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Showing 4 results for Tavakoli
A Second Order Accurate Method in Simulation of Underwater Explosion
A.r. Pishevar Esfahani and M.r.tavakoli Nejad,
Volume 23, Issue 2 (1-2005)
Abstract
In this paper, a numerical scheme is proposed for the multi-fluid compressible flows. This method is applied to the problem of underwater explosion. The proposed scheme is basically the extension of Godunov method in gas dynamic problems to the multifluid environments and is second-order accurate in space. In this method, also, the problem of artificial mixing of two different phases on Eulerian grids is prevented by a front tracking technique. The numerical results of this study are in very good agreement with previous numerical and exprimental results
Effect of Aluminium Injection into the Crystalizator on Type, Composition and Activity of Inclusions in Low Carbon Steel
H. Tavakoli, M. Soltanieh, H. Aghajani, M. Jafarpour,
Volume 34, Issue 1 (Journal of Advanced Materials-Spring 2015)
Abstract

This study was intended to investigate the effect of injection of aluminium into the crystallizator on type, composition and activity of inclusions in low carbon steel grade USD7. The steel is made in Zob-e-Ahan Isfahan factory and its porosities and inclusions results in the problem of rupturing during rolling process. To improve the quality of this steel, 2.4 mm diameter pure aluminum wires were injected in to the crystallizator at the rate of 2, 4, 6 or 8 m/min in certain periods and then sampling was done. The results indicated that much of the added aluminum changed to aluminum oxide slag, and the remaining part altered the chemical composition of the inclusions. Increased aluminum caused an increase in the activity of alumina and reduction in the activity of other oxides in the slag and existing inclusions in the melt. By increasing Al2O3 activity from 0.313 to 0.649, the Al2O3 formation and oxygen exclusion probability increased in the system. Scanning electron microscopy showed that without aluminium injection, most of inclusions were FeO-MnO type placed around existing porosities in the ingot. The optimum rate of aluminum injection was found to be 4 m/min.


Preparation and Characterization of PDMS-SiO2-CuO Nanocomposite Coating on Stainless Steel and Its Super-hydrophobicity Property
Sh. Tavakoli Dehaghi, S. Darvishi, Sh. Nemati, M. Kharaziha,
Volume 37, Issue 3 (Journal of Advanced Materials-Fall 2018)
Abstract
Abstract: With the advances in the development of biomaterials for tissue replacement, the attention of scientists has been focused on the improvement of clinical implant properties. In this regard, despite the appropriate properties of the stainless steel, the application of stainless steel as implants has been limited due to the weak corrosion resistivity. The purpose of this paper was preparation and characterization of hydrophobic polydimethylsiloxane (PDMS)-SiO2-CuO nanocomposite coating on the 316L stainless steel surface. The 316L stainless steel was coated by SiO2 nanoparticles (20 wt. %), CuO nanoparticles (0.5, 1 and 2 wt. %) and biocompatible PDMS. In this research, x-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to characterize the coating. Moreover, the roughness and water contact angle of the coatings consisting of various amounts of CuO nanopowder were estimated. Finally, the effects of various amounts of the CuO nanopowder on the corrosion resistivity of nanocomposite coatings were investigated. XRD patterns confirmed the presence of crystalline CuO nanoparticles on the substrate. Due to the non-crystalline nature of silica nanoparticles and the semi-crystalline PDMS polymer, no peak confirming the presence of these phases was detected on the XRD pattern of the nanocomposite coating. SEM images showed the formation of a lotus leaf-like layer on the surface of the nanocomposite coating containing 1 and 2 wt. % CuO. Moreover, water contact angle evolution revealed that while contact angle was 81 degree without CuO nanoparticles, it was enhanced to 146 degree in the presence of 1 wt. % CuO. Moreover, the corrosion study showed the nanocomposite containing 2 wt.% CuO had the best corrosion resistance, the corrosion current density of 2.1E-7 A.cm-2, and the corrosion potential of 0.22 V.

The Effect of Temperature on the Fracture Surface Morphology and Ductility of La55Al25Ni5Cu10Co5 BMG
M. T. Asadi Khanouki, R. Tavakoli , H. Aashuri,
Volume 38, Issue 2 (Journal of Advanced Materials-Summer 2019)
Abstract
In this research, the effect of temperature on the mean size of fracture surface features, as well as the relation between fracture surface morphologies and ductility of a La-based BMG as a relatively brittle alloy, was systematically investigated. After producing the alloy, three-point bending experiments, over a wide range of temperatures, were conducted on the samples; then the fracture surfaces were analyzed using scanning electron microscopy. The results demonstrated that the width of stable crack growth region (ΔW) was increased upon ductility (δp). Conversely, the mean size of the features on both stable (Ds) and fast (Df) crack growth regions and also, shear offset width (ΔL) were found to decrease with increasing ductility. In this case, the shear band instability was reduced, and the plastic strain could be more homogeneously distributed on the shear bands. The similarity of ΔL and Ds values suggested that the formation of vein pattern was caused by steak-slip behavior and multiple-step sliding inside the shear band through the fluid meniscus instability mechanism. Furthermore, the results obtained from correlation between ductility and fracture surface morphologies in the BMG indicated that the size of features was reduced with increasing ductility.

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