Time filter
Source Type

Rabiee A.,Shahrekord University | Khorramdel H.,Islamic Azad University at Dezful | Aghaei J.,Shiraz University of Technology
Renewable and Sustainable Energy Reviews | Year: 2013

Installing energy storage systems (ESS) for wind turbines power can bring many benefits to both power grids and wind power developers. Considering stochastic nature of wind, electric power generated by wind turbines is highly erratic and may affect both the power quality and the planning of power systems. ESS should play a key role in wind power applications by controlling wind power plants output and providing ancillary services to the power system, and therefore, enabling an increased penetration of wind power in the system. This article deals with the review of various storage systems for wind power applications. The main objectives of the article are the introduction of the operating principles, the presentation of the main characteristics of energy storage systems suitable for stationary applications, and the definition and discussion of potential ESS applications in wind power, according to an extensive literature review. © 2012 Elsevier Ltd. All rights reserved.

Pouranvari M.,Islamic Azad University at Dezful | Marashi S.P.H.,Amirkabir University of Technology
Science and Technology of Welding and Joining | Year: 2013

Spot welding, particularly resistance spot welding (RSW), is a critical joining process in automotive industry. The development of advanced high strength steels for applications in automotive industry is accompanied with a challenge to better understand the physical and mechanical metallurgy of these materials during RSW. The present paper critically reviews the fundamental understanding of structure-properties relationship in automotive steels resistance spot welds. The focus is on the metallurgical characteristics, hardness-microstructure correlation, interfacial to pullout failure mode transition and mechanical performance of steel resistance spot welds under quasi-static, fatigue and impact loading conditions. A brief review of friction stir spot welding, as an alternative to RSW, is also included. © 2013 Institute of Materials, Minerals and Mining.

Pouranvari M.,Islamic Azad University at Dezful | Marashi S.P.H.,Amirkabir University of Technology
Science and Technology of Welding and Joining | Year: 2010

Quasi-static tensile shear mechanical properties of resistance spot welds of three dual phase (DP) grades including DP600, DP780 and DP980 are investigated. Results showed that weld fusion zone size, failure mode and the strength/ductility of failure location are the main factors governing the peak load and the energy absorption of spot welds. Heat affected zone (HAZ) softening plays an important role in mechanical properties of DP steels with higher volume fraction of martensite (i.e. DP780 and DP980). It was shown that the peak load of the spot welds is not proportionally correlated to the tensile strength of the base metal. Pronounced HAZ softening in DP980 resulted in reducing its tendency to fail in interfacial failure mode in comparison to DP780. In addition, despite its lower base metal ductility, DP980 weld exhibits enhanced ductility and energy absorption than DP780 due to its pronounced HAZ softening. © 2010 Maney Publishing.

Ashiri R.,Isfahan University of Technology | Ashiri R.,Islamic Azad University at Dezful
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2014

In the present work, we have tried to study and develop the processing of amorphous BaTiO3 nanothin films, which have amorphous structure and nanometric thickness. It was seen that they exhibit enhanced optical responses. An improved method was used to prepare amorphous BaTiO3 nanothin films, which, compared to other approaches, is simple, cost-effective, and environmentally friendly. It was found that amorphous BaTiO3 films exhibit better optical transmittance in contrast to the similar nanocrystalline, polycrystalline, or thick films. This finding is due to the absence of grain boundaries, which have an important role in light scattering processes. AFM and SEM results indicate that the surface of the nanothin film is uniform, smooth, and amorphous. Moreover, the surface of the nanothin film exhibits a dense structure with no crack and voids. RMS roughness of the prepared nanothin film was quite small and equal to 0.7 nm. This value is very less than other reported RMS roughness values which were in the range of 5 to 11 nm. XRD results indicate that all of the prepared thin films in this work are amorphous, independent of number of dip-coated layers and preparation conditions. The work also aims to study and develop the processing of the amorphous BaTiO3 nanothin films deeply. The results showed that annealing temperature has a more pronounced effect on transmittance, thickness, and shift in the absorption edge of the thin films than annealing time. It was found that the viscosity of the sol has remarkable influence on the transmission spectrum and shift in the absorption edge of the films. The transparency of the films decreases with an increase in the viscosity and concentration of the sol. It was found that size of particle within the sol and rate of the sol-gel reactions have important roles on the transmittance of the films. © 2014 The Minerals, Metals & Materials Society and ASM International.

The great sensitivity of titanium alkoxides to hydrolysis makes their sol-gel transformation very fast and thus difficult to control. A method was proposed to alleviate this drawback. Preparation of highly transparent solutions and nanothin films is another objective of the present research. Employing nanoemulsion method and optimizing the processing conditions, a clear solution of well-dispersed nanosized particles was obtained. With the proposed process BaTiO3 precursor sols and nanothin films with enhanced optical transparency towards the visible were prepared. The optimal formulation of the sol consists of acetic acid, barium acetate, 2-propanol, TTIP and deionized water with 6:1:1:1:150 M ratios, respectively. It was found that the reduction of the temperature in the initial stage of mixing of precursors controls the size of the forming species and accordingly improves the stability and transparency of the sol. The results also showed that the applied modifications and optimizations significantly downsize the particles within the sol to the nanometric scale and accordingly result in a significant improvement in the optical response of the products. © 2014 Taylor & Francis.

Pouranvari M.,Islamic Azad University at Dezful
Canadian Metallurgical Quarterly | Year: 2012

The aim of this paper is to investigate and analyse the failure mode transition from interfacial to pullout in similar and dissimilar resistance spot welds of low carbon steel (LCS) and high strength low alloy (HSLA) steel during the tensile shear test. Correlations between critical fusion zone size required to ensure the pullout failure mode and weld hardness characteristics were established. It was found that HSLA/HSLA combination exhibits the highest tendency to fail in interfacial failure mode, while HSLA/LCS combination exhibited pullout failure mode at much smaller fusion zone size. Finally, peak load, ductility and energy absorption of similar and dissimilar combination were compared. © 2012 Canadian Institute of Mining, Metallurgy and Petroleum.

Pouranvari M.,Islamic Azad University at Dezful
Materials and Design | Year: 2010

Shielded metal arc welding process using nickel based filler metal was used to join grey cast iron. The effect of post weld heat treatment (PWHT) on the microstructure and hardness was studied. PWHT included heating up to 870°C, holding for 1. h at 870°C and then furnace cooling. By using nickel based filler metal, formation of hard brittle phase (e.g. carbides and martensite) in the fusion zone is prevented. Before PWHT, heat affected zone exhibited martensitic structure and partially melted zone exhibited white cast iron structure plus martensite. Applied PWHT resulted in the dissolution of martensite in heat affected zone and graphitization and in turn the reduction of partially melted zone hardness. Results showed that welding of grey cast iron with nickel based filler metal and applying PWHT can serve as a solution for cast iron welding problems. © 2010 Elsevier Ltd.

BaTiO3 nanopowders were prepared at lower temperature and in shorter time span through a newly developed process. To reach an in-detail understanding of mechanism of the process, thermal analysis were performed using DTA/TGA and FT-IR techniques aided by in-depth discussions. The results indicated that thermal evolution of sol-gel-powder transformation consists of following steps: the vaporization of volatile organic solvents, the deformation of gel structure and pyrolysis of the Ba-Ti organic precursors, the decomposition of BaCO3 into BaO and CO2, reaction of resulted BaO with TiO2 to form BaTiO3. The results also elucidated the reaction pattern and formation mechanism of BaTiO3 nanopowders from gel-derived precursor. © 2013 Elsevier B.V.

Nedaei M.,Islamic Azad University at Dezful
International Journal of Renewable Energy Research | Year: 2012

This study presents wind energy potential assessment in Chalus county in Iran. Wind data are collected 14 months from 2006 to 2007 in the time interval of 10 minutes at heights of 30 and 40 meters. The values of k (dimensionless Weibull shape parameter) at 40 m height were ranged from 1 to 1.34 with a mean value of 1.14, whereas the values of c (Weibull scale parameter) were ranged from 1.85 to 3.43 with a mean value of 2.83. At 40 m height, monthly mean wind speeds during 14 months, were ranged from 1.75 to 3.42 m/s with annual mean wind speed of 2.69 m/s. Possibility of monthly mean wind speeds of over 4 m/s has not been observed for both 40 m and 30 m. Feasibility of installing a small wind turbine was studied. The type of the wind turbine is "Bergey XL.1" with cut-in wind speed of 2.5 m/s. In 7 successive months of the year, April, May, Jun, July, August, September and October, especially in August, the mean wind speed is between 2.5 m/s and 3.3 m/s (for both 30 m and 40 m) which seems to be adequate for installing this wind turbine. However because of low energy production of the wind turbine (493 kWh/yr), low capacity factor (5.6 %) and having low monthly mean wind speeds (less than 4 m/s), it is not economical to install this small wind turbine in this site. According to the statistics it was concluded that the wind potential of studied site is not capable for using wind energy in order to produce electricity but is probably capable for mechanical applications such as water pumping.

The paper investigates the failure mode transition from interfacial to pullout in similar and dissimilar combinations of DP600 dual phase steel and low carbon steel (LCS) under tensile-shear (TS) and cross-tension (CT) loading conditions. In both CT and TS loading conditions, a transition in the failure mode from interfacial to pullout was observed with increasing fusion zone size beyond a critical value (D C). The tendency to fail in interfacial mode during the CT loading was increased in the order of LCS/LCS, DP600/LCS and DP600/DP600. It was shown that interfacial to pullout failure mode transition during the CT test is governed by the fracture toughness of the fusion zone and strength of the pullout failure location (i.e. heat affected zone). It was shown that increasing carbon equivalent of the fusion zone promoted interfacial failure mode in CT loading condition. The high carbon equivalent of DP600 steel led to formation of hard and brittle martensite, which in turn promotes crack propagation through fusion zone. In DP600/LCS combination, decreased carbon equivalent and fusion zone hardness through dilution with the LCS promotes pullout failure at smaller weld sizes. D C during the TS loading is increased in the order of DP600/LCS, LCS/LCS and DP600/DP600. No correlation between fusion zone carbon equivalent and the tendency to fail in IF mode during TS loading was found. Failure mode transition during the TS loading is controlled by hardness of fusion zone and stiffness of the joint. The lowest D C for DP600/LCS is a function of its high fusion zone hardness (in comparison to LCS/LCS combination) and its low stiffness (in comparison to DP600/DP600 combination). © 2012 Elsevier B.V.

Loading Islamic Azad University at Dezful collaborators
Loading Islamic Azad University at Dezful collaborators