Slim Bouaziz

• University of Sfax

Unstable spindle rotation can result in vibrations, chatter, and increase in surface roughness, leading to productivity reduction and energy consumption rise. The combined effects of nonlinearity owing to different bearing types and spindle materials significantly impact the stability of the machine tool spindle system, which needs to be considered...

The present study aims at analyzing the free vibration behavior of hybrid fiber-reinforced laminated composites is a complex phenomenon that is influenced by a number of factors, including the type of fibers used, the volume fraction of the fibers, the stacking sequence of the plies, and the boundary conditions of the structure. This study investig...

Modern life is marked with the extensive use of machine tools. The latter stand for high consumers of electrical energy which increase carbon emissions. For this reason, various solutions aiming to reduce energy consumption in industrial sector are elaborated. One solution lies in the use of economical materials for the spindle rotation system supp...

This work focuses on Wire Arc Additive Manufacturing (WAAM) technology using the Tungsten Inert Gas (TIG) welding method with aluminum 5083 as the substrate and aluminum 5356 as the filler material. This method uses a layer-by-layer approach to build the part. A design of experiment (DOE) was carried out with three independent variables, namely (i)...

Abstract Interest in rotary systems whose performance and efficiency are influenced by their weight as well as guidance type has continued to grow over the last decades. Actually, the dynamic analysis of composite shafts supported by active magnetic bearings (AMBs) seems to be neglected by researchers despite its effect on rotating system efficienc...

The detection and location of pipeline leakage can be deduced from the time arrival leak signals measured by acoustic sensors placed at the pipe. Ongoing research in this field is primarily focused on refining techniques for accurately estimating the time delays. This enhancement predominantly revolves around the application of advanced signal proc...

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...

The vibration behavior of wind turbine blades (WTB) must be thoroughly investigated to avert undesirable dynamical phenomena under working conditions. This paper sets out an experimental frequency analysis of a rotating, scaled-down, segmented WTB. The purpose of the present work is twofold: (1) to devise a suitable experiment for the modal identif...

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...

Segmented wind turbine blade (SWTB) development remains a major challenge for constructors so as to reduce blade transport and manufacturing costs. The blade structural properties must be examined in the design stage to enhance their mechanical behavior and fatigue life. This paper presents a numerical investigation of a SWTB prototype. Teeth inser...

The mixing step of fluids at micro-scale is one of the most important operations in the development of micro-fluid systems in chemical reactors for applications in chemical and biochemical engineering, biomedical systems. The apparition of the cavitation phenomenon, in chemical precipitation reactors with rapid micromixing, can significantly affect...

This paper concerns the dynamic analysis of rotating composite shafts and focuses on the formulation of the shear-normal coupling effect using Equivalent Single Layer Theory (ESLT) and Layerwise Shaft Theory (LST). On the one hand, ESLT consists in considering the laminated shaft made of several orthotropic layers as an equivalent single layer havi...

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...

During the development of the wind turbine system, blades are considered as the most critical components. The blades’ dynamic characteristics must be investigated during the design process to improve their mechanical performance. This work presents an experimental updating of a segmented wind turbine blade numerical model. For this purpose, the bla...

The excitation due to the inevitable mass unbalance is the main reason of rotor vibrations. Therefore, this paper studies the rotating shaft dynamic behaviour and the mass unbalance theoretical formulation. Equivalent Single Layer Theory available in the literature is used to model the rotating composite shaft and the rotating hybrid shaft. This fi...

Wind turbine blades structures must be well balanced during the manufacturing and mounting processes in order to avoid the imbalance of the system and the undesirable dynamic effects during the rotor motion. This work presents a numerical frequencies analysis of a segmented wind turbine blade assembled with a steel spar in order to study the effect...

This paper presents a dynamic study of the rotating composite shaft vibratory behavior and the effects of different mechanical coupling. In fact, Modified ESLT is generalized from ESLT to consider not only the effects of fiber orientation, stacking sequences and shear-normal coupling but also the influences of different mechanical coupling on rotat...

Damage characterization tests are applied on bar specimens until total rupture. In order to describe the stress state, two measures are frequently utilized: triaxiality and Lode parameter. We are interesting by analysis numerically the ductile failure of the Al 7075-T6 alloy. Al 7075 has an excellent wear resistance. It is in need of further enhanc...

In this paper, numerical and experimental modal analysis of a segmented wind turbine blade assembled with a steel threaded shaft and a nut are presented. The blade segments are built by a 3D printer using ABS material. The experimental modal parameters identification has been achieved using the Eigen system Realization Algorithm (ERA) method for di...

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 Second International Conference on Acoustics and Vibration (ICAV2018), which was...

Free vibration of sandwich nanobeam based on the nonlocal elasticity theory and both Euler Bernoulli and Timoshenko beams theories are presented in this paper. The differential quadrature method (DQM) is proposed for solving differential equations. The effect of the nonlocal parameter on the first three natural frequencies of Simply Supported - Sim...

This paper deals with the stability analysis of internally damped rotating composite shafts. An Euler-Bernoulli shaft finite element formulation based on Equivalent Single Layer Theory (ESLT), including the hysteretic internal damping of composite material and transverse shear effects, is introduced and then used to evaluate the influence of variou...

The wind turbine blade segmentation development remains a tough challenge for constructors to reduce the blade manufacturing and transport cost. In this paper, numerical analysis is developed in order to study the dynamic characteristics of a segmented wind turbine blade assembled with a spar. The spar and the blade segments are assimilated to a sh...

This paper reports an investigation on thermo-electro-mechanical vibration of graphene/piezoelectric graphene/piezoelectric/graphene sandwich nanobeams. Based on the nonlocal elasticity theory, Timoshenko beam theory and Hamilton's principles, the governing equations are developed and solved using generalized differential quadrature (GDQ) method. T...

This paper deals with the dynamic analysis of rotating laminated shafts. A new multi-layer finite element for rotating laminated shaft based on layerwise and shaft theories is formulated and implemented to dispose of a more realistic description of the displacement field through the laminated shaft thickness. This formulation is developed to take i...

This paper deals with the study of the vibratory behaviour of rotating composite shafts and the effects of stacking sequences and shear-normal coupling on natural frequencies and critical speeds. Equivalent Single Layer Theory (ESLT) including shear deformation, rotary inertia and gyroscopic effects is introduced for the dynamic analysis. A finite...

In this paper, the first investigation on free vibration analysis of three-layered nanobeams with the shear effect incorporated in the mid-layer based on the nonlocal theory and both Euler Bernoulli and Timoshenko beams theories is presented. Hamilton's formulation is applied to derive governing equations and edge conditions. In order to solve diff...

This paper focus on vibration analysis of Graphene/Piezoelectric GPG sandwich nanobeam under electrical loading based on nonlocal elasticity theory. Using the Generalized Differential Quadrature (GDQ) method, the natural frequencies of the studied structure are obtained for several small scale effect and the corresponding mode shapes for different...

The objective of this work is to show the influence of dynamic characteristics of Active Magnetic Bearings (AMBs) on the stability and dynamic response of an asymmetric and unbalanced rotor. Indeed, AMBs have been successfully applied in several industrial machinery facilities. Their main advantages are the contactless working principle, frictionle...

Free vibration of sandwich nanobeam based on the nonlocal beam model is presented in this paper. The governing equations are obtained on the basis of energy approach using Hamilton’s principle. For different edge conditions, these equations are solved numerically at the vibration frequencies of nanobeams. The generalized differential quadrature (GD...

Modal analysis is developed in this paper in order to study the dynamic characteristics of rotating segmented blades assembled with spar. Accordingly, a three dimensional finite element model was built using the three node triangular shell element DKT18, which has six degrees of freedom, to model the blade and the spar structures. This study covers...

In modern production, milling is considered the widespread cutting process in the formatting field. It remains important to study this manufacturing process as it can be subject to some parasitic phenomena that can degrade surface roughness of the machined part, increase tool wear and reduce spindle life span. In fact, the best quality work piece i...

In High-Speed Milling Process (HSM) the machining precision is directly affected by spindle bearing system which has a crucial role and it impacts directly the dynamic performance of the machining system. This study is about an accurate simulation of such system response. In fact, the Timoshenko beam theory with different circular sections is used...

Free vibration of Euler and Timoshenko nanobeams based on the Eringen’s nonlocal elasticity theory is presented in this paper. The governing equations are obtained on the basis of energy approach using Hamilton’s principle. For different edge conditions, these equations are solved numerically at the vibration frequencies of nanobeams. The generaliz...

The high speed milling represents the most important process to produce parts in different fields such as aeronautics, automotive and mould. It allows obtaining parts with complex form and with the best surface quality. So, it remains essential to understand the impact of both the cutting force model and its parameters on the tool tip response. Con...

The use of Active Magnetic Bearings (AMBs) in the High Speed Machining (HSM) field is increasing. In fact, they have important advantages such us: high speed which can reach 150000 rpm, high stiffness and absence of lubrication. Indeed, these bearings operate through magnetic interaction generated between the stator and the rotor. The spindle, prin...

Bearing and gear are one of the most important mechanical sources for vibration and noise generation in machine tool spindles. In this paper, we study the non-linear dynamic behavior of a machine tool spindle system in transient regime. Driving and driver rotors are, respectively, powered by a motor torque and loaded by the cutting force. They are...

This paper reports on the geometrical optimization of T-mixer with exocentric input of two reacting fluids for preparation of homogeneous monodisperses nanoparticles. The inputs are inclined to each other in the plane with the main output tube. The mixing of two streams of different viscosities is modeled using computational fluid dynamics and Ansy...

In this paper, the effect of angular misalignment on the transient dynamics of a rotor-Active Magnetic Bearings (AMBs) system was examined with numerical analysis. A spatial model of a misaligned rotor mounted in two identical AMBs is setup to account angular misalignment with a flexible coupling having torsional and lateral flexibility. The drivin...

We describe a geometrical optimization for a micromixer that generates vortical flow in a cylindrical microchannel with non co-axial inputs. The inputs are inclined to each other in the plane with the main output tube. The mixing of two streams of different viscosities is modeled using computational fluid dynamics and Ansys Fluent software. The flu...

High speed machining (HSM) is a new technology used to product parts in different sectors. This technology permits time and processing cost reduction. One of the principal components of the HSM is the spindle. It is generally supported by active magnetic bearings (AMBs), in order to guarantee the greatest speed without affecting the dynamic charact...

Active magnetic bearings (AMBs) is a device using controlled electromagnetic forces to support a shaft without mechanical contact. One of the primary techniques of condition monitoring of rotors is that of vibration control. Rotating machinery is facing some problems caused by shaft misalignment. This defect leads to a premature failure of the shaf...

The purpose of the present paper is to investigate the effect of elastic deformation of bearing liner on the acoustic behavior of oil lubricated journal bearings. Analysis is performed for hydrodynamic(HD) and elasto-hydrodynamic (EHD) lubrications. Dynamic behavior and acoustical properties are investigated through an analysis of pressure fluctuat...

The dynamic response of a misaligned rotor, mounted in two identical active magnetic bearings (AMBs) was numerically investigated in this work. Three simplified models of current biased radial active magnetic bearings were presented, where four, six and eight electromagnets were powered by the bias current i0 and respective control current. The mag...

In this article, the effect of the bearing elastic deformation on the performance characteristics of a cylindrical journal bearing is analyzed. The variety of simulation models covers hydrodynamic (HD) and elastohydrodynamic (EHD) lubrication theories. The Reynolds equations governing the flow in the clearance space of the journal bearing are obtai...

In this work, the dynamic behaviour of misaligned rotor is presented. The rotor is mounted in two hydrodynamic journal bearings and has two degrees of freedom. Reynolds’ equation is obtained by considering the effect of mass transfer across the fluid film. This is discretized by means of the finite difference method and solved numerically. By integ...

Gearbox power transmissions are widely used in the automotive industry. They have a complex vibro-acoustic behaviour that is influenced by the various acoustic–structural interaction mechanisms. This paper concentrates on modelling these systems using a three-dimensional finite-element (FE) approach for the structure combined with a Rayleigh integr...

The use of hydrodynamic journal bearings supporting geared rotor in a power transmission system requires a consideration of the effect of external loads applied to the journal. In this paper, the effect of unbalance and gear mesh forces on the dynamic behaviour of a hydrodynamic journal bearings-rotor is investigated. The rotor is driven by a motor...