Advances in Mechanical Engineering and Mechanics II

Postural changes, related to increased heel height and its chronic effects, were investigated for many years. However, its relation to low back pain and lumbar vertebra damages may is still controversial. This study aims to determine lumbar kinematic adjustments as high height increase and the contribution of its surrounding muscles to ensure balance and stable motion. In this study, a standard motion capture protocol is used to collect 3D motion data for healthy young females waking with a stiletto shoes with 8.5 cm of heigh. Then a generic full body lumbar model (Rabee 2016) was adjusted to our female subject’s anthropometric parameters (weight and height). Joint kinematics, muscle activations, and muscle forces were calculated for each gait cycle using Opensim software package. Preliminary results showed that wearing high-heeled shoes decrease lumbar joint flexion and the increase of axial rotation and lateral bending and induce a higher amount of spine muscle activities to propel legs during locomotion and to maintain spine balance. Consequently, muscular equilibrium changes around inter-vertebral joints engender higher compressive forces, which may cause discomfort, joint damages, and consequently low back pain. As conclusion, musculoskeletal modeling is a challenging tool to investigate biomechanical effects of altered gaits and predict joint damages in relation to footwear.

The traditional therapy, where the practitioner assists the patient’s affected member along prescribed tasks, presents some limitations such as the restricted number of the available therapists. Considering these issues, Rehabilitation robots have been developed to improve the reeducation quality. They provide repetitive and intense assistance for patients with motor impairment. This paper focuses on the preliminary phase of a cable-driven parallel robot (CDPR) design intended for upper limb rehabilitation. This kind of robot was chosen due to its characteristics that make it suitable for rehabilitation tasks such as their extended workspace, their high velocity and the light weight of their moving parts. In this aim and with the help of ergo-therapists, three most daily activities have been identified. A motion capture (MoCap) system was used to record and extract data needed to analyze these three movements. Five participants were inquired to perform the three motions. Database including the trajectories as well as kinematic characteristics of the recoded exercises is set up. Each motion should remain inside the robot workspace with a positive tension in all cables. As a consequence, a design problem formulation of a robot with 3 translational dof as well as a suitable architecture were proposed.

The aim of this study is to use the conventional inverse problem to identify the parameters of a nonlinear constitutive model of cranial bone under compression loading, which then can be used in numerical simulations such as those involving impact, ballistic and blast events. The dynamic compression of the material was obtained according to the procedure of Polymeric Split Hopkinson Pressure Bar (PSHPB) tests, for high strain rates of approximately 1500 s−1. Five cylindrical specimens of embalmed human cranial bone were tested under dynamic loading. The corresponding 3-D mesh models of these samples were obtained using a micro-Computed tomography (µCT) images. Based on these experiments, corresponding finite element simulations were undertaken using commercial LS-DYNA software. A monolayer elastic-plastic constitutive material model was assigned to the cranial bone which exhibit a foam-type behavior for all compression tests explored in this study. The optimization problems were solved using a commercial optimization code, LS-OPT, based on the Successive Response Surface Methodology (SRSM). The aim was to obtain optimal solutions of the design variables by minimizing the differences in dynamic test responses between simulation and experimental results.

Since the development of additive manufacturing technologies, periodic structures with controlled morphologies have emerged as a new tool for the designing cellular materials. Morphological variabilities are also often noticed in nature, especially in bone structures, and can be inspirational for the design of artificial tissues. It is known that the mechanical properties of cellular biomaterials mimicking bone are dependent on the morphological properties of the structure, including the shape and size of the repeating unit cell from which they are manufactured. Fused Deposition Modeling (FDM) is a powerful method to create porous structures for tissue engineering, thanks to the possibility to print objects of complex geometry and different configurations. The present work deals with the creation of open porosity structures according to different morphologies, we studied the relationship between the wall thickness of polylactic acid (PLA) structures and the mechanical properties, namely the elastic modulus, the yield stress, the plateau stress, and the densification strain. The cellular PLA structures were made with interconnected hollow spherical cells with 10 mm of diameter according to a hexagonal stack and a wall thickness of 0.2 mm, 0.4 mm, 0.6 mm and 0.8 mm. The mechanical properties were evaluated by mechanical compression tests. The experimental results indicated that the PLA structures with controlled morphologies show specific and interesting mechanical properties.

The main objective of this paper is the assessment of the surface characteristics of an orthopedic implant made from Ti6Al4V. Conventional machining of Ti6Al4V samples used in biomechanical applications is considered particularly difficult due to the low thermal conductivity and elongation at fracture of the material as well as the shape complexity and the geometry features of those implants. Hence, electrical discharge machining seems to be a very applicable solution for the long Gamma nail manufacturing, which requires some specific surface properties to ensure osseointegration and biocompatibility. Nevertheless, due to the rapid heating and cooling phases, the heat affected surface is typically a subject to a major phase transformation during the process. In this paper, a thermomechanical simulation was used to investigate the effects of the electrical discharge machining process on phase transformation and surface roughness distribution of Ti-6Al-4V sample. The simulation results were validated by experimental measurements performed in this work.

In recent years the development of health science to improve people’s lives and reduce the death rate from cardiovascular disease, researchers have invested in the solution of stents to treat cardiovascular disease. Usually a permanent implant (metal stent) is used to treat a temporary disease, effective on elastic recoil and negative remodeling, but promoting intimate proliferation. This is combated by an active stent, which nevertheless induces chronic inflammation and delayed healing (because of active drugs), with the risk of late thrombosis. The idea of resolution leads to the study of the behavior of temporary stent biodegradable and bioresorbable, once the healing process is completed. The purpose of this study is to reduce the disadvantages of metal stents, to do this; a biodegradable material (polylactic acid) is used. The fatigue behavior of a stent after its placement using geometric parameters selected from clinical cases (diastole and systole). A finite element numerical study in the field of biomaterial fatigue is proposed in order to investigate and understand the biodegradable behavior of the stent. The results of the numerical study show the predicted lifetime of the biodegradable fragrance.

Development of new materials such as functionally graded material FGM for dental implant applications have been recently received significant attention due to their abilities to satisfy both biocompatibility and mechanical properties simultaneously. The goal of this research is to evaluate the influence of implant diameter dimension on stress distribution around dental prosthesis. For this purpose, an axisymmetric finite element model of the implant and the jaw bone is constructed. The finite element model of implant, cortical bone and cancellous bone is constructed in Abaqus software. The implant body is made of FGM, which is a mixture of titanium (Ti) and hydroxyapatite (HAP). The implant diameter varied as different values so according to material properties of FGM and implant diameter dimension, stress distribution are investigated. Functionally graded material are used to reduce stress concentration in implant, trabecular and cortical bones and to improve biocompatibility.

The principal objective of this work is to model the behavior of a mild steel material from the experimental data using simple and cyclic shear tests on samples taken from different loading directions. The implemented model will use criterial yield functions taking into account equivalent constituents anisotropic coefficients and shape coefficient with, initially, isotropic hardening laws. These functions have been used successfully in proportional loading as simple shear tests. Secondly, the kinematic hardening law is established for complex loading such as cyclic shear tests. For complex testing, two behavior laws (linear kinematic Prager law and nonlinear kinematic Armstrong–Frederick law) are introduced. Then, an identification strategy will be implemented with regard to several hypotheses to identify the parameters of the proposed model. These parameters are determined, with isotropic hardening in simple shear tests and with the combined hardening in cyclic shear tests. From experimental data, a selection is performed to pick out the furthest suitable hardening laws (isotropic law and kinematic law) in order to model the behavior of the mild steel. Finally, a smoothing with experimental hardening shear curves reveals the adequate description of the strong anisotropy of studied material using the plastic behavior model.

The applications of titanium alloys are traditionally present in the transport, particularly in terms of engines and turbojets. The major advantage of these alloys is mainly related to their good mechanical behavior including a good mechanical resistance under different stress conditions. The use of titanium alloys in the field of biomechanics, especially in bone prostheses, is an advantage due to their mechanical properties close to those of bone. This work is concerned with the study of mechanical behavior of the TA6V titanium alloy present in femoral stem of the total hip replacement (THR). To do this, constitutive modeling is proposed to identify the parameters of the material using CPB06 criterion taking into account the microstructural state of the material. The proposed approach provides a reliable model that could be implemented in finite element software. The obtained results can be used to study the mechanical behavior of the prosthetic structure when subjected to several combined solicitations.

As a new kind of composite materials, functionally graded (FG) composite material has been introduced to solve numerous practical problem arisen from several applications. Further, in various engineering applications FGM structures can undergo major displacements and withstand significant deformations and large rotations. The goal of this paper is to conduct nonlinear investigation of ceramic/metal FG beam. In this purpose, a user-defined subroutine (UMAT) is created in Abaqus/Standard. The non-linear feedback of the FG beam is supposed elastoplastic based on the isotropic hardening (Ludwik hardening law). The calculation of the effective material properties is based on the Mori–Tanaka scheme as well as self-consistent approach of Suquet. Elastoplastic material properties are evaluated and supposed to change softly over the thickness of the beam. Numerical results obtained show the effect of material allocation on nonlinear responses. It was revealed that power index has a meaningful impact on the nonlinear reply of the FG cantilever subjected to end moment.

Rubber materials are increasingly used in automotive and aircraft manufacturers companies because their advantages in terms of corrosion resistance, vibration isolation and impact. These materials exhibit the proprieties of hyperelastic and viscoelastic materials where their mechanical proprieties depend on time variation, when subjected to mechanical load. The purpose of this work is to identify the hyper-viscoelastic parameters of polyurethane, natural and silicone rubber (Shore hardness 70 A and 90 A). These three materials are the most popular materials used as flexible punch or soft die in sheet metal forming process. The three specimens were prepared according to the ASTM D575-91 (2018). Standard compression and stress relaxation tests were performed to obtain experimental stress-strain curves of different rubber specimens. These curves were fitting with four model (Mooney Rivlin 1940, Neo-Hookean 1943, Ogden 1972, Yeoh 1993), available in ABAQUS to estimate the hyperelastic parameters of each model. These hyperelastic models are widely used in prediction the hyperelastic behavior of elastomeric material. For viscoelasticity, through the use of Prony series method, parameters are identified from fitting of relaxation curves. Ogden and Mooney Rivlin rubber models are well suited to reproduce experimental stress-strain curves of given rubber comparing to Neo Hooke and Yeoh models.

Papercrete is an ecological building material using paper waste as its main mixture component. Actually, the re-use of paper in the building sector has two very important impacts, namely the ecological and the economic impact. The idea of using paper waste in the construction industry has been around for 80 years. The papercrete is mainly intended for masonry of non load-bearing walls. The study presented in this paper has been developed in order to give a contribution to the knowledge on this material. In this context, we determine the mechanical properties of a specific recipe. Hence, a laboratory experimental study is carried out to determine its compressive and its flexural strengths. The experimental results show that the maximum compressive resistance for the compaction percentages 20%, 30% and 40% are 0.57 MPa, 1.14 MPa and 1.77 MPa, respectively. In addition, the results show that the maximum bending force are between 1095,98 N and 2332,51 N, for the same compaction percentages.

Applied voltage is one of the most influential deposition parameters for electrophoretic deposition processes as it can have a direct impact on the morphology of the film. XRD and SEM have been used to investigate the surface morphology and structure of TiO2 films, respectively. The corrosion behavior was studied by electrochemical impedance spectroscopy and potentiodynamic polarization in an aqueous solution of NaCl at 3.5 wt%. The results show that the film developed at 30 V had the lowest corrosion current density value of 0.211 µA and the highest polarization resistance value of −107.66 mV, this is explained by the decrease in micropore density.

Fluoropolymer’s coatings have been intensively employed to protect metallic components from corrosion and wear in several domains, mainly in food processing and pharmaceutical industries due to their good mechanical, chemical, and tribological properties. In this study, a fluoropolymer PFA was electrostatically deposited onto 304 stainless steel. Structural properties of the coatings were analyzed using the chemical microanalysis technique EDS in combination with scanning electron microscopy. Multi-pass scratch tests were performed at various applied loads to investigate the friction behavior and wear resistance of PFA coating. The corrosion properties were studied by electrochemical technique in 3.5% NaCL. Results showed that PFA coating exhibited a good adhesion to the substrate and an excellent surface smoothness with a low friction coefficient and high corrosion resistance. The investigation of tribological properties of the coating proved that the load affects both the coefficient of friction and wear rate. The PFA coating allowed improving wear and corrosion resistance.

The material behaviour constitutive equations play a central role in the engineering components analysis. Mainly for non-monotonic loading paths, different phenomena appear such as ratchetting, relaxation of mean stress and cyclic hardening, …, which induces an increased complexity in predicting of the mechanical responses of the material. In this study we focus on the analyses of cyclic behaviour of Aluminum alloy 2024 considering different hardening models and identification strategies. A Chaboche’s type combined isotropic and kinematic hardening model is used considering one or two kinematic hardenings. The material parameters are determined using cyclic (one cycle) and monotonic shear tests applied on Aluminum alloy 2024 sheet specimens. Numerical parametric study is done using different variants of the identified model. This study shows the importance of the hardening behaviour as well as the identification strategy in the prediction of stress strains responses in cyclic loadings.

An original simple shear test is developed to assess the mechanical behavior of anisotropic tubular material. Firstly, a shear specimen with a ring shape and a loading test device is developed and presented for performing the shear tests using a universal tensile machine. Electro-discharge Machine using wire cut technique is employed to extract the specimen without residual stress effects. Moreover, 3D Digital Image Correlation (DIC) using the package ARAMIS and GOM correlate software is utilized to probe the current full filed deformations in the center area of the shear section. Based on the homogeneity of the strain in the middle of the shear zone, and considering the previous obtained experimental r-values (r0) and (r90), the identification of the Lankford coefficient at (45°) direction using a simple identification technique is accomplished. Afterwards, the simulation of the simple shear test was conducted using the anisotropic Hill criteria in ABAQUS code. A good agreement between the experimental, theoretical and numerical shear curves is observed. Consequently, the proposed simple shear test is an interesting and reliable alternative to validate anisotropic model for tubular material.

Biomedical TiN coatings has been prepared by PVD cathodic arc evaporation on the Ti6Al4V alloy and 316L stainless steel. Films Morphological and Microstructural characterization were performed using MEB and mechanical properties were evaluated using nanoindentation test. Results show that both of TiN coatings have dense microstructure with more porosities for the TiN coatings deposited on Ti6AL4V (TiN/Ti6Al4V) as compared to that deposited on stainless steel (TiN/316L SS). Results of nanoindentation test showed a significant improvement of mechanical properties with the deposition of TiN thin film. Hardness and Young modulus of TiN coatings were approximately 4 times more than the uncoated material. But the TiN/Ti6Al4V exhibited the higher Hardness and Young Modulus than TiN/316L SS. The corrosion resistance of the film was investigated. Tafel-plot extrapolations curves revealed an important improvement in the corrosion potentials for the TiN coating whatever the substrate. In addition, for variable immersion times (0 days, 7 days and 15 days), the TiN/Ti6Al4V was more resistant to corrosive attack as compared to TiN/316L SS.

Self-heating method has been proposed as a faster alternative which can replace classic fatigue tests. In fact, this methodology has been investigated to evaluate the fatigue behavior of NiTi superelastic alloys at high number of cycles (HCF). The endurance limit of the material has been determined with a particular interest to various parameters linked to the environment and manufacturing process. However, a generalized use of these tests requires a justification of the link existing between the increase in stabilized temperature and the fatigue properties. The aim of this work is to carry out a self-heating model to justify the empirical analysis of the tests and to develop a model of deterministic fatigue with a single limit of endurance which be considered as a parameter of the material. Thus, in order to model self-heating phenomena, it was necessary to use a two-scale model (A macroscopic scale where the behavior remains globally elastic and a microscopic scale with a localized area showing the micro-transformation).

In previous works, a cumulative damage fatigue model was developed and called Damage Stress Model (DSM). This paper deals with a new formulation of the cumulative damage, that is based on DSM parameter, and will be investigated under several fatigue loadings. Indeed, the DSM, previously used, for uniaxial paths, is combined to multiaxial fatigue criteria: Robert (DSM + RB), Sines (DSM + SI) and Dang Van (DSM + DV). Moreover, we have studied the relevance of Miner’s rule for each loading paths.The relevance of the new model is examined using experimental biaxial tests. Using an aluminum alloy 6082-T6, the database includes different tests of biaxial fatigue. They are composed of one-level and cumulative loadings. The last one is composed of two level, three-level and two-level repeated loadings. Otherwise, to calculate the strain/stress field at the bulk of the specimen, a FE model is implemented in ABAQUS software. Finally, for each type of loading, a systematic comparison is realized between the experimental results and the predictions of the different approaches. Good agreement is highlighted, when experimental data is compared to the prediction of the models.

We report thermal aged effect on the cyclic mechanical dissipation in sulfur vulcanized Styrene-Butadiene Rubber (SBR43). An experimental multi-scale characterization carried out on thermally aged and un-aged specimens submitted to cyclic loading at constant strain rate 10–3 s−1 and imposed stretch ratio 1.56. The pre-aging on cyclic uniaxial response induces stiffening and increasing in hysteresis loops. X-ray computed tomography scanner analysis reveals that the local heterogeneities associated with a lower tomographic density are generate during fatigue. The mechanical energy dissipation, is the result of both recoverable and unrecoverable rearrangements in the rubber-filler material systems, i.e. viscoelastic and damage mechanisms. These experimental observations and FE simulation developed to explain the underlying inelastic fatigue mechanisms. A meso-scale observation demonstrates chains density variation using X-ray computed tomography (CT) Scanner. These experiments are compared with those from a predictive capability of a developed FE model.

The purpose of this research work is to investigate the fracture behavior of two carbon-black filled elastomers, NR and SBR, using the Finite Elements Method (FEM). For the Finite Element (FE) analysis, we have identified the hyperelastic potential of the no pre-cracked materials using equal biaxial and pure shear tests. Then, two FE models with pre-cracked specimens, using Ansys software, are established. The investigated parameters are obtained with specimens of Single Edge Notched in Tension (SENT) and Pure Shear (PS). Comparison of the obtained results is examined as a function of the J integral, of Rice’s theory, and the tearing energy T, introduced by Rivlin and Thomas. Through the numerical and analytical analysis, of fracture behavior in rubber materials NR and SBR, carried out on SENT and PS specimens, the mainly obtained conclusions will be: (i) the J-integral calculated far from the deformed crack tip is independent of the chosen contour; (ii) the J-integral for PS specimen, contrary to the SENT specimen, is not affected by the crack size; (iii) the difference of the values of the energy parameters J and T are related to the geometry effects.

Mechanical modeling of the Gas Metal Arc Welding (GMAW) joint and the Gas Tungsten Arc Welding (GTAW) joint were characterized utilizing tensile testing, microhardness testing and finite element (FEM) analysis. Experiments have been done on joints welded in two different directions; longitudinal welds (LW) and transversal welds (TW). The obtained results illustrate the effects of processes and directions of welding on the strength, hardness and brittleness of welded materials. This is suitable for the two welding processes GMAW and GTAW. The results give different characteristics between longitudinal and transverse welds. This is because the fusion zone is wider for the longitudinal weld than in the transverse weld. Good agreement is found between the material properties obtained from analysis by ABAQUS and experimental results. Furthermore, we develop a procedure for the identification of the behavior laws of GMA and GTA welding joints. We use an inverse optimization method based on tensile tests. The hardening behavior of the investigated steel welded joints is determined by Hollomon’s hardening law. The hardening model is completely defined once the coefficients (strength coefficient and strain hardening exponent) of the Hollomon model are determined. The validation of the proposed procedure is ensured by a comparison between numerical and experimental true stress/strain curves.

Flexoelectricity is defined as an electromechanical coupling between polarization and strain gradient which makes its effect largely dominant at the nanoscale. Using a decent electromechanical modelling of a piezoelectric flexoelectric nanobeam made of BaTiO3, we simulate the dynamic behaviour of the device as energy harvester when it is subjected to a base harmonic excitation representing mechanical vibrations from the environment. Considering the aspect ratio of the beam, the Timoshenko beam theory was used to model the energy harvesting system. A bidirectional aspect of the electric filed is considered and a nonlinear variation of the electric potential is adopted providing a more accurate modelling. Using the Hamilton’s principle and then the Galerkin procedure, the reduced-order model is established and solved for respectively the deflection of the nanobeam, the electric potential and the generated electrical voltage across a resistance load. The scale and aspect ratio are varied in order to analyse their effect on the dynamic response of the nanobeam and the generated electrical power. The results showed higher power density generation when the aspect ratio of the nanobeam is increased. The scale effect due to the nonlocal aspect of the formulation reduces the expected performance of the device.

The purpose of this work is to establish a rigorous scientific framework focusing on the feasibility and implementation of adhesive connections for offshore wind installations in marine environments. Recently, the development of offshore wind is expected on a commercial scale. The development of technology on commercial projects, however, requires innovative construction, which, in the context of mass production, can reduce production costs and lead times. Also, until now, concrete or steel structures have been used for maritime installations, including oil rigs, floating platforms. A need for new technology has arisen for existing and new offshore structures capable of connecting or replacing secondary structures, elements such as stairs, ramps, gates and windows that meet the needs of security, maintenance, sustainability and economical. In this context, adhesive seals are explored as an alternative and effective solution (Adams 2005). The use of FRP (fiber reinforced polymers) composite materials as structural elements instead of steel guarantees essential advantages such as weight saving, suitability for construction, maintenance, resistance to corrosion and high wear resistance (Baley et al. 2018).

This study describes an investigation of the load-deflection response of polymeric pipe material. Three point bending tests were performed on curved samples extracted directly from the studied pipes to evaluate their flexural properties, namely the flexural strength, the modulus, the strain to failure, the stress intensity factor, the fracture energy and the mode of failure. Effect of hydrothermal aging was investigated.From the main results, the average flexural stress-strain response of pipe material is characterized by a linear portion curve, followed by a non-linear deformation up to the ultimate failure stress. The presence of notch in pipe material affects also its mechanical properties. A significant decrease of flexural properties was observed for aged pipe samples. Thus, at the microscopic level, hydrothermal aging induces a change in the mode of failure, from ductile to brittle, as a function of temperature and aging time. As a result, it appears that the aging temperature has a significant effect on the severity of damage in materials tested after immersion. The combined effect of both hydrothermal aging and notch affects dramatically the flexural performance of pipe material. Consequently, the service life of pipe structures risks to be reduced.

In this book chapter, the divalent europium-activated alkaline-earth-metal pyrophosphate M2P2O7 (M = Ca, Sr, Ba) phosphors were effectively prepared via a conventional high temperature sintering reaction technique in a reducing atmosphere at 900 ℃. The synthesized materials have been systematically investigated using powder X-ray diffraction. The XRD pattern exhibit that Ca2P2O7 has a β-phase, Sr2P2O7 has an α-phase, Ba2P2O7 has a β-phase and the crystal structure of the M2P2O7 (M = Ca, Sr, Ba) hosts was unaffected with the introduction of Eu2+ ions. The nuclear magnetic resonance (NMR), infrared (IR) and Raman spectroscopy of β-Ca2P2O7, α-Sr2P2O7 and γ-Ba2P2O7 were reported and discussed in accordance with the structural peculiarities of Alkaline earth phosphates. The luminescence properties of Eu2+ in these phosphate materials were explored in detail in both vacuum ultraviolet (VUV) and ultraviolet (UV) regions. The emission spectra of β-Ca2P2O7: 1%Eu2+, α-Sr2P2O7: 1%Eu2+ and γ-Ba2P2O7:1%Eu2+ exhibit a large asymmetric band blue-emitting under the excitation of 320 nm, caused by the 4f65d1 → 4f7[8S7/2] transition of Eu2+ at room temperature. The excitation spectra display a broad and intense absorption in the 250–400 nm wavelengths region, which is matched with the blue emission band using for emitting n-UV (NUV) LED chips (360–400 nm). The above results indicate that diphosphate phosphors could be promising for generating blue-materials for white LED applications.

Additive manufacturing (AM) process are known by the capability to produce complex parts for various sorts of materials (polymers, ceramics, and metals). This family of processes is growing rapidly, and it is the origin of important research activity (dimensional deviations, capability prediction, biomedical applications, etc.). AM technologies provide greater freedom in the design and construction of complex shapes. Many researchers promoted that in AM this complexity is without an increase of the cost because there is no need for additional tooling. In traditional manufacturing processes such as injection molding, there is a direct relationship between geometric complexity and cost. But, the impact of geometric complexity on the production time and Cost of additive Manufacturing technology has not gained significant attention. In this work, we demonstrate the influence of geometric complexity on printing time and cost for additive manufacturing process and dispute the existing hypothesis that additive manufacturing techniques offer complexity with no extra cost. The Results of this paper demonstrates how geometric complexity raises the printing time and the manufacturing cost.

This study is performed on the effect of laser energy density in selective laser melting on 316L stainless steel surfaces characteristics. Process parameters such as scan velocity, power of laser beam and hatch distance were modified and their influence on porosity, surface quality and microstructure were evaluated. The, which depends on process parameters, seems to affect the material overlapping and consequently the porosity distribution generated after cooling. The porosities induced by selective melting process and dropping the component rigidity are minimized when the process is performed at high. It has been established that the surface microgeometric quality of manufactured parts, considered as the main drawback of the selective melting process, can be improved by controlling the volumetric energy density. An improvement of surface roughness was obtained by performing selective laser melting at high energy density. X-ray diffraction analysis were performed on parts produced under different conditions to evaluate the phases transformation resulting from thermal loading cycle applied to material during melting and cooling. The X-ray diffraction analysis reveal an initial pure austenitic stainless steel γ phase. For the manufactured parts the X-ray diffraction analysis show an appearance of a body-centered cubic ferrite phase δ in a microstructure dominated by columnar austenitic grains.

Currently, Additive Manufacturing (AM) is considered as a pioneer technology covering different engineering fields especially for the prototyping of complex mechanical parts and products. Usually, the AM time and cost constraints are the most considered parameters. However, the geometry precision aspect that affects the part quality should be considered with the above parameters. Thus, a new method is proposed to determine the optimal part orientation in the AM based on tolerancing. The material is superposed according to a particular orientation. An algorithm is developed to automate the slicing process. The deposed material model is used to compute the dimensional part features errors. The optimal part orientation is determined by comparing the above errors to tolerance specifications. The conclusion of this work is presented at the end.

Additive manufacturing consists of producing a metallic part by adding material layer by layer, in a single step without specific tooling or material waste. It offers several advantages for both research and industrial sectors. However, as a newly born technology, its main limit is the poor understanding of the process parameters effects on the parts quality. In fact, an improperly chosen parameter could generate defects such as lack of fusion, balling and keyholes during the selective laser melting process. Such defects have a direct relation to the melt pool geometry and can be predicted through several correlations from the literature. This study presents, through a series of numerical simulations of a single track, developed on Ansys Additive©, an investigation of the effect of the scan speed on the melt pool size and, thus, predicting the defect appearing at a fixed laser power. The evolution of the melt pool depth, width and length is depicted at constant laser speed and power. Moreover, the melt pool size is evaluated for a wide range of scan speeds. Results are validated with experimental values from the literature, and show that slow scan speeds generate keyholes and high speeds could generate balling defects.

Interstitial free steels (IF) are generally deep drawn in specific or complex form and manufactured by welding in the automotive industry. Mechanical properties of IF steel grades depend on microstructure (grain size, precipitation state, …) that can be changed by varying thermomechanical processing parameters. To characterize the deep drawing ability of steel sheets, among the mechanical properties the anisotropy coefficient and the strain hardening exponent are the ones that offer the best judgement of the drawability of a sheet metal. IF-type ultra-low carbon steels are commonly soldered by resistance spot welding (RSW) process. However, there is another popular method to join metals which is the laser welding. Its numerous advantages (high power density and welding rate, narrow heat affected zone, …) make it a key process in the automotive industry. In this manuscript, the laser beam welding (LBW) process of an interstitial free (IF) steel is investigated on the basis of numerical simulation. A knowledge of the mechanical properties and microstructure of the fusion zone and the heat affected zone is crucial to ensure the reliability of the process in order to prevent the failure of the welded structure.

Instead of conventional cooling products like oil-based coolants, liquid nitrogen is increasingly used in manufacturing processes for environmental considerations. The main purpose of this study is to examine the impact of deep rolling (DR) under cryogenic cooling on the surface integrity (grain size, phase changes, microhardness and residual stresses) of the AISI 304L metastable austenitic stainless steel. A set of experiments was performed to evaluate the effect of the DR tool depth of penetration (DoP) on the microstructural modifications of the treated material. The enhancement of surface integrity is mainly favored by DR conditions using high depth of penetration. Major findings of this work exhibit that, after cryogenic DR, surface microhardness increases by about 153% at a DoP of 0.16 mm. This is explained mainly by the grain refinement in the near-surface regions and also the formation of 62% volume fraction of strain-induced martensite. It was found that the DR-affected layer thickness increases with the increase of DoP and reaches up to 56 µm. Moreover, high compressive residual stress level of -1181 MPa is introduced at the surface. It was also concluded that the surface integrity modifications strongly depend on the cryogenic DR parameters and particularly the tool DoP, which is investigated in this study.

The incremental forming process (ISF) of sheet metal is a new manufacturing technology. It aims to fabricate mechanical products with complex geometries. This manufacturing process is well known for its capability to create custom-parts, prototypes and small to medium batches. Although its advantages, the single point incremental forming process (SPIF) presents some disadvantages. The major ones are a non-homogeneous thickness distribution and the geometrical inaccuracy. In the other hand, the use of bimetallic sheets gains a particular interest. There are several combinations of material to construct finally a bilayer composite sheet. In the current research paper, we investigate the formability analysis of a bilayer sheet composed of commercially pure titanium (Ti40) and low carbon steel (St-12). In fact, the considered responses are related to punch force monitoring and thickness distribution. Those mechanical and geometrical feedbacks were determined in regards to a variation of some process parameters. These input parameters are the initial thickness of bimetal composite blank, the step size increment and the layer’s sequence. The obtained results show the spifability (the formability under SPIF process) of a bimetallic sheet. It was demonstrated also that the layer arrangement plays an important role. Actually, it constituted the most influencing process parameter.

Hole-flanging process is widely being used in metal forming industry. Using elastomeric punch instead of the rigid one may enhance the quality of surface finish of the produced part. The objective of this paper is to investigate the sheet metal hole-flanging process with soft punch. This investigation is carried out via numerical and experimental analysis using polyurethane rubber with hemispherical end as flexible tool. Material of workpiece is the aluminum AA 1050-H14. Numerical simulation of the flexible hole-flanging process is performed with Abaqus/ Explicit. A Mooney-Rivlin model is adopted to predict the hyperelastic parameters of rubber punch with Shore hardness 70 A. The Coulomb friction law is adopted to model the contact between soft punch/part and part/rigid die. An experimental set up is developed to produce flanges. Numerical result presents a comparison between classical hole-flanging process with rigid tool and flexible process with rubber tool in term of variation of thickness distribution along the flange wall. Using soft tool with hemispherical end may improve the formability of aluminum flanged part compared to conventional forming technique. Numerical prediction of thickness distribution is assessed with the experimental measurement along the wall of the flanged part for validation purpose.

Additive manufacturing abilities of producing highly complex geometries has inspired mould designers to redesign plastic injection moulds. This facility has overcome all conventional manufacturing limitations for designing conformal cooling channels. Such ability ensures a better quality with a homogenized temperature distribution and decreased cooling time. However, in order to improve the cooling system efficiency, its geometry has to be optimized. Thus, multiple algorithms have been developed in order to achieve this goal. However, this depends on the first configuration which is realized according to the designer’s experience. This paper presents an optimization method for geometrical features of the first configuration. A cooling system of a plastic injection mould has been redesigned for additive manufacturing using the optimized dimensions. Thermal analyses of both moulds with conventional and conformal cooling systems have been carried out aiming at comparing the results in terms of cooling time.

Friction Stir Spot Welding (FSSW) is a highly complex joining process, coupling multiple physical phenomena. The thermo-mechanisms taking place during welding are very complex and still not thoroughly elucidated. The investigation of the mechanisms, involved in the weld zone, by experimental means is a very difficult task. Therefore the use of numerical simulation methods is highly required. Since 1996, various Finite Element modeling techniques have been developed for simulating friction stir welding (FSW). It is now well known that one of the most challenging issues in the FE-modeling is the large strains that take place during the process, inducing excessive mesh distortions and hindering convergent solutions. Arbitrary Lagrangian-Eulerian (ALE) and Coupled Eulerian-Lagrangian (CEL) methods are being implemented in FE codes to handle the difficulties in simulating the extremely large deformations. However, each one of these approaches has pros and cons. This paper aims to compare the accuracy and the efficiency of the aforementioned methods in the three dimensional numerical simulation of the FSSW of an AA6082-T6 aluminum alloy using ABAQUS®/Explicit. The computational cost of each model and the temperature distribution results were discussed. Based on these results, some useful guidelines for selecting the most suitable FSSW simulation technique were presented.

The current research work presents an optimization of injection molding parameters using Taguchi technique. The design of experiment (DOE) method of Taguchi is adopted to investigate the impact of the molding process factors on the yielding strength of PC/ABS blend and to set optimal combination factors reached a significant value of the mechanical property studied. Four molding factors such as material temperature (Tma), injection pressure (Pinj), holding time (th) and mold temperature (Tmo) were selected with three levels. Signal to noise (S/N) ratios were used for defining the optimal process combination parameters providing significant yielding strength. Results showed that 260 ℃ of a material temperature, 50 bar of injection pressure, 8 s of holding time and 60 ℃ of mold temperature are the optimum combination parameters. Moreover, the main injection molding process parameters which directly effect on the mechanical property of the injected PC/ABS blend are identified as material temperature, injection pressure, mold temperature and the holding time, respectively. The most effective factor is the injection pressure followed by material temperature and mold temperature. The injection pressure is the most significant parameter on the yielding strength of the injected PC/ABS parts. These worthy findings may have potential applications in automotive part industry.

In the industry, automated inspection is important for ensuring the high quality and allows acceleration of procedures for quality control of parts or mechanical assemblies. Although significant progress has been made in precision machining of complex surfaces, precision inspection of such surfaces remains a difficult problem. Thus the problem of the conformity of the parts of complex geometry is felt more and more. Motivated by the need to increase quality and reduce costs, and supported by the progress made in the field of it as well as the automation of production which in recent years has seen a considerable evolution in all these stages: from design to control through manufacturing. Due to, we used a 3D computer aided inspection technique on a physical gear using a coordinate measuring machine equipped with a “PC-DMIS” measurement and inspection software. Our work consists in developing a procedure for inspection for reproduction of gear profile by reconstruction of a circle involute gear from a cloud point’s measurement. In order to obtain a reliable result. In this works, we design the CAD-model of the part as accurately as possible (using a mathematical model) and matched with the 3D points cloud that represents the measurement that obtained from scanner. we compare the measurement cloud points from coordinate measurement machine with the mathematical model of construction by ICP (Iterative Closest Point) methods in order to obtain a conformed result and to show the impact of the dimensional inspection and geometric.

A comprehensive study on frequency responses of beams made of functionally graded materials (FGM) is presented in this work. A power-law distribution is used to describe the continuous variation of the volumes fractions of the material constituents. The beam is made metal and ceramic portions in its lower and upper surfaces, respectively with a gradually variation of its material properties. A high-order beam theory (HSBDT) is adopted to describe the kinematic of the beam where membrane, bending and shear effects are taken into account in the model. The equilibrium equations are derived from the variational principle in conjunction with the finite element procedure. The discretization of the displacement and strain components is achieved using a two nodes finite beam element with four degrees of freedom. The influence of the gradient index and the slenderness geometrical ratio is investigated via some numerical tests. A comparison of the natural frequencies is first carried out with results from the literature in order to outline the effectives and robustness of the proposed numerical model. Then, tabular and graphical results are presented with the emphasis of the effects of gradient index and length-to-thickness ratio on natural frequencies of FGM beams. It is shown that the material and geometrical parameters are essential factors that should be considered in the control of vibrations.

The aim of this work was to study the mechanical response of bonded of FRP rods into glued laminated timber beams. Experimental and numerical re-sults are compared. To allow for accurate description of the progressive damage into glulam timber, the Cohesive Zone Model (CZM) available in Abaqus was used. The obtained numerical results in terms of load-displacement and failure modes were compared to experimental tests. To evaluate the effect of rod-to-grain angle, many simulations with angle varying from 0° to 90° between fiber direction and bar axis were carried-out and discussed. The used parametric study showed clearly that the effect of this angle on the structural responses and the load-bearing capacities was significant. It was observed that the 3D nonlinear Finite Element Modelling (FEM) was able to simulate the global response of pull-out tests, the failure pattern during loading, and provides a new numerical approach.

This paper intends to present the buckling response of a nanocomposite plate under uniaxial in-plane loads where four types of carbon nanotubes reinforcements are included. Uniform and three functionally graded forms of carbon nanotubes, known as FGV; FGO and FGX are included in the model. These carbon nanotubes reinforcements are axially aligned in the x-direction and functionally graded in the z-direction. The material law behavior is described by a modified rule of mixture. The governing equations of motion are obtained using the finite element method based on the first-order shear deformation theory (FSDT). The shear part of the transverse shear strain deformations is taken into account via a quadratic function that able to describe the parabolic distribution of the transverse shear stresses. The zero condition of the transverse shear stresses at the lower and upper surfaces is also verified. The effects of different parameters like CNT volume fractions and forms, length-to-thickness ratio are studied and examined. It is reveled that the carbon nanotubes reinforcements can enhance the buckling response and the strength of the nanocomposite plates via a selected percentage and form of CNTs. For example, the FGX form with a volume fraction VCNT of 0.17 induces high critical buckling load and therefore the nanocomposite plate can sustain and resist to further applied loads.

This paper purposes to investigate the free vibration response of functionally graded shell structures by using an HOSDT-based solid-shell element. The considered solid-shell element is a higher order element based on the Higher Order Shear Deformation theory (HOSDT) the Enhanced Assumed Strain (EAS) method. Therefore, the presented finite solid-shell element assures the quadratic distribution of the shear strain throughout the thickness of structure and does not require a shear correction factors. To overcome the looking problems, the Assumed Natural Strain (ANS) and the Enhanced Assumed Strain (EAS) method are implemented in finite element formulation. The quality and precision of the current element are evaluated trough comparison between numerical findings obtained from finite element simulation and well-known results. Afterwards, the effects of some material and geometric parameters on the free vibration response of functionally graded shell structures are investigated.

The current investigation plans to examine thermal buckling of functionally graded material (FGM) plates with various power index (p) and under various rise of temperature, uniform and non-uniform by utilizing a HOSDT-based solid-shell element. By applying the Higher Order Shear Deformation Theory (HOSDT) in the incompatible strain part, the shear strains guarantee a quadratic appropriation across the thickness of plate. The presented solid-shell element doesn't need a shear correction factors. Furthermore, the finite element formulation is ready to beat the locking issues due the use of the Enhanced Assumed Strain (EAS) and Assumed Natural Strain (ANS) method. The exhibition of the grew full three-dimensional component is outlined through the correlations of our outcomes with those accessible in the literature. Then, the effects of some geometric and material parameters on the critical thermal buckling temperature of shell structures are investigated.

This study aims to examine the post-buckling comportment of carbon nanotube-reinforced composites (FG-CNTRC) characterized by various single-walled carbon nanotube (SWCNT) distributions by using a HOSDT-based solid-shell element. Our formulation is based on the Higher Order Shear Deformation Theory (HOSDT) applied to the incompatible strained part, thus ensuring that the shear strain distributed throughout the thickness of the shell. Therefore, the presented finite solid-shell element does not require a shear correction factors. Furthermore, the Assumed Natural Strain (ANS) and the Enhanced Assumed Strain (EAS) method are employed to overcome the different locking phenomena. By comparing our numerical results with those in the literature, we can exemplify the performance of the developed complete three-dimensional finite element. Then, the effects of some material parameters on the post-buckling behavior of shell structures are investigated.

Within this study, a numerical simulation of a water jet impacting a new aeronautical material target (Ti17 is) taking into account the Fluid-Structure Interaction (FSI) is modeled using a coupled SPH (Smoothed Particle Hydrodynamics)-FE (Finite Element) method. This numerical investigation aims to predict the impact of the fluid generated at high number of Reynolds. This is in particular at the first moment of impact for a set of target slopes regarding the jet axis. Studied configurations present slops starting from 0° to 35° by a step of 5°. Moreover, The variation of the initial velocities is also investigated where 3 different initial speeds are compared (12 m/s 80 m/s and 113 m/s). Numerical simulations are carried out under ABAQUS without taking in consideration the thermal behavior of the Impact problem.

We will discuss why we are interested in developing a brand new active suspension control approach for trucks that is supported by Deep Learning in this article. The mechanical suspension can be classified as passive, semi-active, or active. The desired output of active suspension control is dependent on the following factors: ride comfort, suspension travels, and road handling. The look of a cushy and efficient active mechanical system for the vehicle was an exciting and difficult problem for control engineering. MATLAB Toolbox was used to build the model. One approach for modelling a system is to use the laws of physics to describe the system and then use experimental data or provided knowledge about the system’s parameters. The aim of this study is to create a robust controller using Deep Learning that will boost the efficiency of the Heavy Truck’s nonlinear active mechanical system. This proposed Deep Learning (DMPSO) based Particle Swarm Optimization technique (PSO) for an efficient non-linear active mechanical system. The DMPSO approach is proposed to extend the results of driving comfort in lighter damping and longer suspension strokes.

The linear and geometrically nonlinear flexural vibration of simply supported simply supported free rectangular plates punctually supported at the free corner is investigated. First, the frequency parameters and mode shapes are calculated with the efficient Rayleigh-Ritz method (RRM). The RRM is used here to study the geometrically nonlinear vibrations occurring at large amplitudes of the plates examined. The test plate functions used are the products of beam functions with appropriate end conditions, i.e. simply supported-free beam functions, in each direction and the point support is modeled by a factious translational spring with a stiffness tending to infinity. The solutions obtained for various plate aspect ratios compare well with available solutions based on different approaches. The nonlinear vibrations have been then examined using spectral analysis and Hamilton’s principle to determine the backbone curves of SSFF plates with various aspect ratios via the so-called the second formulation in order to determine the fundamental nonlinear frequency parameter and its mode shape.

This paper presents a dynamic analysis of a prestressed stiffened circular cylindrical shell with internal distributed pressure using the continuous element method. These types of structures are more and more used in many industrial fields thanks to their lightweight constructions. The suggested approach is based on love’s first approximation model which takes into account the first order shear deformation theory. Natural frequencies are easily processed. Prestressed shell and circumferential stiffener were coupled to build the dynamic stiffness (DS) matrix to formulate the element. This dynamic stiffness matrix is described to study the free vibration of a prestressed ring stiffened cylindrical shell subjected to axisymmetric load. Since the DS method is based on a meshless approach, common encountered disadvantages of conventional methods, such as finite elements and boundaries elements methods can be overcome. The vibration analysis is performed with numerical examples carried out to validate the suggested model, using the frequency spectrum. Elements boundaries were subjected to equivalent loads and the response of the system was determined. Compared to the finite element method, the proposed element has many advantages such as the model size, the computing time, and the accuracy. The presented study can be extended to other types of stiffened cylinders with different, orientations and shapes of the stiffeners.

Rotor faults such as rotor unbalance, shaft cracks, coupling misalignment, etc., cause high vibration in rotating machinery and lead to fatigue failures. Amongst the variety of faults, the unbalanced rotor represents a serious problem and a key source of noise and important vibration in rotating machinery, e.g., the turbochargers, machine tools, ship, and aircraft turbine rotors. Due to the industrial requirements of high-speed rotating machines such as turbochargers, the current trend is to use active magnetic actuators (AMA), which employ a controllable electromagnetic force to control the rotating machines to reduce the unbalance vibration for safe and efficient operation. In this study, we introduce the AMA to the turbocharger-shaft system for reducing the rotating unbalance vibration due to the unbalance forces. The obtained outcomes through the adoption of the linearized expression of electromagnetic force and the presented example therein reveal a significant reduction of the amplitude unbalance response. Additionally, the stability limit speed (SLS) of the turbocharger-shaft system is increased by using the active vibration control. Therefore, the active vibration control represents an effective method for reducing the unbalanced vibrations and improving the stability limit speed of the turbocharger-shaft system, which leads to reliable operation at high-speed machining.

Smart materials are frequently used for vibration control of rotor bearing systems at critical speeds. This paper focuses on the control of vibration of a rotor-bearing system using bearings with magneto-rheological elastomers (MRE) supports which are a new class of smart materials whose dynamics properties such as the stiffness and the damping coefficient can be controlled by a magnetic field intensity. The magneto-rheological elastomer support is modelled using the four-parameter viscoelastic model. Based on the Rayleigh beam theory, the rotor bearing system is modelled using the finite element method including the gyroscopic effect and the shaft’s internal damping. The vibration amplitudes at the disk of the rotor bearing system with and without MRE supports is studied. Also, the effect of the application of the magnetic field intensity on the vibration amplitude and the first critical speed is investigated. Simulation results show the capability of the MRE supports in reducing the rotor vibration response at the disk in the steady-state condition and in shifting the first critical speed. It has also been shown that the application of a magnetic field intensity decreases the first critical speed while increasing the unbalance vibration response of the rotor bearing system at the resonant speed.

Over the last years, a new structural joining technic widespread all industrial domain. In effect, aiming to raise competitively by producing a more aesthetic and safe transport product, there is the development of the adhesive bonding technology. Due to it is several advantages, this technic has gained a primordial role both in the aerospace and automotive industries. This joining technology is capable of joint several materials (for example, glass, metals and composite materials). Additionally, its major benefit by comparison to traditional joining tools as welding is to lead to a continuous joint with homogeneous stress distribution. Furthermore, present transport industries and especially those for bus construction utilizes polyurethane adhesives for door’s aluminium alloys structures mounting. Nevertheless, the high solicitation of those special areas mains to cyclic fatigue problems. Thus, it is worthy to assess the aluminium bonded assemblies after fatigue loadings. For that reason, single-lap joint (SLJ) specimens, aluminium/ aluminium with one-component polyurethane adhesive, were made to handle the experimental process. Samples’ preparation procedure requires a surface roughness with an arithmetic average height Ra ≈ 0.6 µm and an adhesive thickness e = 1 mm. Cyclic fatigue tests were conducted and a low scatter was exhibited in the results.

The vibration study of rectangular plate FG porous is presented. The Hamilton theory is used to evaluate the equations of motion. The results and porosity variables of the graded exponent are studied.

Pyrolysis phenomenon of virgin and compressed woods has been investigated using the thermo-gravimetric curves at various higher heating rates. All species are spruce, and the densified wood samples were compressed until they lose 70% of their initial volume. Thermo-gravimetric analysis of the thermal decomposition of the wood particles has also been used for comparison to calculate the kinetic constants by using the least squares method. Experimental tests are well predicted by means a kinetic model available in the literature used four reactions for three fractions of wood particles. Although some studies have been conducted on pyrolysis of virgin wood particles, most of them were performed in lower heating values. Moreover, the important pyrolysis behavior of densified wood has received little attention. This study proposes a new approach to characterize the kinetics parameters of thermal decomposition of densified wood materials from Thermo-Gravimetric Analysis TGA at high temperatures. The kinetic parameters of four chemical reactions for the pyrolysis of dry wood particles in terms of activation energy and pre-exponential factor have been optimized and estimated using Arrhenius Law of the first-order. For all simulations, it was found that the predicted values are close to the measured values.

Due to its high energetic and environmental potential for heat and power generation, geothermal energy has gained extensive recognition as an alternative energy source to fossil fuel energy. However, the main problem that impedes their use and development is its high cost, especially drilling cost. In this article, we study the energetic and economic impacts of using geothermal water that flows naturally above the surface. Thus, we could benefit from the high energetic and environmental potential of geothermal energy while avoiding the drilling costs. A group of actions dealing with geothermal energy has been worked out on a 150 rooms (300 guests) hotel. Geothermal energy have been used for domestic hot water, sea water tank, interior and exterior pool and rooms heating and some technical loop have been designed to provide cold thermal water. Interesting results have been found. For a geothermal flows used in the project of 9.2 l/s, the induced energy saving would be of 284894 kg LPG. The annual cost saving of the project would be of 131044 TND. The overall annual LPG saving would be of about 71%. Eventually, this study can in part serve as a guideline for similar projects based on geothermal water use.

Environmental regulations concerning emission limitations from the use of fossil fuels in large combustion plants have stimulated interest in fluidized bed technologies. Indeed, these latter offer good options for the replacement of obsolete or polluting power plants. Turbulent fluidized bed has been the subject of considerable research and development. However, its description and characteristics still debated and unclear. This work describes heat and mass transfer mechanisms in a turbulent fluidized bed. The modeled system consists of an identical solid particles bed resting on a porous horizontal grid inside a column and a gas circulating through it at a uniform speed in the ascending direction. This study has been conducted using Ansys Fluent software based on EULER-EULER approach for multiphase flows modeling in a two-dimensional geometry and the K-ɛ approach for turbulence modeling. Different particle size and several functions and parameters were used. These functions and parameters were developed in C++ software and were implemented in Fluent software using the user defined function interface. Presented results demonstrate the influence of particle size, drag force and diffusion coefficient on heat transfer. It was found that particle surface temperature increases if particle size increases. These results appear to be consistent with previous works.

Drag and lift have major effects on the traction of a car. These phenomena of increased resistance lead to a relative increase in fuel consumption as well as an increase in gas emissions. The reduction of air resistance is one of the major areas of work in the automotive industry. It mainly requires handling or controlling the flow at the front and rear of the vehicles. The objective of this study is to minimize the aerodynamic coefficients of a passenger vehicle while varying the diffuser angle of the geometric design. Many reasons that influence drag and lift coefficient, such as flow separation, vortex, the effect of pressure coefficient, detailed velocity profile and pressure distribution plots around the vehicle body, are presented in this article. A prototype car is first prepared using Solid Works software, and then imported into ANSYS Fluent to allow a CFD digital study to evaluate its aerodynamic coefficients. The resolution of the Navier-Stockes equations is performed by the RANS numerical method with the k-ε closure model, and an unstructured fine mesh. By varying the angles of the rear diffusion angle, it can be observed that the rear diffuser angle 15° give the minimum drag coefficient CD.

Power laser machining is carried out according to a well-defined chronology: At the beginning of machining and during the brief start-up time, the system (laser, sample) is in a transient state, during this phase the conduction energy introduced by the laser is stored in the material. When the steady state is established the laser will interact with a volume containing the stored energy. This state is characterized by a machining period called laser material interaction time, during this time the additional energy will melt the heated volume. After a large number of iterations and at the end of machining, the stored energy is ejected with the molten material. The machining process is studied during the interaction time. This work shows that the interaction takes place between the laser and a volume preheated to the melting temperature. Absorbed energy will transmit an additional amount of heat to raise the melted volume temperature from the melting temperature to the evacuation temperature. Evacuation temperature is deducted from the energy stored in the molten volume. The carrier gas contributes to the loss of heat, by natural convection, during the evacuation time. The contribution of the convective and dissipated irradiated energy is then calculated.

Nowadays, electrical power is crucial for all human activities. Several methods are available to produce the electrical energy. Small-scale hydropower is designated as a clean and renewable energy resource that maintain the biodiversity of natural environment. Hydrokinetic rotors are broadly classified based on the rotation axis into two major categories, horizontal axis hydrokinetic rotors and vertical axis hydrokinetic rotors. Although horizontal axis hydrokinetic rotors remain to be commercially appropriate for large-scale hydropower generation, vertical axis hydrokinetic rotors work at low water velocity and are suitable for small-scale hydropower production. Among the vertical axis water turbines, the Darrieus rotors make use for a specific implementation because they are economic and independent to the water direction. Therefore, many investigations have been realized to boost its efficiency. In this work, experimental tests realized in an irrigation canal were performed with a 3D printed Darrieus rotor. With the intention of the performance betterment of the studied rotor, a novel blade shape namely V-shaped blade was tested numerically using the commercial software ANSYS FLUENT 17.0. The maximum value of the power coefficient of the Darrieus rotor reaches 0.17 using twisted blades. However, using V-shaped blades, the highest value of the power coefficient gets at 0.185.

Nowadays, world population is growing very rapidly and need for electricity is rising. Due to adverse influence of non-renewable fuels exploitation on public health, global electricity need for renewable energies is predicted to rise. Hydraulic energy has got a growing interest as one of the clean and renewable energies. Cross flow turbines are more preferred in small-scale hydropower generations. Due to rising cost incurred in experimental studies of the design process of cross flow turbines, researchers have adopted numerical methods mainly CFD (Computational Fluid Dynamics) technique. In fact, the CFD method allows to find out the hydrodynamic specifics as well as the fluid stream behavior near a water rotor as that are hardly evaluated based on experimental tests. Within this study, one of the most used CFD package, the Ansys Fluent 17.0 has been employed to resolve the transient incompressible Reynolds-averaged Navier-Stokes equations and to analyze the impact of the dimension of the rotating domain on the numerical study of a Lucid water rotor. The validation of the numerical model with previous investigations has been fulfilled to choose the adequate rotating domain size. The hydrodynamic specifics of the flow near a Lucid spherical rotor (LSR) have been analyzed and discussed.