Simultaneous amplification of guided wave modes in polymer pipes via a structurally embedded gradient index lens

2021 ◽  
Author(s):  
Hrishikesh Danawe ◽  
Ziqi Wang ◽  
Gorkem Okudan ◽  
Didem Ozevin ◽  
Serife Tol
Keyword(s):  
Guided Wave ◽  
Gradient Index ◽  
Gradient Index Lens ◽  
Wave Modes

Sonic Gradient Index Lens in Water

2010 ◽  
Author(s):  
Theodore P. Martin ◽  
Michael Nicholas ◽  
Gregory J. Orris ◽  
Liang-Wu Cai ◽  
Daniel Torrent ◽  
...  
Keyword(s):  
Gradient Index ◽  
Gradient Index Lens

Three-Dimensional Spatial Image Forming Using Gradient-Index Lens Arrays.

2002 ◽  
Vol 30 (12) ◽  
pp. 731-736
Author(s):  
Fumio OKANO ◽  
Jun ARAI ◽  
Makoto OKUI
Keyword(s):  
Three Dimensional ◽  
Gradient Index ◽  
Spatial Image ◽  
Gradient Index Lens

scholarly journals Two-photon microscopy with simultaneous standard and extended depth of field using a tunable acoustic gradient-index lens

2009 ◽  
Vol 34 (11) ◽  
pp. 1684 ◽  
Author(s):  
Nicolas Olivier ◽  
Alexandre Mermillod-Blondin ◽  
Craig B. Arnold ◽  
Emmanuel Beaurepaire
Keyword(s):  
Depth Of Field ◽  
Gradient Index ◽  
Two Photon Microscopy ◽  
Two Photon ◽  
Gradient Index Lens ◽  
Extended Depth Of Field

Fiber compatible fast acousto‐optic modulator using a gradient index lens as the interaction medium

1993 ◽  
Vol 62 (26) ◽  
pp. 3402-3404 ◽  
Author(s):  
I. Abdulhalim ◽  
C. N. Pannell ◽  
D. N. Payne
Keyword(s):  
Gradient Index ◽  
Acousto Optic Modulator ◽  
Gradient Index Lens

Contribution of Lamb wave modes in the formation of higher order modes cluster (HOMC) guided waves

2021 ◽  
pp. 095440622110424
Author(s):  
Z Abbasi ◽  
F Honarvar
Keyword(s):  
Finite Element ◽  
Wave Packet ◽  
Lamb Wave ◽  
Guided Waves ◽  
Element Model ◽  
Higher Order ◽  
Guided Wave ◽  
Cross Sectional ◽  
Higher Order Modes ◽  
Wave Modes

In recent years, Higher Order Modes Cluster (HOMC) guided waves have been considered for ultrasonic testing of plates and pipes. HOMC guided waves consist of higher order Lamb wave modes that travel together as a single nondispersive wave packet. The objective of this paper is to investigate the effect of frequency-thickness value on the contribution of Lamb wave modes in an HOMC guided wave. This is an important issue that has not been thoroughly investigated before. The contribution of each Lamb wave mode in an HOMC guided wave is studied by using a two-dimensional finite element model. The level of contribution of various Lamb wave modes to the wave cluster is verified by using a 2D FFT analysis. The results show that by increasing the frequency-thickness value, the order of contributing modes in the HOMC wave packet increases. The number of modes that comprise a cluster also increases up to a specific frequency-thickness value and then it starts to decrease. Plotting of the cross-sectional displacement patterns along the HOMC guided wave paths confirms the shifting of dominant modes from lower to higher order modes with increase of frequency-thickness value. Experimental measurements conducted on a mild steel plate are used to verify the finite element simulations. The experimental results are found to be in good agreement with simulations and confirm the changes observed in the level of contribution of Lamb wave modes in a wave cluster by changing the frequency-thickness value.

scholarly journals Fatigue crack detection in pipes with multiple mode nonlinear guided waves

2018 ◽  
Vol 18 (1) ◽  
pp. 180-192 ◽  
Author(s):  
Ruiqi Guan ◽  
Ye Lu ◽  
Kai Wang ◽  
Zhongqing Su
Keyword(s):  
Fatigue Crack ◽  
Crack Detection ◽  
Guided Waves ◽  
Second Harmonic ◽  
Experimental Testing ◽  
Harmonic Wave ◽  
Guided Wave ◽  
Element Analysis ◽  
Fatigue Crack Detection ◽  
Wave Modes

This study elaborates fundamental differences in fatigue crack detection using nonlinear guided waves between plate and pipe structures and provides an effective approach for analysing nonlinearity in pipe structures. For this purpose, guided wave propagation and interaction with microcrack in a pipe structure, which introduced a contact acoustic nonlinearity, was analysed through a finite element analysis in which the material nonlinearity was also included. To validate the simulation results, experimental testing was performed using piezoelectric transducers to generate guided waves in a specimen with a fatigue crack. Both methods revealed that the second harmonic wave generated by the breathing behaviour of the microcrack in a pipe had multiple wave modes, unlike the plate scenario using nonlinear guided waves. Therefore, a proper index which considered all the generated wave modes due to the microcrack was developed to quantify the nonlinearity, facilitating the identification of microscale damage and further assessment of the severity of the damage in pipe structures.

Resonance cones and guided wave modes

1980 ◽  
Vol 24 (1) ◽  
pp. 163-167 ◽  
Author(s):  
Crockett L. Grabbe
Keyword(s):  
Guided Wave ◽  
Magnetized Plasmas ◽  
Bounded Plasma ◽  
Watson Transformation ◽  
Complementary Nature ◽  
Wave Modes

A brief review of resonance cones in magnetized plasmas and their relationship with guided wave modes in bounded plasmas is given. It is shown that these two concepts are related mathematically by a Watson transformation, and physically by being complementary descriptions of waves in a warm bounded plasma. A detailed summary of the complementary nature of these two wave descriptions is given.

scholarly journals High Frequency Ultrasonic Wave Propagation in  Anisotropic Materials

2021 ◽  
Author(s):  
◽  
Andrew Paul Dawson
Keyword(s):  
Wave Propagation ◽  
Ultrasonic Wave ◽  
High Frequency ◽  
Guided Wave ◽  
Ultrasonic Waves ◽  
Tissue Characterisation ◽  
Ultrasonic Wave Propagation ◽  
Matching Layer ◽  
Fibrous Tissues ◽  
Wave Modes

<p>The influence of highly regular, anisotropic, microstructured materials on high frequency ultrasonic wave propagation was investigated in this work. Microstructure, often only treated as a source of scattering, significantly influences high frequency ultrasonic waves, resulting in unexpected guided wave modes. Tissues, such as skin or muscle, are treated as homogeneous by current medical ultrasound systems, but actually consist of highly anisotropic micron-sized fibres. As these systems increase towards 100 MHz, these fibres will significantly influence propagating waves leading to guided wave modes. The effect of these modes on image quality must be considered. However, before studies can be undertaken on fibrous tissues, wave propagation in more ideal structures must be first understood. After the construction of a suitable high frequency ultrasound experimental system, finite element modelling and experimental characterisation of high frequency (20-200 MHz) ultrasonic waves in ideal, collinear, nanostructured alumina was carried out. These results revealed interesting waveguiding phenomena, and also identified the potential and significant advantages of using a microstructured material as an alternative acoustic matching layer in ultrasonic transducer design. Tailorable acoustic impedances were achieved from 4-17 MRayl, covering the impedance range of 7-12 MRayl most commonly required by transducer matching layers. Attenuation coefficients as low as 3.5 dBmm-1 were measured at 100 MHz, which is excellent when compared with 500 dBmm-1 that was measured for a state of the art loaded epoxy matching layer at the same frequency. Reception of ultrasound without the restriction of critical angles was also achieved, and no dispersion was observed in these structures (unlike current matching layers) until at least 200 MHz. In addition, to make a significant step forward towards high frequency tissue characterisation, novel microstructured poly(vinyl alcohol) tissue-mimicking phantoms were also developed. These phantoms possessed acoustic and microstructural properties representative of fibrous tissues, much more realistic than currently used homogeneous phantoms. The attenuation coefficient measured along the direction of PVA alignment in an example phantom was 8 dBmm-1 at 30 MHz, in excellent agreement with healthy human myocardium. This method will allow the fabrication of more realistic and repeatable phantoms for future high frequency tissue characterisation studies.</p>

An alternative method for measuring the index profile of a gradient-index lens

2011 ◽  
Author(s):  
H. C. Hsieh ◽  
W. C. Wu ◽  
W. Y. Chang ◽  
F. S. Hsu ◽  
D. C. Su
Keyword(s):  
Gradient Index ◽  
Index Profile ◽  
Alternative Method ◽  
Gradient Index Lens
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