Nabih Feki

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Verified

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• Associate Professor
• Professor at University of Sousse

This study introduces the first comparative analysis of multiple machine learning models for predicting CBGA solder joint lifespan under thermal cycling, a key factor in electronic reliability. Expanding the dataset from 45 to 295 reveals that data augmentation significantly improves prediction accuracy. Basically, DS2 is well validated as it incor...

Machine learning enhances machine diagnostics through advanced data analysis, pattern recognition, and fault prediction. This study investigates the application of machine learning algorithms for bearing fault detection. The objective is to develop intelligent methodologies for the predictive diagnosis of bearing faults in rotating machinery, empha...

To ensure durable performance and optimal function of electronic components, it is crucial to guarantee their reliability, robustness and goodness of fit. The solder joints used in the BGA (Ball Grid Array) component play an intrinsic role in the reliability of the system. The vibration present in BGA triggers fatigue in solder joints, which raises...

This paper presents a comprehensive study on the application of Artificial Intelligence (AI) methods, specifically machine learning and deep learning, for the diagnosis of bearing faults. The study explores both data preprocessing-dependent methods (Support Vector Machine, Nearest Neighbor, and Decision Tree) and a preprocessing-independent method...

Loosening of an assembly is a critical phenomenon, it can cause damage in the aeronautical field which uses a huge number of bolted joints. It should be studied correctly to avoid catastrophic phenomena. Most of studies focused on the loosening phenomenon resulting from transversal load or axial load. This paper is dedicated to the study of the inf...

The friction occurring between the teeth of gears is a significant contributor to energy loss in gear drives. Factors like the load, speed, and coefficient of friction (µ) play a crucial role in determining the extent of frictional losses in gears. The coefficient of friction (µ) is a complex function influenced by various tribological parameters,...

The dynamic behavior of an active magnetic bearing (AMB) mounted rotor was investigated through an analytical study conducted as part of this research work. A biased AMB model was developed, in which six electromagnets were supplied with a bias current I0, and their respective control currents. The magnetic load was obtained through a differentiate...

This article is dedicated to the development of a passive damping system for the reduction of vibrations of the Nacelle/Rotor of offshore wind turbines in the case of aerodynamic and hydrodynamic charges. The presence of vibration causes deflection at the top of the wind turbine structure, degradation of the blades and reduction of producing energy...

Currently, nanostructures such as nanobeams, nanomembranes and nanoplates have been a hot area of research triggering. The contribution of this research article deals with both the effect of the free and dynamic vibration of a nanobeam as well as the use of the FGM material by integrating the piezoelectric effect. In fact, incorporating the initial...

Blades in wind turbine present a vital role. They are airfoil shaped blades. they harness wind energy and drive the rotor of a wind turbine. Composite materials are the mostly used for the fabrication of blades. They exhibit many high mechanical properties such as high tensile and bending stiffness and weight. These properties give the blades struc...

A 12 degrees of freedom gear model was developed in previous work considering a time-dependent mesh stiffness, damping and mainly a particular parameter for quantifying local coefficient of friction. The local friction coefficient which depends on the following key parameters like axle gear oil kinematic and dynamic viscosity, contact conditions be...

Active Magnetic Bearings (AMBs) have a powerful characteristic which, if they are correctly controlled allow a frictionless relative motion between the rotor and the stator, and grant a high-speed rotational motion without contact. However, because of the active control feature which is an energy-consuming strategy, we introduced different control...

Background Active magnetic bearings (AMBs) are electromechanical actuators commonly used in many industrial applications as alternatives to conventional bearings. They are generally used to ensure rotor levitation in different operating conditions and have several advantages due to its contactless and its active control properties.PurposeThe predic...

In this paper, we tackle the static response of power-law functionally graded piezoelectric materials (FGPM) subjected to electro-mechanical stimulation. Effects of material composition, nonlocal parameter, slenderness ratio and electrical voltage on different characteristics of FGPM nanobeams are addressed. This study corroborates that the power e...

This paper deals with the design of an active fault-tolerant control based on observers for a twin wind turbine, consisting of two wind turbines mounted on the same tower. We consider an asymmetric conditions case, when only one turbine is affected by an inter-turn short circuit fault of a permanent magnet synchronous machine. A diagnosis design is...

In this study, a frictional dynamic gear model is propounded for a lubricated FZG C40 spur gear pairs. The proposed nonlinear dynamic model accounts the actual time variable gear mesh stiffness with considering the frictional effects of meshing gear teeth. This developed model aims to predict with high accuracy the gear power losses and to highligh...

Many manufacturing applications involve high temperatures and high strain rate deformations. Experimental tests are very expensive to study those problems. For that, it is very important to use numerical analysis. The main goal of those studies is to determine the stress state in manufacturing processes, to elaborate characterization tests and to c...

This paper addresses the problem of control of a twin wind turbine which is subject to an electrical fault affecting only one stator phase of one turbine. An active fault tolerant control is proposed. The performance and robustness of the proposed control, comparing to a passive fault tolerant one developed in the literature, are shown through nume...

A 12 degree-of-freedom dynamic model for FZG-A10 spur gears considering the actual time-varying gear mesh stiffness and the frictional effects between meshing gear teeth is investigated. The energetic Lagrange formulation was used to recover the equations of motion of the generalized translational torsional coupled dynamic system. Its dynamic respo...

Free vibration of sandwich nanobeam is presented in this chapter. The upper and lower sheets are modeled considering Euler-Bernoulli beam formulation and for the core the Timoshenko beam formulation is used taking into account the shear effect. The Non-dimensional procedure is used in order to simplify the analysis of governing equations. The sandw...

Magnetic bearings’ modelling is performed using different methodologies. Generally, the linear modelling of these actuators, which is required for the use of linear controllers, gives an approximation of the nonlinear relation between the bearing load and the control current. However, this approach may have some disadvantages because the model is l...

Many manufacturing applications involve high temperatures and high strain rate deformations. Experimental tests are very expensive to study those problems. For that, it is very important to use numerical analysis. The main goal of those studies is to determine the stress state in manufacturing processes, to elaborate characterization tests and to c...

The book provides readers with a snapshot of recent research and industrial trends in field of industrial acoustics and vibration. Each chapter, accepted after a rigorous peer-review process, reports on a selected, original piece of work presented and discussed at the Third International Conference on Acoustics and Vibration (ICAV2021), which was o...

In this work, a nonlinear dynamic model of an FZG-A10 spur gear was investigated by taking into account for the actual time-varying gear mesh stiffness and the frictional effects between meshing gear teeth to evaluate the influence of the dynamic effects on frictional gear power loss predictions. The equations of motion of the generalized translati...

With the ever-increasing complexity and importance of industrial systems, diagnosis techniques allowing to detect, locate, and identify any abnormalities in the system as early as possible have attracted a lot of attention over the past years. In this article, we present a diagnosis method for nonlinear dynamical systems, called sparse recovery dia...

Mechatronic systems are widely used in many industrial applications for their capacity to improve the production performances. However, due to the complexity of these systems, several defects may occur and disrupt the operating of the system. Among these faults, two types can be distinguished: operating faults (e.g., electrical, mechanical, thermal...

The dynamic model of 12-degrees-of-freedom for spur gears pair accounting for nonlinear time-varying stiffness, damping, and coefficient of friction along the path of contact obtained from experimental tests is investigated. The Newmark's integration method is used to solve the equations and obtain the dynamic responses. Elementary mass, stiffness,...

Monitoring of mechatronic systems is one of the essential issues in the industries. In this context, we firstly deal with the modeling of an electro-mechanical system obtained by assembling a mechanical model, which is a single stage of a gear element and an electrical model that is an asynchronous motor. Secondly, we use homogeneous sliding mode o...

The prediction of the gear behavior is becoming major concerns in many industries. For this reason, in this article, an electro-mechanical modeling is developed in order to simulate a gear element driven by an asynchronous motor. The electrical part, which is the induction motor, is simulated by using the Kron’s model while the mechanical part, whi...

The prediction of the gear behavior is becoming major concerns in many industries. For this reason, in this article, an electro-mechanical modeling is developed in order to simulate a gear element driven by an asynchronous motor. The electrical part, which is the induction motor, is simulated by using the Kron’s model while the mechanical part, whi...

With the ultimate goal of rotating machinery diagnosis using Motor Current Signal Analysis (MCSA), this paper provides a coupled electro-magnetic-mechanical model of a rotating shaft supported by rolling bearings and driven by a three-phase squirreled cage motor. The modeling is based on the hypothesis that a bearing defect causes torque and then I...

This paper considers the reliability analysis of mechanical system, especially wind turbine system. Optimization of horizontal axis wind turbine performance is confronted by the aerodynamic complexities such as the instability of the energy source, randomness of loads. The objective of this work is to study the system reliability taking into accoun...

This paper is focused on the characterization of the frequency content of vibration signals issued from a two-stage planetary gearbox. To achieve this goal, two different methodologies are adopted: the lumped-parameter modeling approach and the phenomenological modeling approach. The two methodologies aim to describe the complex vibrations generate...

Understanding the occurrence of bearing defects in electrical current signals using Motor Current Signal Analysis (MCSA) requires the implementation of numerical models. In this paper, an electro-magnetic-mechanical model is proposed to describe the dynamic behavior of a squirrel cage induction motor coupled to a rotating shaft supported by elastic...

Planetary gears are widely used in modern machines as ones of the most effective forms of power transmission. In this paper, a special configuration of a gearbox composed of one stage spiral bevel gear and a two stage helical planetary gear used in a bucket wheel excavator gearbox is presented to investigate its modal properties. A lumped-parameter...

Recently, Motor Current Signal Analysis (MCSA) appears as an effective tool for fault diagnosis in rotating machinery and proved to be sufficient for detecting localized mechanical faults in electromechanical systems operating in stationary conditions. In the case of non-stationary conditions, speed variations must be distinguished from angular vel...

In this paper, the nonlinear dynamic response in a wind turbine system is considered and the quantification of uncertainty effects on the variability of this nonlinear response is investigated. Under dynamic conditions, a lumped model with 12 degrees of freedom is proposed taking into account the uncertainty associated to the power coefficient of t...

In this paper, a new methodology for taking into account uncertainties in a gearbox transmission system of a horizontal-axis wind turbine is proposed. Gearbox transmission is the major part of the wind turbine's drive train. For a more reasonable evaluation of its dynamic behaviour, the influence of the uncertain parameters should be taken into con...

Planetary gears operate frequently in non stationary conditions. In this paper, a variable input speed excites a back to back planetary gearbox. In order to understand its dynamic behaviour, a torsional model is developed. A suitable change in the mesh stiffness functions is operated in the model. Using the Short Time Fourier Transform, an amplitud...

This paper investigates of the dynamic behavior of a two stages gearbox composed of a spiral bevel gear and helical planetary gear mounted in a Bucket Wheel Excavator. A lumped parameters model of this coupled system is developed. All elements are considered as rigid bodies supported by flexible bearings. The different mesh stiffness functions in b...

The purpose of this work is to determine the critical frequencies of planetary gear train connected to bevel gear. A three dimensional model of helical planetary gear is proposed where 6 degrees of freedom per component are considered while 4 degrees of freedom (3 translations and 1 rotation) per component of bevel gear is adopted. Connection betwe...

In this study, an experimental validation of a 3D gear dynamic model in the presence of localised faults such as pitting on tooth flanks is proposed. The corresponding numerical model accounts for spur and helical gear systems including gear errors and deviations along with the supporting shafts and bearings. Simulation results are compared with th...

This paper deals with the simulation of the dynamic behavior of induction motor/gear systems. The corresponding model combines: (i) a permeance network aimed at representing squirrel-cage induction motors and (ii) a 3D dynamic model of spur and helical gears including the shafts and bearings. Some classic motor defects (rotor eccentricity) and gear...

The fault diagnosis in geared transmissions has been traditionally based on vibration monitoring but the implementation of sensors can be expensive and, in some applications, present technical difficulties. In this thesis, an original way of detecting faulty gears driven by electrical motors is proposed based on the monitoring of the motor currents...

Fault diagnosis in geared transmissions is traditionally based on vibration monitoring but, in a number of cases, sensor implementation and signal transfer from rotary to stationary parts can cause problems. This paper presents an original integrated electro-mechanical model aimed at testing the possibility and the interest of tooth fault detection...