Showing 5 results for Emadi
J. Emadi,
Volume 24, Issue 1 (7-2005)
Abstract
Being economical and performing well under cyclic loads, steel sections filled with concrete have been widely used in structural buildings. Extensive studies and experiments have been conducted to investigate the influence of different parameters and loadings on the behavior of these structural components. Based on the data available from previous experiments and studies, this paper discusses the behavior of composite columns. The results of 3D-non-linear finite element analysis of thin-walled steel sections filled with concrete are presented. Lastly, comparisons are made between results from finite element analysis and experimental data available about the specimens. Using a trial and error method, the finite element model was calibrated and was used to evaluate the capacity of specimens that were not tested in the laboratory. The capacities of the sections were calculated
based on the LRFD design method. The results are compared to evaluate the accuracy of the proposed method. Because of the increase in the use of high strength materials in structures, the effects of increase in concrete and steel strengths on the behavior of composite columns are discussed in this paper. Also the effects that the change in the thickness of the steel shell may have on the behavior of composite columns are argued.
V. Omrani Dizajyekan, R. Emadi , H. Salami Jazi ,
Volume 33, Issue 1 (Journal of Advanced Materials- Summer 2014)
Abstract
Employing direct and alternative electric currents at the time of casting and solidification modified grains of Al and Si. The highest wear resistance was obtained in the direct current, and for alternative current the wear resistance corresponded to the electric current. The change of polarity in the pure Al did not influence the wear resistance, but for the Al-Si alloy the highest wear resistance was obtained when the mold was connected to the positive and the molten metal to the negative pole. Direct current used in the Al-Si alloy brought about three different microstructures including the stretched clusters of Si in the electrons' direction near the negative pole, fine clusters of Si in the intermediate zones that surrounded the oval shape of α-Al, and broken Si clusters near the positive pole.
M. Rezazadeh, R. Emadi, A. Saatchi, A. Ghasemi, M. Rezaeinia,
Volume 35, Issue 3 (Journal of Advanced Materials-Fall 2016)
Abstract
Simultaneous application of mechanical pressure and electrical charge on powder samples in spark plasma sintering process, has resulted in a sample with a density close to the theory. In the present study, a thermal-electrical-mechanical coupled finite element model of spark plasma sintering system using multi-objective optimization algorithm is proposed to optimize the mold variable. The simulation performed for Si3N4-SiO2 (1:1 mol) specimen has good agreement with the experimental results. Multi-objective genetic algorithms was used for optimization of mold design in order to maximize the temperature of sample core and minimize the mises stress in the mold. The results show that the optimized dimensions cause 8% increase in sample temperature and about 18% decrease in temperature difference between mold surface and sample core. This leads to better uniformity in the porosity distribution of final sample.
S. Sadeghzade, R. Emadi, Sh. Labbaf,
Volume 37, Issue 1 (Journal of Advanced Materials-Spring 2018)
Abstract
In the recent three decades, Ca-Si-based ceramics have received great attention as an appropriate candidate for tissue engineering applications due to their remarkable bioactivity, biocompatibility, and good bone formation ability. Hardystonite is currently recognized as a bioactive and biocompatible bio-ceramic material for a range of medical applications. In the present study, for the first time, hardystonite powder and 3D hardystonite scaffold with interconnected porosity were produced using mechanical alloying synthesis and the space holder method, respectively. It was found that pure nano-crystalline hardystonite powder formation occurred following 10 h of milling and subsequent sintering at 800 C° for 3 h. The measured crystallite size of particles and the hardystonite scaffold was found to be 28 ± 2 and 79 ± 1 nm, respectively. The results also showed that nanostructured hardystonite scaffolds with the compressive strength and modulus of 0.35 ± 0.02 and 10.49 ± 0.21 MPa, the porosity of 81 ± 1% , and pores size range of 200–500 μm were successfully synthesized after sintering at 1250 °C for 3 h. During the sintering process, NaCl (80wt%, 300-420 µm), as the spacer agent, gradually evaporated from the system,producing porosity in the scaffold. Simulated body fluid (SBF) was used to evaluate the apatite formation ability of the scaffolds. The results showed that the formation of an apatite layer on the scaffold surface could be considered as a bioactivity criterion.
F. Soleimani, R. Emadi,
Volume 38, Issue 3 (Journal of Advanced Materials-Fall 2019)
Abstract
In this study, polycaprolactone/chitosan/1% baghdadite composite coating was applied on anodized AZ91 alloy to improve the corrosion rate of AZ91 alloy in simulated body fluid (SBF) solution for long immersion times, control its degradability and enhance its bioactivity. By applying the composite coating and after seven days of immersion in a phosphate buffer solution, the corrosion rate decreased from 0.21 mg/h.cm2 (for AZ91 sample) to 0.1 mg/h.cm2 (for anodized AZ91 sample). Formation of apatite layer on the surface of specimens is considered a criterion for bioactivity. In order to evaluate the ability of specimens to get covered by an apatite, the SBF test was used. Application of the composite coating yielded the highest ability for apatite formation, controlled release of ions, and the lowest corrosion rate in the SBF so that it could be considered a good choice for bone implants.
