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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. Source

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. Source

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. Source

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. Source

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. Source

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