Liste des documents
Engineering modeling of wear profiles in tooth flank of polyamidespur gears
The present paper is a contribution in developing an engineering model expressing the evolution of tooth flank wear in polyamide spur gears as a function of number of cycles. The method is based on first observing the behavior of wear on tooth flanks in real test conditions. Then progressive flank wear profiles are plotted in order to sort out the corresponding fitting curves together with the associated mathematical equations. The general engineering model controlling the evolution of wear profile is found of the form of quadratic equation where the variable is the circular thickness of a tooth at a given depth from the top land of the tooth. The respective parameters of the engineering wear equation are determined as a function of number of revolutions of the spur gear. A wear correction parameter kw is added in order to catch up the measuring errors when plotting the wear profile curves using the proposed engineering wear model for spur gears. The data are in good agreement with that obtained from experimental measurements. Voir les détails
Mots clés : polyamide, Spur gear, wear, Tooth flank, lubrication
Reliability estimation of pressurized API 5L X70 pipeline steel under longitudinal elliptical corrosion defect.
The probabilistic approach is the best way to give realistic answers for design and maintenance and it is considered as a powerful decision-making tool. In the present paper, assessment of the failure probability of corroded pipeline subjected to internal pressure is estimated by using the first order reliability method (FORM). Measurements of defect dimensions have been achieved changed into collected by using ultra sound inspection probe through a 75-km pipeline portion on one of the main Algerian high pressure gas transportation that has been in service for 30 years. The sensitivity analyses have been carried out on random variables to identify the importance of the parameters within the reliability mechanical model. The modified B31G code has been coupled as a mechanical model, with Rackwitz optimization algorithm by using PHIMECA Software. The limit state function resumes the difference between the pipeline burst pressure and the pipeline operating pressure. The aim of the present work is to make in evidence the competitive importance of pressure service, wall thickness and the defect depth with regards to defect length and to determine the influence of the coefficients of variation on the failure probability and the remaining life of the pipeline. A diagram based on the reliability index results is proposed to predict the pipeline degradation and it can be used as a decision tool for maintenance program. Voir les détails
Mots clés : corrosion, Failure probability, Coefficient of variation, Modified ASME B31G
Correlation between defect depth and defect length through a reliability index when evaluating of the remaining life of steel pipeline under corrosion and crack defects.
Despite the various engineering models existing for lifetime investigation of hydrocarbon steel pipelines under localized corrosion and crack defects there is still a lack of information about the correlation between the two main parameters characterizing the geometrical defect model, depth and length. So the aim of the present work is a contribution in evaluating the remaining life of the pipeline using reliability analysis in order to correlate the two parameters through one common parameter, the reliability index. As a first step, the investigation is carried out on four standard and well established engineering models; Irwin, SINTAP, ASME B31G and Modified ASME B31G methods, aiming to coordinate results given by each of the four models. The potential defect depth and length correlation through a reliability index can be used as a decision-making tool to give realistic answers for replacing and/or repairing a tube subjected to internal pressure and on which flaws of different depths and lengths have been detected from inspection of a pipeline after few years of service. Voir les détails
Mots clés : corrosion, Defect, Reliability, Correlation, Sensitivity
Complexity reduction of ultrasound sub-ultra-harmonic modeling by an input modified volterra approach
Contrast of echographic images has been highly improved by the injection of microbubbles, due to their nonlinear behavior. However, this contrast enhancement is limited by the nonlinear acoustic propagation in tissue. To overcome this drawback, sub and ultra-harmonic contrast imaging can be used, since only microbubbles can generate these components. Nonlinear modeling is a primordial step in the analysis of microbubble signals for sub and ultra-harmonic imaging. Nonlinear models like Volterra model has been applied in harmonic imaging to model harmonics optimally. However, it can model harmonics only. For sub and ultra-harmonic modeling, a multiple input single output (MISO) Volterra has been proposed. The aim of this study is to propose a simpler alternative for the modeling of sub and ultra-harmonics. We propose a modified single input single output (SMISO) Volterra model based on input demodulation. The model is tested using simulated and experimental signals. Results showed that sub and ultra-harmonics are modeled. The number of kernels is reduced to its half using SMISO model compared to MISO model. The relative mean square error between the simulated signal and the modeled signal with SMISO Volterra model is -15.8 dB and it is -60.7 dB for experimental signals. The computational time is reduced by a factor of 4 and 5 in simulated and experimental cases respectively. SMISO model can make easier the sub and ultra-harmonics modeling. Voir les détails
Mots clés : Non lineaire acoustics, contrast enhancement
Thermal and mechanical properties of bio-basedplasticizers mixtures on poly (vinyl chloride)
The use of mixtures of nontoxic and biodegradable plasticizers coming from natural resources is a good way to replaceconventional phthalates plasticizers. In this study, two secondary plasticizers of epoxidized sunflower oil (ESO)and epoxidized sunflower oil methyl ester (ESOME) were synthesized and have been used with two commerciallyavailable biobased plasticizers; isosorbide diesters (ISB) and acetyl tributyl citrate (ATBC) in order to produce flexiblePVC. Different mixtures of these plasticizers have been introduced in PVC formulations. Thermal, mechanical andmorphological properties have been studied by using discoloration, thermogravimetric analysis (TGA), differentialscanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile - strain and scanning electronmicroscopy (SEM). Studies have shown that PVC plasticization and stabilization were improved by addition ofplasticizers blends containing ISB, ATBC, ESO and ESOME. An increase in the content of ESO or ESOME improvedthermal and mechanical properties, whereas ESOME/ATBC formulations exhibited the best properties. Voir les détails
Mots clés : PVC, epoxidized sunflower oil, epoxidized sunflower oil methyl ester, isosorbide diesters, acetyl tributyl citrate.
Microstructure and microindentation of Ti3SiC2–Titaniumfiller brazedjoints by tungsten inert gas (TIG) process.
Herein we study the joining of Ti3SiC2- a MAX phase - with a Tifiller (Ti3SiC2/Ti-filler) using a TIG-brazingprocess. The microstructures of the interfaces were investigated by scanning electron microscopy and energydispersive spectrometry. When Ti3SiC2comes into contact with the molten Ti -filler during the TIG-brazingoperation, it starts decomposing into TiCxand a Si-rich liquid. Simultaneously, the molten Ti infiltrates into theTi3SiC2resulting in a 200 µm thick duplex region, comprised of TiCxand a Ti-rich phase with some dissolved Si.Both Si and C are found in the solidified Ti; the Si source is from the Si-rich liquid, while the presence of Cindicates that some of the C diffused into the Ti. Upon cooling, C- containing Ti- rich lamellae form the solidifiedTi. Microindentation results of the decomposed Ti3SiC2layer show an increase in hardness and a decrease inelastic modulus relative to T3SiC2. Notably, no cracks were observed Voir les détails
Mots clés : MAX Phases, Microstructures, Joining, hardness, Micro-indentation
Maximum Power Point Tracking of Wind Energy Conversion System Using Multi-objective grey wolf optimization of Fuzzy-Sliding Mode Controller
Ongoing electricity demand and the increasing growth of population have become necessary to provide alternative and clean sources of energy. Wind energy is one of the most important sustainable energies but the irregular characters of the primary source, which is characterized by a random wind speed variation, makes the process of control is difficult in order to maximize the power. This paper presents a multi objective grey wolf optimization (MOGWO) of fuzzy sliding mode controller in order to maximize the power captured by wind turbine; meanwhile, the mechanical loads are alleviated for variable speed wind energy conversion system (VS-WECS); firstly, Fuzzy logic theory based sliding mode control is developed by collecting the sliding surface data to reduce the chattering effect caused by the SMC, then the Grey Wolf Optimization is introduced to solve multi-objectives functions of WECS which are extracting the maximum power and alleviation the mechanical loads in order to find the optimal parameters of Fuzzy-Sliding mode controller to drive the conversion system to the optimal operating point. The obtained results are compared with those given by Sliding mode controller and Fuzzy-Sliding mode controller in which our proposed method can ensure a better dynamic behavior of the WECS. Voir les détails
Mots clés : Wind Energy Conversion System WECS, Maximum Power Point Tracking MPTT, Sliding mode control, fuzzy logic control, MO-GWO
Fuzzy-PSO controller design for maximum power point tracking in photovoltaic system
Photovoltaic power generation system becomes increasingly important, highly attractive as a clean and renewable energy sources, widely used today in many applications. Recently, researchers have strongly promoted the use of solar energy as a viable source of energy due to its advantages and which it can be integrated into local and regional power supplies. The P–V curve of photovoltaic system exhibits multiple peaks under various conditions of functioning and changes in meteorological conditions which reduces the effectiveness of conventional maximum power point tracking (MPPT) methods and the Particle swarm optimization (PSO) algorithm is considered to be highly efficient for the solution of complicated problems.In this paper, the application of this approach based MPPT algorithm for Photovoltaic power generation system operating under variable conditions is proposed to optimize and to design an intelligent controller comparing to conventional one. PSO Approaches is considered to select and generate an optimal duty cycle which varies with photovoltaic parameters in order to extract the maximum Power. Simulation results show that the proposed approach can track the maximum power point faster and can improve the performance of the system compared to the conventional method. Voir les détails
Mots clés : Particle Swarm Optimization (PSO), photovoltaic System, Boost, PWM, MPPT, FLC
Particle Swarm Optimization Backstepping Controller for a Grid-Connected PV/Wind Hybrid System.
The current paper investigates Backstepping controller using Particle Swarm Optimization for Photovoltaic "PV"/Wind hybrid system. The tested system was connected to the grid by three-phase inverter commissioned to address current depending on the grid parameters and still deliver its reactive power to zero. Backstepping control is a recursive methodology that uses Lyapunov function which can ensure the system stability. The best selection of Lyapunov function gains values should give a good result. In most of the literatures, the choice was based on the expertise of the studied system using hurwitzienne method considered as heuristic choice. The aim of this work is to propose an optimization using a powerful method commonly called Particle Swarm Optimization "PSO" able to calculate the gains values depending on the grid parameters by minimizing a selected criterion. The simulation results show that the PSO Backstepping controller gives good results shown in the current injected to grid with a small harmonic distortion despite climate change in the wind speed and the irradiation, which also shows the robustness of the applied control. Voir les détails
Mots clés : PV/Wind Grid-Connected, MPPT, Backstepping Controller, PSO, Matlab/Simulink
Reliability of the High Strength Pipeline Steelunder Corrosion Defect
The demand of energy based on hydrocarbons, such as gas and oil, requires construction of more and more newpipelines. Therefore, the assessment of the remaining life of these pipeline structures became increasingly importantto ensure the continuity of production and distribution operations. The reliability of these industrial facilities islargely conditioned by specific characteristics of each system, by its conditions of use and its environment. Generally,the causes of deterioration of hydrocarbon transportation pipelines are related to the presence of apparent defects(pinholes, cracks, corrosion, etc). This study is aimed to estimate the reliability of pipeline structures. The B31Gmechanical model of degradation was used to assess the probability of failure through dimensions of defects. Voir les détails
Mots clés : Reliability, pipeline, Defects, Mechanical Model