Ahmed Jemai | Université Grenoble Alpes (original) (raw)
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Papers by Ahmed Jemai
MATEC Web of Conferences, 2016
The use of active-fiber composites (AFC) instead of traditional ceramic piezoelectric materials i... more The use of active-fiber composites (AFC) instead of traditional ceramic piezoelectric materials is motivated by flexibility and relatively high actuation capacity. Nevertheless, their energy harvesting capabilities remain low. As a first step toward the enhancement of AFC's performances, a mathematical model that accurately simulates the dynamic behavior of the AFC is proposed. In fact, most of the modeling approaches found in the literature for AFC are based on finite element methods. In this work, we use homogenization techniques to mathematically describe piezoelectric properties taking into consideration the composite structure of the AFC. We model the interdigitated electrodes as a series of capacitances and current sources linked in parallel; then we integrate these properties into the structural model of the AFC. The proposed model is incorporated into a vibration based energy harvesting system consisting of a cantilever beam on top of which an AFC patch is attached. Finally, analytical solutions of the dynamic behavior and the harvested voltage are proposed and validated with finite element simulations.
Conference Presentations by Ahmed Jemai
The use of multi-layer cantilever beam represents a potential method to increase the performance ... more The use of multi-layer cantilever beam represents a potential method to increase the performance of the structure. Generally, researchers have concentrated their efforts to study a multilayer actuators, which show a large developed displacement for the same applied voltage compared to a single-layer actuator. Nevertheless, the multi-layer energy harvester is not very investigated. In fact, most of modeling found in the literature for multi-layer harvester is based on finite element methods and experimentation. In this paper, we propose an analytical model for multi-layer energy harvester with parallel and series connection cases. In fact, we develop a reduced-order model of the harvester, which we use in turn to obtain closed-form expressions for the tip displacement and the power output generated by the structure, which are validated with finite element simulations using ANSYS. MEDYNA 2013 23-25 Apr 2013, Marrakech (Morocco)
The use of Active Fiber Composite (AFC) instead of traditional ceramic piezoelectric materials is... more The use of Active Fiber Composite (AFC) instead of traditional ceramic piezoelectric materials is characterized by high flexibility and large displacements. However, energyharvesting capabilities of AFC are relatively low. To remedy this drawback, it is necessary to optimize its geometry in order to increase the produced electrical power. An analytically model of the system including the structural, the piezoelectric as well as electromechanical coupling of AFC piezocomposite, is proposed. The model takes into account the interdigitated electrode (IDE) disposition. Large deflection of the flexible beam is taking into account using a nonlinear von-Karman strain. The piezoelectric beam is composed of bi-layered cantilever beam in which a substrate layer is partially covered by an AFC piezocomposite patch. The model provides an improved approach to design and analyze the electrical performance of the considered energy harvester. It takes into account the quadratic distribution voltage between two constitutive IDE. The extended Hamilton principle and the Gauss law are used to derive a reduced-order model of the active fiber composite energy harvester using a Galerkin procedure. The limit-cycle solutions are calculated using a Finite-Difference Method (FDM). The obtained frequency-response curves of the harvested electrical voltage measured across the external resistor R representing the external load are validated using Finite Element Analysis developed using ANSYS with a homogenized piezoelectric composite.
The use of Active fibers Composites (AFC) instead of classical ceramic piezoelectric materials is... more The use of Active fibers Composites (AFC) instead of classical ceramic piezoelectric materials is motivated by their light weight, flexibility and high actuation capacity. Nevertheless, their detection and energy harvesting capacities stays weak. As a first step toward the enhancement of the AFC performances, a mathematical modeling that accurately simulates the dynamic behavior of the AFC is proposed. In fact, most of the modeling found in the literature for AFC is based on empiric and finite element methods. We use homogenization techniques to correctly model the composite structure of the AFC regarding its piezoelectric and electrostatic properties. Then we integrate these properties into the structural model of the AFC. The proposed model in incorporated into a vibration based energy harvesting system consisting on a cantilever beam on top of which an AFC patch is attached. Analytical solutions of the dynamic behavior and the harvested electrical power of the system are finally proposed.
The use of multi-layer piezoelectric active structure represents an important potential technique... more The use of multi-layer piezoelectric active structure represents an important potential technique to increase electrical and/or mechanical performances for energy harvesters and/or actuators applications. Many research studies have investigated the modeling and design of multi-layer actuators, however, only few of them treated the case of energy harvesters. In this paper, we propose an analytical model of a multi-layer energy harvester for parallel and series connection cases. In addition, a quadratic electric voltage across the layer thickness is assumed in order to take into account the non-uniform distribution of the transversal electric field between two consecutive electrodes. We obtain closed-form solutions for the tip displacement and the electrical power output generated by the energy harvester. These solutions are used to conduct a parametric study of the system's dynamic behaviors. As a result, we propose a set of design parameters that improves the generated electrical power of the multi-layer energy harvester. The effects of the type of connection, the number of layer, the thickness ratio, the load resistance and the type of substrate's material on the electrical capabilities are investigated. The developed analytical results are validated by Finite Element simulations using ANSYS.
The optimization of the interdigitated electrode (IDE) design for piezoelectric composite energy ... more The optimization of the interdigitated electrode (IDE) design for piezoelectric composite energy harvester is performed using Finite Element (FE) analysis. The effect of the IDE geometry on the generating electrical power is modeled. Parametric analysis is performed to optimize electrical power produced by energy harvesters using different cross-section of electrode. Numerical simulations show that the novel electrode designs can significantly ameliorate the electrical performances by selecting the appropriate geometrical parameters. In addition, the modeling results show that the electrical field concentrations, in case of newly electrode edge, can be highly decreased. Therefore, the risk of premature failure, due to the breakdown voltage, may be expected to decrease. The results developed here are used to gain an insight into the influence of the novel IDE designs on the electrical capabilities.
Nous proposons l'optimisation de la forme des électrodes interdigitées des Composites à Fibres Ac... more Nous proposons l'optimisation de la forme des électrodes interdigitées des Composites à Fibres Actives (AFC). L'effet de la disposition particulière des électrodes sur la déformation développée dans la couche en Epitaxial-PZT a été modélisé en utilisant la Méthode des Eléments Finis. Les résultats numériques développés ici sont utilisés pour confronter l'influence de la géométrie des électrodes (largeur, l'épaisseur et l'espacement des électrodes) pour différentes formes géométriques des électrodes (plates, triangulaires et circulaires). Pour une même tension appliquée aux bornes des électrodes, 60% et 70% d'augmentation de déformation maximale sont obtenues pour des formes triangulaires et circulaires par rapport aux électrodes classiques.
Teaching Documents by Ahmed Jemai
Book Reviews by Ahmed Jemai
En témoignage de ma gratitude pour l'amour et le soutien de mon père ALI et de ma chère mère NEJI... more En témoignage de ma gratitude pour l'amour et le soutien de mon père ALI et de ma chère mère NEJIBA, je leurs dédis ce travail. Je dédis aussi ce travail à toute ma famille ainsi que mes frères MOHAMMED et HATEM. Mes profonds remerciements à tous mes amis pour leurs sympathies et leurs encouragements, ce travail leurs est aussi dédié. À tous ceux qui ont contribué pour la réussite de ce travail, d'une manière ou d'une autre, je leurs le dédis aussi.
MATEC Web of Conferences, 2016
The use of active-fiber composites (AFC) instead of traditional ceramic piezoelectric materials i... more The use of active-fiber composites (AFC) instead of traditional ceramic piezoelectric materials is motivated by flexibility and relatively high actuation capacity. Nevertheless, their energy harvesting capabilities remain low. As a first step toward the enhancement of AFC's performances, a mathematical model that accurately simulates the dynamic behavior of the AFC is proposed. In fact, most of the modeling approaches found in the literature for AFC are based on finite element methods. In this work, we use homogenization techniques to mathematically describe piezoelectric properties taking into consideration the composite structure of the AFC. We model the interdigitated electrodes as a series of capacitances and current sources linked in parallel; then we integrate these properties into the structural model of the AFC. The proposed model is incorporated into a vibration based energy harvesting system consisting of a cantilever beam on top of which an AFC patch is attached. Finally, analytical solutions of the dynamic behavior and the harvested voltage are proposed and validated with finite element simulations.
The use of multi-layer cantilever beam represents a potential method to increase the performance ... more The use of multi-layer cantilever beam represents a potential method to increase the performance of the structure. Generally, researchers have concentrated their efforts to study a multilayer actuators, which show a large developed displacement for the same applied voltage compared to a single-layer actuator. Nevertheless, the multi-layer energy harvester is not very investigated. In fact, most of modeling found in the literature for multi-layer harvester is based on finite element methods and experimentation. In this paper, we propose an analytical model for multi-layer energy harvester with parallel and series connection cases. In fact, we develop a reduced-order model of the harvester, which we use in turn to obtain closed-form expressions for the tip displacement and the power output generated by the structure, which are validated with finite element simulations using ANSYS. MEDYNA 2013 23-25 Apr 2013, Marrakech (Morocco)
The use of Active Fiber Composite (AFC) instead of traditional ceramic piezoelectric materials is... more The use of Active Fiber Composite (AFC) instead of traditional ceramic piezoelectric materials is characterized by high flexibility and large displacements. However, energyharvesting capabilities of AFC are relatively low. To remedy this drawback, it is necessary to optimize its geometry in order to increase the produced electrical power. An analytically model of the system including the structural, the piezoelectric as well as electromechanical coupling of AFC piezocomposite, is proposed. The model takes into account the interdigitated electrode (IDE) disposition. Large deflection of the flexible beam is taking into account using a nonlinear von-Karman strain. The piezoelectric beam is composed of bi-layered cantilever beam in which a substrate layer is partially covered by an AFC piezocomposite patch. The model provides an improved approach to design and analyze the electrical performance of the considered energy harvester. It takes into account the quadratic distribution voltage between two constitutive IDE. The extended Hamilton principle and the Gauss law are used to derive a reduced-order model of the active fiber composite energy harvester using a Galerkin procedure. The limit-cycle solutions are calculated using a Finite-Difference Method (FDM). The obtained frequency-response curves of the harvested electrical voltage measured across the external resistor R representing the external load are validated using Finite Element Analysis developed using ANSYS with a homogenized piezoelectric composite.
The use of Active fibers Composites (AFC) instead of classical ceramic piezoelectric materials is... more The use of Active fibers Composites (AFC) instead of classical ceramic piezoelectric materials is motivated by their light weight, flexibility and high actuation capacity. Nevertheless, their detection and energy harvesting capacities stays weak. As a first step toward the enhancement of the AFC performances, a mathematical modeling that accurately simulates the dynamic behavior of the AFC is proposed. In fact, most of the modeling found in the literature for AFC is based on empiric and finite element methods. We use homogenization techniques to correctly model the composite structure of the AFC regarding its piezoelectric and electrostatic properties. Then we integrate these properties into the structural model of the AFC. The proposed model in incorporated into a vibration based energy harvesting system consisting on a cantilever beam on top of which an AFC patch is attached. Analytical solutions of the dynamic behavior and the harvested electrical power of the system are finally proposed.
The use of multi-layer piezoelectric active structure represents an important potential technique... more The use of multi-layer piezoelectric active structure represents an important potential technique to increase electrical and/or mechanical performances for energy harvesters and/or actuators applications. Many research studies have investigated the modeling and design of multi-layer actuators, however, only few of them treated the case of energy harvesters. In this paper, we propose an analytical model of a multi-layer energy harvester for parallel and series connection cases. In addition, a quadratic electric voltage across the layer thickness is assumed in order to take into account the non-uniform distribution of the transversal electric field between two consecutive electrodes. We obtain closed-form solutions for the tip displacement and the electrical power output generated by the energy harvester. These solutions are used to conduct a parametric study of the system's dynamic behaviors. As a result, we propose a set of design parameters that improves the generated electrical power of the multi-layer energy harvester. The effects of the type of connection, the number of layer, the thickness ratio, the load resistance and the type of substrate's material on the electrical capabilities are investigated. The developed analytical results are validated by Finite Element simulations using ANSYS.
The optimization of the interdigitated electrode (IDE) design for piezoelectric composite energy ... more The optimization of the interdigitated electrode (IDE) design for piezoelectric composite energy harvester is performed using Finite Element (FE) analysis. The effect of the IDE geometry on the generating electrical power is modeled. Parametric analysis is performed to optimize electrical power produced by energy harvesters using different cross-section of electrode. Numerical simulations show that the novel electrode designs can significantly ameliorate the electrical performances by selecting the appropriate geometrical parameters. In addition, the modeling results show that the electrical field concentrations, in case of newly electrode edge, can be highly decreased. Therefore, the risk of premature failure, due to the breakdown voltage, may be expected to decrease. The results developed here are used to gain an insight into the influence of the novel IDE designs on the electrical capabilities.
Nous proposons l'optimisation de la forme des électrodes interdigitées des Composites à Fibres Ac... more Nous proposons l'optimisation de la forme des électrodes interdigitées des Composites à Fibres Actives (AFC). L'effet de la disposition particulière des électrodes sur la déformation développée dans la couche en Epitaxial-PZT a été modélisé en utilisant la Méthode des Eléments Finis. Les résultats numériques développés ici sont utilisés pour confronter l'influence de la géométrie des électrodes (largeur, l'épaisseur et l'espacement des électrodes) pour différentes formes géométriques des électrodes (plates, triangulaires et circulaires). Pour une même tension appliquée aux bornes des électrodes, 60% et 70% d'augmentation de déformation maximale sont obtenues pour des formes triangulaires et circulaires par rapport aux électrodes classiques.
En témoignage de ma gratitude pour l'amour et le soutien de mon père ALI et de ma chère mère NEJI... more En témoignage de ma gratitude pour l'amour et le soutien de mon père ALI et de ma chère mère NEJIBA, je leurs dédis ce travail. Je dédis aussi ce travail à toute ma famille ainsi que mes frères MOHAMMED et HATEM. Mes profonds remerciements à tous mes amis pour leurs sympathies et leurs encouragements, ce travail leurs est aussi dédié. À tous ceux qui ont contribué pour la réussite de ce travail, d'une manière ou d'une autre, je leurs le dédis aussi.