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Papers by mhammed el allami
Proceedings of the 2nd International Conference on Computing and Wireless Communication Systems, 2017
In this paper we study numerical modelling of Lamb waves propagation and its interaction with del... more In this paper we study numerical modelling of Lamb waves propagation and its interaction with delamination in orthotropic plate. Firstly a theoretical model is established to obtain the equation of lamb modes propagation. Secondly dispersion curves are plotted using Matlab program for the laminate [0]4. The simulations were then carried out using ABAQUS CAE by exciting the fundamental A0 Lamb mode in the frequency 225 kHz. The reflection is finally investigated in the case of asymmetric delamination.
The article presents a study of guided ultrasonic waves in a tri-layer structure formed of two al... more The article presents a study of guided ultrasonic waves in a tri-layer structure formed of two aluminium plates assembled with a layer of epoxy resin. The resolution of the dispersion equation was used to plot the dispersion curves and to determine the energy distribution of a given mode propagating within the structure. On the other hand, the evaluation of the interaction of guided modes at low frequency with hidden defect placed either in one of the aluminium plates at the interface between aluminium and the adhesive layer was presented. The analyse of the reflected and transmitted waves in the dual space (wave number, frequency) permitted the separation and the identification of the propagating guided modes and showed the conversion phenomenon of the incident mode into other guided modes after the reflection and the transmission. Finally a quantification of the energy of the reflected and transmitted modes is presented.
ITM Web of Conferences
It is well known that the propagation of Lamb waves in elastic solid medias depends on the freque... more It is well known that the propagation of Lamb waves in elastic solid medias depends on the frequency and on the material properties, but it does not depend on the propagation direction in isotropic medias and gives rise to two basic types of modes, symmetric and antisymmetric ones. This paper presents an application of the semi-analytical finite element (SAFE) method on an isotropic aluminum plate of thickness e = 2mm. The main goal of this paper is to make a quantitative evaluation of the SAFE method by carrying out the following tasks: a) calculation of the dispersion curves (wavenumber, phase velocity, group velocity, b) calculation of the relative error and validation of the proposed algorithm, c) comparison between the curves obtained by SAFE method on those obtained by Bisection method. It should be noted here that our study is restricted on the propagative modes.
ITM Web of Conferences
Investigation into ultrasonic Non-destructive evaluation (NDE) methods for assessing complex desi... more Investigation into ultrasonic Non-destructive evaluation (NDE) methods for assessing complex designs depends firmly on displaying apparatuses that calculate dispersion curves. These expectations are vital for empowering the best assessment methodologies to be distinguished and their aversions to being assessed. This study, the main purpose of this work is to do a quantitative evaluation of the SAFE technique by calculating dispersion curves (wavenumber, phase velocity, and group velocity) and comparing them to those generated by Disperse Software.
MATEC Web of Conferences
Composite Materials are widely used thanks to their mechanical characteristics. Non destructive e... more Composite Materials are widely used thanks to their mechanical characteristics. Non destructive evaluation requires knowing the exact dispersion curves to determine the propagative waves and to resolve the phase velocity of symmetrical and antisymmetrical modes. The aim of this paper is to plot the dispersion curves of a Carbon Fibre Reinforced Polymer plate using Semi Analytical Finite Element Method algorithm. This method combines the analytical expression of the displacement and the finite element method procedure. The resultant advantage is both simplicity and rapidity. The obtained results showed that the method accuracy depends on the elements number of meshing. To ensure good precision and fast computation of the method, the elements number and the order of the interpolation functions must be optimized.
Proceedings of the Third International Conference on Computing and Wireless Communication Systems, ICCWCS 2019, April 24-25, 2019, Faculty of Sciences, Ibn Tofaïl University -Kénitra- Morocco, 2019
In this paper we study numerical modeling of Lamb waves propagation and its interaction with the ... more In this paper we study numerical modeling of Lamb waves propagation and its interaction with the edges of symmetric delamination in unidirectional orthotropic plate [0] 4. The simulations were carried out using ABAQUS CAE by exciting the fundamental A 0 Lamb mode in the frequency 300 kHz. The delamination was then characterized by analyzing the signal picked up at two sensors using two technics: two Dimensional Fast Fourier Transform (2D-FFT) to identify the propagating and converted modes, and Wavelet Transform (WT) to measure the arrival times. The results showed that the mode A 0 is sensible to symmetric delamination. Besides, based on signal changes with the delamination edges, a localization method is proposed to estimate the position and the length of the delamination.
Advances in Computer and Electrical Engineering
In this chapter, we model by Finite Element Method (FEM) the Lamb waves' propagation and thei... more In this chapter, we model by Finite Element Method (FEM) the Lamb waves' propagation and their interactions with symmetric and asymmetric delamination in sandwich skin. Firstly, a theoretical model is established to obtain the equation of lamb modes propagation. Secondly, dispersion curves are plotted using Matlab program for the laminate [0]4. The simulations were then carried out using ABAQUS CAE by exciting the fundamental A0 Lamb mode in the frequency 300 kHz. The delamination was then estimated by analyzing the signal picked up at two sensors using two techniques: Two Dimensional Fast Fourier Transform (2D-FFT) to identify the propagating and converted modes, and Wavelet Transform (WT) to measure the arrival times. The results showed that the mode A0 is sensible to symmetric and asymmetric delamination. Besides, based on signal changes with the delamination edges, a localization method is proposed to estimate the position and the length of the delamination. In the last sect...
Comptes Rendus. Mécanique
A semi-analytical finite element method algorithm was established to plot the dispersion curves o... more A semi-analytical finite element method algorithm was established to plot the dispersion curves of isotropic aluminum and orthotropic plates. The curves obtained are compared with those plotted by the DISPERSE software and with previous experimental work. The results showed that the accuracy of the method depends on the number of elements for meshing. To ensure good precision and speed of the method, the number of elements per plate thickness must be optimized.
Advances in Acoustics and Vibration
In this work we model by finite element method (FEM) the Lamb waves’ propagation and their intera... more In this work we model by finite element method (FEM) the Lamb waves’ propagation and their interactions with symmetric and asymmetric delamination in sandwich skin. The simulations were carried out using ABAQUS CAE by exciting the fundamental A0 Lamb mode in the frequency 300 kHz. The delamination was then estimated by analysing the signal picked up at two sensors using two technics: Two-Dimensional Fast Fourier Transform (2D-FFT) to identify the propagating and converted modes, and wavelet transform (WT) to measure the arrival times. The results showed that the mode A0 is sensible to symmetric and asymmetric delamination. Besides, based on signal changes with the delamination edges, a localization method is proposed to estimate the position and the length of the delamination. In the last section an experimental FEM verification is provided to validate the proposed method.
The paper proposes a wavelet spectral analysis method of Lamb waves in thin isotropic plates. A n... more The paper proposes a wavelet spectral analysis method of Lamb waves in thin isotropic plates. A numerical code is developed on the Comsol Multiphysics software to solve, by the finite element method, the equation of motion and determine the displacement field. The post processing of the obtained displacement field is done, on the Matlab software, by a method based on the wavelet transform (WT). The considered application aims to determine the dispersion curves of symmetric S0 and antisymmetric A0 Lamb modes of a plane steel plate. These curves are obtained by the WT of displacement field and are compared to the analytic curves. Several mother wavelets are tested showing that the complex mother wavelet Shan 1-1.5 gives the better agreement.
Cet article présente un modèle des éléments finis et propose un traitement par les ondelettes des... more Cet article présente un modèle des éléments finis et propose un traitement par les ondelettes des ondes de Lamb dans une plaque isotrope mince. Le code numérique est développé sur le logiciel Comsol Multiphysics pour résoudre l'équation du mouvement et déterminer le champ de déplacements. Le traitement du champ de déplacement obtenu est réalisé sur le logiciel Matlab, par une méthode basée sur la transformée en ondelettes (WT). L'application considérée utilise un cas d'une plaque d'acier avec un défaut interne, rectangulaire et symétrique. L'ondelette mère de Morlet est utilisée dans le post traitement du champ de déplacement pour déterminer les coefficients énergétiques de réflexion ou de transmission des modes de Lamb. La comparaison entre ces coefficients et ceux déterminés avec le traitement par la transformée de Fourier bidimensionnelle (FFT2D) montre une bonne concordance 1 Introduction En industrie, certaines structures subissent d'importantes charges ...
In this paper, we present a finite element modeling of A0 and S0 Lamb modes in a plate with an in... more In this paper, we present a finite element modeling of A0 and S0 Lamb modes in a plate with an internal defect. The complex mother wavelet Shan 1-1.5 and the 2D fast Fourier transform are used for the post processing of the FE modeling predicted displacement field in order to compute the power coefficients of the reflected and the transmitted Lamb modes by the defect. The comparison between coefficients found by the two processing methods shows a good agreement.
Physical and Chemical News
This paper presents an ultrasound propagation model in plane plates based on the finite element m... more This paper presents an ultrasound propagation model in plane plates based on the finite element method. This model is implanted in the computer commercial code Comsol Multiphysics. The crucial parameters (spatial and temporal steps) are optimised to ensure the convergence of the algorithm toward the solution (displacement field). The aim is to analyze the interaction of S0 and A0 Lamb modes with a rectangular defect in an elastic and isotropic plate. This analysis is quantified by calculating the reflection and transmission power coefficients from a double Fourier transform of displacements depicted on the upper surface of the plate, before and after the defect. Three applications are presented here: the two first ones consider the case of an internal rectangular defect, one located on the median axis of the plate, the other out of this axis. The third application concerns the case of an emerging rectangular defect. In the three considered applications, the results of numerical simu...
In this work we model by finite element method (FEM) the Lamb waves' propagation and their intera... more In this work we model by finite element method (FEM) the Lamb waves' propagation and their interactions with symmetric and asymmetric delamination in sandwich skin. The simulations were carried out using ABAQUS CAE by exciting the fundamental A 0 Lamb mode in the frequency 300 kHz. The delamination was then estimated by analysing the signal picked up at two sensors using two technics: Two-Dimensional Fast Fourier Transform (2D-FFT) to identify the propagating and converted modes, and wavelet transform (WT) to measure the arrival times. The results showed that the mode A 0 is sensible to symmetric and asymmetric delamination. Besides, based on signal changes with the delamination edges, a localization method is proposed to estimate the position and the length of the delamination. In the last section an experimental FEM verification is provided to validate the proposed method.
Proceedings of the 2nd International Conference on Computing and Wireless Communication Systems, 2017
In this paper we study numerical modelling of Lamb waves propagation and its interaction with del... more In this paper we study numerical modelling of Lamb waves propagation and its interaction with delamination in orthotropic plate. Firstly a theoretical model is established to obtain the equation of lamb modes propagation. Secondly dispersion curves are plotted using Matlab program for the laminate [0]4. The simulations were then carried out using ABAQUS CAE by exciting the fundamental A0 Lamb mode in the frequency 225 kHz. The reflection is finally investigated in the case of asymmetric delamination.
The article presents a study of guided ultrasonic waves in a tri-layer structure formed of two al... more The article presents a study of guided ultrasonic waves in a tri-layer structure formed of two aluminium plates assembled with a layer of epoxy resin. The resolution of the dispersion equation was used to plot the dispersion curves and to determine the energy distribution of a given mode propagating within the structure. On the other hand, the evaluation of the interaction of guided modes at low frequency with hidden defect placed either in one of the aluminium plates at the interface between aluminium and the adhesive layer was presented. The analyse of the reflected and transmitted waves in the dual space (wave number, frequency) permitted the separation and the identification of the propagating guided modes and showed the conversion phenomenon of the incident mode into other guided modes after the reflection and the transmission. Finally a quantification of the energy of the reflected and transmitted modes is presented.
ITM Web of Conferences
It is well known that the propagation of Lamb waves in elastic solid medias depends on the freque... more It is well known that the propagation of Lamb waves in elastic solid medias depends on the frequency and on the material properties, but it does not depend on the propagation direction in isotropic medias and gives rise to two basic types of modes, symmetric and antisymmetric ones. This paper presents an application of the semi-analytical finite element (SAFE) method on an isotropic aluminum plate of thickness e = 2mm. The main goal of this paper is to make a quantitative evaluation of the SAFE method by carrying out the following tasks: a) calculation of the dispersion curves (wavenumber, phase velocity, group velocity, b) calculation of the relative error and validation of the proposed algorithm, c) comparison between the curves obtained by SAFE method on those obtained by Bisection method. It should be noted here that our study is restricted on the propagative modes.
ITM Web of Conferences
Investigation into ultrasonic Non-destructive evaluation (NDE) methods for assessing complex desi... more Investigation into ultrasonic Non-destructive evaluation (NDE) methods for assessing complex designs depends firmly on displaying apparatuses that calculate dispersion curves. These expectations are vital for empowering the best assessment methodologies to be distinguished and their aversions to being assessed. This study, the main purpose of this work is to do a quantitative evaluation of the SAFE technique by calculating dispersion curves (wavenumber, phase velocity, and group velocity) and comparing them to those generated by Disperse Software.
MATEC Web of Conferences
Composite Materials are widely used thanks to their mechanical characteristics. Non destructive e... more Composite Materials are widely used thanks to their mechanical characteristics. Non destructive evaluation requires knowing the exact dispersion curves to determine the propagative waves and to resolve the phase velocity of symmetrical and antisymmetrical modes. The aim of this paper is to plot the dispersion curves of a Carbon Fibre Reinforced Polymer plate using Semi Analytical Finite Element Method algorithm. This method combines the analytical expression of the displacement and the finite element method procedure. The resultant advantage is both simplicity and rapidity. The obtained results showed that the method accuracy depends on the elements number of meshing. To ensure good precision and fast computation of the method, the elements number and the order of the interpolation functions must be optimized.
Proceedings of the Third International Conference on Computing and Wireless Communication Systems, ICCWCS 2019, April 24-25, 2019, Faculty of Sciences, Ibn Tofaïl University -Kénitra- Morocco, 2019
In this paper we study numerical modeling of Lamb waves propagation and its interaction with the ... more In this paper we study numerical modeling of Lamb waves propagation and its interaction with the edges of symmetric delamination in unidirectional orthotropic plate [0] 4. The simulations were carried out using ABAQUS CAE by exciting the fundamental A 0 Lamb mode in the frequency 300 kHz. The delamination was then characterized by analyzing the signal picked up at two sensors using two technics: two Dimensional Fast Fourier Transform (2D-FFT) to identify the propagating and converted modes, and Wavelet Transform (WT) to measure the arrival times. The results showed that the mode A 0 is sensible to symmetric delamination. Besides, based on signal changes with the delamination edges, a localization method is proposed to estimate the position and the length of the delamination.
Advances in Computer and Electrical Engineering
In this chapter, we model by Finite Element Method (FEM) the Lamb waves' propagation and thei... more In this chapter, we model by Finite Element Method (FEM) the Lamb waves' propagation and their interactions with symmetric and asymmetric delamination in sandwich skin. Firstly, a theoretical model is established to obtain the equation of lamb modes propagation. Secondly, dispersion curves are plotted using Matlab program for the laminate [0]4. The simulations were then carried out using ABAQUS CAE by exciting the fundamental A0 Lamb mode in the frequency 300 kHz. The delamination was then estimated by analyzing the signal picked up at two sensors using two techniques: Two Dimensional Fast Fourier Transform (2D-FFT) to identify the propagating and converted modes, and Wavelet Transform (WT) to measure the arrival times. The results showed that the mode A0 is sensible to symmetric and asymmetric delamination. Besides, based on signal changes with the delamination edges, a localization method is proposed to estimate the position and the length of the delamination. In the last sect...
Comptes Rendus. Mécanique
A semi-analytical finite element method algorithm was established to plot the dispersion curves o... more A semi-analytical finite element method algorithm was established to plot the dispersion curves of isotropic aluminum and orthotropic plates. The curves obtained are compared with those plotted by the DISPERSE software and with previous experimental work. The results showed that the accuracy of the method depends on the number of elements for meshing. To ensure good precision and speed of the method, the number of elements per plate thickness must be optimized.
Advances in Acoustics and Vibration
In this work we model by finite element method (FEM) the Lamb waves’ propagation and their intera... more In this work we model by finite element method (FEM) the Lamb waves’ propagation and their interactions with symmetric and asymmetric delamination in sandwich skin. The simulations were carried out using ABAQUS CAE by exciting the fundamental A0 Lamb mode in the frequency 300 kHz. The delamination was then estimated by analysing the signal picked up at two sensors using two technics: Two-Dimensional Fast Fourier Transform (2D-FFT) to identify the propagating and converted modes, and wavelet transform (WT) to measure the arrival times. The results showed that the mode A0 is sensible to symmetric and asymmetric delamination. Besides, based on signal changes with the delamination edges, a localization method is proposed to estimate the position and the length of the delamination. In the last section an experimental FEM verification is provided to validate the proposed method.
The paper proposes a wavelet spectral analysis method of Lamb waves in thin isotropic plates. A n... more The paper proposes a wavelet spectral analysis method of Lamb waves in thin isotropic plates. A numerical code is developed on the Comsol Multiphysics software to solve, by the finite element method, the equation of motion and determine the displacement field. The post processing of the obtained displacement field is done, on the Matlab software, by a method based on the wavelet transform (WT). The considered application aims to determine the dispersion curves of symmetric S0 and antisymmetric A0 Lamb modes of a plane steel plate. These curves are obtained by the WT of displacement field and are compared to the analytic curves. Several mother wavelets are tested showing that the complex mother wavelet Shan 1-1.5 gives the better agreement.
Cet article présente un modèle des éléments finis et propose un traitement par les ondelettes des... more Cet article présente un modèle des éléments finis et propose un traitement par les ondelettes des ondes de Lamb dans une plaque isotrope mince. Le code numérique est développé sur le logiciel Comsol Multiphysics pour résoudre l'équation du mouvement et déterminer le champ de déplacements. Le traitement du champ de déplacement obtenu est réalisé sur le logiciel Matlab, par une méthode basée sur la transformée en ondelettes (WT). L'application considérée utilise un cas d'une plaque d'acier avec un défaut interne, rectangulaire et symétrique. L'ondelette mère de Morlet est utilisée dans le post traitement du champ de déplacement pour déterminer les coefficients énergétiques de réflexion ou de transmission des modes de Lamb. La comparaison entre ces coefficients et ceux déterminés avec le traitement par la transformée de Fourier bidimensionnelle (FFT2D) montre une bonne concordance 1 Introduction En industrie, certaines structures subissent d'importantes charges ...
In this paper, we present a finite element modeling of A0 and S0 Lamb modes in a plate with an in... more In this paper, we present a finite element modeling of A0 and S0 Lamb modes in a plate with an internal defect. The complex mother wavelet Shan 1-1.5 and the 2D fast Fourier transform are used for the post processing of the FE modeling predicted displacement field in order to compute the power coefficients of the reflected and the transmitted Lamb modes by the defect. The comparison between coefficients found by the two processing methods shows a good agreement.
Physical and Chemical News
This paper presents an ultrasound propagation model in plane plates based on the finite element m... more This paper presents an ultrasound propagation model in plane plates based on the finite element method. This model is implanted in the computer commercial code Comsol Multiphysics. The crucial parameters (spatial and temporal steps) are optimised to ensure the convergence of the algorithm toward the solution (displacement field). The aim is to analyze the interaction of S0 and A0 Lamb modes with a rectangular defect in an elastic and isotropic plate. This analysis is quantified by calculating the reflection and transmission power coefficients from a double Fourier transform of displacements depicted on the upper surface of the plate, before and after the defect. Three applications are presented here: the two first ones consider the case of an internal rectangular defect, one located on the median axis of the plate, the other out of this axis. The third application concerns the case of an emerging rectangular defect. In the three considered applications, the results of numerical simu...
In this work we model by finite element method (FEM) the Lamb waves' propagation and their intera... more In this work we model by finite element method (FEM) the Lamb waves' propagation and their interactions with symmetric and asymmetric delamination in sandwich skin. The simulations were carried out using ABAQUS CAE by exciting the fundamental A 0 Lamb mode in the frequency 300 kHz. The delamination was then estimated by analysing the signal picked up at two sensors using two technics: Two-Dimensional Fast Fourier Transform (2D-FFT) to identify the propagating and converted modes, and wavelet transform (WT) to measure the arrival times. The results showed that the mode A 0 is sensible to symmetric and asymmetric delamination. Besides, based on signal changes with the delamination edges, a localization method is proposed to estimate the position and the length of the delamination. In the last section an experimental FEM verification is provided to validate the proposed method.