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S. A. Hashemi,A. Fattahi,G. A. Sheikhzadeh,N. Hajialigol,M. Nikfar 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.11
Axisymmetric sudden-expansion geometry of a co-flowing methane-air diffusion flame is considered to investigate the effect of air inlet conditions on NOx formation, flow field and temperature distribution using the k-ε turbulence and β-PDF combustion model. The predicted results are in acceptable agreement with the published experimental and numerical data. The obtained results show that increasing air turbulence intensity results in considerable decrease in NO formation. Increasing the inlet angle of the air causes the NO formation to decrease due to raising vorticity strength. As a new index, the mass-averaged integral of vorticity magnitude is introduced to investigate the effect of altering inlet angle of the air on the flow field.
Analytical study on elastic transition in short-fiber composites for plane strain case
A. M. Fattahi,M. Mondali 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.11
An analytical approach for short-fiber-reinforced composites is developed for three-dimensional (3D) elastic stress field distribution subjected to an applied axial load. Two sets of exact displacement solutions for matrix and fiber, which are respectively called far-field and transient solutions, are derived based on the theory of elasticity. The superposition state of these solutions are then used to obtain the analytical expressions for the 3D stress field components over the entire composite system, including the fiber end region, through the adding imaginary fiber technique. The fiber/matrix 3D stress field components fully satisfy the equilibrium and compatibility conditions in the theory of elasticity. The stress field components also satisfy the overall boundary, interface continuity, and axial force equilibrium conditions. The analytical results obtained are then validated by finite element method modeling.
A. M. Fattahi,E. Moaddab,N. Bibishahrbanoei 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5
An analytical model has been performed to analyze the stress transfer in platelet reinforced composite subjected to both tensile loadingand residual thermal stresses. Two sets of the matrix/platelet displacement solutions, which were called respectively as the far-field solutionand the transient solution, were exactly derived based on the theory of elasticity. These two sets of the displacement solutions werethen superposed to obtain simplified analytical expressions for the matrix/platelet stress field components. The main difference with theprevious works here were that the thermal residual stresses were considered in this article. The analytical results obtained here are thenvalidated by the FEM modeling. Interestingly, good agreements are found between the analytical and numerical predictions. Anothersuperiority of the proposed analytical model was in its capability of solving problems with platelet/matrix debonding defect.
A.M. Fattahi,Babak Safaei,Elham Moaddab,Zahra Pezeshki Techno-Press 2023 Advances in nano research Vol.14 No.1
In this work, the effect of the addition of Aerosil 200, an insulating resin applied in many industries, on the water absorption of cement plast mixture has been experimentally evaluated. First, the preparation stages of cement plast mixture was evaluated based on corresponding standards and then, the effect of the addition of Aerosil 200 nanoparticles (NPs) to cement plast mixtures with sand weight percentage range of 0-0.1% on the variation of water absorption properties was evaluated based on National Standard Institution of Iran 20185 for Concrete Flooring Blocks - Requirements and Test Procedures. Based on the obtained results, it could be found that excessive addition of NPs did not affect the physical properties of the final product. Water absorption percentage was increased in the weight percentage of cement. By the increase of the amount of Aerosil 200 NPs in the prepared cement plast mixture, the percentage of water absorption in weight percentage of sand was decreased. Cement plast with NPs presented significantly lower water absorption than that without NPs.
THE REPEATED ENVELOPING SEMIGROUP COMPACTIFICATIONS
FATTAHI, A,MILNES, P 호남수학회 2002 한국수학학술지 Vol.24 No.1
This note consists of some efficient examples to support the notion of enveloping semigroup campactigication and also employ this notion to obtain the universal reductive compactification
A. M. Fattahi,Babak Safaei,Zhaoye Qin,Fulei Chu 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.2
The effect of nanoparticle volume fraction on the elastic properties of a polymer-based nanocomposite was experimentally investigated and the obtained results were compared with various existing theoretical models. The nanocomposite was consisted of high density polyethylene (HDPE) as polymeric matrix and 0, 0.5, 1 and 1.5 wt.% multi walled carbon nanotubes (MWCNTs) prepared using twin screw extruder and injection molding technique. Nanocomposite samples were molded in injection apparatus according to ASTM-D638 standard. Therefore, in addition to morphological investigations of the samples, tensile tests at ambient temperature were performed on each sample and stress-strain plots, elastic moduli, Poisson’s ratios, and strain energies of volume units were extracted from primary strain test results. Tensile test results demonstrated that 1 wt.% nanoparticles presented the best reinforcement behavior in HDPE-MWCNT nanocomposites. Due to the agglomeration of nanoparticles at above 1 wt.%, Young’s modulus, yielding stress, fracture stress, and fracture energy were decreased and Poisson’s ratio and failure strain were increased.
The application of nonlocal elasticity to determine vibrational behavior of FG nanoplates
A. M. Fattahi,Babak Safaei,Elham Moaddab 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.2
Nonlocal elasticity and Reddy plant theory are used to study the vibration response of functionally graded (FG) nanoplates resting on two parameters elastic medium called Pasternak foundation. Nonlocal higher order theory accounts for the effects of both scale and the effect of transverse shear deformation, which becomes significant where stocky and short nanoplates are concerned. It is assumed that the properties of FG nanoplate follow a power law through the thickness. In addition, Poisson’s ratio is assumed to be constant in this model. Both Winkler-type and Pasternak-type foundation models are employed to simulate the interaction of nanoplate with surrounding elastic medium. Using Hamilton’s principle, size-dependent governing differential equations of motion and corresponding boundary conditions are derived. A differential quadrature approach is being utilized to discretize the model and obtain numerical solutions for various boundary conditions. The model is validated by comparing the results with other published results.
THE REPEATED ENVELOPING SEMIGROUP COMPACTIFICATIONS
FATTAHI, A.,MILNES, P. The Honam Mathematical Society 2002 호남수학학술지 Vol.24 No.1
This note consists of some efficient examples to support the notion of enveloping semigroup compactification and also employ this notion to obtain the universal reductive compactification.
Investigation of a flame holder geometry effect on flame structure in non-premixed combustion
S. A. Hashemi,N. Hajialigol,A. Fattahi,K. Mazaheri,R. Heydari 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.11
In this paper the effect of flame holder geometry on flame structure is studied. The obtained numerical results using realizable k-ε and β-PDF models show a good agreement with experimental data. The results show that increasing in flame holder length decreases flame length and increases flame temperature. Additionally, it is observed that flame lengths decrease by increasing in flame holder radius and increase for larger radii. Furthermore in various radii, the flame temperature is higher for smaller flame lengths. It was found that behavior of flame structure is mainly affected by the mass flow rate of hot gases that come near the reactant by the recirculation zone.