2016
23
1
1
0
http://scientiairanica.sharif.edu/3823.html
10.24200/sci.2016.3823
Numerical and analytical approaches for improving the die design in the radial forging process of tubes without mandrel
Numerical and analytical approaches for improving the die design in the radial forging process of tubes without mandrel
2
2
Radial forging without a mandrel offers a cost effective method for production of tubular components. However, nonuniform deformation, thickness variation, poor surface quality and undesirable residual stress distribution are the problems which should be overcome in order to achieve an optimal process. In this paper, radial forging dies with curved-shape profiles are proposed to alleviate some of the mentioned difficulties. Finite element simulations are used to prove the advantage of the proposed dies over the conventional linear dies. A novel analytical approach based on the slab method of analysis is developed to verify the finite element modeling. The obtained results provide useful guidelines for design and optimization of the radial forging process without mandrel.
2
Radial forging without a mandrel offers a cost effective method for production of tubular components. However, nonuniform deformation, thickness variation, poor surface quality and undesirable residual stress distribution are the problems which should be overcome in order to achieve an optimal process. In this paper, radial forging dies with curved-shape profiles are proposed to alleviate some of the mentioned difficulties. Finite element simulations are used to prove the advantage of the proposed dies over the conventional linear dies. A novel analytical approach based on the slab method of analysis is developed to verify the finite element modeling. The obtained results provide useful guidelines for design and optimization of the radial forging process without mandrel.
167
173
H.
Afrasiab
H.
Afrasiab
Mechanical Engineering Department, Babol University of Technology, Babol, Iran
Iran
afrasiab@nit.ac.ir
Radial forging process without Mandrel
Die profile design and optimization
Finite element method
Slab method
http://scientiairanica.sharif.edu/3824.html
10.24200/sci.2016.3824
The Effect of Ductile Damage on Plastic Behavior of a Rotating Disk with Variable Thickness Subjected to Mechanical Loading
The Effect of Ductile Damage on Plastic Behavior of a Rotating Disk with Variable Thickness Subjected to Mechanical Loading
2
2
In this work, the effect of ductile damage on distributions of strain and displacement components in rotating annular disks with variable thicknesses under plane stress condition is studied using semi-analytical and finite element methods. The plastic behavior of disks under mechanical loading is studied on the basis of continuum damage mechanics. The semi-analytical method is developed using the Prandtl-Reuss relations, the method of successive elastic solution and damage plasticity model proposed by Xue and Wierzbicki that is used for the finite element analysis as well. The proposed damage plasticity model incorporates effects of both hydrostatic stress and the Lode angle to define the fracture envelope. The results obtained by semi-analytical method are then compared with the results obtained by the finite element method. Numerical calculations for different ranges of thickness parameter with and without damage effect are carried out and results are compared. It is shown that the damage has a significant effect on values of maximum von Mises stress and the limit angular velocity of annular disks. Results of the present study confirm the credibility of the proposed model in predicting the damage limit angular velocity and can be extend to other state of loadings.
2
In this work, the effect of ductile damage on distributions of strain and displacement components in rotating annular disks with variable thicknesses under plane stress condition is studied using semi-analytical and finite element methods. The plastic behavior of disks under mechanical loading is studied on the basis of continuum damage mechanics. The semi-analytical method is developed using the Prandtl-Reuss relations, the method of successive elastic solution and damage plasticity model proposed by Xue and Wierzbicki that is used for the finite element analysis as well. The proposed damage plasticity model incorporates effects of both hydrostatic stress and the Lode angle to define the fracture envelope. The results obtained by semi-analytical method are then compared with the results obtained by the finite element method. Numerical calculations for different ranges of thickness parameter with and without damage effect are carried out and results are compared. It is shown that the damage has a significant effect on values of maximum von Mises stress and the limit angular velocity of annular disks. Results of the present study confirm the credibility of the proposed model in predicting the damage limit angular velocity and can be extend to other state of loadings.
174
193
R.
Akbari Alashti
R.
Akbari Alashti
Mechanical Engineering Department, Babol University of Technology; P.O. Box 484, Babol, Mazandaran, Iran
Iran
raalashti@nit.ac.ir
S.
Jafari
S.
Jafari
Mechanical Engineering Department, Babol University of Technology; P.O. Box 484, Babol, Mazandaran, Iran
Iran
jaafari.sanaz@yahoo.com
Rotating disk
Ductile damage
Successive elastic solution
Finite Element Analysis
Angular velocity
http://scientiairanica.sharif.edu/3825.html
10.24200/sci.2016.3825
Aeroelastic Analysis of a Typical Section using Euler and Navier-Stokes Mesh-less Method
Aeroelastic Analysis of a Typical Section using Euler and Navier-Stokes Mesh-less Method
2
2
The main aim of this paper is to develop an efficient aeroelastic tool for predicting the flutter speed of a typical section in transonic regime. An implicit mesh-less method based on the Euler and Navier-Stokes equations are conducted to simulate the transonic fluid flow around an airfoil. This technique is applied directly to the differential form of the aerodynamic governing equations and the time integration is carried out using a dual-time implicit time discretization scheme. The capabilities of the flow solution method are demonstrated by flow computations around NACA0012 airfoil at different flow conditions. For structural dynamics simulation, a typical section model with pitching and plunging motion capability is considered. Finally, the aeroelastic analysis of the 2D model is performed by the consecutive simulation of both structural and aerodynamic domains. Also, the effect of viscosity and time interval choice between two structural and aerodynamic solvers on the flutter instability is studied. The comparison between the obtained results and those available in the literature shows the good accuracy of the present method.
2
The main aim of this paper is to develop an efficient aeroelastic tool for predicting the flutter speed of a typical section in transonic regime. An implicit mesh-less method based on the Euler and Navier-Stokes equations are conducted to simulate the transonic fluid flow around an airfoil. This technique is applied directly to the differential form of the aerodynamic governing equations and the time integration is carried out using a dual-time implicit time discretization scheme. The capabilities of the flow solution method are demonstrated by flow computations around NACA0012 airfoil at different flow conditions. For structural dynamics simulation, a typical section model with pitching and plunging motion capability is considered. Finally, the aeroelastic analysis of the 2D model is performed by the consecutive simulation of both structural and aerodynamic domains. Also, the effect of viscosity and time interval choice between two structural and aerodynamic solvers on the flutter instability is studied. The comparison between the obtained results and those available in the literature shows the good accuracy of the present method.
194
205
S.
Sattarzadeh
S.
Sattarzadeh
Department of Aerospace Engineering, Amirkabir University of Technology, 424 Hafez Avenue, Tehran, Iran
Iran
sattarzadeh@aut.ac.ir
A.
Jahangirian
A.
Jahangirian
Department of Aerospace Engineering, Amirkabir University of Technology, 424 Hafez Avenue, Tehran, Iran
Iran
ajahan@aut.ac.ir
H.
Shahverdi
H.
Shahverdi
Department of Aerospace Engineering, Amirkabir University of Technology, 424 Hafez Avenue, Tehran, Iran
Iran
h_shahverdi@aut.ac.ir
Aeroelastic instability – Compressible flow – Flutter speed – Mesh-less method –– Navier-Stokes equations – Transonic flow
http://scientiairanica.sharif.edu/3826.html
10.24200/sci.2016.3826
A Parametric Study of Optimal Number and Location of Radiant Heaters in Enclosures with Participating Media
A Parametric Study of Optimal Number and Location of Radiant Heaters in Enclosures with Participating Media
2
2
An inverse solution technique is applied to the design of radiant enclosures when design variables are discrete and radiation is the dominant mode of heat transfer.The enclosure contains an absorbing, emitting and linear anisotropic scattering medium in radiative equilibrium. The discrete ordinate method is employed to solve the radiative transfer equation. The goal of the design problem is to find the best number and location of discrete equally power heaters which produce the desired (specified) temperature and heat flux profile over the design surface of enclosures. The inverse problem is formulated as an optimization problem and is solved using a micro-genetic algorithm. Results show that the micro genetic algorithm is able to find the optimal solution by just searching a few percent of feasible solutions.The ability of this methodology is demonstrated by finding the optimal number and location of heaters in an irregular enclosure.Then, the effect of some thermophysical properties, such as extinction coefficient, scattering albedo, scattering phase function, and design surface emissivity, on the optimal solution is considered.
2
An inverse solution technique is applied to the design of radiant enclosures when design variables are discrete and radiation is the dominant mode of heat transfer.The enclosure contains an absorbing, emitting and linear anisotropic scattering medium in radiative equilibrium. The discrete ordinate method is employed to solve the radiative transfer equation. The goal of the design problem is to find the best number and location of discrete equally power heaters which produce the desired (specified) temperature and heat flux profile over the design surface of enclosures. The inverse problem is formulated as an optimization problem and is solved using a micro-genetic algorithm. Results show that the micro genetic algorithm is able to find the optimal solution by just searching a few percent of feasible solutions.The ability of this methodology is demonstrated by finding the optimal number and location of heaters in an irregular enclosure.Then, the effect of some thermophysical properties, such as extinction coefficient, scattering albedo, scattering phase function, and design surface emissivity, on the optimal solution is considered.
206
217
Hossein
Amiri
Hossein
Amiri
Department of Energy, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advance Technology, Haftbagh Highway, P. O. Box: 76315-117, Kerman, Iran
Iran
hosseinamiri2010@gmail.com
Pedro J.
Coelho
Pedro J.
Coelho
IDMEC, LAETA, Instituto Superior Técnico, Universidade de Lisboa Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
Iran
pedro.coelho@tecnico.ulisboa.pt
optimization
participating media
Micro-genetic algorithm
discrete ordinates method
anisotropic scattering
http://scientiairanica.sharif.edu/3827.html
10.24200/sci.2016.3827
Designing an Optimal Fuzzy Controller for a Fuel Cell Vehicle Considering Driving Patterns
Designing an Optimal Fuzzy Controller for a Fuel Cell Vehicle Considering Driving Patterns
2
2
Design of an optimal fuzzy scheme, for a fuel cell/battery vehicle to control the power flow between the main components, fuel cell, electric motor, and battery, at various driving conditions is considered in this paper. For this purpose, firstly, the optimum sizes of the main components are calculated by means of particle swarm optimization (PSO) algorithm. Subsequently, a fuzzy logic controller (FLC) is devised for the control of the power flow. Finally, the FLC is optimized for various driving patterns and an optimal control scheme, based on PSO application, is proposed for energy management of the fuel cell vehicle (FCV) at various traffic conditions. In each one of the mentioned stages, the same optimization process is conducted by applying genetic algorithm (GA) for comparison with the result of the PSO. The results of the computer simulation are compared over diverse driving conditions. The results give an acceptable indication of progress in fuel economy at various driving patterns, using the proposed optimal fuzzy controller.
2
Design of an optimal fuzzy scheme, for a fuel cell/battery vehicle to control the power flow between the main components, fuel cell, electric motor, and battery, at various driving conditions is considered in this paper. For this purpose, firstly, the optimum sizes of the main components are calculated by means of particle swarm optimization (PSO) algorithm. Subsequently, a fuzzy logic controller (FLC) is devised for the control of the power flow. Finally, the FLC is optimized for various driving patterns and an optimal control scheme, based on PSO application, is proposed for energy management of the fuel cell vehicle (FCV) at various traffic conditions. In each one of the mentioned stages, the same optimization process is conducted by applying genetic algorithm (GA) for comparison with the result of the PSO. The results of the computer simulation are compared over diverse driving conditions. The results give an acceptable indication of progress in fuel economy at various driving patterns, using the proposed optimal fuzzy controller.
218
227
Mohsen
Kandi-D
Mohsen
Kandi-D
Department of Mechanical Engineering, Faculty of Engineering, Arak University, Arak 38156-8-8349, Iran
Iran
kandi.mohsen@gmail.com
Mehdi
Soleymani
Mehdi
Soleymani
Department of Mechanical Engineering, Faculty of Engineering, Arak University, Arak 38156-8-8349, Iran
Iran
m-soleymani@araku.ac.ir
Ali Asghar
Ghadimi
Ali Asghar
Ghadimi
Department of Electrical Engineering, Faculty of Engineering, Arak University, Arak 38156-8-8349, Iran
Iran
a-ghadimi@araku.ac.ir
Optimal fuzzy controller
FCV
driving pattern
PSO
http://scientiairanica.sharif.edu/3828.html
10.24200/sci.2016.3828
The Importance of Fluid-Structure Interaction Simulation for Determining the Mechanical Stimuli of Endothelial Cells and the Atheroprone Regions in a Coronary Bifurcation
The Importance of Fluid-Structure Interaction Simulation for Determining the Mechanical Stimuli of Endothelial Cells and the Atheroprone Regions in a Coronary Bifurcation
2
2
The function and morphology of endothelial cells (ECs) play a key role in atherosclerosis. The mechanical stimuli of ECs such as wall shear stress (WSS) and arterial wall strains greatly influence the function and morphology of these cells. The present article deals with computations of these stimuli for a 3D model of a healthy coronary artery bifurcation. The focus of the study is to propose an accurate method for computations of WSS and strains. Two approaches are considered. The coupled simultaneous simulation of arterial wall and blood flow called Fluid-Structure Interaction (FSI) simulation and decoupled one,which simulates each domain (fluid and solid domain) separately. The study demonstrates that the computed circumferential strain resulting from both methods are identical. However, longitudinal strain and WSS are very different from these two approaches. The resulting time averaged wall shear stress (TAWSS) from decoupled fluid model is always higher than corresponding value from FSI simulation. While, oscillatory shear index (OSI) from rigid wall model is lower than the values resulting from FSI. Therefore, the decoupled simulation may underestimate the atheroprone sites of the artery and suggests that using FSI simulation for mechanical stimuli of ECs is inevitable.
2
The function and morphology of endothelial cells (ECs) play a key role in atherosclerosis. The mechanical stimuli of ECs such as wall shear stress (WSS) and arterial wall strains greatly influence the function and morphology of these cells. The present article deals with computations of these stimuli for a 3D model of a healthy coronary artery bifurcation. The focus of the study is to propose an accurate method for computations of WSS and strains. Two approaches are considered. The coupled simultaneous simulation of arterial wall and blood flow called Fluid-Structure Interaction (FSI) simulation and decoupled one,which simulates each domain (fluid and solid domain) separately. The study demonstrates that the computed circumferential strain resulting from both methods are identical. However, longitudinal strain and WSS are very different from these two approaches. The resulting time averaged wall shear stress (TAWSS) from decoupled fluid model is always higher than corresponding value from FSI simulation. While, oscillatory shear index (OSI) from rigid wall model is lower than the values resulting from FSI. Therefore, the decoupled simulation may underestimate the atheroprone sites of the artery and suggests that using FSI simulation for mechanical stimuli of ECs is inevitable.
228
237
H.A.
Pakravan
H.A.
Pakravan
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
Iran
pakravan@mech.sharif.edu
M.S.
Saidi
M.S.
Saidi
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
Iran
mssaidi@sharif.edu
B.
Firoozabadi
B.
Firoozabadi
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
Iran
firoozabadi@sharif.edu
Fluid-structure interaction
hemodynamics
coronary artery
wall shear stress
cyclic stretch
endothelial cells
http://scientiairanica.sharif.edu/3829.html
10.24200/sci.2016.3829
Probing into the Effects of Fuel Injection Pressure and Nozzle Hole Diameter on Spray Characteristics under Ultra-high Injection Pressures Using Advanced Breakup Model
Probing into the Effects of Fuel Injection Pressure and Nozzle Hole Diameter on Spray Characteristics under Ultra-high Injection Pressures Using Advanced Breakup Model
2
2
In this article, non-evaporating and non-reacting diesel spray is modeled under ultra-high injection pressure using an Eulerian-Lagrangian scheme. This is accomplished in order to probe into the effects of injection pressure, nozzle diameter, and ambient density on spray characteristics. An advanced hybrid breakup model that takes into consideration the transient processes during spray injection has been added to the open source code OpenFOAM. Reynolds-Average Navier-Stokes (RANS) equations are solved using standard turbulence model and fuel droplet is tracked by a Lagrangian scheme. Published experimental data have been used for validation of spray characteristics at 15 kg/m3 ambient density and injection pressures of 100, 200 and 300MPa. Also, three nozzle diameters of 0.08, 0.12 and 0.16mm have been implemented for investigating the effect of this parameter on spray formation. Computed spray shape, jet penetration, spray volume, equivalent ratio along the injector axis and Sauter Mean Diameter (SMD) illustrate good agreement with experimental data of single hole nozzle and symmetric spray. The effects of fuel injection pressure, nozzle hole diameter and ambient density on main spray parameters are presented. It is concluded that numerical model presented here is quite suitable for accurately predicting diesel spray shapes under ultra-high injection pressures.
2
In this article, non-evaporating and non-reacting diesel spray is modeled under ultra-high injection pressure using an Eulerian-Lagrangian scheme. This is accomplished in order to probe into the effects of injection pressure, nozzle diameter, and ambient density on spray characteristics. An advanced hybrid breakup model that takes into consideration the transient processes during spray injection has been added to the open source code OpenFOAM. Reynolds-Average Navier-Stokes (RANS) equations are solved using standard turbulence model and fuel droplet is tracked by a Lagrangian scheme. Published experimental data have been used for validation of spray characteristics at 15 kg/m3 ambient density and injection pressures of 100, 200 and 300MPa. Also, three nozzle diameters of 0.08, 0.12 and 0.16mm have been implemented for investigating the effect of this parameter on spray formation. Computed spray shape, jet penetration, spray volume, equivalent ratio along the injector axis and Sauter Mean Diameter (SMD) illustrate good agreement with experimental data of single hole nozzle and symmetric spray. The effects of fuel injection pressure, nozzle hole diameter and ambient density on main spray parameters are presented. It is concluded that numerical model presented here is quite suitable for accurately predicting diesel spray shapes under ultra-high injection pressures.
238
248
Mahdi
Yousefifard
Mahdi
Yousefifard
Department of Marine Technology, Amirkabir University of Technology, Tehran, Iran
Iran
Parviz
Ghadimi
Parviz
Ghadimi
Department of Marine Technology, Amirkabir University of Technology, Tehran, Iran
Iran
pghadimi@aut.ac.ir
Seyed Mostafa
Mirsalim
Seyed Mostafa
Mirsalim
Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran
Iran
Diesel spray
Ultra-high injection pressure
Nozzle hole diameter
Penetration length
Breakup model
OpenFOAM
http://scientiairanica.sharif.edu/3830.html
10.24200/sci.2016.3830
A global Ritz formulation for the free vibration analysis of hybrid metal-composite thick trapezoidal plates
A global Ritz formulation for the free vibration analysis of hybrid metal-composite thick trapezoidal plates
2
2
A general variational formulation for free vibration analysis of hybrid (metalcomposite) plates with a trapezoidal platform is presented in this paper. The plate is composed of two distinguished parts in the span direction, where the inboard section is assumed to be made of an isotropic metal, and the outboard section is from a laminated composite material. Kinematics, corresponding to the First-order Shear Deformation plate Theory (FSDT), is used to take into account the non-classic eects of transverse shear deformation and rotational inertia for both sections in the analysis. The developed approach is based on the global Ritz method, where the transverse de flection and two rotations of the plate are independently approximated by simple and Legendre polynomials. The algorithm allows one to obtain an approximate analytical solution for the hybrid plate with dierent geometric aspect ratios, numbers of layers, staking sequences and metal to composite ratios. The results of the present work for special cases, including pure metal and pure composite plates, are in good agreement with previous works.
2
A general variational formulation for free vibration analysis of hybrid (metalcomposite) plates with a trapezoidal platform is presented in this paper. The plate is composed of two distinguished parts in the span direction, where the inboard section is assumed to be made of an isotropic metal, and the outboard section is from a laminated composite material. Kinematics, corresponding to the First-order Shear Deformation plate Theory (FSDT), is used to take into account the non-classic eects of transverse shear deformation and rotational inertia for both sections in the analysis. The developed approach is based on the global Ritz method, where the transverse de flection and two rotations of the plate are independently approximated by simple and Legendre polynomials. The algorithm allows one to obtain an approximate analytical solution for the hybrid plate with dierent geometric aspect ratios, numbers of layers, staking sequences and metal to composite ratios. The results of the present work for special cases, including pure metal and pure composite plates, are in good agreement with previous works.
249
259
S.
Shokrollahi
S.
Shokrollahi
Department of Aerospace Engineering, Malek Ashtar University of Technology, Tehran, Iran
Iran
S.
Shafaghat
S.
Shafaghat
Department of Aerospace Engineering, Malek Ashtar University of Technology, Tehran, Iran
Iran
Ritz method
Hybrid plate
Thick trapezoidal plates
natural frequency
http://scientiairanica.sharif.edu/3831.html
10.24200/sci.2016.3831
A Computational Model for Estimation of Mechanical Parameters in Chemotactic Endothelial Cells
A Computational Model for Estimation of Mechanical Parameters in Chemotactic Endothelial Cells
2
2
A cell migration numerical simulation is presented to mimic the motility of endothelial cells subjected to the concentration gradients of Forebrain embryonic cortical neuron conditioned medium (CM). This factor was previously shown to induce the directional chemotaxis of endothelial cells with over-expressed G protein coupled receptor 124 (GPR 124). A cell simulator program incorporates basic elements of the cell cytoskeleton including membrane, nucleus and cytoskeletons. The developed 2D cell model is capable of responding to concentration gradients of biochemical factors by changing the cytoskeleton arrangement. Random walk force, cell drag force and the cell inertial effects are also implemented into the cell migration to complete the simulation of the phenomenon. The obtained results of cell migration were calibrated with experimental cell chemotaxis data. This model can be implemented for prediction of cell behavior during cell chemotaxis and also it provides a powerful tool to explain the cell migration phenomenon mechanistically.
2
A cell migration numerical simulation is presented to mimic the motility of endothelial cells subjected to the concentration gradients of Forebrain embryonic cortical neuron conditioned medium (CM). This factor was previously shown to induce the directional chemotaxis of endothelial cells with over-expressed G protein coupled receptor 124 (GPR 124). A cell simulator program incorporates basic elements of the cell cytoskeleton including membrane, nucleus and cytoskeletons. The developed 2D cell model is capable of responding to concentration gradients of biochemical factors by changing the cytoskeleton arrangement. Random walk force, cell drag force and the cell inertial effects are also implemented into the cell migration to complete the simulation of the phenomenon. The obtained results of cell migration were calibrated with experimental cell chemotaxis data. This model can be implemented for prediction of cell behavior during cell chemotaxis and also it provides a powerful tool to explain the cell migration phenomenon mechanistically.
260
267
Amir
Kiyoumarsioskouei
Amir
Kiyoumarsioskouei
Mechanical Engineering School, Sharif University of Technology, Tehran, Iran
Iran
Amir
Shamloo
Amir
Shamloo
Mechanical Engineering School, Sharif University of Technology, Tehran, Iran
Iran
shamloo@sharif.edu
Sajjad
Azimi
Sajjad
Azimi
Mechanical Engineering School, Sharif University of Technology, Tehran, Iran
Iran
Mohammad
Abeddoust
Mohammad
Abeddoust
Mechanical Engineering School, Sharif University of Technology, Tehran, Iran
Iran
Mohammad Said
Saidi
Mohammad Said
Saidi
Mechanical Engineering School, Sharif University of Technology, Tehran, Iran
Iran
Cell motility
chemotaxis
reaction-diffusion model
cell cytoeskeleton simulation
http://scientiairanica.sharif.edu/3832.html
10.24200/sci.2016.3832
2D hierarchical heat transfer computational model of natural fiber bundle reinforced composite
2D hierarchical heat transfer computational model of natural fiber bundle reinforced composite
2
2
In this paper, a two-dimensional (2D) hierarchical computational model was developed for analysis of heat transfer in unidirectional composites filled with doubly periodic natural fiber bundle. The reinforcement in the composite encloses large number of small lumens, which hints the composite consisting of matrix and natural fiber bundles involves structures at several level scales. In the model, the unit representative volume element (RVE) of composite with fibers arranged periodically was taken into consideration and equivalent models were converted from differently scaled RVEs by a two-step homogenized procedure. Subsequently, numerical simulation of heat–transfer process in each model was performed by finite element analysis and the overall transverse thermal conductivity of each model was obtained numerically. To verify the developed composite models, an optional interrelationship between the overall thermal conductivity of the equivalent natural fiber bundle and the solid region phase in it was obtained for the first-step homogenization and then was compared with analytical results or numerical results from other methods. Finally, a sensitivity analysis was conducted with the models to investigate how changes in the values of important variables such as thermal conductivity and volume fraction of constituent can affect the effective thermal properties of the composite.
2
In this paper, a two-dimensional (2D) hierarchical computational model was developed for analysis of heat transfer in unidirectional composites filled with doubly periodic natural fiber bundle. The reinforcement in the composite encloses large number of small lumens, which hints the composite consisting of matrix and natural fiber bundles involves structures at several level scales. In the model, the unit representative volume element (RVE) of composite with fibers arranged periodically was taken into consideration and equivalent models were converted from differently scaled RVEs by a two-step homogenized procedure. Subsequently, numerical simulation of heat–transfer process in each model was performed by finite element analysis and the overall transverse thermal conductivity of each model was obtained numerically. To verify the developed composite models, an optional interrelationship between the overall thermal conductivity of the equivalent natural fiber bundle and the solid region phase in it was obtained for the first-step homogenization and then was compared with analytical results or numerical results from other methods. Finally, a sensitivity analysis was conducted with the models to investigate how changes in the values of important variables such as thermal conductivity and volume fraction of constituent can affect the effective thermal properties of the composite.
268
276
Hui
Wang
Hui
Wang
Institute of Scientific and Engineering Computation, Henan University of Technology, Zhengzhou, 450001, China
Iran
Yi
Xiao
Yi
Xiao
Research School of Engineering, Australian National University, Canberra, ACT 2601, Australia
Iran
Qing-Hua
Qin
Qing-Hua
Qin
Research School of Engineering, Australian National University, Canberra, ACT 2601, Australia
Iran
qinghua.qin@anu.edu.au
Hierarchical composite
natural fiber bundle
lumen
heatconduction
finite elementmethod
thermal conductivity
http://scientiairanica.sharif.edu/3833.html
10.24200/sci.2016.3833
An Eulerian-Lagrangian model to study the operation mechanism of Stirling pulse tube refrigerators
An Eulerian-Lagrangian model to study the operation mechanism of Stirling pulse tube refrigerators
2
2
This paper is aimed to study the operation mechanism of Stirling pulse tube refrigerators (PTRs) by tracing working gas elements characteristics at the cold end of the system using both Eulerian and Eulerian-Lagrangian (E-L) methods. The main objective of the investigations is to demonstrate non-symmetry effects in the pulse tube section of the system. Elemental cyclic-enthalpy transfer of simple (S), double-inlet (DI) and multi-mesh regenerator (MM) PTRs are also investigated to demonstrate the effects of DI and MM systems on the refrigeration mechanism of PTRs. It is shown that the elemental cyclic-enthalpy transfer of SPTR is less than those of DIPTR, MMPTR and MMDIPTR, though it's elemental cyclic-temperature reduction is more than the others; because, the mass flow rate upon cold end of the SPTR is less than the others. Regarding the reduction of losses in DIPTR and MMPTR, their cold end mean pressure and density increase which consequently lead the cold end mass flow rate and cyclic-enthalpy transfer to increases. Increase in enthalpy transfer of MM-PTR, MM-DIPTR and DIPTR consequently improves their cooling performance.
2
This paper is aimed to study the operation mechanism of Stirling pulse tube refrigerators (PTRs) by tracing working gas elements characteristics at the cold end of the system using both Eulerian and Eulerian-Lagrangian (E-L) methods. The main objective of the investigations is to demonstrate non-symmetry effects in the pulse tube section of the system. Elemental cyclic-enthalpy transfer of simple (S), double-inlet (DI) and multi-mesh regenerator (MM) PTRs are also investigated to demonstrate the effects of DI and MM systems on the refrigeration mechanism of PTRs. It is shown that the elemental cyclic-enthalpy transfer of SPTR is less than those of DIPTR, MMPTR and MMDIPTR, though it's elemental cyclic-temperature reduction is more than the others; because, the mass flow rate upon cold end of the SPTR is less than the others. Regarding the reduction of losses in DIPTR and MMPTR, their cold end mean pressure and density increase which consequently lead the cold end mass flow rate and cyclic-enthalpy transfer to increases. Increase in enthalpy transfer of MM-PTR, MM-DIPTR and DIPTR consequently improves their cooling performance.
277
284
A.
Kardgar
A.
Kardgar
Faculty of Mechanical Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran, Iran
Iran
A.
Jafarian
A.
Jafarian
Faculty of Mechanical Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran, Iran
Iran
jafarian@modares.ac.ir
M.
Arablu
M.
Arablu
Faculty of Mechanical Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran, Iran
Iran
Eulerian-Lagrangian model
Pulse tube refrigerator
numerical simulation
Enthalpy flow
http://scientiairanica.sharif.edu/3834.html
10.24200/sci.2016.3834
Softening Effect of the Nonlocality against the Hardening Effect of the Stretching in a Capacitive Micro-beam
Softening Effect of the Nonlocality against the Hardening Effect of the Stretching in a Capacitive Micro-beam
2
2
This paper investigates the nonlinear resonant behavior of a capacitive micro-beam based on the nonlocal theory of elasticity. The micro-beam is deflected by a DC voltage, where it acts as a micro-resonator by superimposing an AC voltage. Taking into account stretching effects, the Galerkin projection method is used to discretize the partial differential equations into a set of nonlinear, ordinary differential equations. Multiple-scales method is used to obtain an approximate analytical solution to construct the nonlinear resonant curves of the transverse vibration amplitude. Taking into account the classical and nonlocal elasticity theories, the frequency response curves are plotted for different values of DC voltage. Effects of mid-plane stretching on the resonant curves are also examined. The hardening behavior of the system is shown to decrease due to the presence of the nonlocality as well as the DC voltage. However, mid-plane stretching increases the hardening effects. The results show that, in spite of the existence of nonlinearity in the system, this conflict effect can result in a linear frequency response curve for some values of the nonlocal parameter.
2
This paper investigates the nonlinear resonant behavior of a capacitive micro-beam based on the nonlocal theory of elasticity. The micro-beam is deflected by a DC voltage, where it acts as a micro-resonator by superimposing an AC voltage. Taking into account stretching effects, the Galerkin projection method is used to discretize the partial differential equations into a set of nonlinear, ordinary differential equations. Multiple-scales method is used to obtain an approximate analytical solution to construct the nonlinear resonant curves of the transverse vibration amplitude. Taking into account the classical and nonlocal elasticity theories, the frequency response curves are plotted for different values of DC voltage. Effects of mid-plane stretching on the resonant curves are also examined. The hardening behavior of the system is shown to decrease due to the presence of the nonlocality as well as the DC voltage. However, mid-plane stretching increases the hardening effects. The results show that, in spite of the existence of nonlinearity in the system, this conflict effect can result in a linear frequency response curve for some values of the nonlocal parameter.
285
294
Shiva
Valilou
Shiva
Valilou
Department of Mechanical Engineering, Urmia University, Urmia, Iran
Iran
Rasoul
Shabani
Rasoul
Shabani
Department of Mechanical Engineering, Urmia University, Urmia, Iran
Iran
r.shabani@urmia.ac.ir
Ghader
Rezazadeh
Ghader
Rezazadeh
Department of Mechanical Engineering, Urmia University, Urmia, Iran
Iran
grezazadeh44@yahoo.com
Nonlocal theory
nonlinear dynamics
frequency response
Perturbation method
http://scientiairanica.sharif.edu/3835.html
10.24200/sci.2016.3835
A Meshless Method to Simulate the Interactions Between A Large Soft Tissue and A Surgical Grasper
A Meshless Method to Simulate the Interactions Between A Large Soft Tissue and A Surgical Grasper
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2
Realistic simulation of tool-tissue interactions can help to develop more effective surgical training systems and simulators. This study used a finite element and meshless modeling approaches to simulate the grasping procedure of a large intra-abdominal organ, i.e., kidney, during laparoscopic surgery. Results indicated that the accuracy of meshless method was comparable with that of the finite element, with the root mean square errors in the range of 0.8 to 2.3 mm in different directions. For the model presented in this study, the computational cost of the meshless method, was much less than that of the finite element model.
2
Realistic simulation of tool-tissue interactions can help to develop more effective surgical training systems and simulators. This study used a finite element and meshless modeling approaches to simulate the grasping procedure of a large intra-abdominal organ, i.e., kidney, during laparoscopic surgery. Results indicated that the accuracy of meshless method was comparable with that of the finite element, with the root mean square errors in the range of 0.8 to 2.3 mm in different directions. For the model presented in this study, the computational cost of the meshless method, was much less than that of the finite element model.
295
300
Zeinab
Saghaei Nooshabadi
Zeinab
Saghaei Nooshabadi
Mechanical Engineering Department Sharif University of Technology P.O.Box 11155-9567 Azadi Ave, Tehran, Iran
Iran
Elahe
Abdi
Elahe
Abdi
Institute of Microengineering EPFL CH-1015 Lausanne, Switzerland
Iran
elahe.abdi@epfl.ch
Farzam
Farahmand
Farzam
Farahmand
Mechanical Engineering Department Sharif University of Technology RCBTR, Tehran University of Medical Sciences P.O.Box 11155-9567 Azadi Ave, Tehran, Iran
Iran
farahmand@sharif.edu
Roya
Narimani
Roya
Narimani
Mechanical Engineering Department Sharif University of Technology P.O.Box 11155-9567 Azadi Ave, Tehran, Iran
Iran
narimani@sharif.edu
Mahmoud
Chizari
Mahmoud
Chizari
Mechanical Engineering Department Sharif University of Technology P.O.Box 11155-9567 Azadi Ave, Tehran, Iran
Iran
chizari@sharif.edu
Intra-abdominal
Large Deformation
Finite Element
meshless method