012 ◽

Cited By ~ 2

Author(s):

Lin Cui ◽

Say Ian Lim ◽

Miao Shi ◽

Yu Liu ◽

Chee Kiong Soh

Keyword(s):

Fiber Composite ◽

Torsional Wave ◽

Cylindrical Structures ◽

Macro Fiber Composite

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Synthesis of Vortex Rossby Waves. Part II: Vortex Motion and Waves in the Outer Waveguide

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-15-0005.1 ◽

2015 ◽

Vol 72 (10) ◽

pp. 3958-3974 ◽

Cited By ~ 5

Author(s):

Israel Gonzalez ◽

Amaryllis Cotto ◽

Hugh E. Willoughby

Keyword(s):

Nonlinear Model ◽

Rossby Waves ◽

Critical Radius ◽

Vortex Motion ◽

Low Frequency ◽

Wave Interaction ◽

Linear Acceleration ◽

Propagation Speed ◽

Large Radius ◽

Subsequent Work

Abstract Beta, the meridional gradient of planetary vorticity, causes tropical cyclones to propagate poleward and westward at approximately 2 m s−1. In a previous shallow-water linear model, the simulated vortex accelerated without limit, ostensibly because beta forced a free linear mode. In the analogous nonlinear model, wave–wave interaction limited the propagation speed. Subsequent work based upon the asymmetric balance (AB) approximation was unable to replicate the linear result. The present barotropic nondivergent model replicates the linear beta gyres as a streamfunction dipole with a uniform southeasterly ventilation flow across the vortex. The simulated storm accelerates to unphysical, but finite, speeds that are limited by vorticity filamentation. In the analogous nonlinear model, nonlinearly forced wavenumber-1 gyres have opposite phase to the linear gyres so that their ventilation flow counteracts advection by the linear gyres to limit the overall vortex speed to approximately 3 m s−1. A bounded mean vortex with zero circulation at large radius must contain an outer annulus of anticyclonic vorticity to satisfy the circulation theorem. The resulting positive mean vorticity gradient constitutes an outer waveguide that supports downstream-propagating, very-low-frequency vortex Rossby waves. It is confined between an inner critical radius where the waves are absorbed and an outer turning point where they are reflected. Vorticity filamentation at the critical radius limits the beta-drift acceleration. The original unlimited linear acceleration stemmed from too-weak dissipation caused by second-order diffusion applied to velocity components instead of vorticity. Fourth-order diffusion and no outer waveguide in the Rankine-like vortex of the AB simulations plausibly explain the different results.

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An optical method for direct measurements of strain in a torsional Hopkinson-bar apparatus

Journal of Strain Analysis ◽

10.1243/03093247v103172 ◽

1975 ◽

Vol 10 (3) ◽

pp. 172-179 ◽

Cited By ~ 5

Author(s):

M G Stevenson ◽

J D Campbell

Keyword(s):

Torsion Test ◽

Hopkinson Bar ◽

Gauge Length ◽

Wave Reflections ◽

Multiple Wave ◽

Torsional Waves ◽

Direct Measurements ◽

Angular Velocities ◽

Bar Test

A method has been developed to measure the related rotation of the flanges of a thin-walled tubular specimen during a torsion test. The method, which is based on the Moiré-fringe technique, is capable of use at the high rates of strain encountered during a Hopkinson-bar test, as well as at low rates of strain. In the application described, the specimen gauge length is very short, but the method could be used for specimens of considerably longer gauge length. Direct calibration of the system is easily carried out at low angular velocities. The method can then be used to measure directly the specimen strain during a Hopkinson-bar test, and thus to check the value derived from measuremets of torsional waves in the elastic bars. Results of such comparisons are given, and it is found that the values given by the two method agree well, the differnce being attributable largely to inaccuracies in the torque measurement. The new method permits the determination of specimen deformation during the later stages of the test when multiple wave reflections render the wave analysis iaccurate. In particular, it has been found that the specimen may be subjected to reversed plastic straining, so that the total plastic strain connot be determined from the permenent deformation at the end of the test.

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