2024-03-28T17:39:37Z
https://ajme.aut.ac.ir/?_action=export&rf=summon&issue=246
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
Numerical Analysis of Critical Heat Flux Phenomenon in a Nuclear Power Plant Core Channel in the Presence of Mixing Vanes
A.
Rabiee
L.
Moradi
A.
Atf
The necessity and importance of a high heat removal potential in various areas particularlyin nuclear applications are in a direct relationship with the excessively applied heat flux level. One wayto increase the heat transfer performance and subsequently enhance the threshold of the critical heatflux is to employ spacer grids accompanied by mixing vanes. In this study, the effect of the spacerswith mixing vanes on the critical heat flux characteristics in the dryout condition has been numericallyinvestigated employing the benefits of the Eulerian-Eulerian framework. In the current research, severalvane angles, including vane with 0, 15 and 25 degrees in comparison with the effect of the bare spacerwithout any mixing vanes on the flow characteristics were examined. It was shown that the existence ofthe spacer alone, delays the temperature jump under critical heat flux conditions. It was also concludedthat increasing the angle of the mixing vanes, further improves the heat transfer performance of thesystem by postponing the sudden temperature jump occurring in the channel; however, the presence ofthe spacers and vanes in the flow field imposes an increase of the pressure drop due to the constrictionon the coolant flow area.
Boiling
Critical heat flux
Mixing vane
Spacer grid
2017
12
01
119
130
https://ajme.aut.ac.ir/article_2746_428d5aad5a444a8f697e67ea69a926f0.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
An Exact Analytical Solution for Convective Heat Transfer in Elliptical Pipes
M. M.
Shahmardan
M.
Norouzi
M. H.
Sedaghat
In this paper, an analytical solution for convective heat transfer in straight pipes withthe elliptical cross section is presented. The solution is obtained for steady-state fluid flow and heattransfer under the constant heat flux at walls using the finite series expansion method. Here, the exactsolution of Nusselt number as well as temperature distribution in terms of aspect ratio is presented as thecorrelation in the Cartesian coordinate system and validated with the previous investigations. It is shownthat the minimum amount of Nusselt number, as well as the maximum absolute value of dimensionlesstemperature at the center of the cross section, are related to the aspect ratio equal to 1 (circular pipe). Thesolution indicated that the amount of Nusselt number is increased by changing the geometry of crosssection from circular to an elliptical shape and it finally tends to 4356/833 at large enough aspect ratios.Our results also show that 95% of the increase in Nusselt number to the circular cylinder is related toaspect ratio equal to 18.36. The present method of solution could be used to obtain the exact solution ofconvective heat transfer in elliptical pipes for other thermal boundary conditions and fluid rheologicalbehaviors.
Convective Heat Transfer
Exact Solution
Elliptical Pipe
Aspect Ratio
2017
12
01
131
138
https://ajme.aut.ac.ir/article_2752_c6b926525682a13dc365340f595ce402.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
A Unified Velocity Field for Analysis of Flat Rolling Process
P.
Amjadian
H.
Haghighat
The subject of this paper is analysis of the flat rolling process by upper bound method.In this analysis the arc of contact has been replaced by a chord and the inlet and outlet shear boundariesof the deformation zone have been assumed as arbitrarily exponential curves. A unified kinematicallyadmissible velocity field has been proposed that permits the possible formation of internal defects. Byminimizing the required total power with respect to the neutral point position and the shape of the inletand outlet shear boundaries, the rolling torque has been determined. The velocity components obtainedfrom the upper bound method have been compared with the FE simulation. The analytical results havebeen showed a good agreement between the upper bound data and the FE results. A criterion has beenpresented to predict the occurrence of the split ends and central bursts defects during flat rolling process.Comparison of analytically developed approach for rolling torque and internal defects with publishedtheoretical and experimental data have been showed a good agreement. Finally, the effects of processparameters on the safe and unsafe zones sizes have been investigated. It is shown that with increasing ofthe friction factor, the safe zone size is decreased.
Velocity field
Flat rolling
Central bursts
Split ends
2017
12
01
139
148
https://ajme.aut.ac.ir/article_2748_a4f63188a446ab4a9a05b6df9637711e.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
On the Elastic Field of Al/SiC Nanocomposite
H.
Pourhashemi
M. R.
Dashtbayazi
This study aims to analyze the linear elastic behavior of an aluminum matrixnanocomposite reinforced with SiC nanoparticles. Once, a representative volume element was consideredfor the nanocomposite with a cuboidal inclusion. The elastic moduli of the matrix and the inclusion werethe same, but it contained eigenstrain. The stress and the strain fields were obtained for the inclusionand the aluminum by Galerkin vector method. The stress and the strain fields in the inclusion problemwere in a good agreement with the results in the literature. A similar representative volume element wasconsidered for the nanocomposite with a cuboidal inhomogeneity. The elastic moduli of the matrix andthe inhomogeneity were different, but it did not have any eigenstrain. For the calculation of the Eshelbytensor and the elastic fields for the inhomogeneity problem, the equivalent inclusion method (EIM) wasapplied. In the EIM, the uniform and equivalent eigenstrain were considered. The stress and the strainfields within the inhomogeneity and the matrix were obtained. Results showed that the stress and thestrain in the cuboidal inclusion were less than the cuboidal inhomogeneity due to the difference betweenthe matrix and the reinforcement materials.
Nanocomposite
Inclusion
Inhomogeneity
stress
Strain
2017
12
01
149
158
https://ajme.aut.ac.ir/article_2756_ffa25e29bdf25abdc5161723f26469e5.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
A New Method to Investigate the Progressive Damage of Imperfect Composite Plates Under In-Plane Compressive Load
S. A. M.
Ghannadpour
M.
Shakeri
Numerous studies have been conducted for failure criteria of fiber reinforced composites.The aim of this study is to present a new computational and mathematical method to analyze theprogressive damage and failure behavior of composite plates containing initial geometric imperfectionsunder uniaxial in-plane compression load. A new methodology is presented based on collocation methodin which the interested domain is discretized with Legendre-Gauss-Lobatto nodes. In order to avoid anexcessive number of nodes, an appropriate weight coefficient is considered for each node. The method isbased on the first order shear deformation theory and small displacement theory. Several failure criteria,including Maximum stress, Hashin and Tsai-Hill, are used to predict the failure mechanisms. The stiffnessdegradation is carried out by instantaneous and complete ply degradation model. Two different types ofboundary conditions are considered in this study. The effects of thickness, initial imperfections, andboundary conditions are studied, as well. The results are compared with the previously published data.It is found that the boundary conditions have significant effects on the ultimate strength of imperfectcomposite plates.
Progressive damage
Hashin failure criterion
Tsai-Hill failure criterion
Maximum-stress failure criterion
Collocation
2017
12
01
159
168
https://ajme.aut.ac.ir/article_2745_6fe17a6bb5c1b6bbee2e96b0fafc50d0.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
Analysis and Optimization of Mining Truck Operation Based on the Driver Whole Body Vibration
M. J.
Rahimdel
M.
Mirzaei
J.
Sattarvand
Ho.
Mirzaei Nasirabad
The present paper studies the whole body vibration of a three-axle dump truck duringvarious operational conditions in Zonuz Kaolin Mine of Iran. At first, the root mean square of vibrationsat different speeds, as well as in payloads and distribution qualities of materials in the truck dump bodyand also on different haul road qualities are experimentally obtained. Then, the vibrational health riskin all operational conditions is statistically analyzed based on ISO 2631-1 standard. As a result of thisanalysis, an optimization problem is constructed and solved to obtain the optimum operating conditionsof the truck. In the proposed problem, at first, regression analysis in terms of RMS of vibrationsand truck speed is applied. Then, the total RMS at the consequential working phases of the truck isminimized in the presence of some constraints related to the health risk and productivity levels. Solvingthe proposed constrained optimization problem determines the optimum payload and truck speed invarious conditions to keep materials hauling at the lowest possible vibrational health risk level while themine productivity at the planned level remains.
Mining truck
Whole body vibration
Non-linear optimization
Operational conditions
Zonuz Kaolin Mine
2017
12
01
169
178
https://ajme.aut.ac.ir/article_2757_ad0a81c88a541966bbfddb9e841b2c18.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
Natural Frequency Analysis of Composite Skew Plates with Embedded Shape Memory Alloys in Thermal Environment
S.
Kamarian
M.
Shakeri
In this study, free vibration analysis of laminated composite skew plates with embeddedshape memory alloys under thermal loads is presented. The plates are assumed to be made of NiTi/Graphite/Epoxy with temperature-dependent properties. The thermo-mechanical behavior of shape memory alloywires is predicted by employing one-dimensional Brinson’s model. The governing equations are derivedbased on first-order shear deformation theory and solved using generalized differential quadraturetechnique as an efficient and accurate numerical tool. Some examples are provided to show the accuracyand efficiency of the applied numerical method by comparing the present results with those availablein the literature. A parametric study is carried out to demonstrate the influence of skew angle, pre-strainand volume fraction of shape memory alloys, temperature, and stacking sequence of layers on the naturalfrequencies of the structure. Results represent that shape memory alloys can change the vibrationalcharacteristics of shape memory alloy hybrid composite skew plates by a considerable amount. Thenumerical results also reveal that the effect of shape memory alloy wires on natural frequencies ofcomposite plates with simply supported boundaries is higher than those with clamped boundaries.
Shape memory alloys
Hybrid composites
Skew plates
Natural frequency
2017
12
01
179
190
https://ajme.aut.ac.ir/article_2747_acbf46f2c5a9e6bd9bdea0f84566edc9.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
A Parametric Study on Flutter Analysis of Cantilevered Trapezoidal FG Sandwich Plates
H.
Afshari
K.
Torabi
In this paper, supersonic flutter analysis of cantilevered trapezoidal plates composed oftwo functionally graded face sheets and an isotropic homogeneous core is presented. Using Hamilton’sprinciple, the set of governing equations and external boundary conditions are derived. A transformationof coordinates is used to convert the governing equations and boundary conditions from the originalcoordinates into the new dimensionless computational ones. Generalized differential quadrature method(GDQM) is employed as a numerical method and critical aerodynamic pressure and flutter frequenciesare derived. Convergence, versatility, and accuracy of the presented solution are confirmed usingnumerical and experimental results presented by other authors. The effect of power-law index, thicknessof the core, total thickness of the plate, aspect ratio and angles of the plate on the flutter boundaries areinvestigated. It is concluded that any attempt to increase the critical aerodynamic pressure leads to adecrease in lift force or rise in total weight of the plate.
Aeroelasticity
Flutter
Trapezoidal plate
Sandwich plate
2017
12
01
191
210
https://ajme.aut.ac.ir/article_2758_415c7c8dcf48f46145d01478f8ffde2e.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
An Analytical Procedure for Buckling Load Determination of an Axisymmetric Cylinder with Non-Uniform Thickness Using Shear Deformation Theory
F.
Mahboubi Nasrekani
H. R.
Eipakchi
In this article, the buckling load of an axisymmetric cylindrical shell with a variablethickness is determined analytically by using the perturbation method. The loading is axial and thematerial properties are defined by the Hooke’s law. The displacement field is predicted by using thefirst order shear deformation theory and the nonlinear von-Karman relations are used for the kinematicdescription of the shell. The stability equations, which are the system of nonlinear differential equationswith variable coefficients, are derived by the virtual work principle and are solved using the perturbationtechnique. Also, the buckling load is determined by using the finite element method and it is comparedwith the analytical solution results, the classical shell theory, and other references. The effects of linearand nonlinear shell profiles variation on the axial buckling load are investigated. Also, we studied theeffects of geometric parameters on the buckling load results. The results show that the first order sheardeformation theory is more useful for buckling load determination of thicker shells.
Buckling load
Cylindrical shell
Varying thickness
Shear deformation theory
Perturbation technique
2017
12
01
211
218
https://ajme.aut.ac.ir/article_2751_40c3631ca18291500241313c75ee630d.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
Computational Investigation of Unsteady Compressible Flow over a Fixed Delta Wing Using Detached Eddy Simulation
H.
Ansarian
M.
Hadidoolabi
Unsteady compressible flows over a stationary 60-degree swept delta wing with a sharpleading edge were computationally simulated at different Mach numbers and moderate angles of theattack. An unstructured grid, Spalart-Allmaras Detached Eddy Simulation turbulence model, and adual-time implicit time integration were used. Vortical flow structures associated with various freestreamconditions are displayed and their variations versus time are studied. Variations of flow fieldparameters, such as u velocity component and pressure coefficient with the flow time are demonstratedat several point probes in the flow field. A Power Spectral Density frequency analysis is performed forsuch unsteady behaviours to identify the dominant frequencies which exist in each flow condition. Thefrequency analyses show that low frequencies associated with vortex breakdown oscillation are the mostdominant frequencies in all cases where vortex breakdown occurs. Dominant frequencies associated withhelical mode instability are also present at the probes downstream of breakdown. Dominant frequenciesrelated to the shear layer instabilities were observed for the low subsonic regime.
Delta wing
Unsteady flow
DES turbulence model
Frequency analysis
2017
12
01
219
232
https://ajme.aut.ac.ir/article_2750_39f8fa8b7d3fab2852be3308ac719375.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
Dynamic Response of a Red Blood Cell in Shear Flow
Z.
Hashemi
M.
Rahnama
Three-dimensional simulation of a red blood cell deformation in a shear flow isperformed using immersed boundary lattice Boltzmann method for the fluid flow simulation, as well asfinite element method for membrane deformation. Immersed boundary method has been used to modelinteraction between fluid and membrane of the red blood cell. Red blood cell is modeled as a biconcavediscoid capsule containing fluid with an elastic membrane. Computations are performed at relativelysmall and large shear rates in order to study the dynamic behavior of red blood cell, especially tumblingand swinging modes of its motion. A rigid-body-like motion with the constant-amplitude oscillationof deformation parameter and continuous rotation is observed for red blood cell at its tumbling mode.However, at a relatively large shear rate, red blood cell follows a periodic gradual deformation andelongation with a final ellipsoidal shape. The effect of different initial orientations of red blood cell isalso investigated in the present paper. Results show that the dynamic response of red blood cell is notsensitive to this parameter.
Red blood cell
Three-dimensional deformation
Tumbling motion
Swinging motion
2017
12
01
233
242
https://ajme.aut.ac.ir/article_2749_43072e42dc7beb8bf9b58e622115d13d.pdf
AUT Journal of Mechanical Engineering
AJME
2588-2937
2588-2937
2017
1
2
Phase Field Method to the Interaction of Phase Transformations and Dislocations at Nanoscale
M.
Javanbakht
V. I.
Levitas
In this paper, a new phase field method for the interaction between martensitic phasetransformations and dislocations is presented which is a nontrivial combination of the most advancedphase field methods to phase transformations and dislocation evolution. Some of the important points inthe model are the multiplicative decomposition of deformation gradient into elastic, transformational andplastic parts, defining a proper energy to satisfy thermodynamic equilibrium and instability conditions,including phase-dependent properties of dislocations. The system of equations consists of coupledelasticity and phase field equations of phase transformations and dislocations. Finite element methodis used to solve the system of equations and applied to study the growth and arrest of martensitic plateand the evolution of dislocations and phase in a nanograined material. It is found that dislocations playa key role in eliminating the driving force of the plate growth and their arrest which creates athermalfriction. Also, the dual effect of plasticity on phase transformations is revealed; due to dislocationspile-up and its stress concentration, the phase transformation driving force increases and consequently,martensitic nucleation occurs. On the other hand, the dislocation nucleation results in decreasing thephase transformation driving force and consequently, the phase transformation is suppressed.
Phase field
Interaction
Phase transformations
Dislocations
Nanoscale
2017
12
01
243
246
https://ajme.aut.ac.ir/article_2759_abb6bfa2dc485f909ab3fae80d0080f4.pdf