Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201Numerical Analysis of Critical Heat Flux Phenomenon in a Nuclear Power Plant Core Channel in the Presence of Mixing Vanes119130274610.22060/mej.2017.12928.5472ENA.RabieeSchool of Mechanical Engineering, Shiraz University, Shiraz, IranL.MoradiSchool of Mechanical Engineering, Shiraz University, Shiraz, IranA.AtfSchool of Mechanical Engineering, Shiraz University, Shiraz, IranJournal Article20170524The necessity and importance of a high heat removal potential in various areas particularly<br />in nuclear applications are in a direct relationship with the excessively applied heat flux level. One way<br />to increase the heat transfer performance and subsequently enhance the threshold of the critical heat<br />flux is to employ spacer grids accompanied by mixing vanes. In this study, the effect of the spacers<br />with mixing vanes on the critical heat flux characteristics in the dryout condition has been numerically<br />investigated employing the benefits of the Eulerian-Eulerian framework. In the current research, several<br />vane angles, including vane with 0, 15 and 25 degrees in comparison with the effect of the bare spacer<br />without any mixing vanes on the flow characteristics were examined. It was shown that the existence of<br />the spacer alone, delays the temperature jump under critical heat flux conditions. It was also concluded<br />that increasing the angle of the mixing vanes, further improves the heat transfer performance of the<br />system by postponing the sudden temperature jump occurring in the channel; however, the presence of<br />the spacers and vanes in the flow field imposes an increase of the pressure drop due to the constriction<br />on the coolant flow area.https://ajme.aut.ac.ir/article_2746_428d5aad5a444a8f697e67ea69a926f0.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201An Exact Analytical Solution for Convective Heat Transfer in Elliptical Pipes131138275210.22060/mej.2017.12310.5311ENM. M.ShahmardanDepartment of Mechanical Engineering, Shahrood University of Technology, Shahrood, IranM.NorouziDepartment of Mechanical Engineering, Shahrood University of Technology, Shahrood, IranM. H.SedaghatDepartment of Mechanical Engineering, Shahrood University of Technology, Shahrood, IranJournal Article20161231In this paper, an analytical solution for convective heat transfer in straight pipes with<br />the elliptical cross section is presented. The solution is obtained for steady-state fluid flow and heat<br />transfer under the constant heat flux at walls using the finite series expansion method. Here, the exact<br />solution of Nusselt number as well as temperature distribution in terms of aspect ratio is presented as the<br />correlation in the Cartesian coordinate system and validated with the previous investigations. It is shown<br />that the minimum amount of Nusselt number, as well as the maximum absolute value of dimensionless<br />temperature at the center of the cross section, are related to the aspect ratio equal to 1 (circular pipe). The<br />solution indicated that the amount of Nusselt number is increased by changing the geometry of cross<br />section from circular to an elliptical shape and it finally tends to 4356/833 at large enough aspect ratios.<br />Our results also show that 95% of the increase in Nusselt number to the circular cylinder is related to<br />aspect ratio equal to 18.36. The present method of solution could be used to obtain the exact solution of<br />convective heat transfer in elliptical pipes for other thermal boundary conditions and fluid rheological<br />behaviors.https://ajme.aut.ac.ir/article_2752_c6b926525682a13dc365340f595ce402.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201A Unified Velocity Field for Analysis of Flat Rolling Process139148274810.22060/mej.2017.12585.5374ENP.AmjadianMechanical Engineering Department, Razi University, Kermanshah, IranH.HaghighatMechanical Engineering Department, Razi University, Kermanshah, IranJournal Article20170226The subject of this paper is analysis of the flat rolling process by upper bound method.<br />In this analysis the arc of contact has been replaced by a chord and the inlet and outlet shear boundaries<br />of the deformation zone have been assumed as arbitrarily exponential curves. A unified kinematically<br />admissible velocity field has been proposed that permits the possible formation of internal defects. By<br />minimizing the required total power with respect to the neutral point position and the shape of the inlet<br />and outlet shear boundaries, the rolling torque has been determined. The velocity components obtained<br />from the upper bound method have been compared with the FE simulation. The analytical results have<br />been showed a good agreement between the upper bound data and the FE results. A criterion has been<br />presented to predict the occurrence of the split ends and central bursts defects during flat rolling process.<br />Comparison of analytically developed approach for rolling torque and internal defects with published<br />theoretical and experimental data have been showed a good agreement. Finally, the effects of process<br />parameters on the safe and unsafe zones sizes have been investigated. It is shown that with increasing of<br />the friction factor, the safe zone size is decreased.https://ajme.aut.ac.ir/article_2748_a4f63188a446ab4a9a05b6df9637711e.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201On the Elastic Field of Al/SiC Nanocomposite149158275610.22060/mej.2017.12281.5303ENH.PourhashemiDepartment of Mechanical Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, Kerman, IranM. R.DashtbayaziDepartment of Mechanical Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, Kerman, IranJournal Article20161226This study aims to analyze the linear elastic behavior of an aluminum matrix<br />nanocomposite reinforced with SiC nanoparticles. Once, a representative volume element was considered<br />for the nanocomposite with a cuboidal inclusion. The elastic moduli of the matrix and the inclusion were<br />the same, but it contained eigenstrain. The stress and the strain fields were obtained for the inclusion<br />and the aluminum by Galerkin vector method. The stress and the strain fields in the inclusion problem<br />were in a good agreement with the results in the literature. A similar representative volume element was<br />considered for the nanocomposite with a cuboidal inhomogeneity. The elastic moduli of the matrix and<br />the inhomogeneity were different, but it did not have any eigenstrain. For the calculation of the Eshelby<br />tensor and the elastic fields for the inhomogeneity problem, the equivalent inclusion method (EIM) was<br />applied. In the EIM, the uniform and equivalent eigenstrain were considered. The stress and the strain<br />fields within the inhomogeneity and the matrix were obtained. Results showed that the stress and the<br />strain in the cuboidal inclusion were less than the cuboidal inhomogeneity due to the difference between<br />the matrix and the reinforcement materials.https://ajme.aut.ac.ir/article_2756_ffa25e29bdf25abdc5161723f26469e5.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201A New Method to Investigate the Progressive Damage of Imperfect Composite Plates Under In-Plane Compressive Load159168274510.22060/mej.2017.12985.5490ENS. A. M.GhannadpourNew Technologies and Engineering Department, Shahid Beheshti University, G.C, Tehran, IranM.ShakeriNew Technologies and Engineering Department, Shahid Beheshti University, G.C, Tehran, IranJournal Article20170607Numerous studies have been conducted for failure criteria of fiber reinforced composites.<br />The aim of this study is to present a new computational and mathematical method to analyze the<br />progressive damage and failure behavior of composite plates containing initial geometric imperfections<br />under uniaxial in-plane compression load. A new methodology is presented based on collocation method<br />in which the interested domain is discretized with Legendre-Gauss-Lobatto nodes. In order to avoid an<br />excessive number of nodes, an appropriate weight coefficient is considered for each node. The method is<br />based on the first order shear deformation theory and small displacement theory. Several failure criteria,<br />including Maximum stress, Hashin and Tsai-Hill, are used to predict the failure mechanisms. The stiffness<br />degradation is carried out by instantaneous and complete ply degradation model. Two different types of<br />boundary conditions are considered in this study. The effects of thickness, initial imperfections, and<br />boundary conditions are studied, as well. The results are compared with the previously published data.<br />It is found that the boundary conditions have significant effects on the ultimate strength of imperfect<br />composite plates.https://ajme.aut.ac.ir/article_2745_6fe17a6bb5c1b6bbee2e96b0fafc50d0.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201Analysis and Optimization of Mining Truck Operation Based on the Driver Whole Body Vibration169178275710.22060/mej.2017.12574.5371ENM. J.RahimdelDepartment of Mining Engineering, Sahand University of Technology, Tabriz, IranM.MirzaeiDepartment of Mechanical Engineering, Sahand University of Technology, Tabriz, IranJ.SattarvandDepartment of Mining Engineering, Sahand University of Technology, Tabriz, IranHo.Mirzaei NasirabadDepartment of Mining Engineering, Sahand University of Technology, Tabriz, IranJournal Article20170225The present paper studies the whole body vibration of a three-axle dump truck during<br />various operational conditions in Zonuz Kaolin Mine of Iran. At first, the root mean square of vibrations<br />at different speeds, as well as in payloads and distribution qualities of materials in the truck dump body<br />and also on different haul road qualities are experimentally obtained. Then, the vibrational health risk<br />in all operational conditions is statistically analyzed based on ISO 2631-1 standard. As a result of this<br />analysis, an optimization problem is constructed and solved to obtain the optimum operating conditions<br />of the truck. In the proposed problem, at first, regression analysis in terms of RMS of vibrations<br />and truck speed is applied. Then, the total RMS at the consequential working phases of the truck is<br />minimized in the presence of some constraints related to the health risk and productivity levels. Solving<br />the proposed constrained optimization problem determines the optimum payload and truck speed in<br />various conditions to keep materials hauling at the lowest possible vibrational health risk level while the<br />mine productivity at the planned level remains.https://ajme.aut.ac.ir/article_2757_ad0a81c88a541966bbfddb9e841b2c18.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201Natural Frequency Analysis of Composite Skew Plates with Embedded Shape Memory Alloys in Thermal Environment179190274710.22060/mej.2017.12655.5389ENS.KamarianDepartment of Mechanical Engineering, Amirkabir University of Technology, Tehran, IranM.ShakeriDepartment of Mechanical Engineering, Amirkabir University of Technology, Tehran, IranJournal Article20170312In this study, free vibration analysis of laminated composite skew plates with embedded<br />shape memory alloys under thermal loads is presented. The plates are assumed to be made of NiTi/Graphite/<br />Epoxy with temperature-dependent properties. The thermo-mechanical behavior of shape memory alloy<br />wires is predicted by employing one-dimensional Brinson’s model. The governing equations are derived<br />based on first-order shear deformation theory and solved using generalized differential quadrature<br />technique as an efficient and accurate numerical tool. Some examples are provided to show the accuracy<br />and efficiency of the applied numerical method by comparing the present results with those available<br />in the literature. A parametric study is carried out to demonstrate the influence of skew angle, pre-strain<br />and volume fraction of shape memory alloys, temperature, and stacking sequence of layers on the natural<br />frequencies of the structure. Results represent that shape memory alloys can change the vibrational<br />characteristics of shape memory alloy hybrid composite skew plates by a considerable amount. The<br />numerical results also reveal that the effect of shape memory alloy wires on natural frequencies of<br />composite plates with simply supported boundaries is higher than those with clamped boundaries.https://ajme.aut.ac.ir/article_2747_acbf46f2c5a9e6bd9bdea0f84566edc9.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201A Parametric Study on Flutter Analysis of Cantilevered Trapezoidal FG Sandwich Plates191210275810.22060/mej.2017.12329.5314ENH.AfshariDepartment of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr/Isfahan, IranK.TorabiFaculty of Mechanical Engineering, University of Isfahan, Isfahan, IranJournal Article20170108In this paper, supersonic flutter analysis of cantilevered trapezoidal plates composed of<br />two functionally graded face sheets and an isotropic homogeneous core is presented. Using Hamilton’s<br />principle, the set of governing equations and external boundary conditions are derived. A transformation<br />of coordinates is used to convert the governing equations and boundary conditions from the original<br />coordinates into the new dimensionless computational ones. Generalized differential quadrature method<br />(GDQM) is employed as a numerical method and critical aerodynamic pressure and flutter frequencies<br />are derived. Convergence, versatility, and accuracy of the presented solution are confirmed using<br />numerical and experimental results presented by other authors. The effect of power-law index, thickness<br />of the core, total thickness of the plate, aspect ratio and angles of the plate on the flutter boundaries are<br />investigated. It is concluded that any attempt to increase the critical aerodynamic pressure leads to a<br />decrease in lift force or rise in total weight of the plate.https://ajme.aut.ac.ir/article_2758_415c7c8dcf48f46145d01478f8ffde2e.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201An Analytical Procedure for Buckling Load Determination of an Axisymmetric Cylinder with Non-Uniform Thickness Using Shear Deformation Theory211218275110.22060/mej.2017.12557.5364ENF.Mahboubi NasrekaniFaculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, IranH. R.EipakchiFaculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, IranJournal Article20170219In this article, the buckling load of an axisymmetric cylindrical shell with a variable<br />thickness is determined analytically by using the perturbation method. The loading is axial and the<br />material properties are defined by the Hooke’s law. The displacement field is predicted by using the<br />first order shear deformation theory and the nonlinear von-Karman relations are used for the kinematic<br />description of the shell. The stability equations, which are the system of nonlinear differential equations<br />with variable coefficients, are derived by the virtual work principle and are solved using the perturbation<br />technique. Also, the buckling load is determined by using the finite element method and it is compared<br />with the analytical solution results, the classical shell theory, and other references. The effects of linear<br />and nonlinear shell profiles variation on the axial buckling load are investigated. Also, we studied the<br />effects of geometric parameters on the buckling load results. The results show that the first order shear<br />deformation theory is more useful for buckling load determination of thicker shells.https://ajme.aut.ac.ir/article_2751_40c3631ca18291500241313c75ee630d.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201Computational Investigation of Unsteady Compressible Flow over a Fixed Delta Wing Using Detached Eddy Simulation219232275010.22060/mej.2017.12863.5455ENH.AnsarianMalek Ashtar University of Technology, Tehran, IranM.HadidoolabiMalek Ashtar University of Technology, Tehran, IranJournal Article20170507Unsteady compressible flows over a stationary 60-degree swept delta wing with a sharp<br />leading edge were computationally simulated at different Mach numbers and moderate angles of the<br />attack. An unstructured grid, Spalart-Allmaras Detached Eddy Simulation turbulence model, and a<br />dual-time implicit time integration were used. Vortical flow structures associated with various freestream<br />conditions are displayed and their variations versus time are studied. Variations of flow field<br />parameters, such as u velocity component and pressure coefficient with the flow time are demonstrated<br />at several point probes in the flow field. A Power Spectral Density frequency analysis is performed for<br />such unsteady behaviours to identify the dominant frequencies which exist in each flow condition. The<br />frequency analyses show that low frequencies associated with vortex breakdown oscillation are the most<br />dominant frequencies in all cases where vortex breakdown occurs. Dominant frequencies associated with<br />helical mode instability are also present at the probes downstream of breakdown. Dominant frequencies<br />related to the shear layer instabilities were observed for the low subsonic regime.https://ajme.aut.ac.ir/article_2750_39f8fa8b7d3fab2852be3308ac719375.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201Dynamic Response of a Red Blood Cell in Shear Flow233242274910.22060/mej.2017.12467.5345ENZ.HashemiDepartment of Mechanical Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, Kerman, Iran0000-0002-0007-4793M.RahnamaDepartment of Mechanical Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, Kerman, IranJournal Article20170130Three-dimensional simulation of a red blood cell deformation in a shear flow is<br />performed using immersed boundary lattice Boltzmann method for the fluid flow simulation, as well as<br />finite element method for membrane deformation. Immersed boundary method has been used to model<br />interaction between fluid and membrane of the red blood cell. Red blood cell is modeled as a biconcave<br />discoid capsule containing fluid with an elastic membrane. Computations are performed at relatively<br />small and large shear rates in order to study the dynamic behavior of red blood cell, especially tumbling<br />and swinging modes of its motion. A rigid-body-like motion with the constant-amplitude oscillation<br />of deformation parameter and continuous rotation is observed for red blood cell at its tumbling mode.<br />However, at a relatively large shear rate, red blood cell follows a periodic gradual deformation and<br />elongation with a final ellipsoidal shape. The effect of different initial orientations of red blood cell is<br />also investigated in the present paper. Results show that the dynamic response of red blood cell is not<br />sensitive to this parameter.https://ajme.aut.ac.ir/article_2749_43072e42dc7beb8bf9b58e622115d13d.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29371220171201Phase Field Method to the Interaction of Phase Transformations and Dislocations at Nanoscale243246275910.22060/mej.2017.11892.5209ENM.JavanbakhtDepartment of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, IranV. I.LevitasIowa State University, Departments of Mechanical and Aerospace Engineering, Ames, IA, USAJournal Article20160817In this paper, a new phase field method for the interaction between martensitic phase<br />transformations and dislocations is presented which is a nontrivial combination of the most advanced<br />phase field methods to phase transformations and dislocation evolution. Some of the important points in<br />the model are the multiplicative decomposition of deformation gradient into elastic, transformational and<br />plastic parts, defining a proper energy to satisfy thermodynamic equilibrium and instability conditions,<br />including phase-dependent properties of dislocations. The system of equations consists of coupled<br />elasticity and phase field equations of phase transformations and dislocations. Finite element method<br />is used to solve the system of equations and applied to study the growth and arrest of martensitic plate<br />and the evolution of dislocations and phase in a nanograined material. It is found that dislocations play<br />a key role in eliminating the driving force of the plate growth and their arrest which creates athermal<br />friction. Also, the dual effect of plasticity on phase transformations is revealed; due to dislocations<br />pile-up and its stress concentration, the phase transformation driving force increases and consequently,<br />martensitic nucleation occurs. On the other hand, the dislocation nucleation results in decreasing the<br />phase transformation driving force and consequently, the phase transformation is suppressed.https://ajme.aut.ac.ir/article_2759_abb6bfa2dc485f909ab3fae80d0080f4.pdf