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Papers by Mohamed DJEMANA

Research paper thumbnail of Detection of unbalance and looseness faults in a ventilation turbine using vibration signature analysis

IOP conference series, Jun 1, 2022

Research paper thumbnail of Numerical Simulation of Electromechanical Impedance Based Crack Detection of Heated Metallic Structures

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences

Among the many health monitoring techniques for structures, one relatively new technique is based... more Among the many health monitoring techniques for structures, one relatively new technique is based on electromechanical impedance (EMI) measurements. The goal of this investigation was to see if the EMI approach could be used to assess the health of metallic structures. In order to achieve this objective, the feasibility of numerical simulation of piezoelectric transducer – structure interaction in the field of the EMI technique to perform structural health monitoring using commercial finite element (FE) software, ANSYS was investigated. The numerical simulations were carried out to find the effect of different types of damage such as crack and to investigate the effect of temperature on the crack detection. When compared to experimental impedance responses found in the literature, where EMI is used to monitor different undamaged and damaged structures made of steel and aluminium, the developed FE models successfully obtained similar results with good agreement. This research reveale...

Research paper thumbnail of Temperature influence on electromechanical impedance method used for damage detection in metallic structure

Research paper thumbnail of Using Electromechanical Impedance and Extreme Learning Machine to Detect and Locate Damage in Structures

Journal of Nondestructive Evaluation, 2017

The main objective in structural health monitoring is to keep track of the changes in the dynamic... more The main objective in structural health monitoring is to keep track of the changes in the dynamic characteristics of the structural system in order both to detect and locate the damage, and to make a decision automatically whether the damage is in dangerous level for the structure or not. In particular, electromechanical impedance (EMI) techniques give simple and low cost solutions for detecting damage in different structures. When it is question of damage

Research paper thumbnail of Impedance Based Detection of Delamination in Composite Structures

IOP Conference Series: Materials Science and Engineering, 2017

Nowadays commercial and military aircrafts are increasingly using composite materials to take adv... more Nowadays commercial and military aircrafts are increasingly using composite materials to take advantage of their excellent specific strength and stiffness properties but impacts on composites due to bird-strike, hail-storm cause barely visible impact damage (BVID) that underscores the need for robust structural health monitoring methods. Hence, damage identification in composite materials is a widely researched area that has to deal with problems coming from the anisotropic nature of composites and the fact that much of the damage occurs beneath the top surface of the laminate. This paper focuses on understanding self-sensing piezoelectric wafer active sensors (PWAS) to conduct electromechanical impedance (EMI) in glass fibre reinforced polymer composite to perform structural health monitoring. With the aid of a 3D ANSYS finite element model, an analysis of different techniques for the detection of position and size of a delamination in a composite structure using piezoelectric patches had been performed. The real part of the impedance is used because it is known to be more reactive to damage or changes in the structure’s integrity and less sensitive to ambient temperature changes compared to the imaginary part. Comparison with experimental results is presented to validate the FE results. The experimental setup utilizes as its main apparatus an impedance analyser HP4194 that reads the in-situ EMI of PWAS bonded to the monitored composite structure. A good match between experimental and numerical results has been observed for low and high frequencies. The analysis in this paper provides necessary basis for delamination detection in composite structures using EMI technique.

Research paper thumbnail of Modelling and Simulation of Impedance-Based Damage Monitoring of Structures

International Journal of Simulation Modelling, 2016

Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current ... more Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current engineering structures. With the help of piezoelectric sensors, the EMI technique is used for monitoring the health of such structures. Generally, potential damage to the host structure is detected by examining the EMI signature and identifying changes in that unique signature. Since this technique has the potential to offer greater safety and reliability while lowering maintenance costs, it is becoming increasingly popular. This paper investigates the use of finite element method (FEM) to simulate the electro-mechanical impedance technique. A numerical analysis of simple models, such as free piezoelectric patches of various shapes and thicknesses is used to comprehend the fundamentals of this technique. Then, studies on different parts of the structure are conducted to find the effect on the output of system when both damage and loading co-exist, and investigate the effect of temperature for structural health monitoring based on EMI. The simulation results are then compared to experimental data and a very good agreement is observed.

Research paper thumbnail of Damage Detection in Structures Using Electromechanical Impedance and Finite Element Analysis

Applied Mechanics and Materials, 2015

Impedance-based structural health monitoring (SHM) techniques have been developed as a promising ... more Impedance-based structural health monitoring (SHM) techniques have been developed as a promising tool for real-time structural damage assessment, and are considered as a new non-destructive evaluation method. It is gaining popularity due to its potential of reducing maintenance costs while increasing safety and reliability. This article present the results of Finite Element analysis performed for aluminum beam with bonded piezoelectric transducer (PZT). Modeled structure was excited to vibrate at high frequency range and electromechanical impedance (EMI) plots were obtained from the harmonic analysis. Notches were introduced in the beam and the damage metrics were used to asses qualitative changes in structural properties of the system. Furthermore, a parametric study of the effects of different variables was carried out. The numerical results show a good agreement was observed.

Research paper thumbnail of Improving Electromechanical Impedance Damage Detection Under Varying Temperature

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2022

The field of structural health monitoring has seen a fundamental shift in recent years, as resear... more The field of structural health monitoring has seen a fundamental shift in recent years, as researchers strive to replace conventional non-destructive evaluation techniques with smart material-based techniques. Perhaps the most promising of smart material techniques for developing structural health monitoring (SHM) systems is electromechanical impedance (EMI) which can be used for real-time structural damage assessment. In EMI, mechanical resonances of structure can be seen in electrical characteristics of piezoelectric transducers due to electromechanical coupling of transducer with the structure. Existence of damage will cause a structural stiffness change and therefore the resonant characteristics of the structure will be altered. This article presents an experimental and numerical study to investigate the effects of notch damage with temperature on the electrical impedance of the piezoelectric sensor used in the EMI technique. The practical implementation of the compact EMI metho...

Research paper thumbnail of MODELLING AND SIMULATION OF IMPEDANCE-BASED DAMAGE MONITORING OF STRUCTURES

Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current ... more Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current engineering structures. With the help of piezoelectric sensors, the EMI technique is used for monitoring the health of such structures. Generally, potential damage to the host structure is detected by examining the EMI signature and identifying changes in that unique signature. Since this technique has the potential to offer greater safety and reliability while lowering maintenance costs, it is becoming increasingly popular. This paper investigates the use of finite element method (FEM) to simulate the electro-mechanical impedance technique. A numerical analysis of simple models, such as free piezoelectric patches of various shapes and thicknesses is used to comprehend the fundamentals of this technique. Then, studies on different parts of the structure are conducted to find the effect on the output of system when both damage and loading co-exist, and investigate the effect of temperature for structural health monitoring based on EMI. The simulation results are then compared to experimental data and a very good agreement is observed.

Research paper thumbnail of Damage Detection in Structures using Electromechanical Impedance and Finite Element Analysis

Impedance-based structural health monitoring (SHM) techniques have been developed as a promising ... more Impedance-based structural health monitoring (SHM) techniques have been developed as
a promising tool for real-time structural damage assessment, and are considered as a new nondestructive evaluation method. It is gaining popularity due to its potential of reducing maintenance
costs while increasing safety and reliability. This article present the results of Finite Element
analysis performed for aluminum beam with bonded piezoelectric transducer (PZT). Modeled
structure was excited to vibrate at high frequency range and electromechanical impedance (EMI)
plots were obtained from the harmonic analysis. Notches were introduced in the beam and the
damage metrics were used to asses qualitative changes in structural properties of the system.
Furthermore, a parametric study of the effects of different variables was carried out. The numerical
results show a good agreement was observed.

Research paper thumbnail of Electromechanical Impedance Modeling for Adhesively Bonded Piezo-transducers

The electromechanical impedance (EMI) technique for structural health monitoring (SHM) and nondes... more The electromechanical impedance (EMI) technique for structural health monitoring (SHM) and nondestructive evaluation (NDE) employs piezoelectric-ceramic (PZT) patches, which are surface bonded to the monitored structures using adhesives. The adhesive forms a finitely thick, permanent interfacial layer between the host structure and the patch. Hence, the force transmission between the structure and the patch occurs through the bond layer, via shear mechanism, invariably causing shear lag. However, the impedance models developed so far ignore the associated shear lag and idealize the force transfer to occur at the ends of the patch. This paper analyses the mechanism of force transfer through the bond layer and presents a step-by-step derivation to integrate the shear lag effect into impedance formulations, both one-dimensional and two-dimensional. Further, using the integrated model, the influence of various parameters (associated with the bond layer) on the electromechanical admittance response is studied by means of a parametric study. It is found that the bond layer can significantly modify the measured electromechanical admittance if not carefully controlled during the installation of the PZT patch.

Research paper thumbnail of Detection of unbalance and looseness faults in a ventilation turbine using vibration signature analysis

IOP conference series, Jun 1, 2022

Research paper thumbnail of Numerical Simulation of Electromechanical Impedance Based Crack Detection of Heated Metallic Structures

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences

Among the many health monitoring techniques for structures, one relatively new technique is based... more Among the many health monitoring techniques for structures, one relatively new technique is based on electromechanical impedance (EMI) measurements. The goal of this investigation was to see if the EMI approach could be used to assess the health of metallic structures. In order to achieve this objective, the feasibility of numerical simulation of piezoelectric transducer – structure interaction in the field of the EMI technique to perform structural health monitoring using commercial finite element (FE) software, ANSYS was investigated. The numerical simulations were carried out to find the effect of different types of damage such as crack and to investigate the effect of temperature on the crack detection. When compared to experimental impedance responses found in the literature, where EMI is used to monitor different undamaged and damaged structures made of steel and aluminium, the developed FE models successfully obtained similar results with good agreement. This research reveale...

Research paper thumbnail of Temperature influence on electromechanical impedance method used for damage detection in metallic structure

Research paper thumbnail of Using Electromechanical Impedance and Extreme Learning Machine to Detect and Locate Damage in Structures

Journal of Nondestructive Evaluation, 2017

The main objective in structural health monitoring is to keep track of the changes in the dynamic... more The main objective in structural health monitoring is to keep track of the changes in the dynamic characteristics of the structural system in order both to detect and locate the damage, and to make a decision automatically whether the damage is in dangerous level for the structure or not. In particular, electromechanical impedance (EMI) techniques give simple and low cost solutions for detecting damage in different structures. When it is question of damage

Research paper thumbnail of Impedance Based Detection of Delamination in Composite Structures

IOP Conference Series: Materials Science and Engineering, 2017

Nowadays commercial and military aircrafts are increasingly using composite materials to take adv... more Nowadays commercial and military aircrafts are increasingly using composite materials to take advantage of their excellent specific strength and stiffness properties but impacts on composites due to bird-strike, hail-storm cause barely visible impact damage (BVID) that underscores the need for robust structural health monitoring methods. Hence, damage identification in composite materials is a widely researched area that has to deal with problems coming from the anisotropic nature of composites and the fact that much of the damage occurs beneath the top surface of the laminate. This paper focuses on understanding self-sensing piezoelectric wafer active sensors (PWAS) to conduct electromechanical impedance (EMI) in glass fibre reinforced polymer composite to perform structural health monitoring. With the aid of a 3D ANSYS finite element model, an analysis of different techniques for the detection of position and size of a delamination in a composite structure using piezoelectric patches had been performed. The real part of the impedance is used because it is known to be more reactive to damage or changes in the structure’s integrity and less sensitive to ambient temperature changes compared to the imaginary part. Comparison with experimental results is presented to validate the FE results. The experimental setup utilizes as its main apparatus an impedance analyser HP4194 that reads the in-situ EMI of PWAS bonded to the monitored composite structure. A good match between experimental and numerical results has been observed for low and high frequencies. The analysis in this paper provides necessary basis for delamination detection in composite structures using EMI technique.

Research paper thumbnail of Modelling and Simulation of Impedance-Based Damage Monitoring of Structures

International Journal of Simulation Modelling, 2016

Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current ... more Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current engineering structures. With the help of piezoelectric sensors, the EMI technique is used for monitoring the health of such structures. Generally, potential damage to the host structure is detected by examining the EMI signature and identifying changes in that unique signature. Since this technique has the potential to offer greater safety and reliability while lowering maintenance costs, it is becoming increasingly popular. This paper investigates the use of finite element method (FEM) to simulate the electro-mechanical impedance technique. A numerical analysis of simple models, such as free piezoelectric patches of various shapes and thicknesses is used to comprehend the fundamentals of this technique. Then, studies on different parts of the structure are conducted to find the effect on the output of system when both damage and loading co-exist, and investigate the effect of temperature for structural health monitoring based on EMI. The simulation results are then compared to experimental data and a very good agreement is observed.

Research paper thumbnail of Damage Detection in Structures Using Electromechanical Impedance and Finite Element Analysis

Applied Mechanics and Materials, 2015

Impedance-based structural health monitoring (SHM) techniques have been developed as a promising ... more Impedance-based structural health monitoring (SHM) techniques have been developed as a promising tool for real-time structural damage assessment, and are considered as a new non-destructive evaluation method. It is gaining popularity due to its potential of reducing maintenance costs while increasing safety and reliability. This article present the results of Finite Element analysis performed for aluminum beam with bonded piezoelectric transducer (PZT). Modeled structure was excited to vibrate at high frequency range and electromechanical impedance (EMI) plots were obtained from the harmonic analysis. Notches were introduced in the beam and the damage metrics were used to asses qualitative changes in structural properties of the system. Furthermore, a parametric study of the effects of different variables was carried out. The numerical results show a good agreement was observed.

Research paper thumbnail of Improving Electromechanical Impedance Damage Detection Under Varying Temperature

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2022

The field of structural health monitoring has seen a fundamental shift in recent years, as resear... more The field of structural health monitoring has seen a fundamental shift in recent years, as researchers strive to replace conventional non-destructive evaluation techniques with smart material-based techniques. Perhaps the most promising of smart material techniques for developing structural health monitoring (SHM) systems is electromechanical impedance (EMI) which can be used for real-time structural damage assessment. In EMI, mechanical resonances of structure can be seen in electrical characteristics of piezoelectric transducers due to electromechanical coupling of transducer with the structure. Existence of damage will cause a structural stiffness change and therefore the resonant characteristics of the structure will be altered. This article presents an experimental and numerical study to investigate the effects of notch damage with temperature on the electrical impedance of the piezoelectric sensor used in the EMI technique. The practical implementation of the compact EMI metho...

Research paper thumbnail of MODELLING AND SIMULATION OF IMPEDANCE-BASED DAMAGE MONITORING OF STRUCTURES

Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current ... more Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current engineering structures. With the help of piezoelectric sensors, the EMI technique is used for monitoring the health of such structures. Generally, potential damage to the host structure is detected by examining the EMI signature and identifying changes in that unique signature. Since this technique has the potential to offer greater safety and reliability while lowering maintenance costs, it is becoming increasingly popular. This paper investigates the use of finite element method (FEM) to simulate the electro-mechanical impedance technique. A numerical analysis of simple models, such as free piezoelectric patches of various shapes and thicknesses is used to comprehend the fundamentals of this technique. Then, studies on different parts of the structure are conducted to find the effect on the output of system when both damage and loading co-exist, and investigate the effect of temperature for structural health monitoring based on EMI. The simulation results are then compared to experimental data and a very good agreement is observed.

Research paper thumbnail of Damage Detection in Structures using Electromechanical Impedance and Finite Element Analysis

Impedance-based structural health monitoring (SHM) techniques have been developed as a promising ... more Impedance-based structural health monitoring (SHM) techniques have been developed as
a promising tool for real-time structural damage assessment, and are considered as a new nondestructive evaluation method. It is gaining popularity due to its potential of reducing maintenance
costs while increasing safety and reliability. This article present the results of Finite Element
analysis performed for aluminum beam with bonded piezoelectric transducer (PZT). Modeled
structure was excited to vibrate at high frequency range and electromechanical impedance (EMI)
plots were obtained from the harmonic analysis. Notches were introduced in the beam and the
damage metrics were used to asses qualitative changes in structural properties of the system.
Furthermore, a parametric study of the effects of different variables was carried out. The numerical
results show a good agreement was observed.

Research paper thumbnail of Electromechanical Impedance Modeling for Adhesively Bonded Piezo-transducers

The electromechanical impedance (EMI) technique for structural health monitoring (SHM) and nondes... more The electromechanical impedance (EMI) technique for structural health monitoring (SHM) and nondestructive evaluation (NDE) employs piezoelectric-ceramic (PZT) patches, which are surface bonded to the monitored structures using adhesives. The adhesive forms a finitely thick, permanent interfacial layer between the host structure and the patch. Hence, the force transmission between the structure and the patch occurs through the bond layer, via shear mechanism, invariably causing shear lag. However, the impedance models developed so far ignore the associated shear lag and idealize the force transfer to occur at the ends of the patch. This paper analyses the mechanism of force transfer through the bond layer and presents a step-by-step derivation to integrate the shear lag effect into impedance formulations, both one-dimensional and two-dimensional. Further, using the integrated model, the influence of various parameters (associated with the bond layer) on the electromechanical admittance response is studied by means of a parametric study. It is found that the bond layer can significantly modify the measured electromechanical admittance if not carefully controlled during the installation of the PZT patch.