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About this book

This book reports on cutting-edge research in the broad fields of mechanical engineering and mechanics. It describes innovative applications and research findings in applied and fluid mechanics, design and manufacturing, thermal science and materials. A number of industrially relevant recent advances are also highlighted. All papers were carefully selected from contributions presented at the International Conference on Advances in Mechanical Engineering and Mechanics, ICAMEM2019, held on December 16–18, 2019, in Hammamet, Tunisia, and organized by the Laboratory of Electromechanical Systems (LASEM) at the National School of Engineers of Sfax (ENIS) and the Tunisian Scientific Society (TSS), in collaboration with a number of higher education and research institutions in and outside Tunisia.

Table of Contents


Applied Mechanics


Dynamic and Post-buckling Analysis of Structures Like-Shell Using a Quadrilateral Shell Element with In-plane Drilling Rotational Degree of Freedom and a Conservative Implicit Time Integration Scheme

In this work, post-buckling problems of structures like shell are investigated using an implicit conservative time integration dynamic scheme. We have proposed the use of a four nodded quadrilateral flat shell element, with the drilling rotation degree of freedom (D. Boutagouga., A new enhanced assumed strain quadrilateral membrane element with drilling degree of freedom and modified shape functions, Int. J. Numer. Meth. Eng. 2017; 110:573–600) and based upon the updated Lagrangian formulation. An implicit conservative scheme (K.J, Bathe., G, Noh., Insight into an implicit time integration scheme for structural dynamics. Comput. Struct. 2012; 98–99: 1–6) is chosen to obtain the solution to the nonlinear dynamic behaviour and geometric nonlinear post-buckling response.Several numerical simulations are considered in the aim to investigate the ability of the considered time integration scheme to deal with unstable branches after the limit point in non-linear post-buckling response of shell structures with no prerequisite structural damping, though it is required when using conventional time integration schemes. The obtained results illustrate a very satisfying performance of the implicit conservative-dissipative direct time integration scheme combined with the quadrilateral shell element with drilling rotation.

Djamel Boutagouga, Said Mamouri

Influence of Material Gradient Index on Stress Distribution of Functionally Graded Dental Implants

Dental implant have important role in restoration of damaged or lost teeth, but some problem is found in their utilization. In fact, the chewing forces are applied directly in the bone system, which necessitates studying the relationship between the stress distributions and the characteristics of dental implant near bone system interface and dental implant. Recently functionally graded materials FGM play an important role on dental clinical implant application thanks to their abilities and advantages of their mechanical properties. The objective of this study is to focus on mechanical properties of FGM denal implant in order to investigate the effect of the material gradient index on the stress distribution around dental prosthesis. The FGM properties change gradually from titanium (Ti) to hydroxyapatite (HAP). The implant body is subjected to an axial load to simulate masticatory forces. The effect of FGM properties on reduction of stress distributions in the implant-prosthesis components are highlighted.

Sameh Elleuch, Hanen Jrad, Mondher Wali, Fakhreddine Dammak

Parameter Identification of a Viscohyperelastic Constitutive Model for Fiber Reinforced Thermoplastic Composites

Short glass fiber reinforced thermoplastic materials exhibit visco-hyperelastic behavior which can be analyzed using different techniques such as instrumented indentation and dynamic mechanical analysis. In the present study, the mechanical response of polyamide (PA) as matrix reinforced by different ratio of glass fiber is studied experimentally and numerically. Force-displacement curves of composite materials are obtained through uniaxial tensile test. Moreover, as viscoelastic behavior takes place due to deviation from static deformation, stress relaxation test is investigated to give a good deal of information about the time dependence of the material’s behavior. Then, a visco-hyperelastic constitutive model is proposed for the behavior of these orthotropic incompressible fiber-reinforced polymer composites. The experimental data are fit in order to obtain the unknown adjustable parameters in constitutive equations using available model in commercial FEM soft-ware, such as ABAQUS. A good agreement is shown between the experimental and numerical results for all compositions. Therefore, it can be noted that the adapted model can accurately predict the nonlinear behavior of molded composites.

M. Allouch, M. Kamoun, J. Mars, M. Wali, F. Dammak

Industrial Applications and Technology Transfer


The Importance of Ergonomic Risk and the Methods to Follow for a Problem of Assembly Line Balancing

In this paper, we consider the problem of the assembly line balancing, which allows us to find the assignment of each task that respects fixed constraints while optimizing the repair of working time. However, some other factors can affect productivity and workers, such as repetitive work, handling heavy loads. In this last case, workers in the assembly are subject to ergonomic risks. Besides, it is very important to reduce these risks which is the aim of this research where we attempt to show the importance of ergonomic of an assembly line and to prove the influence of its risks on an assembly line balancing problem. In fact, poor division of labor between stations can lead to unnecessary idle time and unnecessary additional costs for each part produced. In addition, the ergonomic risks can be included in inactivity and this underlines the importance of reducing this risk and its effect on the line. Thus, we expose in this paper a mathematical model to perform the assembly line balancing problem with ergonomic risks which are to reduce.

Jihene Sdiri, Khaoula El Bedoui, Kamel Mehdi

Modeling of the Cutting Effort

Cutting is a process for obtaining parts that are widely used in the press tool industry. The calculation of cutting force is generally done by the simplified formula which only describes the shear force of the sheet (Fc = P.e.Rc). In this formula, we only see the perimeter of the part, the thickness and shear strength of the sheet.In practice, other factors can influence this effort, such as, the clearance between the punch and the die, the speed of the cutting operation, the thickness of the sheet, the friction between the cut pieces and the die, etc. This work consists in making an experimental study, according to a complete experimental plan, to study the effect of some parameters, such as, the play between the punch and the matrix, the speed of cutting and the thickness of the sheet, on the cutting effort. This study is completed by a statistical analysis of the results and a modeling of the Fc effort according to the parameters studied.

Taoufik Kamoun, Kamel Guemri

Improving Performance of Production Lines: Integration of Maintenance and Quality Policies: A Literature Review

Production scheduling, quality management and maintenance planning are the main functions of operational management in industrial plants. Although in reality they are interdependent, in practice these three fields are treated separately. This has generated as a fact independent models for each function that might yield suboptimal solutions. Hence, an appropriate understanding of the dependency between the mentioned parameters may improve the production systems efficiency and result in significant savings in costs. The objective of this study was to review the literature on models which deal with different integration issues in the production scheduling, quality management and maintenance planning, to point gaps which exist in current works to be able to deal with, in order to solve a simulation-based industrial system representing this integration.

Z. Boumallessa, H. Chouikhi, M. Elleuch, H. Bentaher

Design and Manufacturing


The Impact of Abrasive Water Jet Cutting on Tensile Behavior of Woven Fabric CFRP

In the present work, the quasi-static tensile tests of woven carbon/epoxy (CFRP) laminates used for aeronautic structures were carried out using a tensile testing machine with a high performance. These tests were performed according to different specimen standards ASTM D5766 and ASTM D3039. This study aims to focus on the effect of the cutting process through the abrasive water jet (AWJ) on the tensile strength of carbon CFRP composite material. The laminate was tested with different orientation angles of plies that vary from 0 to 90° giving different composite stacking configurations. On another hand, the effect of stress concentration was verified with testing the specimens through open hole tensile (OHT). Test results show that the tensile behavior represents high strength and stiffness for different stacking configurations. This evaluation confirmed the quasi-isotropic behavior of stacking sequence configurations. However, the composite strength is affected significantly by stress concentration generated on the hole surface.

Adel Abidi, Sahbi Ben Salem, Abderrezak Bezazi, Haithem Boumediri

Modeling of Heat Transfer and Transport Phenomena During Laser Welding Of Aluminum/Magnesium Alloys

The weld geometry is an important factor which determines the quality of the weld. This work proposes a transitional and three-dimensional numerical model performed by the hydrodynamic software Ansys-Fluent. We are interested in the heterogeneous assembly of Al alloy and Mg alloy by laser beam welding. Aluminum and Magnesium plates are joined in butt configuration. The objective of this work is to simulate the temperature field, velocity field, fluid flow during the interaction between the laser beam and the material and to predict the dimensional characteristics of the laser welded joint. This makes it possible to better understand different physical phenomena (e.g. heat transfer, mass transport) generated in the molten pool. The results show that the simulated weld bead profile is in good agreement with those obtained by experiment.

S. Ben Halim, S. Bannour, K. Abderrazek, W. Kriaa, M. Autric

Optimal Planning of Multi-pass Turning Operations

This study presents a decision-making methodology for multi-pass turning operations that integrates tool life and cutting conditions optimization. In this approach, the initial machining plan considers all possible roughing passes and a finishing pass. At the end of the computation process, the existence of a roughing pass in the final program of the operation is evaluated using a combinatorial variable associated to this pass. On the other hand, the tool replacement is considered in the optimal selection of the cutting conditions so that this tool can achieve an exact number of operations. However, the developed optimization model which minimizes production cost is able to predict the number of required passes, the optimal cutting conditions for each pass, and the number of parts per tool. Finally, an example is presented to discuss the influence of the integration of combinatorial variables on the planning of operations. For several different total depths of cut, the obtained results show the capacity to produce a complete machining program in which even the tool replacement moment is clearly determined.

Toufik Ameur

Ductile Damage Prediction of DD13 Sheet Material in Single Point Incremental Forming Process

The purpose of this study is devoted to an “advanced” coupled ductile damage model that describes the elastoplastic behavior of DD13 (Hot rolled steel) sheet material deformed using for the first time a single point incremental forming (SPIF) process. This numerical approach is carried out using a non-associated plasticity model coupled with continuum ductile damage. The constitutive elastoplastic equations and the calculation algorithms are implemented on Abaqus/Explicit via the user interface (VUMAT) subroutine. The numerical simulation is scrutinized two phenomena in this study: the damage behavior and the springback of DD13 sheet material when a conical shape is manufactured using the SPIF process to assess where the damage can accumulate. The simulation results included the damage area of the DD13 sheets, the Hill’48 stress distribution as long as a quadratic function of Hill’48 is used in this formulation, and a comparative figure to explain the final shape of the manufactured part after springback.

A. Bouhamed, L. Ben Said, H. Jrad, M. Wali, F. Dammak

Effect of Shot Peening Parameters on Parabolic Leaf Spring’s Residual Stress

Shot peening applied on parabolic leaf spring is a mechanical surface treatment intended to improve the fatigue strength by generating residual compressive stress. However, a systematic investigation of the effect of shot peening parameters on residual stresses is still required.The aim of the present work is to improve the knowledge of the role of shot peening in manufacturing leaf springs vehicles, through analyzing effects of different shots peening parameters by X-ray diffraction analysis. Among this investigation the parameters of the shot penning machine; turbine speed, amperage presented by the Almen intensity and the deflection of spring has been varied to optimal performance regarding residual stress. X-ray diffraction analysis shows that; on the one hand; the increase of shots speed and subsequently the Almen Intensity improves the residual stress at depth but the surface stress decreases. On the other hand, spring deflection improves the residual stress profile.

Sari Guimaji, Akram Khalifa, Raouf Fathallah

Influence of Sliding Speed and Normal Loads on the Wear Resistance of Hardox 500 Steel Ground Surfaces

This work focuses on the characterization of the tribological behavior of Hardox 500 steel in the ground state with different types of lubrication (dry and soluble oil), by using the technique of single cycle scratch testing. A CSM scratch testing machine equipped with a 50 µm radius Rockwell indenter was used for the experiments. The scratch length was set to 5 mm and different scratching loads (5 N, 10 N and 15 N) and speeds (10 mm/min, 50 mm/min and 100 mm/min) were considered. Results show that the friction coefficient and worn volume increase with the increase of the scratching load and speed and that samples ground using soluble oil have a martensitic microstructure characterized by very fine martensite laths that offers better wear resistance than sample ground under dry conditions. Thus, it could be conducted that the wear resistance of the Hardox 500 ground surfaces depends not only on the sliding speed and scratching normal load, but on the material microstructure also.

Kamel Bensaid, Nabil Ben Fredj

Development of STEP-NC Compliant Manufacturing for Machining Strategies of Aeronautical Components

Aeronautics is certainly one of the most demanding industries of the world on a technical level. With materials that are increasingly difficult to machine, drastic specifications and ever tighter deadlines, the manufacture of aeronautical parts must exceed many limits while the production rate is constantly increasing. This paper aims to provide complete solutions for the machining of typical parts. Indeed, the evolution of CNC technology, combined with advances in computer systems, provided the basis for re-evaluating the way computer-assisted systems, can be used to enable universal manufacturing. The G code no longer meets the current expectations of programming more and more sophisticated machines. In reality, the STEP-NC standard (STEP-Numerical Control) provides new solutions and integration of manufacturing within the complete digital chain. This paper proposes a new numerical channel CAD/CAM based on a STEP-NC conceptual high-level standard for the machining of aeronautical parts, which aims to develop intelligent and powerful tools for data sharing and integration in the numerical chain of CAD-CAD/CAM systems.

Romdhane Ben Khalifa, Noureddine Ben Yahia

Numerical Study for the Cutting of Unidirectional CFRP

Carbon Fiber Reinforced Polymer (CFRP) composites are heavily used for advanced structural applications owing to their special mechanical properties like high strength, corrosion resistance and slight weight, etc. The intrinsic characteristics of these materials generate several defects during machining such as fiber pull-out, matrix crack and burr. The understanding of the machining operation of these materials are essential to eliminate the workpiece damage and to achieve a good surface quality. In this work, the effect of the fiber orientation angle and the cutting speed on the chip formation mechanisms has been analyzed. For this reason, a finite element model with equivalent homogeneous material (EHM) was developed using Abaqus/Explicit code. A hashin criterion was adopted to predict the damage of CFRP. The results revealed that the numerical and experimental findings are in good agreement. The fiber orientation angle and the cutting speed have a notable effect on the chip formation mechanisms.

A. Hassouna, S. Mzali, F. Zemzemi, S. Mezlini

2-Axis Tool Strategy Applied on NC Lathe Machine to Manufacture Revolved Parts by Means of SPIF Process

ISF process is a promising flexible process that attracts several researches during the last decade. Applied on a CNC machine thin sheet are shaped through incremental plastic deformation trigged by a tool path programmed with a G-Code. This paper presents an experimental investigation on Single Point Incremental Forming applied on NC turning machine to manufacture revolved parts made of AA1050-H14 material. The idea is to use a 2-axis tool path strategy through the program of a paraxial roughing cycle used in machining to bore cylindrical parts. In fact, using this program, sheet metal can be shaped by incremental plastic deformation to the desired part. The effect of penetration increment, the shape of the final part on formability, appearance of cracks and the part finishing quality is analyzed. Results carried out show the efficiency of this tool strategy to manufacture parts usually manufactured through a 3-axis milling strategy in SPIF process. Certainly, SPIF applied in NC lathe gain the advantage of a rapid procedure and a low cost.

L. Ben Said, A. Bouhamed, M. Wali, F. Dammak

Evaluating Assembly Sequences with the Assembly Tools Operation Space Criteria

The generation of assembly sequences (AS) is a topical subject aimed to help designers for the determination and the simulation of the different stages of a mechanical product assembly. So, it is considered as an important step in the process of designing a new mechanical product. In addition, it allows minimizing the design cost and reducing the time of maintenance. For that, researches are developed several methods to optimize the determination of assembly sequences.In this paper, an approach based on the evaluation of AS, generated by our old work, is proposed. The generated AS are feasible and respect the stability between components during the assembly operation. The criterion of the Assembly Tools Operation Space (ATOS) is used to deduce assembly sequences with high quality. Also, those assembly sequences will be more conformed to industrial practices. For that reason, the algorithm will detect fastener, calculate the movement length (ML), of the last one, to be demounted and select the appropriate tool (AT) to make the necessary tests.An illustrative example is adopted to highlight the importance of this proposed approach.

Akram Bedeoui, Riadh Benhadj, Moez Trigui, Nizar Aifaoui

Evaluating the Capability Index of a Process Integrating Sampling Plan and the Measurement System Number of Distinct Categories NDC

To assess the capability of a process, the collected data are influenced by the errors of the used measurement system. This study aims to integrate these errors in determining the acceptance threshold value of the capability index $$ C_{p} $$ C p that is referred as in this work. An expression of that depends on the Number of Distinct Categories (NDC), type I and type II errors, the index of the capability process corresponding to both rejectable and acceptable quality levels (CpRQL) and (CpAQL), respectively, was developed. These parameters effects and their existing interactions on the variability in the defective parts per million ppm (Δppm) were examined using a response surface experimental design with a total of 81 runs. Analysis of the results of this experimental design showed that it is possible to propose a technique for overcoming the inaccuracy of the used measurement system by targeting higher CpAQL values as the same value of can be obtained by several combinations of CpAQL and NDC.

Adel Brik, Mohamed Goddi, Nabil Ben Fredj

Simulation of Low Velocity Impact of Epoxy-Flax Fibers Composite Using Solid Shell Finite Element

The objective of the present paper is to predict numerically the effect of low velocity impact on the composite epoxy reinforced with quasi-unidirectional flax fabrics. The composite circular plate is meshed with a solid shell finite element (SS). Only one element in the thickness direction is adopted. This SS element is implemented into the user element (UEL) interface of ABAQUS in order to overcome numerical locking problems that may occurred when using the ABAQUS solid and shell elements. The epoxy/flax composite is characterized by a elasto-visco-plastic behavior. The Hill’s anisotropic criterion of plasticity with isotropic hardening and the Johnson-Cook viscoplastic model are applied. The simulations are accomplished via ABAQUS/Standard. The obtained results present the efficiency of the developed model using one solid shell element in the thickness direction from a computational point of view.

A. Chaker, S. Koubaa, J. Mars, F. Gehring, F. Dammak, A. Vivet

Finite Element Residual Stress Computation for Combined Grinding/Burnishing Applied to 100Cr6 Steel

Combining grinding with ball burnishing: “REGAL” is a newly developed technique consisting in grinding and burnishing performing simultaneously by placing the burnishing tool on the grinding machine. This combined manufacturing process ensures obtaining a better surface quality by taking advantage of the workpiece being thermally affected by the grinding process, reducing surface damages obtained after grinding like tensile residual stress results and enhancing roughness results by the burnishing process. REGAL ensures also reducing manufacturing energy and time by combining grinding and burnishing acting simultaneously instead of each one acting separately. Further, the surface integrity would be enhanced by REGAL process in terms of hardness, surface roughness, and compressive residual stress obtained at a more important depth compared to burnishing process, which extends workpiece lifetime, decreases fatigue and improves wear resistance. In this paper, the residual stress results are studied thanks to 3D finite element simulations of the grinding, ball burnishing and combined grinding/ball-burnishing processes. The finite element method helps to compare the residual stress results obtained after combining two different processes one thermomechanical (grinding) and the other purely mechanical (burnishing) both with different manufacturing parameters to regular grinding and burnishing process.

Yasmine Charfeddine, Sawsen Youssef, Salem Sghaier, Hédi Hamdi

Inspection on a Three-Dimensional Measuring Machine for a Virtual Model for Additive Manufacturing

Today, and to quickly meet the high demands of variability, supply chain efficiency and energy optimization, business markets are looking for modern manufacturing technologies and as a solution, industry 4.0 is using the benefits of integrating modern manufacturing technologies and information systems to promote production capabilities. In this context, intelligent industry represents a new generation of automatic production systems based on the concepts of intelligent industry, intelligent manufacturing, control and intelligent inspection, such as inspection on coordinate measuring machines (CMMs). This technology allows many machines to be integrated into a plant and controlled online using the MBD (Model Based Design) quality system. The problem of conformity of parts with complex geometry is becoming more and more important. The objective of this work is to present a 3D inspection technique on a virtual model (MBD: Model Based Design), using a coordinate measuring machine equipped with a “POWER INSPECT” measurement and inspection software. The interest of this technique is to show the impact of the dimensional inspection and geometric tolerance process of the CAD model for the CAI (Computer aided Inspection) approach on the fidelity of the finished product for additive manufacturing (AM) including intelligent industry.

Hacene Ameddah, Rabia Selloum, Mourad Brioua

Simulation of the Local Heating Effect on Incremental Sheet Forming Process

Incremental sheet forming is a process which is primarily used for prototyping, small series production and unique parts. The combination of this technology with a heating system can improve the formability of existing alloys known by poor room-temperature formability. In order to further study the performance of the numerical tools, the present work deals with finite element modeling of heat-assisted incremental sheet forming process using ABAQUS/EXPLICIT software. Thus, the numerical simulation for this thermomechanical problem was developed to state and clarify the temperature distribution during sheet metal forming and its major influence on the enhancement of process formability and the avoidance of the part failure. In this case, the heat loss due to radiation and natural convection boundary conditions were neglected. This FE model is utilized to control the damage parameter evolution at different temperature values. Also, the two process technologies (incremental sheet forming combined with global/local heating) have been evaluated. Consequently, the results showed that the Ti6Al4V titanium alloy exhibits good hot incremental forming ability.

M. Sbayti, R. Bahloul, H. Belhadjsalah

A CAD Model for the Tolerancing of Non-rigid Parts Assemblies

The study of the mechanical assembly behavior during the design stage requires the modeling of components with manufacturing defects. However, the integration of tolerances in the CAD model, only with geometrical and dimensional errors without taking into account several factors such as the deformations of parts during the assembly task, generates an important difference between the digital and the real models. Thus, a new model for the tolerancing of assemblies in CAD is developed considering the deformations of parts under loads. The realistic assembly configurations are obtained basing on the parts with defects. The dimensional and geometrical defects of parts are represented in the CAD modeler basing on the worst-case tolerancing approach and the Small Displacement Torsor (SDT) parameters. The Finite Elements (FE) computation is executed with realistic part models. Sub-algorithms are developed to update the mechanical joints between couples of Non-Rigid/Non-Rigid (NR/NR) components. The tolerance analysis is performed basing on the obtained realistic assembly. A case study is used to show the highlights of the proposed method.

Anis Korbi, Mehdi Tlija, Borhen Louhichi, Abdelmajid Benamara

A Developed Static Model for Tool Deflection in Ball-End Milling

Accuracy of the workpiece geometry is negatively affected by several sources of errors during milling operation, the most important one is tool deflection which will result in the deviation of the tool path and cutting force is the most significant factor responsible for this error.A static model of tool deflection in ball-end milling is proposed to predict the unwanted displacements along X, Y and Z, results are then considered in the compensation strategy by tool path modification in order to avoid failure of the tool.The tool and the tool holder are modeled as a multi-section cantilever beam with a concentrated cutting force load and the cross-section method is used to faithfully determine the deflection, the analytical model shows a good agreement with the finite element method (FEM) which is the proposed method employed to estimate the deflection of the tool in the three directions.Predicted displacements of the tool are also compared against experimental measurements and a good correlation is found between measured and predicted deflection leading to the validation of the static model proposed for ball-end milling.

Rami Mallek, Moez Smaoui, Maher Baili, Gilles Dessein, Zoubeir Bouaziz

Thermal Sciences and Renewable Energy


Effect of Steam Explosion and Torrefaction Treatments of Wood Chips on the Heating Value of Pellets

The surplus of wood chips from sawmills is increasing due to the reduction in the demand for newsprint paper. Thus, this study aims to promote the use of wood chips for bioenergy by producing high-quality pellets. More specifically, this project aimed to evaluate the impact of various heat treatment approaches on the heating value of wood pellets made from black spruce (BS), jack pine (JP) and balsam fir (BF). The studied heat treatments were steam explosion and torrefaction. The resulting energy pellets were characterized in terms of density, high heat value (HHV) and durability. The heat treatment improved pellet HHV. Regardless of the type of wood, the HHV of torrefied pellets is significantly higher (27.6–31.1 MJ/kg) compared to steam exploded pellets (21.9–22.7 MJ/kg) and untreated pellets (18–19 MJ/kg). However, as a result of the deterioration of the hydroxyl groups due to torrefaction, the durability of the torrefied pellets is low compared to that of the steam-exploded pellets. Irrespective of the treatment used, JP pellets, with a maximum of 98.9%, had the best durability.

Safa Arous, Mariem Mharssi, Hassine Bouafif, Besma Bouslimi, Chedly Bradai, Ahmed Koubaa

A CFD Investigation of a Turbulent Flow in a Corrugated Plate Heat Exchanger

This paper presents a three dimensional analysis with the computational fluid dynamics CFD code of a turbulent flow through a plate heat exchanger with corrugated wall. For the calculation, the standard k-ε model with “wall-functions” is employed with Reynolds number Re range of 400, 900, 1000.This paper describes the effect of rib height on the thermal performance of the PHE. To simulate the flow through a corrugated plate and discover the flow characteristics and structure, the commercial CFD software Ansys Fluent R15.0 is used. In order to simplify the simulation, the computational domain was considered as one corrugated plate with chevron angle β = 45°. The geometry is obtained by the Computed aided design software Solidworks. It consists of chevron plate with different rib height h of 3, 5, 7 mm and a constant chevron angle β = 45°. The hot water enters the fluid domain with temperature of 60 ℃ through the corrugated wall which has a constant temperature of 20 ℃. The contours of temperature, velocity and turbulence intensity were presented and analyzed numerically.

Sirine Chtourou, Hassene Djemel, Mohamed Kaffel, Mounir Baccar

CFD Simulation of CO2 Adsorption onto Activated Carbon for Gas Separation and Storage Applications

The increase in global energy demand, the scarcity of fossil fuels resources, climate change and global warming are undeniable realities. In this energy context, the implementation of concrete measures in favor of greater energy efficiency systems becomes urgent. Among these systems, the integration of environmental friendly, low energy adsorption technologies is gaining more interest in many chemical, residential and industrial applications such as adsorption refrigeration systems, quality treatment and energy storage processes. Pressure swing adsorption and temperature swing adsorption are among the promising techniques for CO2 capturing and separation from exhaust gases. In this study, corrected adsorption rates of CO2 onto activated carbon powder were investigated using computational fluid dynamics simulation. The modified linear driving force (mLDF) model was used as the adsorption kinetics equation by fitting of experimental data with isothermal assumption. Then the adsorbent layer temperature was estimated with CFD simulation which allowed to adjust the diffusion time constants for accurate performance investigation of CO2 adsorption cooling, storage and separation applications.

Skander Jribi, Boutheina Zallama, Takahiko Miyazaki

Enhancement of Fixed-Wing Space Drone Performance Through Thermoelectric Power Generation

The thermal effects of wing color for drones performing in the Martian atmosphere are investigated during the summer and winter seasons. The optimal wing color configuration is identified in each season. This study focuses on two useful consequences of the thermal effects of wing color: the skin friction drag reduction and the thermoelectric generation of power. According to its color, every side has a certain temperature affecting the local skin friction drag. Investigations of various configurations have shown that the thermal effect on the wing boundary layer is insignificant because of the low atmospheric pressure. However, the large temperature difference the top and the bottom of the wing has a great potential of thermoelectric power generation. The maximum temperature differences between the top and bottom surfaces for the summer and winter seasons are, respectively, 65 K and 30 K. The drag reduction and the power generation via thermoelectric generators both contribute to enhancing the endurance of drones. Future drone designs will benefit from the increased endurance through optimizing the wing color configuration.

Devyn Rice, Samah Ben Ayed, Stephen Johnstone, Abdessattar Abdelkefi

Simulation of Cellulose Pyrolysis Kinetics

By definition, the controlled pyrolysis of cellulose is the physical and chemical decomposition of organic compound under the action of heat and in the absence of oxygen. Understanding this phenomenon firstly involves identifying the reaction mechanisms and the kinetic parameters involved in the thermal degradation of cellulose. The diversity of results from the literature reflects the difficulty of explaining these complex kinetics related to pyrolytic degradation of such large biological macromolecules. This study consists in determining the effect of different temperatures and kinetic parameters which influence the mass Damköhler number on the pyrolysis of cellulose in a perfectly agitated reactor that ensures the uniformity and homogenization of the medium. The results of our simulation show that higher conversion is obtained for high values of mass Damköhler number which increases with temperature. We have also noticed that the conversion rate of cellulose pyrolysis process depends on the mass Damköhler imposed by the reaction model.

Amal Masmoudi, Moez Hammami, Mounir Baccar

Systems and Dynamics


Free Vibration Analysis of Torsional Line Shafts of Four-Stroke Engine

The free vibration analysis of torsional line shafts is the preliminary step for any torsional forced vibration system and, in certain cases, can be sufficiently accurate. This work introduces a stream-lined approach for free vibration analysis of the torsional line of a four-stroke engine with four cylinders (operating range 600–5500 rpm). The equivalent torsional model, calculated by the British International Combustion Engine Research Association empirical method, has eighteen degrees of freedom. On the basis of some simplifying hypothesis, the equations of motion are obtained using Lagrange’s formalism. Then the Rutishuser method is used to calculate natural frequencies and mode shapes. The main objective is to determine particularly dangerous crankshaft rotational speeds, as well as the magnitudes of the torsional vibrations of the different disks during resonance. The adaptation example of the motor shaft line shows that for the investigated configuration a speed of 710 rpm (importance 2.36 for harmonic 2), is a particularly dangerous rotational speed for the entire operating range of the motor.

Abdelouahab Rezaiguia, Salah Guenfoud, Debra F. Laefer

Stability Analysis of One Degree of Freedom System Equipped with Friction Vibration Absorber

In this paper, the free vibration response of a linear one degree of freedom system equipped with a friction vibration absorber is analyzed. The friction between the two systems is modeled using Coulomb friction law. The effect of the friction parameters on the stability of the linear one degree of freedom system is studied. First, around the equilibrium point, the local stability is analyzed using the Routh-Hurwitz criterion: the discontinuous non-smooth description of the friction force is approximated by a tangent hyperbolic continuous smooth function. Second, the global stability is analyzed using the Lyapunov direct method. The effect of negative viscous damping and the limit cycle behavior are considered

Aymen Nasr, Charfeddine Mrad, Rachid Nasri



Study of Fe-W-P Coating Performance Under Scratch Test: Modeling and Experiments

Fe-W-P coating was deposited on stainless steel 316 L using electrodeposition process. An experimental and numerical evaluation of the adhesion strength between this coating and the stainless steel was studied with a scratch test using Rockwell indenter and progressive load from 0 to 165 N. Scanning electron microscopy and 3D profilometry were used to determine the morphology of the scratch track and the indenter penetration, respectively. The main experimental result shows the propagation of cracks inside and outside of the scratch track which increase with the increasing of the normal applied load. Moreover, a pile-up phenomenon was detected in the border. The obtained numerical results are in good agreement with the experimental one. In fact, a stress concentration was observed in the center and the border of the track due to the pile-up phenomenon which is the origin of the creation of the crack network. Besides, the cross sectional numerical profile in the maximum penetration area show clearly a pile-up phenomenon. A good agreement was found when comparing the numerical and the experiemental results prouve the robustness of the model.

F. Zouch, A. Bahri, K. Elleuch

Corrosion Resistance Enhancement of AISI 304 Stainless Steel by Deep Rolling Treatment

As one of severe plastic deformation (SPD) techniques, the deep rolling treatment was carried out after machining to enhance the surface integrity (microstructure, grain size, residual stress, etc.) of many materials. Re-crystallized surface layers containing submicron-scaled grains could be produced during deep rolling process due to severe plastic deformation. These ultra-fine grained materials showed improved mechanical properties (fatigue, wear resistance, corrosion resistance, etc.). In this work, deep rolling process was performed to enhance the corrosion behavior of Stainless Steel type AISI 304 in severe environments like seawater. Findings of this study depicts that deep rolling generates an ultra-fine grain structure, multi-directional mechanical twins, strain-induced martensite in the surface layers. In addition, the application of deep rolling produced high and deep compressive residual stress distributions. As a matter of fact, the corrosion rate was reduced by 53% for deep rolled sample comparatively to machined one. Thus, the enhancement of AISI 304 corrosion behavior results from microstructural changes, deformation-induced martensite and compressive residual stresses.

Khouloud Gharbi, Naoufel Ben Moussa, Nabil Ben Fredj

Numerical Simulation of Reciprocating Sliding Test: Effects of Surface Topography on the Wear Behavior

In recent years, researchers have shown an increased interest in the investigation of the wear track evolution.The present work proposes a Finite Element Approach (FEA) to evaluate the impact of the surface properties and the wear resistance of a 5083 aluminum alloy. Reciprocated sliding test was carried out numerically, using Abaqus/Explicit software. Based on python scripts, it was possible to consider the tribological behavior of a real surface profile. Tests were performed with a rigid ball (R = 5 mm) under a normal load of 1 N at a maximum number of sliding cycles of 10 cycles.During the numerical simulation, the wear track evolution was inspected for different surface topographies. A comparison of the findings with those of experimental studies confirms the validity of the numerical results. This numerical investigation has revealed the significant impact of the surface topography and the number of sliding cycles (N) on the wear track evolution.

Fatma Elwasli, Slah Mzali, Farhat Zemzemi, Salah Mezlini

Ni-Ti Superelastic Wire Coupled with Conventional Brackets During Bending Tests: Cross-section Effect Comparison

Ni-Ti shape memory alloy has become a famous alloy in the dental field. This alloy is used to design orthodontic wire suitable for the alignment stage. The Ni-Ti superelasticity has permitted to the clinicians to ensure an optimal orthodontic displacement during long period. The choice of round or rectangular cross section wire depended on the force delivered by the Ni-Ti wire, since this archwire exhibits a different mechanical behavior compared to an ordinary alloy. Thus, the aim of this work is to examine the effect of varying the cross-sectional dimension of superelastic Ni-Ti wire inserted in three brackets during bending tests which reproduce the most accurately the mechanical response of the wire as it is inserted in the oral cavity. The experimental findings showed that, when studying the cross-section size effect, the engagement loading, and the orthodontic force are dominated by the martensitic transformation process rather than the moment of inertia wherein the pseudo-elastic behavior is revealed. Moreover, the activation and deactivation loads have been affected by the brackets ligated system when comparing the experimental results to the literature ones. This was due to the friction resistance induced by the wire and the braces coupled with the ligatures.

Aroua Fathallah, Tarek Hassine, Fehmi Gamaoun

A Comparative Investigation of the Tribological and the Mechanical Behavior of Polyester Powder Coatings Filled with Graphite Depending on the Filling Percentage and the Size of the Graphite Particles

Composite coatings are used in order to reduce the friction and protect contacting surfaces against wear with good adhesive to substrate.The present study deals with two sizes of solid particles used in composite coatings. As received graphite G1, the mean size is 20 µm and the crushed one, obtained by ball mill, is 10 µm.The resulting tribological behavior and micromechanical properties were discussed and compared. As expected, the smaller the particle size the greater reduction in the coefficient of the friction and wear rate. The experimental findings show that adding 5 wt% of crushed graphite provide similar COF than when introducing 10 wt% of as received graphite. Coatings scratch behavior is affected by the size and percentage of fillers inside the polyester matrix. In fact, the scratch resistance is observed with polyester coatings filled at 5 wt% G2 and 10 wt% G1.

Nedia Gafsi, Mohamed Kharrat, Maher Dammak, Raquel Verdejo, Miguel Angel Lopez Manchado, Massimiliano Barletta

Physicochemical, Morphological and Thermal Characterization of Composites Based on Olive Wood Flour

This study deals with the evaluation of the physicochemical, morphological and thermal properties of a biocomposite material based on polypropylene (PP) reinforced with vegetable fibers olive wood flour (OWF). Initially, the olive wood flour was chemically treated with a coupling agent (amino-silane) and then characterized to provide the modification influx. In a second step, various PP/OWF bio-composites with variable contents of OWF (0, 10, 20 and 30% by weight) were implemented by twin-screw extrusion and then shaped by injection molding. The effect of the OWF content on the one hand and the chemical modification of the latter by adding silane as coupling agent on the other hand, are the two parameters that are the subject of the present sensitivity study. Finally, the characterization results are compared and discussed. The significant influence of the treatment of OWF with the silane coupling agent is demonstrated, clearly demonstrating that the silane promotes the adhesion of the plant-based filler that is OWF with the PP polymer matrix.

Nesrine Bouhamed, Slim Souissi, Pierre Marechal, Mohamed Ben Amar, Olivier Lenoir

A Comparative Study on the Physical and Mechanical Behavior of AA6082-T6 and AA5083- H116 Aluminum Alloys in Friction Stir Spot Welding

Aluminum alloys are widely used in manufacturing industry due to its beneficial combination of formability and strength. However, these alloys are prone to imperfections when joined using conventional fusion welding technologies. A revolutionary solid-state welding technique, labeled Friction Stir Welding (FSW), was demonstrated to be particularly suited for aluminum alloys joining. This solid-state welding process produces joining by mixing materials under intense plastic deformation and heat generation. To gain insight into the base material flow and heat generation during FSW, 3D coupled thermo-mechanical finite element model (FEM) was developed to reproduce the friction stir spot welding (FSSW) variant of FSW process. The numerical model, which uses an Arbitrary Lagrangian Eulerian (ALE) formulation, was implemented in ABAQUS/Explicit. The constitutive behavior of the base material was modeled using the classical Johnson-Cook model. The developed FE model was used to predict and compare the temperature distributions, forces and torques during FSSW of AA6082-T6 and AA5083-H116 aluminum alloys. Some conclusions on AA6082-T6 and AA5083-H116 aluminum alloys weldability in FSSW will be presented based on the comparative analysis of numerical and experimental results.

Nasra Hannachi, Ali Khalfallah, Carlos Leitao, Dulce M. Rodrigues

Tribological Characterization of Composites Based on Si3N4 Ceramics

Silicon nitride (Si3N4) has excellent mechanical properties even at high temperatures, low inertia, high hardness, very good resistance to thermal shock and excellent friction and wear behavior. For this purpose, silicon nitride is used in various applications such as for welding nozzles, tools for metal transformation, calibration, control, bearing balls and prosthetic components for orthopedic surgery.This paper presents tribological behavior of two shades of nano-sized silicon nitride ceramics, the first is silicon nitride with 10 wt% of boron nitride (SN-BN) and the second is silicon nitride in β phase (β-SN). Tribological behavior was studied in dry sliding condition, by means of reciprocating ball-on-flat tribometer.The aim of this work is to study the effect of normal load and the counterface materials on tribological properties of SN-BN and β-SN ceramics. The results have shown that tribological properties of studied materials strongly depends on normal load and counterface material.

Amine Charfi, Ismail Dhaou, Mohamed Kharrat, Mohd Farooq Wani, Maher Dammak

The Effect of the Loading Path History on the Fracture Loci

Theoretical analysis and experimental studies have shown that the stress triaxiality η is one of the most important factor that characterizes the ductile fracture of metallic materials. However, there is another variable that should be involved in fracture prediction models, which is Lode angle parameter ξ. In this study, two uncoupled phenomenological models are used for predicting the ductile fracture of a cast A356 aluminium alloy. These models define the equivalent strain to fracture in function of variables that characterize the stress state. The first considers only the stress triaxiality, while the other takes into account the mean pressure and the Lode angle parameter. Two groups of experimental tests were considered: (i) tensile tests on smooth and notched round bars and (ii) tensile plane strain tests on flat grooved plates. The numerical results show that both stress triaxiality and Lode angle parameter evolve during the tests. Therefore, it is necessary to understand the impact of this variation on the calibration of the parameters of uncoupled ductile fracture models. Note that the aim is to be able to predict the fracture under non-proportional, complex loading conditions. In order to assess the effect of the evolution of the stress triaxiality on the prediction of ductile fracture, two strategies are proposed for calibrating a 2D fracture locus, for a wide range of positive stress triaxiality, named direct and inverse, since the first is based on the initial value of the stress triaxiality, while the second uses the average. The numerical results show that if ductile fracture occurs before the onset of localized deformation, the stress triaxiality and the Lode angle present quite constant values, although there is a small variation in the transition between the elastic and the plastic regime. However, when ductile fracture occurs after the onset of localized deformation, these variables can present a strong variation, which should be taken into account in the calibration of the 2D fracture loci.

Meriem Nouira, Marta Oliveira, Ali Khalfallah, José Alves, Luís Menezes

Characterization of CrAlN Films Synthesized by DC Reactive Magnetron Sputtering

CrAlN films were synthesized by DC reactive magnetron sputtering. The influence of the aluminium content on the microstructure, hardness and the friction coefficient of the CrAlN films have been investigated. Results indicate that all CrAlN coatings present a columnar and dense structure. Also, CrAlN coatings present a better hardness than CrN coating. The increase of Al rate from 3.5 to 11% is accompanied by a decrease of hardness from 28 to 24 GPa and then it increases for an Al rate of 24%. The addition of Al to the CrN system causes an increase of the friction coefficient and the wear resistance.

K. Aouadi, C. Nouveau, A. Besnard, B. Tlili, A. Montagne, M. Chafra

Mechanical Characterization of a Composite Sandwich Core Under Shear Stress Based on a Torsion Test

The development of modern technologies requires the use of materials with high mechanical properties and lightest weight structure. With their low density, high strength, high rigidity and excellent durability, the sandwich structures are one of the best materials to meet these requirements. Despite of these advantages, sandwich structure is rather sensitive to failure by shear load. Previous work has shown that standard shear characterization tests of a sandwich structure (ASTM C273, Standard Test Method for Shear Properties of Sandwich Core Materials) exhibits shear stress concentrations at the edges, which negatively affect the results of this test. To solve this issue, this research work proposes a new test methodology to determine shear proprieties using a torsion test. A custom test rig has been developed in order to exert a torsional moment on a cylindrical specimen made of PVC foam. Based on the experimental results, this new test method provides a more precise characterization of the sandwich core materials since it eliminates the phenomenon of concentration of shear stresses on the edges found in the standard test.

Karim Mharsi, Pascal Casari, Amira Sellami, Jamal Fajoui, Mohamed Kchaou

Study of the Wear Behavior of HDPE-Molybdenum Disulphide Composites

This work investigates tribological study of high-density polyethylene-molybdenum disulphide (HDPE-MoS2) bio-composites via an alternative pin-disk tribotester in the dry conditions. The stainless steel pin (M30NW) was used as a counter-part. The obtained HDPE powder after crushing was blended with MoS2 particles with various proportions (0, 2, 4, 6, 10 and 25 wt%). HDPE composite specimens were elaborated with thermal-compression molding press. The coefficient of friction of the HDPE composite decreased considerably after reinforcing with MoS2 for all loadings. The specific wear rate was improved by over 40% for up to a loading of 6 wt% MoS2. It was found that the utilization of molybdenum disulphide improves tribological behavior of the elaborated composites in respect of the unfilled HDPE and the optimal content was about 4 wt%. In fact, after the wear test the optimized percent exhibited a decrease of 30% for the coefficient friction and 55% for the specific wear rate.

A. Salem, M. Guezmil, W. Bensalah, S. Mezlini

Microstructural and Mechanical Characterization of a Baby Diaper

Baby diaper, despite their evolution, still caused serious problems after using on the baby’s skins, as diaper rash or seat dermatitis. To avoid these problems, understanding of the structure of the material in contact with the baby’s skin and its mechanical behavior is necessary. Therefore, the study of the non-wovens fabrics of the top-sheet is compulsory. Our aim is to relate mechanical properties of the tissues to their microstructure. To achieve that goal, the microscopic observation have been performed to study the composition and the structure of the textile, particularly the distribution of the fibers orientation. Also, tensile tests in both longitudinal and transversal directions and compression tests have allowed to mechanically characterize some mechanical properties, as stiffness. Results show that longitudinal directions are favored comparing to the transversal ones and that actual baby diapers are more rigid than others under study.

Basma Ajmi, Mohamed Kchaou, Amilcar Ramalho, Amira Sellami, Antonio J. Gamez, Nabil Bouzayani

Numerical Modelling of Undulatory Elastic Behavior of Metallic Glasses Ribbon

In this work a numerical study is developed via Abaqus software that describes the undulatory elastic behavior of arc-shaped metallic glass (MG) ribbon subjected to normal progressive loading. The pre-deformed ribbon is prepared based on the experimental condition which should ensure the initial amplitude hover the boundary fixation L less than ½. The objective is to estimate numerically the maximum number of undulation that the arc-shaped ribbon could reach before plasticity. The control and estimation of the elasticity becomes very difficult when the miniaturization is requested. This result is very interested when the elastic undulation response of MG ribbon will be used as a flat spring or electromechanical switch for micro-machines and Micro-Electromechanical Systems (MEMS). The obtained numerical results are compared to the experimental available data and we have found a good agreement. This numerical study is done for the first time on the metallic glass ribbon and the improvement of the obtained results is in progress.

M. A. Yousfi, C. Ammari, K. Hajlaoui, Z. Tourki

Application of the Acoustic Emission Technique for Damage Monitoring of 3D C/C

This paper deals with the detection and monitoring of damage of a three-dimensional carbon/carbon composite (3D C/C) under tensile loading. In fact, due to the manufacturing process, the existing cracking network of 3D C/C at the initial state may be quite extended which may affect the mechanical behavior and in some cases lead to the premature rupture under loading. The objective of this work is to investigate the validity of the acoustic emission as an advanced health monitoring system to provide warning of the distress and characterize the damage state during loading. Load-unload-reload tensile tests have been conducted and monitored in parallel with the Digital Image Correlation (DIC) method and the acoustic emission (AE) technique. The AE technique allows to monitor the evolution of damage inside the volume of the material and the growth in situ. This is very interesting since the other non-destructive techniques usually used allow only a posteriori evaluation of damage. The influences of stress states on tensile properties and the dependency with the AE activity have been analysed. Different stages of damage have been identified based on the acoustic emission activity and AE signals parameters. In addition, the AE technique provides accurate location of damage based on the density of AE events location maps.

Jacqueline Saliba, Jalal El Yagoubi, Ludovic Hallo

Composite Materials in Epoxy Resin Matrix Using Curaua Fibers

Vegetable fibers have good mechanical properties, low density, no toxicity, are renewable and have low cost among other properties. The use of lignocellulosic fibers as reinforcement in polymeric composite materials in substitution of synthetic fibers is in the direction of sustainability. In the current investigation, an evaluation of biocomposite materials elaborated using curaua fibers as reinforcement in an epoxy resin is carried out. The objective of this work is to highlight the influence of the quantity of fiber and the interaction between the fibers and the resin with different chemical treatments looking for a greater adhesiveness of the fibers in the matrix leading to an increase of the composite tensile properties. The treatments with NaOH consist of varying the concentration and the fiber immersions time in the solutions. Steel molds were used to manufacture the test bodies with dimensions according to the standards for mechanical tensile tests. A Taguchi design of experiment is used to identify the effects of fiber fraction, alkaline treatment concentration and treatment time. The data obtained were statistically evaluated, obtaining good results for Curauá fiber compounds, which may in the future replace glass fiber.

Gilberto Garcia Del Pino, Abderrezak Bezazi, Haithem Boumediri, Antonio Claudio Kieling, Jose Luis Valin Rivera, Jamile Dehaini, Francisco Rolando Valenzuela Díaz

Composite Cross-Ply Laminates Stacking Sequence Effect on Post Flexural Fatigue Residual Strength

This paper concerns an experimental approach to the stacking sequence influence on cross-ply laminates behaviour. Effects of fatigue on the residual strength and stiffness are investigated through performing post fatigue static test after specific numbers of cycles. Residual strengths were measured by testing specimens to a certain number of cycles then static tests to rupture were performed after the specimen had been unloaded without being removed. The results obtained indicate that as well as there is a drop in the specimen’s stiffness, there is a drop in the strength of the laminate as the number of cycle increases. However, this is also accompanied by an increase in the displacement mainly at higher number of cycles. The hysteresis loops revealed that a significant decrease in the maximum fatigue load was occurring as the number of cycles increased. It is also noted that the slope of the hysteresis loops decreased with respect to the number of cycles. However, a less significant drop in the minimum fatigue load than the maximum fatigue one was also observed.

Abderrezak Bezazi, Abderrahim El Mahi, Boudjema Bezzazi, Gilberto Garcia Del Pino, Fabrizio Scarpa

Impact Simulation of PA66-GF Composites Using Finite Solid Shell Element

This study is focusing on the finite element simulation of low velocity impact applied to glass fiber-reinforced composites. Elasto-visco-plasticity is adopted taking into account strain rate effect, with isotropic hardening. To avoid numerical locking, hexahedral solid shell finite element SS is developed. The formulation is based on the mixed Assumed Natural Strain (ANS) and the Enhanced Assumed Strain (EAS) methods. A geometrical non linear condition is applied. The finite element is implemented in UEL subroutine via the commercial software ABAQUS/Standard. The numerical element proved its efficiency comparing to conventional element and previous experimental results in (Mars et al. 2018). Numerical simulations with solid element are conducted using Abaqus/standard via user material UMAT subroutine. In terms of computation time, the solid shell element is less time consuming when comparing to conventional solid element. This is due to the fact that a single element through the thickness direction is adopted. Element efficiency is assessed for various fibers contents.

S. Koubaa, A. Chaker, J. Mars, A. Vivet, F. Dammak

Application of Factorial Design to Study the Effect of Recycling of HDPE on Rheological and Mechanical Properties

In the plastic industry, scrap is common and can reach important amounts in some applications. For that reason, reprocessing in the format of mechanical recycling is pretty common among plastic industry for its simplicity and efficiency. However, the stated type of reprocessing causes the degradation of the proprieties of plastic. Hence, recycled plastic is mixed with virgin one. The objective of this work is the investigation of the effect of the variation of the fraction of the recycled plastic (X1) in virgin/recycled blends and number of recycled cycles (X2) using factorial design for HDPE. To attend this objective, two sets of specimens were injected according to 22 factorial design. Mechanical and rheological proprieties were characterized in terms of melt flow index, Vicat softening temperature, elastic tensile strength at 5% ( $$ \sigma_{\varvec{e}} $$ σ e ) and tensile strength at yield ( $$ \sigma_{\varvec{m}} $$ σ m ). Using nemrodw software, effects plots were plotted. It was depicted that X1 and X2 have no significant effect on $$ \sigma_{\varvec{e}} $$ σ e , $$ \sigma_{\varvec{m}} $$ σ m and on Vicat softening temperature. Nevertheless, they have a significant effect on MFI.

Karama Elfehri, Ameur Chtourou, Sana Koubaa, Basma Samet

Viscoelastic Mechanical Behavior of Fresh Human Bone of Lower Limbs

Despite significant developments in orthopedic medicine, prostheses and joint implants have an unlimited life span and various problems citing loosening. Indeed, they are made from a very rigid material which has a mechanical behavior different from that of the human bone. This work is about the study of mechanical behavior of the human bone like dynamic viscosity and elasticity modulus. Accentuating on the viscoelastic nature of the bone, the samples of fresh bone specimens are used directly after their removal. The dynamic viscosity of the cancellous bone was determined by relaxation test. Thirteen human cancellous bone samples of the knee joint are used. The dynamic viscosity is in the order of 8683.3 MPa.s. The dynamic viscosity of human cancellous bone can be used in femoral cement filling during bone grafting.

Saida Benhmida, Dorra Salhi, Montassar Zrida, Ahmed Hichem Hamzaoui, Hamza Essaddam

Insights into Researches on the Tribological, Microstructural and Micromechanical Properties of Thermoplastic Based Composites

Two disjoint filler materials in a powder form are added to a polycarbonate (PC) matrix. The micro sized additives are Graphite (Gr) and molybdenum disulfide (MoS2) introduced as layered solid lubricants. Two distinct development methodologies are employed in order to prepare the composites; the first process is industrial by using directly an injection molding machine, while the second process is composite preparation in a laboratory scale. The experimental results of the two process are compared. From friction and wear tests, it is established that MoS2 particles improved the wear resistance and reduced the coefficient of friction of steel/PC contact with both development methodologies. On the contrary, Gr decreases the tribological properties of PC. Fracture morphologies and x-ray micro-tomography are performed to characterize the microstructural aspects of PC/solid lubricant composites. Micrographs show microcracking, filler agglomeration and the presence of voids with direct injection molding. Besides, the composites present poor scratch resistance properties. The different results are improved with the second development methodology including the powders surface treatment by an amino-silane and mechanical mixing with the PC matrix.

Basma Ben Difallah, Mabrouka Akrout, Mohamed Kharrat, Maher Dammak, Guy Monteil

Mechanical Characterization of PP/Alfa Bio-composite Obtained by Thermocompression

This study contributes to the research of new materials from natural resources. It aims to exploit the natural fibres extracted from the Alfa plant in combination with a thermoplastic polymer matrix of polypropylene type in order to develop bio-composite materials. The biocomposite are composite materials made from natural or biofibre and non-biodegradable polymers such as polypropylene (PP), polyethylene (PE) and epoxies, or with biopolymers such as polylactic acid (PLA). The biocomposite made in this study was classified as eco-friendly and green since natural fibre and a renewable resource-based polymer were used. Various approaches have been used, including retting in salt water and chemical alkaline treatment. The extraction fibres was improved according to a two-step investigation. Firstly, the processing temperature, duration and the sodium hydroxide (NaOH) concentration, together with the usefulness of the post-treatment, were studied based on visual examinations. Morphological analyses carried out on the fibres obtained show an increase in the cellulose content and a decrease in the size of the treated fibres. Polypropylene/Alfa biocomposites have been formulated from zero to 30% in mass of fibres using the thermocompression molding process followed by injection molding. Tensile tests show the increase in Young’s modulus and mechanical strength as a function of cellulose content and fibre dimensions. Chemical treatment with the sodium hydroxide (NaOH) solution with a concentration of 3.25 M at 100 °C during 2.5 h with 6-day retting together with applying the post-treatment has the best mechanical properties.

Ismahen Zaafouri, Montassar Zrida, Khaled Labidi, Ahmed Hichem Hamzaoui, Moufida Borni

Modeling of Iron Based Shape Memory Alloys Behavior Within Finite Strain Formulation

This paper presents a finite-strain thermomechanical constitutive model for Iron based Shape Memory Alloys (Fe-SMAs). The model considers the multiphysical coupling between the phase transformation and the plasticity which distinguishes Fe-SMAs from classical SMAs (Ni-Ti and Copper based ones). Based on the multiplicative decomposition of deformation gradient into elastic, transformation and plastic components, the model is developed within a thermodynamically consistent framework. Model constitutive equations associated with the internal variables (volume fraction of martensite $$\chi $$ χ and the accumulative plastic strain $$\gamma $$ γ ) are derived from the reduced form the constructed Lagrangian, which is the sum of the Helmholtz free energy function and the inner potential, and the Clausius-Duhem inequality. The model is used to simulate tensile experiments on Fe-SMAs specimens at different thermomechanical loadings. The good agreement of the model predictions demonstrates the capabilities of the proposed model to well the specific behavior of Fe-SMAs.

Achref Sallami, Walid Khalil, Tarak Bouraoui, Tarak Ben Zineb

Surface Properties and Adhesion Behavior of PVD Thin Film Using Multi-cyclic Nanoindentation and Scratch Test

PVD thin film based on chromium nitride was deposited on XC100 steel substrate with reactive radio frequency magnetron sputtering. Thin film was characterized in terms of both surface properties and adhesion behavior. The characterization of surface properties was based on the measurement of mechanical properties coupled with a preliminary microstructural study using SEM and AFM. Fatigue resistance was considered as an important surface properties and it was investigated using multi-cyclic nanoindentation test. Results indicated that chromium-based coatings have a smooth, dense and compact microstructure with a grain size of about 109 nm and a roughness of about 11 nm. CrSiN showed a high adhesion quality, critical loads were LC1 = 16 N, LC2 = 20 N and LC3 = 25 N. PVD coatings exhibited a hardness of about 30.52 GPa and Young’s modulus of about 338.32 GPa. Moreover, multi-cycle nanoindentation technique, with variation of loading mode (progressive and quasi-static) and loading rate (from 200 mN/mn, 400 mN/mn and to 600 mN/mn) was used to analyze superficial fatigue behavior and surface resistance. Whatever, the cyclic loading mode, an elasto-plastic behavior was observed and an appearance of hysteresis loops in the unloading-reloading curves witch was explained by a fatigue effect. In addition, a hardening phenomenon was found when the loading rate increase.

Kaouther Khlifi, Hafedh Dhiflaoui, Najoua Barhoumi, Ahmed Ben cheikh Larbi

Fluid Mechanics


Investigating the Free-Surface Flow Behavior Due to Sluice-Gate Maneuvers

This paper explored the free-surface wave behavior in prismatic open-channel. The one-dimensional Boussinesq model was used for transient flow description, along with the (2/4)-dissipative scheme implemented for numerical computations. Investigation addressed the flow behavior in a rectangular open-channel supplied by a constant depth reservoir and equipped with a sluice gate at its outlet inlet. The determination of the fundamental pulsation of the hydraulic system followed from the water-hammer concept, used in pressurized-pipe flows. Two kinds of boundary conditions were investigated; involving the abrupt closure and/or the sine-excitation of the sluice-gates. Results showed that the sine excitation case, using the fundamental pulsation of the hydraulic system, induced a significant depth rise; which may lead to the flood of the channel. Furthermore, it was found that the free-surface wave pattern was driven by the sine excitation using submultiple value of the fundamental pulsation; however, this pattern was controlled by the abrupt closure maneuver for the case using submultiple values of the fundamental pulsation.

Ali Triki

Effect of Anchor Conditions on Structural Responses During Fluid Transients in Pipelines

This paper deals with the evolution of structural responses accompanying water hammer in quasi-rigid straight pipelines with emphasis on the effect of the support rigidity. The coupled discrete vapour cavity model (DVCM) is used to simulate axial stress and axial displacement of the pipe in presence of column separation. Transient is caused by a fast-downstream valve closure. The method of characteristics (MOC) with wave-speed adjustment scheme is used in calculation. The numerical results obtained for rigid and viscoelastic supports are performed and compared. The cavity collapse involves greater stress peak at the valve with rigid support, but the stress spikes are reduced in case of viscoelastic support. The axial displacement is more important for this last case because of junction coupling effect. The results obtained are assumed to be important in hydraulic engineering.

Abdelaziz Ghodhbani, Ezzeddine Haj Taieb, Mohsen Akrout

Investigation of Blade Exit Angle Effects on the Performance of a Centrifugal Pump

To achieve the goal of developing energy-efficient mechanical systems, centrifugal pump designers often encounter problems of selecting and optimizing pump impeller geometry. This paper presents a theoretical approach to investigate the blade exit angle effects on the performance of a low specific speed centrifugal pump with standard closed impeller. The governing equations of the flow through pump impeller have been numerically solved by the one-directional method of characteristics of specified time intervals. The mathematical model is validated with the pump experimental performance curves. The numerical results have clearly shown the influence of impeller blade exit angle on the head, input power and efficiency of the considered pump. Indeed it has been found that both head and shaft power increased with the increase of the blade exit angle. Best efficiency is obtained for impellers with 15° and 30° exit angle.

Faouzi Omri, Sami Elaoud, Noura Bettaieb, Issa Chalghoum, Ezzeddine Hadj Taieb

New Proposed Design of Rotor Shaft Equipped with Blades Inside a SSHE

Thermal treating of highly viscous product is associated with many problems such as fouling, an inhomogeneous treatment and burn-on of product. The efficiency of a SSHE lies behind its simple design; the rotating blades continuously scrape the film of product deposed at the heat transfer surface, thus providing a large heat transfer coefficient. The bulk mixing phenomena is purposely induced in SSHE by adopting a new arrangement of blades noted alternate blade in order to ameliorate the thermal performance within the SSHE. A three dimensional numerical simulation of the coupled hydrodynamic and thermal behavior within a conventional SSHE and an alternate blade SSHE was conducted for comparison purpose. Continuity, momentum and energy equation were solved using the finite volume ANSYSFLUENT 19.0 tool. Results of the simulation show that the new design offer a heat transfer coefficient equal to 647.55 W/m2K, around 63% higher than the heat transfer coefficient within the conventional SSHE design.

Rabeb Triki, Hassene Djemel, Mounir Baccar

Different Applied Boundary Condition Within SSHE Treating Non-Newtonian Shear Thinning Fluid

Scraped surface heat exchanger (SSHE) is widely spread in different chemical, food pharmaceutical and petrochemical industry. The attractive feature behind its design is their capability to handle highly viscous, sensitive, sticky product and slurry system. A numerical study of the performance of different cooling process (different applied boundary condition) within SSHE equipped with blades was conducted using ANSYSFLUENT 19.0. Three boundary conditions are examined in this study; a constant applied wall temperature, a constant applied heat flux and a variable wall temperature. The cooling process of 2% Carboxylmethyl cellulose (cmc) is investigated under steady state, non-isothermal, laminar flow condition. Numerical simulation shows that the thermal behavior within SSHE is highly dependent on the boundary condition applied at the stator wall. The hydrodynamics behaviour within SSHE is controlled by scraper rotation. The outlet temperature of fluid reaches the desired cooling temperature for a constant applied heat flux, although it was higher for the other applied boundary condition. It is more effective to cool the fluid gradually by applying a variable fluid temperature.

Rabeb Triki, Hassene Djemel, Mounir Baccar

Experimental Investigation of Air Conditioning in a Bi-climatic Room

This paper is a preliminary study to the investigation of hygrothermal behavior of wall implemented as separating wall of bi-climatic rooms. One room simulates indoor environment while the second simulates exterior climatic solicitations (temperature and relative humidity). Four typical Tunisian winter climate are selected for this study. The aims are to check the homogeneity of ambient conditions in the rooms, the reaching of the set point, the delay to reach it after setting then if the ambient conditions remain constant once they are reached, and finally the response time of the whole system. The results underline that some climate are easy to reach while other may be difficult to obtain due to competitions between climatic systems. This may be solved by acting on the device management. The typical response times are short enough to plan daily cyclic variations in the following steps of the study and ambient conditions are homogeneous in the room.

Naima Boumediene, Florence Collet, Sylvie Pretot, Lazhar Ayed, Sami Elaoud

Numerical Study of Droplets Coalescence in an Oil-Water Separator

Through this paper a numerical modeling of oil-water flow through parallel plates integrated into a rectangular oil-water separator is conducted. Oil droplets of tiny sizes are dispersed in water and rectangular plates are used as coalescing chambers. Results have shown that upgrading a conventional API skimmer by introducing parallel coalescing chambers enhances coalescence of oil droplets by increasing their sizes. Since the buoyancy force that enables oil to float on water surface is proportional to the volume of the submerged oil droplet, droplets of greater sizes are then susceptible to rise to the water surface. Droplets floating on the water surface can be then easily skimmed. COMSOL Multiphysics modeling of two phase flow between two plates of the coalescing chamber has enabled to visualize the coalescence phenomenon and to determine coalesced droplets diameters. Further, the capability of enhancing oil water separation through coalescing chambers was discussed for the studied case.

Zahreddine Hafsi, Sami Elaoud, Manoranjan Mishra, Ines Wada

An Alternative Approach for Minimum Independent Loops Identification in Water Distribution Networks

In the management and design of water distribution network, the knowledge of the flows in pipes and pressures in nodes is indispensable. Such knowledge requires a prior analysis of the network topology to be used for equilibrium procedure. The incidence matrix linking pipes to loops is one of the main topological representations of networks necessary for the process. Even though different algorithms have been presented by several researchers, the question of the minimum independent loops, which effects computing complexity, still raises. Different approaches in the selection of these loops have been established. However, few have arrived to determine the minimum independent loops matrix. The aim of this paper is to present an alternative approach for determining the sparsest pipes/loops matrix possible using Matlab® and graph theory. The reliability of the proposed algorithm was tested and verified through a real test case. The performances of the algorithm were also compared to other recent methods available in literature in terms of the sparsity of the independent loops’ matrix.

Oussama Choura, Zahreddine Hafsi, Sami Elaoud


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