Laser Vibrometer Imaging of Delamination Interaction with Lamb Waves Using a Chirp Excitation Method

2017 ◽  
Vol 754 ◽  
pp. 375-378 ◽  
Author(s):  
Ifan Dafydd ◽  
Zahra Sharif Khodaei
Keyword(s):  
Guided Waves ◽  
Lamb Waves ◽  
Laser Doppler Vibrometer ◽  
Composite Panel ◽  
Chirp Signal ◽  
Laser Vibrometry ◽  
Post Processing ◽  
Frequency Range ◽  
Narrowband Signal ◽  
Excitation Method

One method that has shown great potential in visualising and characterising the interaction of guided waves with damage in composites is Laser Vibrometry. A Laser Doppler Vibrometer (LDV) can be used to produce 2D wavefield images of guided Lamb waves but a single scan is very time consuming and normally multiple scans are required at various frequencies in order to determine the best input signal. This paper demonstrates the use of a chirp excitation method requiring only a single scan and a post-processing algorithm to obtain results corresponding to any narrowband signal within the frequency range of the chirp signal. The method was used on an artificially delaminated composite panel and showed that the S0 mode, dominant at higher frequencies, mainly caused mode conversions whilst the A0 mode, dominant at lower frequencies, mainly caused a change in phase and amplitude across the delaminationOne method that has shown great potential in visualising and characterising the interaction of guided waves with damage in composites is Laser Vibrometry. A Laser Doppler Vibrometer (LDV) can be used to produce 2D wavefield images of guided Lamb waves but a single scan is very time consuming and normally multiple scans are required at various frequencies in order to determine the best input signal. This paper demonstrates the use of a chirp excitation method requiring only a single scan and a post-processing algorithm to obtain results corresponding to any narrowband signal within the frequency range of the chirp signal. The method was used on an artificially delaminated composite panel and showed that the S0 mode, dominant at higher frequencies, mainly caused mode conversions whilst the A0 mode, dominant at lower frequencies, mainly caused a change in phase and amplitude across the delamination.

scholarly journals Core–skin debonding detection in honeycomb sandwich structures through guided wave wavefield analysis

2018 ◽  
Vol 30 (9) ◽  
pp. 1306-1317 ◽  
Author(s):  
Lingyu Yu ◽  
Zhenhua Tian ◽  
Xiaopeng Li ◽  
Rui Zhu ◽  
Guoliang Huang
Keyword(s):  
Guided Waves ◽  
Sandwich Structures ◽  
Lamb Waves ◽  
Laser Doppler Vibrometer ◽  
Low Frequency ◽  
Guided Wave ◽  
Honeycomb Sandwich ◽  
Debonding Detection ◽  
The Waves ◽  
Detection And Quantification

Ultrasonic guided waves have proven to be an effective and efficient method for damage detection and quantification in various plate-like structures. In honeycomb sandwich structures, wave propagation and interaction with typical defects such as hidden debonding damage are complicated; hence, the detection of defects using guided waves remains a challenging problem. The work presented in this article investigates the interaction of low-frequency guided waves with core–skin debonding damage in aluminum core honeycomb sandwich structures using finite element simulations. Due to debonding damage, the waves propagating in the debonded skin panel change to fundamental antisymmetric Lamb waves with different wavenumber values. Exploiting this mechanism, experimental inspection using a non-contact laser Doppler vibrometer was performed to acquire wavefield data from pristine and debonded structures. The data were then processed and analyzed with two wavefield data–based imaging approaches, the filter reconstruction imaging and the spatial wavenumber imaging. Both approaches can clearly indicate the presence, location, and size of the debonding in the structures, thus proving to be effective methods for debonding detection and quantification for honeycomb sandwich structures.

scholarly journals On the Directivity of Lamb Waves Generated by Wedge PZT Actuator in Thin CFRP Panel

2020 ◽  
Author(s):  
Sergey Shevtsov ◽  
Valery Chebanenko ◽  
Maria Shevtsova ◽  
Shun-Hsyung Chang ◽  
Evgenia Kirillova ◽  
...  
Keyword(s):  
Wave Attenuation ◽  
Lamb Waves ◽  
Propagation Distance ◽  
Dispersion Analysis ◽  
Layered Composite ◽  
Guided Wave ◽  
Composite Panel ◽  
Fe Model ◽  
Frequency Range ◽  
Cfrp Composite

This paper addresses investigation of guided-wave excitation by angle-beam wedge piezoelectric transducers in multi-layered composite plate structure with orthotropic symmetry of the material. The aim of the present study is to determine the capability of such actuators to provide the controlled generation of an acoustic wave of a desirable type with the necessary wavelength, propagation distance and directivity. The studied CFRP panel is considered as homogenous with effective elastic moduli and anisotropic structural damping, whose parameters were determined experimentally. According to the results of dispersion analysis and taking into account the data of wave attenuation in a highly damping CFRP composite, the two types of propagating waves A0 and S0 were considered theoretically and experimentally in the frequency range 10 - 100 kHz. Using the results of a previous study, the structure of the wedge actuator was reconstructed to develop its finite element (FE) model, and a modal analysis was carried out, which revealed the most intense natural vibration modes and their eigenfrequencies within the used frequency range. Both experimental and numerical studies of the generation, propagation, directivity and attenuation of waves in the orthotropic composite panel under study revealed the influence of the angular orientation of the actuator on the formation of wave patterns and allowed to determine the capabilities of the wave's directivity control.

scholarly journals On the Directivity of Lamb Waves Generated by Wedge PZT Actuator in Thin CFRP Panel

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 907 ◽  
Author(s):  
Sergey Shevtsov ◽  
Valery Chebanenko ◽  
Maria Shevtsova ◽  
Shun-Hsyung Chang ◽  
Evgenia Kirillova ◽  
...  
Keyword(s):  
Wave Attenuation ◽  
Lamb Waves ◽  
Propagation Distance ◽  
Dispersion Analysis ◽  
Guided Wave ◽  
Composite Panel ◽  
Fe Model ◽  
Frequency Range ◽  
Reinforced Plastic ◽  
Cfrp Composite

This paper addresses investigation of guided-wave excitation by angle-beam wedge piezoelectric (PZT) transducers in multilayered composite plate structure with orthotropic symmetry of the material. The aim of the present study is to determine the capability of such actuators to provide the controlled generation of an acoustic wave of a desirable type with the necessary wavelength, propagation distance and directivity. The studied CFRP (Carbon Fiber Reinforced Plastic) panel is considered to be homogenous, with effective elastic moduli and anisotropic structural damping, whose parameters were determined experimentally. According to the results of dispersion analysis and taking into account the data of wave attenuation in a highly damping CFRP composite, the two types of propagating waves A0 and S0 were considered theoretically and experimentally in the frequency range of 10–100 kHz. Using the results of a previous study, we reconstructed the structure of the wedge actuator, to develop its finite-element (FE) model, and a modal analysis was carried out that revealed the most intense natural vibration modes and their eigenfrequencies within the frequency range used. Both experimental and numerical studies of the generation, propagation, directivity and attenuation of waves in the orthotropic composite panel under study revealed the influence of the angular orientation of the actuator on the formation of wave patterns and allowed to determine the capabilities of the wave’s directivity control.

scholarly journals On the Directivity of Lamb Waves Generated by Wedge PZT Actuator in Thin CFRP Panel

2019 ◽  
Author(s):  
Sergey Shevtsov ◽  
Valery Chebanenko ◽  
Maria Shevtsova ◽  
Shun-Hsyung Chang ◽  
Evgenia Kirillova ◽  
...  
Keyword(s):  
Wave Attenuation ◽  
Lamb Waves ◽  
Propagation Distance ◽  
Dispersion Analysis ◽  
Layered Composite ◽  
Guided Wave ◽  
Composite Panel ◽  
Fe Model ◽  
Frequency Range ◽  
Cfrp Composite

This paper addresses investigation of guided-wave excitation by angle-beam wedge piezoelectric transducers in multi-layered composite plate structure with orthotropic symmetry of the material. The aim of present study is to determine the capability of such actuators to provide the controlled generation of acoustic wave of desirable type with the necessary wavelength, propagation distance and directivity. The studied CFRP panel is considered as homogenous with effective elastic moduli and anisotropic structural damping, whose parameters were determined experimentally. According to the results of dispersion analysis and taking into account the data of wave attenuation in a highly damping CFRP composite, two types of propagating waves A0 and S0 were considered theoretically and experimentally in the frequency range 10 - 100 kHz. Using the results of a previous study, the structure of the wedge actuator was reconstructed to develop its finite element (FE) model, and a modal analysis was carried out, which revealed the most intense natural vibration modes and their eigenfrequencies within the used frequency range. Both experimental and numerical studies of the generation, propagation, directivity and attenuation of waves in the orthotropic composite panel under study revealed the influence of the angular orientation of the actuator on the formation of wave patterns and allowed to determine the capabilities of the wave's directivity control.

Laser vibrometry of air-coupled Lamb waves

2005 ◽  
Vol 47 (3) ◽  
pp. 123-128 ◽  
Author(s):  
Igor Solodov ◽  
Klaus Pfleiderer ◽  
Gerhard Busse
Keyword(s):  
Lamb Waves ◽  
Laser Vibrometry

scholarly journals Acoustic Panels Made of Paper Sludge and Clay Composites

2021 ◽  
Vol 13 (2) ◽  
pp. 637
Author(s):  
Tomas Astrauskas ◽  
Tomas Januševičius ◽  
Raimondas Grubliauskas
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Core Material ◽  
Paper Sludge ◽  
Frequency Range ◽  
Absorption Properties ◽  
Air Gaps ◽  
The Core

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (αavg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (αavg. = 0.51).

Electromagnetic Wave Absorbing and Mechanical Properties of Cement-Based Composite Panel with Different Nanomaterials

2017 ◽  
Vol 26 (1) ◽  
pp. 096369351702600
Author(s):  
Sun Yafei ◽  
Gao Peiwei ◽  
Peng Hailong ◽  
Liu Hongwei ◽  
Lu Xiaolin ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Electromagnetic Wave ◽  
Double Layer ◽  
Mechanical Performance ◽  
Interface Structure ◽  
Composite Panel ◽  
Effective Bandwidth ◽  
Composite Panels ◽  
Frequency Range ◽  
Triple Layer

This paper presents the microstructures and mechanical and absorbing properties of double and triple layer, cement-based, composite panels. The results obtained show that the frequency range in 2-18GHz had less than −10dB effective bandwidth, which correlates with 3.7and 10.8GHz in double and triple layer cement-based composite panels. Furthermore, the double layer panel's compressive strength at 7 and 28 days was 40.2 and 61.2MPa, respectively. For the triple layer panel, the strength values were 35.6MPa and 49.2MPa. The triple layer panel's electromagnetic wave (EMW) absorbing properties were superior compared to the properties of the double layer panel. However, the triple layer panel's mechanical performance was inferior to that of the double layer panel. This study proposes that carbon nanotubes can effectively improve the compressive strength and interface structure of cement-based composite panels.

Inspection of Concrete-Metal Rod Interface Using Guided Waves

2000 ◽  
Author(s):  
Won-Bae Na ◽  
Tribikram Kundu ◽  
Mohammad R. Ehsani
Keyword(s):  
Lamb Wave ◽  
Guided Waves ◽  
Lamb Waves ◽  
Guided Wave ◽  
Ultrasonic Transducers ◽  
Interface Debonding ◽  
Long Distance ◽  
Steel Rebar ◽  
Steel Bars ◽  
Steel Rebars

Abstract The feasibility of detecting interface degradation and separation of steel rebars in concrete beams using Lamb waves is investigated in this paper. It is shown that Lamb waves can easily detect these defects. A special coupler between the steel rebar and ultrasonic transducers has been used to launch non-axisymmetric guided waves in the steel rebar. This investigation shows that the Lamb wave inspection technique is an efficient and effective tool for health monitoring of reinforced concrete structures because the Lamb wave can propagate a long distance along the reinforcing steel bars embedded in concrete as the guided wave and is sensitive to the interface debonding between the steel rebar and concrete.

Silicon Pillars as Resonators in an Acoustical Metamaterial

2014 ◽  
Author(s):  
Bernard Bonello ◽  
Rémi Marchal ◽  
Rayisa Moiseyenko ◽  
Yan Pennec ◽  
Bahram Djafari-Rouhani ◽  
...  
Keyword(s):  
Thin Plate ◽  
Lamb Waves ◽  
Mass Density ◽  
Resonant Mode ◽  
Ultrasonic Technique ◽  
Frequency Range ◽  
Negative Mass ◽  
Laser Ultrasonic ◽  
Compressional Mode ◽  
Bending Modes

We have investigated the propagation of Lamb waves in structures made of either an isolated resonant pillar or a set of pillars arranged in a line on a thin plate. The resonators as well as the plate are made of silicon. FEM computations show that two bending modes and one compressional mode are unambiguously identified in the frequency range of interest (0–10 MHz). We used a laser ultrasonic technique to map both the amplitude and the phase of the normal displacements on top of the pillars and at the surface of the sample. When the frequency is tuned to a resonant mode, either compressional or bending, the pillars vibrate 180° out-of-phase with respect to the Lamb waves, resulting in a negative modulus or negative mass density respectively.

Determination of Vibration Source Locations in Laminated Composite Plates Using Lamb Wave Analysis

2010 ◽  
Vol 123-125 ◽  
pp. 899-902
Author(s):  
Chao Du ◽  
Qing Qing Ni ◽  
Toshiaki Natsuki
Keyword(s):  
Lamb Wave ◽  
Guided Waves ◽  
Lamb Waves ◽  
Laminated Composite ◽  
Composite Plates ◽  
Wave Dispersion ◽  
Laminated Plates ◽  
Vibration Source ◽  
Arrival Times ◽  
Wave Velocities

Signals propagate on plate-like structures as ultrasonic guided waves, and analysis of Lamb waves has been widely used for on-line monitoring. In this study, the wave velocities of symmetric and anti-symmetric modes in various directions of propagation were investigated. Since the wave velocities of these two modes are different, it is possible to compute the difference in their arrival times when these waves propagated the distance from the vibration source to sensor. This paper presents an evaluation formulation of wave velocity and describes a generalized algorithm for locating a vibration source on a thin, laminated plate. With the different velocities of two modes based on Lamb wave dispersion, the method uses two sensors to locate the source on a semi-infinite interval of a plate. The experimental procedure supporting this method employs pencil lead breaks to simulate vibration sources on quasi-isotropic and unidirectional laminated plates. The transient signals generated in this way are transformed using a wavelet transform. The vibration source locations are then detected by utilizing the distinct wave velocities and arrival times of the symmetric and anti-symmetric wave modes. The method is an effective technique for identifying impact locations on plate-like structures.

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