Liste des documents
New Optimal Control of Permanent Magnet DC Motor for Photovoltaic Wire Feeder Systems
This article aims to improve the permanent magnet DC (PMDC) motor performance for photovoltaic (PV) wire-feeder systems (PVWFSs) of arc welding machines. The considered technique is designed by direct speed control based on optimal Fractional-order Fuzzy PID FO-Fuzzy-PID controller. The purpose is to ensure optimal control of wire feed speed reference to reduce torque ripples and hence, the performance of the WFS is improved. The dynamic reaction of the proposed solar PVWFS relies upon the scaling factors of FO-Fuzzy-PID controller, which are optimized by using teaching-learning algorithm based on Particle Swarm Optimization (PSO) method. The maximum power point tracking (MPPT) is achieved using an intelligent FO-Fuzzy-PID current controller based Perturb and Observe (P&O) MPPT algorithm. The PVWFS system incorporating the proposed method is tested and compared with the conventional PID control scheme under different weather conditions. The simulation of the proposed system by MATLAB\SIMULINK is carried out. The simulation results indicate the effectiveness of the considered control strategy in terms of the reduction in torque oscillations, optimizing electrical power and wire feed speed. Voir les détails
Mots clés : Solar photovoltaic (PV) module, wire feeder systems (WFSs), DC-DC buck converter, MPPT control, FO-Fuzzy PID controller, Particle Swarm Optimization (PSO) algorithm
New Optimal Control of Permanent Magnet DC Motor for Photovoltaic Wire FeederSystems
This article aims to improve the permanent magnet DC (PMDC) motor performance forphotovoltaic (PV) wire-feeder systems (PVWFSs) of arc welding machines. Theconsidered technique is designed by direct speed control based on optimal Fractional-orderFuzzy PID FO-Fuzzy-PID controller. The purpose is to ensure optimal control of wire feedspeed reference to reduce torque ripples and hence, the performance of the WFS isimproved. The dynamic reaction of the proposed solar PVWFS relies upon the scalingfactors of FO-Fuzzy-PID controller, which are optimized by using teaching-learningalgorithm based on Particle Swarm Optimization (PSO) method. The maximum powerpoint tracking (MPPT) is achieved using an intelligent FO-Fuzzy-PID current controllerbased Perturb and Observe (P&O) MPPT algorithm. The PVWFS system incorporatingthe proposed method is tested and compared with the conventional PID control schemeunder different weather conditions. The simulation of the proposed system byMATLAB\SIMULINK is carried out. The simulation results indicate the effectiveness ofthe considered control strategy in terms of the reduction in torque oscillations, optimizingelectrical power and wire feed speed. Voir les détails
Mots clés : Solar photovoltaic (PV) module, wire feeder systems (WFSs), DC-DC buck converter, MPPT control, FO-Fuzzy PID controller, Particle Swarm Optimization (PSO) algorithm
Maximum power extraction framework using robust fractional-order feedback linearization control and GM-CPSO for PMSG-based WECS
The most important issue in the use of wind energy conversion systems is to ensure maximum power extraction in terms of efficiency. Therefore, maximum power point tracking algorithms are as important as the maximum power point tracking controller. In this study, maximum power extraction frameworks operating the state-of-the-art optimization methods are presented for permanent magnet synchronous generator–based wind energy conversion system. These frameworks consist of a Gauss map–based chaotic particle swarm optimization and a hybrid maximum power point tracking approach that combines feedback linearization technique with fractional-order calculus. The feedback linearization control strategy can fully decouple and linearize the original state variables of the nonlinear system and thus provide an optimal controller crossing wide-range operating conditions. The objective is to maintain the tip speed ratio at its optimal value, which implies the use of a rotational speed loop. The method is based on the feedback linearization technique and the fractional control theory. Gauss map–based chaotic particle swarm optimization, which is a remarkable and recent optimization technique, is utilized to achieve optimum coefficients to efficiently ensure the maximum power point tracking operation in here. A simulation study is carried out on a 3-kW wind energy conversion system to show the effectiveness of the proposed control scheme. Voir les détails
Mots clés : Permanent Magnet Synchronous generator, Maximum Power Point Tracking, Feedback linearization control, fractional-order theory, Gauss map–based chaotic particle swarm optimization
On the corrosion behaviour of as-cast and heat-treated Mg-RE alloys in 0.9% NaCl solution
The microstructure and corrosion behaviour of as-cast and heat-treated Mg-1.44Ndand Mg-1.43Ce (wt.%) alloys in 0.9% NaCl (wt.%) solution were investigated usingelectrochemical tests, X-ray diffraction (XRD) and scanning electron microscopy,combined with energy-dispersive X-ray spectroscopy (SEM-EDS). The as-castmicrostructure of both alloys revealed the presence of second phases. Heat treatmentat 535°C for 6 h led to a more uniform distribution of the second phases in Mg-1.44Ndalloy and their dissolution along the grains boundaries in the Mg-1.43Ce alloy. As aresult, the corrosion resistance was improved in the heat-treated alloys. Accordingly,the corrosion resistance values for the heat-treated alloys were much higher than thoseof the as-cast alloys, indicating that the heat-treated alloys were less susceptible to thecorrosion. Also, the heat-treated Mg-1.43Ce alloy seems to have very good corrosionresistance (26890 Ω cm 2 ) compared to the Mg-1.44Nd alloy (6156 Ω·cm 2 ) bypreventing pitting corrosion along the grains boundaries. The corrosion product wasmade up mainly of magnesium hydroxide Mg(OH) 2 and magnesium oxide MgO andmore uniform corrosion morphology were found in the heat-treated alloys. Voir les détails
Mots clés : Corrosion resistance Heat treatment Magnesium alloy NaCl solution Rare earth
Stability, rigidity and thermal vacancies evolution in Fe-Cr-Mn alloys with C and N additions: DFT and Wagner-Schottky model investigations
The pseudo-potential Density Functional Theory (PP-DFT) combined with the statistical Wagner-Schottky model, are applied to study the Fe-xMn-(26-x)Cr-5Mo-3Cu-0.6C-0.7N austenitic alloys (x 1⁄4 6, 9, 12 and 15 wt%). The obtained results show that the rigidity and the thermal vacancy behavior isvery sensitive to the system composition. The overall system stability is found to be governed by thepresence of nitrogen. Both carbon and nitrogen favor the vacancy creation at T~1200K and prevent thethermal vacancy activation at T~1600K. Interestingly, beyond 1273K, carbon atom could migrate towardthe substitution sites while nitrogen atoms do not leave their favorable octahedral sites. Voir les détails
Mots clés : Fe-Cr-Mon Alloys;, Structural Stability;, Rigidity, Thermal Vacancies, DFT, Wagner-Schottky Model
Impact of rare-earth elements on the corrosion performance of binarymagnesium alloys
The corrosion behaviour of Mg-0.3Ce, Mg-0.41Dy, Mg-0.63Gd, Mg-1.44Nd and Mg-1.43La (wt.%) alloys in3.5 wt% NaCl solution was investigated using electrochemical tests. The as-cast microstructures of theMg-RE alloys were characterized by the presence of second phases (MgxCe, Mg41Dy5 , Mg12Gd, Mg12Nd, Mg41Nd5, Mg24Nd and Mg12La) with different volume fraction and distribution. Results show that thecorrosion mechanism was altered from uniform to localized corrosion mechanism depending on thespecific RE alloying elements. The corrosion resistance of the Mg-RE alloys is increasing in the followingorder: Mg-1.43La, Mg-1.44Nd, Mg-0.3Ce, Mg-0.63Gd and Mg-0.41Dy. Accordingly, the corrosionmorphology in the best resistant Mg-0.41Dy alloy and the worst Mg-1.43La alloy were observed andcompared after 2h and 24 h of immersion using SEM-EDS, XPS and XRD analysis. The formation of theDy 2 O 3 oxide prevents the Mg-0.41Dy alloy from pitting corrosion and lead to an excellent corrosionsurface even after 24 h of immersion. Meanwhile, the presence of a high fraction of the Mg 12 La phasealong the grains boundaries in the Mg-1.43La alloy causes severe pitting corrosion by acting as anodicphase. Voir les détails
Mots clés : corrosion resistance, Chloride ion, Magnesium Alloy, Rare earth element
Physical properties investigation of Fe1−xAlx(x≤50%-at) alloys using DFT and Wagner-Schottky model
Atomistic modeling based on the Density Functional Theory (DFT) is used to study thestructural, magnetic, electronic and mechanical properties of Fe1−xAlx alloys (x≤50%-at) with and without B, C and N additions over the selected range of Al atomic concentration. It is shownthat a singularity around x Al ∼ 40%-at is observed for the lattice parameters while the magneticmoment decreases uniformly without unexpected trend. The enthalpies of formation indicatethat the presence of B stabilizes the system for Al concentration in the range of 25%-at
Mots clés : iron aluminides, Magnetic Properties, elastics proprieties, Electronic structures, DFT calculations, thermal defects, Wagner-Schottky Model
Effect of aging temperature on the microstructure, local-mechanical properties and wear behavior of a UNS S32750 super-duplex stainless steel
In this paper, the effect of aging temperature on the microstructure, local-mechanical properties and wear behavior of a UNS S32750 super-duplex stainless steel is investigated. A massive preferential precipitation of σ phase and Cr2N is detected at the periphery of ferrite with an increase in their extent as aging temperature increases. Simultaneously, the δ phase decomposition is accentuated with temperature and reaches its maximum at 850°C.This behavior results in an enhancement in hardness and Young’s modulus accompanied by a higher plasticity ratio. The wear resistance of the aged samples is investigated in terms of friction coefficients and wear rates against two counterparts. The wear performance follows σ phase presence, the higher σ phase extent, the higher the wear resistance. It is found that the change in wear mechanisms in the 850°C aged samples from abrasive against AISI-304L counterpart to adhesive-oxidative against Al2O3 counterpart is responsible in the increase in wear resistance. Voir les détails
Mots clés : 2507 SDSS, Aging temperature, microstructure, precipitates, Nano-indentation, Wear resistance.
Microstructure and Tribological Behavior of In SituTiC-Ni(Si,Ti) Composites Elaborated from Ni and Ti3SiC2 Powders
Herein, we study the effect of Ti3SiC2 on the microstructures and tribological properties of an in situ TiC reinforced Ni(Si, Ti) composites elaborated from Ni and Ti3SiC2 MAX phase powders against steel(100Cr6). Pressureless sintering at 1080 C for 4 h of Ni and Ti3SiC2 powders was used to elaborate these composites with 10, 20 and 30 wt.% of Ti3SiC2. The microstructures of the composites were investigated by scanning electron microscopy (SEM), x-rays diffraction and Raman spectroscopy. Standard ball-on-disk friction wear tests under different applied loads were conducted on the composites surfaces at room temperature. For the three elaborated composites, Ti3SiC2 was totally decomposed and transformed to TiC phase, while the released Si and Ti atoms from Ti3SiC2 diffused into Ni matrix forming Ni(Si, Ti) solid solution. As compared with reference (Ni) sinter, the addition of 20 wt.% Ti3SiC2 in the Ni matrix improved the hardness by 250%. The addition of Ti3SiC2 particles also had a beneficial effect on the tribological performance of these composites against steel. The worn surfaces of the elaborated composites under all applied loads are characterized by the presence of a lubricious Fe3O4-aFe2O3 tribofilms. The effect of chemical compositions and different applied loads on the wear mechanisms of the three elaborated composites is discussed. Voir les détails
Mots clés : In situ composites, MAX phase, Microstructures, wear
Probabilistic analysis of corroded pipeline under localizedcorrosion defects based on the intelligent inspection tool
A methodology is developed in this paper to estimate the time-dependent reliability of a pipeline in Algeria, which is in exploitation from 1981 and with internal and external localized corrosiondefects detected in 2009. A probabilistic approach was applied to a pipeline made of API 5L X60steel for the long-distance transportation of natural gas (55 km), which crossing several geographical reliefs in different country areas. The analysis was carried out by taking into consideration the potential stochastic variables altering drastically the reliability of the pipeline, i.e.,dimensions of the localized corrosion defects, their locations, and distribution, and the corrosionrate. The correlations between the pipeline spatial corrosion defects distribution and their dimensions, obtained by using an intelligent inspection tool are used to analyze the actual inservice corrosion attack rate and for enhancement of the accuracy of the reliability assessment.The failure scenario was considered as the moment when the pipeline operating pressure exceedsthe failure pressure defined analytically in accordance with different commonly used standards.The assessment of the reliability index of the corroded pipeline subjected to internal pressure andthe failure probability was done. The detailed reliability analysis is carried out by using thesecond order reliability method (SORM) for the basic random variables with different probabilistic density within a nonlinear limit state function. The latter is based on the limit analysis ofthe failure pressure model for different standards and the numerical analysis using the finiteelement method and ANSYS software. Voir les détails
Mots clés : Reliability, corrosion, Inspection, FEM