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1

Numerical simulation of fundamental elastic wave modes coupling in composite plates

Barski Marek, Stawiarski Adam, Chwał Małgorzata, Augustyn Marcin

Vibrations in Physical Systems

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2023

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Vol. 34, nr 1

art. no. 2023120

EN

In the case of the piezoelectric actuators of the cube-shaped installed symmetrically and perfectly bonded on both external surfaces of the plate-like structures, the symmetric and shear horizontal elastic wave modes are excited at the same time. The current work concerns the numerical simulation of the coupling of the above-mentioned elastic wave modes in a composite plate of angle ply configuration. In the first step, the dispersion curves for all studied composite configurations are estimated. Next, for the arbitrary chosen fixed frequency of the excitation, finite element simulations are performed. As a result of these simulations, the group velocities of the observed elastic modes are estimated. Next, the appropriate wave modes are identified by the comparison of the group velocities obtained from the analysis of the dispersion curves and from the simulations. In the cases for which the identification is possible, a good agreement between analytical and simulation results is observed.

2

Subsurface profiling of a region in Jamshedpur city using active MASW: a case study

Imam Ashhad, Sharma Keshav K., Kumar Virendra, Singh Neeraj

Acta Geophysica

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2022

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Vol. 70, no 4

1601--1617

EN

This paper deals specifically with the active MASW method, which was applied for subsurface exploration of a region in Jamshedpur city, India, to study the various lithological and stiffness properties of subsurface materials. The study investigates the impact of data acquisition parameters on obtaining a high-resolution dispersion image, based on the ongoing MASW survey. A linear array of 24 numbers of 4.5 Hz geophones was used to collect raw wavefield traces generated by a 10 kg sledgehammer. Wavefields were regulated using a range of sampling frequencies (500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, and 8000 Hz), as well as offset distances (1, 2 m, 4 m, 6 m, 8 m, 10 m, and 12 m) and inter receiver spacing (1 m and 2 m). Based on the results, the best data collection parameters for a high signal-to-noise ratio were determined to be: 1000 Hz sampling frequency, 8 m offset distance, and 1 m inter receiver spacing, resulting in a sufficient resolution dispersion image. Moreover, 1D and 2D shear-wave velocity profiles for the chosen site were derived. The stiff silty clay soil (up to a depth of 5 m) and dense to very dense weathered mica schist was found (at variable locations and depths from 8 to 30 m or beyond). The average Vs30 is 402 m/s, and the site is classed as Type C as per NEHRP Site Classification. The shear-wave velocity profiles show a high level of agreement with borehole data, demonstrating the effectiveness of the non-invasive technology for sub-surface investigation.

3

Stopband effect and sound transmission loss of periodic locally resonant structures

Juros Klara, Kras Aleksander, Kamisiński Tadeusz

Vibrations in Physical Systems

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2021

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Vol. 32, nr 1

art. no. 2021105

EN

This paper investigates the theoretical aspects of sound attenuation of periodic structures with locally resonant elements. The stopband effect in frequency characteristics of infinite periodic structures created by the resonant elements is investigated. The dispersion curves calculation procedure is described in details with the influence of resonance frequency and mass of added locally resonant structure on width of the obtained stopband is investigated. The theoretical formulation for calculation of the sound transmission loss for periodic structure is derived. The performance of the structure with locally resonant elements is evaluated based on dispersion curves obtained for an infinite periodic structure and transmission loss calculated for finite structure is conducted.

4

The influence of the configuration of the fiber-metal laminates on the dispersion relations of the elastic wave modes

Barski Marek, Muc Aleksander, Stawiarski Adam

Vibrations in Physical Systems

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2020

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Vol. 31, nr 2

art. no. 2020202

EN

The current work is devoted to the determination of dispersion curves for elastic wave modes. The studied elastic waves propagate across metal-fiber hybrid composites. In order to solve the problem, special software has been developed with the use of C++. This software works with the MS Windows operating system and the proposed solution is based on the multi-threading mechanism. It makes possible to significantly speed up the calculations. The relatively new approach is used namely the stiffness matrix method. At the very beginning, the dispersion curves are determined for the traditional composite materials of cross-ply configuration, for which the layers are made of glass fiber/epoxy resin and carbon fiber/epoxy resin. The impact of the total number of layers on the dispersion curves is investigated. Next, the influence of the thickness of the layers, which are made of aluminum alloy, on the dispersion characteristic is studied. In the second case, it is assumed that the total thickness of the composite material wall for all cases is identical.

5

Analytical and numerical identification of lamb waves modes for hybrid composites

Barski M., Pająk P.

Journal of KONES

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2017

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Vol. 24, No. 1

31--38

EN

The current work is devoted to the problem of analytical and numerical identification of fundamental elastic waves' modes, namely symmetric mode S0 and antisymmetric mode A0, in the case of hybrid composite. The investigated material consists of one layer made of aluminum alloy Pa38 and six layers made of glass fabric/epoxy resin. At the very beginning, the dispersion curves are determined with the use of stiffness matrix method. The calculated values of phase velocities are verified by numerical simulation. The semi – analytical finite element method is applied. Next, the numerical simulations of elastic waves propagation are performed. In the studied model, the plane state of strain is assumed. These simulations are carried out with the use of finite element method. The excitation signal is a sine wave modulated by Hanning window. The simulation is repeated for different excitation frequency. The group velocities of wave modes S0 and A0 are estimated and compared with the analytical results. The evaluation of the group velocities is based on the analysis of the appropriate components of displacement. The two different method are employed, namely: cross – correlation method and envelope extraction by Hilbert transform. Generally, the obtained results are in a good agreement. However, the method based on envelope extraction by Hilbert transform provides better correlation between analytical and numerical results. The significant discrepancy is observed in the case of symmetric mode S0 for relatively high values of frequency. It is caused by the dispersion phenomena. The analytical calculations are performed with the use of SCILAB 5.5.2 free software and the numerical simulations are carried out with the use of finite element system ANSYS 13.0.

6

Expanding seismic surface waves measurements towards low periods with gravity measurements

Wilde-Piórko M., Dykowski P., Polkowski M., Olszak T., Grad M., Kryński J., Sękowski M., Krankowski A., Rajner M.

Geoinformation Issues

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2017

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Vol. 9, no. 1(9)

5--13

EN

Seismic events in gravity measurements are considered as disturbances and are usually removed from the records. However, the physical properties of tidal gravimetric instruments allow researchers to record seismic surface waves of very long periods. In the case of a superconducting gravimeter, periods of even up to 400 s can be determined. Simultaneous seismic and gravity records at the same locations allow the study of a wider response for incoming seismic waves by using two quite different instruments. For test purposes 4 seismometer-gravimeter pairs were temporarily deployed in Poland at three locations: Borowa Gora Geodetic-Geophysical Observatory (BG), Jozefoslaw Astro-Geodetic Observatory (JO), and Lamkowko Satellite Observatory (LA). During the test period from December 2016 to May 2017 several large teleseismic events were observed with well-formed surface waves. Group velocity dispersion curves for long surface waves, as well as periods of free oscillations are presented for selected events. The correlation of a broadband seismometer signal with different types of gravimetric sensors signals gives the opportunity to analyse gravimeter noise components, in the instrumental and micro-seismic domains.

PL

Zjawiska sejsmiczne w pomiarach grawimetrycznych są traktowane jako zakłócenia i zwykle ich efekty są usuwane z zapisów grawimetrycznych. Jednakże, grawimetry dzięki swojej konstrukcji umożliwiają rejestrację sejsmicznych fal powierzchniowych o bardzo długich okresach. W przypadku grawimetru nadprzewodnikowego, możliwe jest zaobserwowanie fal powierzchniowych, generowanych przez trzęsienia ziemi, o okresach nawet do 400 s. Przeprowadzenie równoczesnych rejestracji sejsmicznych i grawimetrycznych instrumentami zlokalizowanymi w tym samym miejscu, powinno umożliwić przeanalizowanie szerszego zakresu częstości sygnału sejsmicznego niż w przypadku użycia tylko jednego typu instrumentu. W celu sprawdzenia prawdziwości powyższego stwierdzenia, 4 pary instrumentów: sejsmometrów i grawimetrów zostały zainstalowane w Polsce w trzech lokalizacjach, w Obserwatorium Geodezyjno-Geofizycznym Borowa Góra (BG), Obserwatorium Astronomiczno-Geodezyjnym Józefosław (JO) oraz Obserwatorium Satelitarnym Lamkówko (LA). W czasie projektu pilotażowego, trwającego od grudnia 2016 do maja 2017 roku, zarejestrowano kilka dużych trzęsień ziemi z dobrze wykształconymi falami powierzchniowymi. W pracy zaprezentowano krzywe dyspersji grupowych prędkości fal powierzchniowych, jak również okresy oscylacji swobodnych dla wybranych zjawisk. Korelacja szerokopasmowego sygnału sejsmicznego z sygnałem zarejestrowanym przez różnego typu grawimetry umożliwi analizę szumu grawimetrycznego w zakresie częstości pływowych instrumentów, jak i w zakresie mikrosejsmicznym.

7

Application of Multichannel Analysis of Surface Waves to S-Phase Wave Anisotropy Estimation

Stan-Kłeczek I., Mendecki M. J.

Acta Geophysica

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2016

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Vol. 64, no. 5

1593--1604

EN

The Multichannel Analysis of Surface Waves (MASW) is an increasingly used technique for recognition of a shallow geological structure and estimation of geotechnical parameters, e.g., S-wave velocity, layer density, layer thickness, shear modulus, estimated P-wave velocity, and estimated Poisson ratio. MASW surveys were carried out in two limestone quarries in the southern part of Poland. The experimental areas are characterised by a simple geological structure: consolidated Triassic limestone. Measurement profiles were arranged as a shapely six-pointed star. For each survey line, 12 geophones with 2-meter (Deposit 1) and 3-meter (Deposit 2) spacing were applied. The research allowed to compare P- and S-wave velocity changes with the main crack systems in the studied rock masses.

8

Sequential stochastic identification of elastic constants using Lamb waves and particle filters

Słoński M.

Computer Assisted Methods in Engineering and Science

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2014

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Vol. 21, no. 1

15--26

EN

Sequential stochastic identification of elastic parameters of thin aluminum plates using Lamb waves is proposed. The identification process is formulated as a Bayesian state estimation problem in which the elastic constants are the unknown state variables. The comparison of a sequence of numerical and pseudoexperimental fundamental dispersion curves is used for an inverse analysis based on particle filter to obtain sequentially the elastic constants. The proposed identification procedure is illustrated by numerical experiments in which the elastic parameters of an aluminum thin plate are estimated. The results show that the proposed approach is able to identify the unknown elastic constants sequentially and that this approach can be also useful for the quantification of uncertainty with respect to the identified parameters.

9

A semi-analytical method for identification of thin elastic plate parameters basing on LWM

Pabisek E., Waszczyszyn Z., Ambroziński Ł.

Computer Assisted Methods in Engineering and Science

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2014

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Vol. 21, no. 1

5--14

EN

A new semi-analytical method, discussed in the presented paper, is composed of two stages. Stage A corresponds to the direct analysis, in which the Lamb Waves Measurements (LWM) technique enables obtaining an experimental set of points D(fj , kj) Jj =1, where f and k are frequency and wavenumber, respectively. After the preprocessing in the transform space an experimental approximate curve kexp(f | D) can be formulated. In Stage B the identification procedure is simulated as a sequence of direct analyses. The dimensionless Lamb Dispersion curves are computed by means of the dimensionless simulation curve ksim(f | par), where the vector of plate parameters par = {E,ν, d, ρ} is adopted, in which Young modulus E, Poisson ratio ν, plate thickness d and density ρ are used. The main idea of the proposed approach is similar to that in the classical method of error minimization. In our paper we propose to apply the zero error value of relative criterion Reky = 0, cf. formula (15). The formula can be applied for the identification of a single plate parameter, assuming a fixed value of the other plate parameters. This approach was used in a case study, in which Stages A and B were analysed for an aluminum plate.

10

Determination of near-surface structures from multi-channel surface wave data using multi-layer perceptron neural network (MLPNN) algorithm

Caylak C., Kaftan I.

Acta Geophysica

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2014

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Vol. 62, no. 6

1310--1327

EN

This study proposes the use of multi-layer perceptron neural networks (MLPNN) to invert dispersion curves obtained via multi-channel analysis of surface waves (MASW) for shear S-wave velocity profile. The dispersion curve used in inversion includes the fundamental-mode dispersion data. In order to investigate the applicability and performance of the proposed MLPNN algorithm, test studies were performed using both synthetic and field examples. Gaussian random noise with a standard deviation of 4 and 8% was added to the noise-free test data to make the synthetic test more realistic. The model parameters, such as S-wave velocities and thicknesses of the synthetic layered-earth model, were obtained for different S/N ratios and noise-free data. The field survey was performed over the natural gas pipeline, located in the Germencik district of Aydın city, western Turkey. The results show that depth, velocity, and location of the embedded natural gas pipe are successfully estimated with reasonably good approximation.