IFC
text
article
2017
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
0
0
http://mme.modares.ac.ir/article_16448_3d6ffdb612954f5d5934cdae9f3bf30a.pdf
Fracture assessment of specimens weakened by Unotch made of functionally graded materials under mode I loading
Mohammad Reza
Mosadeghi
دانشکده مهندسی مکانیک، دانشگاه صنعتی امیرکبیر
author
Hadi
Salavati
دانشکده مهندسی مکانیک، دانشگاه شهید باهنر کرمان
author
Yoness
Alizadeh
دانشکده مهندسی مکانیک، دانشگاه صنعتی امیرکبیر
author
Amir
Abdollah
دانشکده مهندسی مکانیک، دانشگاه صنعتی امیرکبیر
author
text
article
2017
per
In this paper, fracture behavior of functionally graded material weakened by Unotches under mode I loading has been investigated. Electro slag remelting process has been used to produce functionally graded specimens in a notch arrester configuration. Hardness test has been utilized to define the position of each layer. Mechanical properties, including elastic modulus and poisson's ratio, vary along the width of Unotched specimens. The critical fracture load (Fcr) was achieved by performing three point bending examination and using forcedisplacement curve. Then, the process simulation was done by finite element software. Firstly, Jcr of each specimen was calculated by using critical value of strain energy averaged over a welldefined control volume. Then the critical fracture load was evaluated by means of the J Integral criterion. In this research, the effect of the notch root radius, for a fixed notch depth, on the Jcr value as well as the critical fracture load has been studied. To compare fracture behavior of the FG specimens with the corresponding homogeneous ones, have the same properties with the notch root layer in FG specimen, Fcr and Jcr value of each have been investigated. The average difference between the predicted Fcr by J integral criteria and experimental results is 17.84%. Finally, the effect of number of graded area layers on Jcr and Fcr has been investigated. The results shows, the value of Jcr and Fcr do not be affected while the number the number of layers more than 20.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
1
9
http://mme.modares.ac.ir/article_16121_8029fda98a6b333a3af6656256b71331.pdf
Pore Scale Modelling of Cathode Catalyst Layer of PEM Fuel Cell to Investigate the Tortuosity and Effective Diffusivity
Hossein
Fathi
PhD candidate
author
seyed Hossein
Mansouri
عضو هیئت علمی
author
Amir
Raoof
Faculty staff
author
text
article
2017
per
According to the significant effect of the structure and saturation of cathode catalyst layer (CCL) on the operation of proton exchange membrane fuel cell (PEMFC), a pore scale model is presented to simulate the transport processes in CCL. Using this model, the tortuosity and macroscopic effective diffusivity of CCL with different porosities and saturation levels were obtained. The water distribution was obtained by solving twophase flow equations using volume of fluid (VOF) method. The structure of CCL was reconstructed by assuming agglomerates as equallysized circles and spheres in twoand threedimensional domains, respectively. A sequential algorithm was used to determine the location of agglomerates in the computational domain with specific overlap. A comparison was made between the results obtained for three and twodimensional domains which showed 2D assumption results in an overestimating on effective diffusivity. However, the variation trend of effective diffusivity versus porosity was about the same. According to the results, due to the blocking effect of water presence in CCL, the increase of saturation causes less available pathways for gas to diffuse. Therefore, the effective diffusivity decreases by the increase of saturation level. Moreover, the decrease of porosity leads to the increase of tortuosity which results in lower pathways for gas to diffuse into the domain and hence less effective diffusivity was obtained. The decrease of oxygen effective diffusivity of CCL causes a lack of oxygen concentration at the electrochemical reaction sites and leads to the decrease of the PEMFC performance.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
10
18
http://mme.modares.ac.ir/article_16100_17212badb64254998fd601cb885399ea.pdf
Determination of blast pressure distribution around cylindrical shape based on numerical simulation of explosion
Aliakbar
Aghakouchak
دانشگاه تربیت مدرس
author
Seyed Hamed
Khalilpour
کارشناسی ارشد مهندسی عمران
author
Ghasem
Dehghani
استادیار دانشگاه مالک اشتر
author
text
article
2017
per
Explosion is considered as the most hazardously event in petrochemical facilities and offshore structures. In these facilities, pressure vessels are very important because their explosion may result in damage to other modules. In practical design, external blast load is applied to one side of pressure vessels as uniform load.In this paper we try to propose more realistic distribution to conform experimental results. This paper includes validation of Eulerian domain capability in finite element program ABAQUS to carryout uncoupled Eulerian Lagrangian analysis .The results show good agreement between Eulerian capability and experimental results in locations that do not have high turbulence effect, but in points where turbulence effects and vortexes are increased, error in numerical model is larger. Also, this paper shows that the method which is usually used to apply blast loads to cylindrical materials has a great error in comparison with numerical simulation and experimental results. Thus, in this paper is presented a blast load distribution which can be used in future research and industrial designs for vertical shape or horizontal shape of cylindrical materials with a variety of different diameters.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
19
28
http://mme.modares.ac.ir/article_16084_92b4784f06bbdecd1b91a2740fbe3ca1.pdf
Double acting expansion engine simulation performance based on control valve type and gas composition
Mahmood
Farzaneh Gord
Shahrood Univ. of Tech.  Department of Mechanical Engineering
author
Mohsen
Jannatabadi
دانشجوی دکترا، مهندسی مکانیک، دانشگاه صنعتی شاهرود، شاهرود
author
text
article
2017
per
Replacement of expansion valves which are used in natural gas pressure reduction stations, with expansion engine, to recycle wasted energy to generate electricity is the main objective of this study. In these engines, ports are used for inlet and outlet the gas. Control valve geometry set on these ports has a great impact on performance of this engine. In this research, simulation and optimization of the optimum opening and closing time of these valves according to two types of valve, piston and spool valves, to maximize the Exergy Efficiency has been done for the first time which Genetic Algorithm is used for this optimization. Simulation has been conducted with regard to the composition of gas stations which to calculate the thermodynamic properties of natural gas, AGA8 standard is used. For optimization constrain of having no back flow has been applied. Results showed that exergy destruction due to outlet processing in piston valve and due to inlet processing in cylinder valve is more than other destruction sources. Overall engine with cylinder valve has better performance than engine with piston valve. Variation of supply line pressure showed that engine with cylinder valve could not be used in inlet pressure of 30 bar, because engine doesn’t produce power.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
29
40
http://mme.modares.ac.ir/article_16098_8c9dd7b24a0d9dc31ebb1a2a0c550813.pdf
Coarsegraining of proteins using collective coordinates of the residues
Reza
Soheilifard
دانشگاه حکیم سبزواری
author
text
article
2017
per
Many phenomena in molecular biophysics happen over time and length scales that are inaccessible by fully atomistic computer simulations. Therefore, coarsegraining has become a common strategy for bridging the gap in time and length scale between the atomistic simulation and biological processes. Furthermore, in many cases the system dynamics is better represented in terms of collective coordinates. This study is concerned with a rigorous coarsegraining method for dynamics of linear systems using collective coordinates of the resiudes rather than coordinates of individual atoms. In this method an invertible linear timeindependent map is considered to relate the original displacements to the collective coordinates. Then, the conformational space of the transformed system is divided into master and slave degrees of freedom. Under the assumption that the masters are slower than the slaves and by expanding the masters’ displacements in Taylor series with respect to time variable, the method results in effective stiffness, friction and mass for the coarsegrained system in terms of collective coordinates of the residues. Center of mass and hydrodynamic center of reaction coordinates of the residues are considered as collective coordinates. Application of the method to finding the relaxation dynamics of various proteins shows that using center of mass coordinates significantly improves the results.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
41
46
http://mme.modares.ac.ir/article_16122_b46d997f7f481855e31f61e839602d5a.pdf
Vibration analysis of a microplate in contact with a fluid based on the modified couple stress theory
Soroush
OmidDezyani
M.Sc. Student, Department of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran
author
RamazanAli
JafariTalookolaei
Assistant Professor, Babol Noshirvani University of Technology
author
Maryam
Abedi
Department of Mechanical Engineering, Faculty of Engineering and Technology, University of Mazandaran, Babolsar, Iran
author
Hamed
Afrasiab
Assistant Prof., Department of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran
author
text
article
2017
per
In this study, the hydrostatic vibration analysis of an isotropic rectangular microplate in partial contact with a bounded fluid is studied. Modified couple stress theory based on the Kirchhoff plate assumptions are used to mathematically model the problem. The extended Hamilton’s principle is employed to drive the governing differential equation of motion and the corresponding boundary conditions. The transverse displacement of the microplate is approximated by a set of admissible functions which must satisfy the geometric boundary conditions. The fluid is assumed to be incompressible, inviscid and irrotational and the fluid velocity potential is obtained using the boundary and compatibility conditions. Natural frequencies of the microplate are calculated using the RayleighRitz method. To validate the present results, the natural frequencies of an isotropic macroplate in contact with fluid are compared with the available data in the literature and very good agreements are observed. Finally using the numerical data, the effect of different parameters such as thickness to length scale parameter, aspect ratio, length to thickness ratio and boundary conditions on the natural frequencies of the microplate are discussed in detail. We have observed that the difference between the natural frequencies predicted using the classical theory and the one evaluated by the modified couple stress theory is significant when thickness of the microplate is small, but diminishes as thickness increases.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
47
57
http://mme.modares.ac.ir/article_16123_b0d8d63054af0e9abdb0a6a71bd837a5.pdf
Low Velocity Impact Response of CARALL composites reinforced with nano particles
Reza
Amooyi Dizaji
کارشناس ارشد دانشگاه صنعتی سهند
author
Mojtaba
Yazdani
Associate Professor of Mechanical Engineering  (Applied Mechanics, Solid)
author
text
article
2017
per
In, this research, the effects of adding silica and multiwall carbon nanotubes (MWCNT) nano particles on the low velocity impact response are experimentally studied. Vacuum assisted resin transfer molding (VARTM) method has been used to manufacture nano composite with 11 layers of plain weave carbon fibers 200 g⁄m^2 , resin R510 and hardener H515 with 66% fiber volume fraction. Samples made of nano silica and MWCNT particles have been dispersed with 1 wt. %. The prepared CARALL is made of two Aluminum 2024 facing sheets. Low velocity impact tests have been conducted using by drop weight device at the impact energy of 20, 40 and 60 j with velocity of 2.6, 3.68 and 4.5 m⁄s . The results of the low velocity impact experiments indicates that the MWCNT improves performance of fiber metal composite material and the effects of MWCNT in improving the impact properties of fiber metal laminate composite is better than of nano silica. Better adhering and dispersion of MWCNT and strong interfacial creation are some other effect factors of impact response sample reinforced with multiwall carbon nanotubes in comparison to nano silica.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
58
64
http://mme.modares.ac.ir/article_16126_47e2db65073b9c8cd121e98b1240079f.pdf
A BEM/RANS Coupled Method for Numerical Simulations of Podded Drive System
Reza
Shamsi
Amirkabir University of Technology
author
Hassan
Ghassemi
Amirkabir University of Technology
author
text
article
2017
per
Podded drive systems are one the recent innovation in marine propulsion systems. Hydrodynamic analysis of this system is more complicated than conventional propellerrudder systems. The different numerical methods have been used in the hydrodynamic analysis of podded drive systems. The range of these methods is from the potential method or potential/viscous approach to pure viscous methods. In this paper, we applied coupled approach in this regard. The main purpose of this research is developing a BEM/RANS coupled method for numerical simulation of podded drives. In the proposed Potential/Viscous coupled method, the flow around rotating part (propeller) is simulated by a BEM code. Then fixed parts (pod and strut) are modelled by a RANS solver. In RANS solver, the propeller can be substituted by a set of equivalent forces which called body force and added in the right hand of momentum equation. Two cycles are available for coupling the result between potential and viscous method. The coupled method is ﬁrst studied and validated with a single propeller. Afterward, the propulsive performance of the podded drive systems is studied. The results include the propeller thrust coefﬁcient, the propeller torque coefﬁcient, and the axial force coefﬁcient. The results obtained by coupled method are compared to and verified by the experimental data.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
65
76
http://mme.modares.ac.ir/article_16124_267de41fe7d4308af1587a15355dd66f.pdf
Analytical Investigation of Anode Electrothermal Process in a MPD Thruster
Mahdy
Ahangar
گروه هوافضا، دانشگاه شهید بهشتی
author
Akram
Sedigh
پژوهشگر / آزمایشگاه پیشرانش، سوخت و احتراق / دانشکده مهندسی هوافضا / دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2017
per
In this research, the electrothermal characteristics of anode have been analytically investigated by considering two subzones including the quasineutral and nonneutral plasma flow near the anode surface. A correlation between current density and anode fall voltage has been derived by using the continuity and momentum equations for electron in the nonneutral plasma subzone. Also, two relations have been deduced from the magnetic field induction equation and Ohm’s law to determine the current densities and voltage drops in the quasineutral plasma subzone. The suggested solution algorithm has been based on the satisfaction of current continuity condition to be converged by a trial and error method. The Princeton benchmark thruster has been investigated for the discharge current of 8 kA with mass flow rates of 4 and 24 gr/s to evaluate the developed algorithm. The obtained analytical results show that under operating conditions with mass flow rates of 4 and 24 g/s, the heat flux values are respectively in the range of 480 to1350 and 400 to1490 W/cm2, the current densities vary from 24 to 90 and from 33 to 140 A/cm2, and also the anode falls change from 5.8 to 11 and 4.9 to 6 V. The analytical algorithm has predicted the heat fluxes, current densities, and anode falls along the anode face in good agreement with measurements. It has been seen that the heat flux and current density around the anode midlip, where the anode fall has its minimum value, have been maximized. By using the second thermodynamic law, it has been shown that the probability density function of effective velocity has a Gaussian distribution. Therefore, under this circumstance, entropy has been maximized, and consequently the heat flux and current density profiles have been taken the summit form.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
77
84
http://mme.modares.ac.ir/article_16125_8fcc2b37fcb0d77111c164ec40fd4ae2.pdf
Numerical Modeling of HighSpeed Tunneled Hull Turning Circle Maneuver for Investigating the Speed and Rudder Angle Effects on Maneuver Parameters
Armin
Najarian
دانشجو کارشناسی ارشد دانشگاه صنعتی نوشیروانی بابل
author
Rouzbeh
Shafaghat
عضو هیات علمی دانشگاه صنعتی نوشیروانی بابل
author
text
article
2017
per
Demands for high speed vessels are increasing due to various usages. Reducing the resistance to achieve high speeds is an important objective in design of high speed crafts. Creating longitudinal side tunnels in the hull causes resistance reduction. Designing the boat is not right only for reducing drag force; stability and maneuverability are also important factors. In this paper, high speed tunneled hull performance is evaluated considering numerical simulation of turning circle maneuver as a standard maneuver. The numerical approach is implemented due to high and acceptable accuracy compared with mathematical models and lower cost compared to experimental tests. Among the various techniques, modeling of maneuver of the boat was performed by considering mesh movement with boat and combination of sliding mesh and movement of domain as an effective method. Reducing computation time and increasing the accuracy of solution is of its advantages. Finite volume method and kω model is used respectively for discretization equations and simulation of turbulence. In free surface modeling, mixture model was preferred instead of free surface model. Solution methodology was validated using experimental results of a singlehull boat. Path of the boat in various tests was presented in the result section, considering the effect of angle of rudder, thrust and movement mode of the boat on the maneuver parameters. The results show enhancing maneuverability of the boat by approaching the planing mode so that by increasing the speed and closing to planing mode, tactical diameter is reduced up to 7.5% compared to the displacement mode.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
85
92
http://mme.modares.ac.ir/article_16127_793bbed4dabe0c0d057325d06d7be0a9.pdf
The Effect of Low Power CO2 Laser Cutting Process Parameters on Polycarbonate Cut Quality Produced By Injection Molding
Mahmoud
Moradi
Malayer University
author
Omid
Mehrabi
Department of Mechanical Engineering, Faculty of Engineering, Malayer University, Malayer, Iran
author
Taher
Azdast
Department of Mechanical Engineering, Urmia University, Urmia, Iran
author
Khaled Y.
Benyounis
School of Mechanical & Manufacturing Engineering. Dublin City University, Dublin, Ireland
author
text
article
2017
per
In the present study, the effect of gas pressure and laser beam focal plane position (FPP) on the geometry and roughness of kerf quality of the injected polycarbonate with the thickness of 3.2 mm in laser cutting by using low power continuous CO2 laser is investigated. Gas pressure and FPP were variable parameters in this research, while other processing parameters (i.e. laser power and cutting speed) are considered constant. Gas pressure experiments were carried out by varying the gas pressure from 0.5 to 3.5 bars and the FPP experiments were performed in FPP= 0 to FPP= 4mm. Kerf geometry quality (upper and lower kerf width, kerf taper, upper heat affected zone) and surface roughness of the kerf wall were also considered as the responses. Results show that gas pressure and FPP has a significant effect on the kerf quality. Increasing the gas pressure and the position of the laser beam focal point increases the upper and lower kerf width. Results also reveal that upper heat affected zone value decreases by reduction in FPP and increases the gas pressure. Increasing the gas pressure will reduce the kerf taper angle and reduction in the FPP reduces the surface roughness of the kerf wall. Observations indicated that by locating the laser spot point in the depth of the workpiece the laser cutting quality increases.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
93
100
http://mme.modares.ac.ir/article_16128_256d9ce343f4a2a93efe05b5f50a0b6f.pdf
Experiment investigation of plane stress fracture toughness for aluminum sheets produced by Cold Roll Bonding Process
Davood
Rahmatabadi
کارشناس ارشد دانشگاه علم و صنعت
author
Ramin
Hashemi
Assistant professor / Iran University of Technology
author
Bijan
Mohammadi
استادیار دانشگاه علم و صنعت
author
Taghi
Shojaee
دانشجوی دکترای علم و صنعت
author
text
article
2017
per
Cold roll bonding process is one methods for production of multilayered sheets with same and dissimilar materials that, in the past decade has been attention of many researchers. In this research, for the first time and according to ASTME561 and using compact tension specimens investigated plane stress fracture toughness for thin for two layers of aluminum sheets produced by Cold Roll Bonding Process. The fracture toughness is an important parameter in the design that their analysis can predict crack growth and life for material has crack. In addition to the fracture toughness, mechanical properties and tensile fracture surfaces were evaluated by using of uniaxial tensile test, micro hardness and scanning electron microscopy, respectively. Results of these test demonstrated that value of tensile strength, micro hardness and plane stress fracture toughness for two layers of aluminum sheets produced by Cold Roll Bonding process is far more than annealed sample that compared to the initial sheet respectively 150%, 80% and 51% improved. But value of elongation decreased. Also results of SEM demonstrated that dimples shallower and smaller than the initial sample that this factor confirmed increasing strength and reducing ductility. Of course the main role of this variation, applying high strain and cold working plays.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
101
108
http://mme.modares.ac.ir/article_16129_c51b817ee642465ca5dfc9579688d128.pdf
The Investigation of mechanical and metallurgical properties of multilayered Al/Cu composite produced by Accumulative Press Bonding (APB) process
Amir
Mostafapour
دانشیار، دانشکده مهندسی مکانیک، دانشگاه تبریز
author
Vahid
Mohammadi Nia
کارشناس ارشد
author
Mosayeb
Ahmadi
کارشناس ارشد
author
text
article
2017
per
Accumulative press bonding (APB) process is one of the newest approaches of SPD processes in which the applying of strain in materials lead to the substantial plastic deformation and microscopic changes. In this study, APB method was used to production of Al/Cu composite and AA1100 and pure commercial Copper sheets used as matrix and reinforcement respectively. Microstructure evolutions samples proceeding by APB process were studied by Scan Electron Microscopy (SEM) and Optical Microscopy (OM). Mechanical characteristics were accomplished by conducting standard tensile and microhardness tests. The microscopic analysis indicates that as the number of APB passes increased, the reinforcement phase (Cu) dispersion be improved and result in Cu continues layers discrete in to shorter layers. As well, by increasing the number of APB passes up to 3 the ultimate strength, microhardness and elongation had been increased so that, the ultimate strength is raised to 375Mpa, it about 3.1 and 2.7 times is more than as Al and Cu respectively. Under the 3 cycles of APB, the hardness of Al and Cu were reached to 62 and 152.6 HV respectively which are 1.6 and 2.6 times greater than those of corresponding pure materials. Furthermore, SEM observations demonstrated the failure mode in Al/Cu composite proceeding by APB process is shear ductile rupture.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
109
114
http://mme.modares.ac.ir/article_16130_fb1602cbb263ff0c9cdec8d11d126da6.pdf
Investigation of convectiondiffusion process in a twophase airwater flow using Smoothed Particle Hydrodynamics
Hassan
Zamanipour
دانشجوی کارشناسی ارشد دانشگاه یاسوج
author
Pourya
Omidvar
استادیار گروه مهندسی مکانیک دانشگاه یاسوج
author
Ali
Tayebi
استادیار گروه مهندسی مکانیک دانشگاه یاسوج
author
text
article
2017
per
In this paper, the convectiondiffusion process in a twophase airwater flow is investigated. Twophase flows of air and water are important and are widely used in the industrial applications. Simulation of such a flow needs a proper understanding of the interface between two phases where these is a change in fluids properties. Smoothed Particle Hydrodynamics (SPH) is a fully Lagrangian and meshless method which can simply detect the interface of multiphase flows. Here, we develop the opensource SPHyiscs2D code into two phase and implement the convectiondiffusion equation by looking carefully at surface tension forces. To validate, first the stillwater problem is investigated to ensure that the hydrostatic pressure at the interface is predicted and then the dambreak problem on an infinite bed is compared with the available experimental data. Results show that the combination of surface tension formulations and an additional artificial force gives a better result. Finally, the convectiondiffusion process and the concentration distribution are shown for the airbubble rising problem for different diffusive coefficients. It will be shown that the SPH method is a useful tool for studying multiphase flows and convectiondiffusion processes.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
115
125
http://mme.modares.ac.ir/article_16150_d2558fad4299d3bad3f75627f33cb95f.pdf
Effect of Superhydrophobic Surface on Drag Coefficient of SD7003 Foil: A Numerical Approach
Ebrahim
Najafi
دانشکده مهندسی مکانیک دانشگاه تهران
author
Amir
Nejat
Mechanical Eng Department, University of Tehran
author
Seyed Farshid
Chini
Assistant Professor, Mechanical Engineering Department, University of Tehran
author
text
article
2017
per
Due to low surface energy and hierarchical roughness, fluids on superhydrophobic surfaces are mobile. The slip velocity on these surfaces is formulated using Navier’s slip length. On regular surfaces, slip length is only a few nanometers. On superhydrophobic surfaces, slip length can be as large as 500 µm. Literature studies usually make the entire surface superhydrophobic which may not be the optimum situation. To find the desirable regions, the problem should be analyzed numerically. Most of the numerical studies are for flat plates. On curved surfaces (e.g. foils), due to the adverse pressure gradient and possibility of separation, analysis is more complicated. Here, the effect of using superhydrophobic surface for a SD7003 hydrofoil is studied numerically and at different Reynolds numbers and slip lengths. The flow pattern is considered laminar, incompressible and isothermal and a hydrofoil made of aluminum with a chord length of 10cm is selected. Results of the shear stress, pressure coefficient and the drag coefficient on the typical boundary condition were compared with the case of slip boundary condition. It was found that by increasing the slip length, the drag coefficient decreases. It was also found that the effectiveness of using superhydrophobic surfaces in decreasing the drag coefficient improves at higher Reynolds numbers. By increasing the Reynolds number from 4.5×〖10〗^4 to 7.5×〖10〗^4 and at the slip length of 50 µm, the drag coefficient reduction increases from 0.7% to 7%.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
126
134
http://mme.modares.ac.ir/article_16194_2ef4ac5dad1342af3b4383d151f23358.pdf
Numerical investigation of the effect of a liquid fuel droplets diameter in combustion in a 2D axisymmetric geometry
Tohid
Khakzand
University Of Guilan
author
Ramin
Kouhikamali
دانشیار دانشکده فنی دانشگاه گیلان
author
Javad
Mahmoudimehr
Assistant Prof. , University Of Guilan
author
text
article
2017
per
Spray combustion is utilized in a number of engineering applications such as energy conversion, military industrial, furance and propulsion devices. Current work focused on the effect of liquid fuel droplet diameter on the efficiency of the combustion chamber and formed emission such as NOx and CO in a twodimensional axisymmetric combustion chamber. The discrete phase model approach employed for simulating Combustion. The gas phase is simulated using an Eulerian approach; while the droplets are treated with a Lagrangian method. The coupling between the two phases and effect of radiation is considered. The mixturefraction/probability density function (PDF) equilibrium chemistry model is used to predict the combustion of the vaporized fuel. Also, the conservative equations of mass, momentum and energy in the turbulent flow field were solved in conjunction with the k–ε two equation turbulence model. A numerical simulation was carried out to study the influence of droplet size on the formation and emission of NOx and other contaminants. This effect was investigated under different droplet diameter and type of injection. The following conclusions be drawn: Smaller droplets produce higher NOx emission than the larger ones. Larger droplets produce higher CO than Smaller ones.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
135
146
http://mme.modares.ac.ir/article_16151_0f5c4f80a4d0fbef603aa6211e26ba54.pdf
Flow Control via CoFlow Jet over ClarkY Airfoil
AhmadAli
Rabienataj Darzi
Assi
author
Saman
Vadudi Mofid
دانشگاه پردیسان فریدونکنار
author
text
article
2017
per
In this study, the effects of CoFlow jet and injection temperature on the enhancement of airfoil performance in the compressible flow are investigated numerically. CoFlow jet is a method of increasing lift to drag ratio and varying the Stall Degree which works via injecting the air from the edge of airfoil and suction from the tail. The much number of studied flow changes from 0.4 to 0.6. ClarkY airfoil has been chosen for this study because of its application in compressible flow, it is the base airfoil for development of new airfoils. A validation is performed for ClarkY airfoil by comparing the present numerical result and available experimental data in the literature. Results indicate that the enhancement induced by the CoFlow jet on the compressible flow is less than one in the incompressible flow. The drag and lift coefficients reduces and increases by increasing the jet momentum coefficient, respectively. Using the CoFlow Jet increase the stall degree. The maximum of lift decrement and drag increment occurs around the stall degree. Increasing the temperature increases lift coefficient slightly where it seems to be better choice in comparison with increment of Jet momentum coefficient due to ease of operation.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
147
156
http://mme.modares.ac.ir/article_16178_23e1c617ae6cc745e036eb448ce6a338.pdf
Numerical estimation of the wing boundary layer transition in propeller flowfield
Hamzeh
Aminaei
دانشجوی دکتری
author
Mojtaba
Dehghan Manshadi
دانشیار دانشگاه صنعتی مالک اشتر اصفهان
author
Alireza
Mostofizadeh
دانشیار
author
text
article
2017
per
This work aims to prediction of laminar/turbulent transition which plays an important role on aerodynamics of wing section. In this respect the flow around the NACA2415 airfoil simulated in a Computational Fluid Dynamics (CFD) solver in different regimes with and without propeller flowfield. For predicting the transition onset, two approaches were used: The first is based on time history of the skinfriction coefficient for determining the transition onset and the transition length on the airfoil. The second is to apply transition γ〖Re〗_θ model for laminar/turbulent transition simulation. For investigation of transition effect, the simulation repeated by use of a classical turbulent model and both results was compared with experimental data. The comparison shows that taking into account the transition effects gives a good agreement with experiment. Relative error of calculated drag coefficients for the transition based simulation is lower than 10%, while fully turbulent simulation are 70% overestimated in some incidences. Slipstream of upstream propeller changes flow pattern and boundary layer characteristics over the wing. Indeed in presence of propeller, spanwise load distribution and laminar/turbulent transition onset were affected. In propeller flowfield, increasing of velocity normal component over wing surface causes transition delay. Movement of transition onset to trailing edge on the upper surface in propeller downwash is representative of such phenomenon. On the other hand, in upwash region, the transition onset moves upstream. With the increasing propeller rotational speed, this tendency augments and so the transition onset on the wing upper surface moves far downstream in propeller downwash.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
157
165
http://mme.modares.ac.ir/article_16198_acb4985c3e9ad83a35212c9aa1fd3a53.pdf
Stability and bifurcation analysis of a beammassspringdamper system under primary and onetothree internal resonances
Morteza
Homayoun Sadeghi
دانشگاه تبریز
author
Saeed
Lotfan
دانشجوی دکترا/دانشگاه تبریز
author
text
article
2017
per
In this paper nonlinear modal interactions and stability of a Rayleigh beam carrying a massspringdamper system are investigated. For this purpose, the dimensionless equations governing the vibration of the system are analyzed based on multiple scales method. By considering viscoelastic KelvinVoigt damping in the beam, complex mode shapes and timedependent resonance frequencies are extracted. Using the traditional form of the multiple scales method results in physical contradiction in the time response of the concentrated mass which should be resolved. After free vibration analysis, the forced response of the system under harmonic force with frequency close to the first natural frequency and occurrence of onetothree internal resonance is studied. The parameters of the one degree of freedom system are considered in a way that the modal interaction occurs via internal resonance mechanism. In this condition, frequency response of the system and its stability are investigated and it is shown that the unstability associated with the jump and Hopf bifurcation occurs in the vibration amplitude. Plots of the time response, phase and Poincare show that periodic, quasiperiodic and chaotic vibration may take place in the system. In order to verify the present paper’s results, the natural frequencies of the system are compared to those of the previous studies; in addition to this comparison, the frequency response based on numerical integration validates the results of the present paper.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
166
176
http://mme.modares.ac.ir/article_16200_fdd528bcb672cf3e0bac48bb5cf58198.pdf
Study the effect of the incompatible elements on the elasticplastic behavior of isotropic plates and beams under axial and bending loading
Hamed
Mahmoud Soltani
دانشجوی دکترا دانشکده مهندسی مکانیک دانشگاه صنعتی سهند
author
Mahsa
Kharazi
استادیار دانشکده مکانیکدانشگاه صنعتی سهند تبریز
author
text
article
2017
per
One of the most remarkable achievements of finite element method is introducing isoparametric elements. Although these elements are able to use in numerous applications, the lower order isoparametric elements make some difficulties such as shear locking, volumetric locking and hourglass. These issues may improve with an increase in the number of the elements or by increasing the order of the elements, which increases the computational time. Therefore for solving these problems, using the lower order elements with incompatible modes, which enhances accuracy and reduces the computational time, could be considered as an alternative solution option. The aim of this paper is to study the effect of using the incompatible elements on the elastoplastic behavior of isotropic plates and beams under uniform axial and bending loadings. For this purpose, 3D standard elements with eight and twenty nodes and incompatible eightnode elements are used in modeling the 3D case studies. Besides, the 2D standard elements with four and eight nodes and incompatible ones with four nodes are employed to analyze the 2D plane stress problems. The obtained results show that using 3D incompatible elements achieves the faster rate of convergence in the solution procedure for obtaining the displacement components and also makes significant runtime reduction. However, there are not any remarkable differences between the obtained plastic VonMises stresses using 2D standard and incompatible elements.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
177
186
http://mme.modares.ac.ir/article_16195_4ee8bf3854d7ce1a3ef71a0486fe5561.pdf
Modeling of large scale relative motion of two satellite in elliptical orbit
Mahdi
Fakoor
University of Tehran
author
Fatemeh
Amozegary
دانکده علوم و فنون نوین دانشگاه تهران
author
Majid
Bakhtiari
دانشگاه علم و صنعت ایران
author
text
article
2017
per
For formation flying of two satellites in a satellite constellation, the relative motion and attitude determination algorithms are the key components that affect the quality of flight and mission efficiency. In this paper orbital relative motion of two satellites with arbitrary Keplerian elliptic orbit and in large distance will be analyzed and also exact and efficient solution for relative motion of the satellite with j2 perturbation which is one of the important perturbation in Low Earth Orbit (LEO) using spherical geometry is proposed. Direct geometric method using spherical coordinates are utilized to achieve this solution. In this method relative position and relative velocity of two satellites are calculated in the satellite constellation based on orbital elements. The obtained results from simulation with STK software, comparison of results with extracted results from equations for satellite with different eccentricity and analysis of the proposed method’s accuracy and fault show that the solution obtained from the geometric method presents the relative motion of the satellite with high accuracy. Thus, the proposed solution will be applicable and effective for relative motion of constellation satellites in space missions.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
187
198
http://mme.modares.ac.ir/article_16196_e2aca8d80bc9ba4414d0201367f3eae5.pdf
MultiObjective Multidisciplinary Design Optimization of a General Aviation Aircraft
Jafar
Roshanian
faculty member/Khaje Nasir Toosi University of Technology
author
Aliasghar
Bataleblu
PHD student/Khaje Nasir Toosi University of Technology
author
Mohammad Hossein
Farghadani
MS member/Khaje Nasir Toosi University of Technology
author
Benyamin
Ebrahimi
MS student/Khaje Nasir Toosi University of Technology
author
text
article
2017
per
In this paper, conceptual design of a General Aviation Aircraft (GAA) is explained as a multiobjective Multidisciplinary Design Optimization (MDO). In the early sizing phase, preliminary aircraft configuration is defined based on a predetermined requirements and statistical Study. Afterwards, conceptual design disciplines are developed and integrated based on Multidisciplinary Design Feasibility (MDF) structure to improve the aircraft performance. The MDF loop is established by implementing a multidisciplinary analysis which includes disciplines as engine selection, weight and sizing, aerodynamics, performance and stability. In this design process, Constraints and algorithms are considered based on the Gudmundsson design approach. Design variables are selected carefully using sensitivity analysis on design objectives (i.e. reducing the weight and increasing the range). In order to obtain a feasible design, static stability constraints are considered. The NSGAII multiobjective evolutionary optimization algorithm is utilized to demonstrate a set of possible answers in the form of the Pareto front. By selecting different engines and illustrating the Pareto fronts resulted from optimization process, the feasibility and effectiveness of rapid GAA conceptual design is demonstrated.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
199
210
http://mme.modares.ac.ir/article_16197_c570e5ba0e2579a29f1892156970a27e.pdf
Simulation of compressible multimaterial flow by 2D hydrodynamic code
Saeed
Parvar
مربی، مهندسی هوافضا، دانشگاه پیام نور، رشت
author
Hamid Reza
Anbarlooei
دانشجوی پسا دکتری، دانشگاه ریودوژانرو، برزیل
author
Alireza
Alipoor
Assistant Professor/ Shahid Chamran University of Ahvaz
author
text
article
2018
per
Numerical simulation of multi material or multiphase flows are one of the most challenging problems between computational fluid dynamics researches. The main difficulty of these problems is producing some unexpected and nonphysical oscillation at material interface which causes entering some error in to computation domain. For eliminating this source of error, many sophisticated algorithm have been proposed recently. By neglecting diffusion processes, Euler equations and HLLC reimann solver are applied. In addition, Level set algorithm is implemented to track interferences between two materials. An accurate, easily developed and low computation cost algorithm, proposed by Abgrall and Karni, is used to prevent generating the oscillations in the interfaces. In the current work, the algorithm is developed to 2 dimensional algorithm. Afterwards, the result of 1 and 2 dimensional code are evaluated to verify the developed algorithm by some standard problems such as sod problem. Finally, shock –bubble (Air – Helium) interaction problem is simulated to investigate the effect of the algorithm in 2 dimensional simulation. The comparison shows that the code and its result have very good accuracy with very low computational cost.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2018
211
220
http://mme.modares.ac.ir/article_16199_8f793871354162c7d84cff634e808ff2.pdf
Numerical simulation of shear thickening fluid impregnated polypropylene fabric and comparing with experimental results
Hamid Reza
Zarei
دانشیار مدیر گروه/دانشگاه شهید ستاری
author
Mohammad
Rezaei
دانشجوی دکتری
author
Salem
Soveity
کارشناس ارشد
author
text
article
2017
per
Recently shear thickening fluids (STF) are applied more and more to improve the penetration resistance of fabrics. In this research, at first, the performance of the neat and STF impregnated fabric subjected to the impact of 8.7 mm diameter steel spherical projectile is investigated experimentally. Then, the numerical analysis is done to study the effective parameters such as fabric density, static and dynamic coefficients of friction between yarns and between projectile and fabric, boundary conditions and number of layers of fabric by using commercial tool LSDYNA software. Previous studies expressed that the major factor that improves the energy absorption capacity of STF impregnated fabrics is the friction between the impact projectile, fabric, and yarns within the fabric, however here the investigations showed that in addition to the friction, the mass of added STF is effective in the results. Increasing the mass of the fabric by adding STF, is considered as the increasing density of the fabric. Empirical investigations showed that STFimpregnated fabrics exhibited a significant enhancement in penetration resistance performance as compared to neat fabric such that the projectile penetration subjected to the fabric with 44% wt STF decreased 63% compared to neat fabric. The simulation results showed that, if the STF effects just assign to increased friction, the projectile penetration decreased 43% compared to neat fabric. But if in addition to friction, the mass of the STF is considered as the effective parameter, the penetration decreased 58% which have good agreement with experimental data.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
221
230
http://mme.modares.ac.ir/article_16258_8d5e629bbcf9d95b91801cefa1fe903f.pdf
Numerical simulation of hydrodynamics of a highspeed planning hull with two degrees of freedom
Hassan
Ghoshchi
دانشگاه امیر کبیر
author
Mohamadreza
Ansari

author
Reza
Azadi
فرهیخته کارشناشی ارشد
author
text
article
2017
per
In the present research, hydrodynamical and aerodynamical characteristics of a highspeed planning hull is studied using computational fluid dynamics. Simulations are threedimensional with considering a twophase turbulent flow. To obtain sinkage and trim of the hull, two degrees of freedom is assumed for it. Rigid body dynamic equations and governing equations of the fluid are coupled using 6DOF solver and dynamic mesh technique. Based on the available experimental results, simulations of the aimed high speed hull are performed in the linear velocity range of 0.98.31 m/s. Comparing the present numerical results with the experimental data, shows that maximum average error for resistance, trim and sinkage in different velocities does not exceed 10%. This shows the accuracy and proficiency of the current model. Mesh independency of solutions is studied for all velocities and the results are reported based on the most suitable mesh. At the end, the effect of applying steps on reducing the drag and improving stability of the hull is investigated for several states in one and two steps. Finally, the most optimized state is introduced and relating results are given. Results show that applying steps to the mentioned high speed hull reduce the overall resistance by 11%.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
231
239
http://mme.modares.ac.ir/article_16257_b961d467636f4c856691e2990b142db5.pdf
Intelligent fault diagnosis of cooling radiator based on thermal image processing and artificial intelligence techniques
Amin
TaheriGaravand
دانشگاه لرستان
author
Mahmoud
Omid
دانشگاه تهران
author
Hojjat
Ahmadi
دانشگاه تهران
author
Seyed Saeid
Mohtasebi
دانشگاه تهران
author
Giovanni Maria
Carlomagno
University of Naples Federico II, Naples, Italy
author
text
article
2017
per
In this study, an intelligent diagnosis systems have been developed and applied for classifying six types of cooling radiator conditions by means of infrared thermal images; namely, radiator tube blockage, radiator fin blockage, loose connections between fins and tubes, radiator door failure, coolant leakage and normal. The proposed system is consisted of several subsequent procedures including thermal image acquisition, preprocessing, of images via two dimensional discrete wavelet transform (2DDWT), feature extraction, feature selection, and classification. The 2DDWT was implemented to decompose the thermal images. Subsequently, statistical texture features were extracted from the original and decomposed thermal images. Consequently, statistical texture features are extracted from the original and decomposed thermal images to develop ANFIS classifiers. In this paper, the significant and relevant features are selected based on genetic algorithm (GA) in order to enhance the performance of ANFIS classifier. For evaluating ANFIS classifier performance, the values of the confusion matrix, such as specificity, sensitivity, precision and accuracy were computed. The overall accuracy of the classifier was 94.11 %. The results demonstrated that this system can be employed satisfactorily as an intelligent condition monitoring and fault diagnosis for a class of cooling radiator.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
240
250
http://mme.modares.ac.ir/article_16259_27cdeaf60cf33fa42f471e06f31d0779.pdf
An analytical investigation on shape of a falling viscose drop at low Reynolds number
Amin
Emamian
دانشکده مهندسی مکانیک دانشگاه صنعتی شاهرود
author
Mahmood
Norouzi
Shahrood University of Technology
author
Mahdi
Davoodi
دانشکده مهندسی دانشگاه لیورپول
author
text
article
2017
per
Motion and deformation of the drop falling in an immiscible fluid has become a benchmark problem in fluid mechanics and has a wide range of application in petroleum, medicine processing, metals extraction, power plant and heat exchanger. In this paper, an exact analytical solution of a falling viscous drop at low Reynolds number is investigated. Analytical solution for both internal and external flows is obtained using the perturbation method. The Reynolds numbers and capillary are considered as the perturbation parameters. Drop’s shape remains spherical for sufficient small ones. The falling drop’s shape at Newtonian phase, deforms from its spherical shape as its volume increases. Inertial forces, surface tension, normal components stresses have the most influence on the falling drop’s shape. Drop’s deformation is due to the forces at the interfaces acting between two fluids. By volume increase of the falling drop, normal components stresses overcome to the surface tension and cause a dimple at the bottom drops in addition to the inertial force enhancement. For small nondimensional parameters (Reynolds number and capillary) drop’s deformation is exactly similar to a sphere and then by increase in Reynolds number and capillary, the drop’s shape alters and cause a dimple at the bottom drops. Analytical solution show suitable agreement in terminal velocity and drop shape estimation with experimental results.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
251
262
http://mme.modares.ac.ir/article_16260_b20cf26070a9eb2e7405cb9bce5eb9ac.pdf
Combination of ghost fluidlattice Boltzmann and refilling methods for simulation of the moving curved boundaries with heat transfer
Mohsen
MozafariShamsi
Yazd university
author
Mohammad
Sefid
عضو هیات علمی دانشکده مهندسی مکانیک  دانشگاه یزد
author
Gholamreza
Imani
Persian Gulf University
author
text
article
2017
per
In this article, the ghost fluidlattice Boltzmann method, used to simulate the curved boundaries is combined with an extrapolation based refilling method to cope with the moving curved boundaries, where in each iteration some of the solid nodes step into the fluid domain. The refilling method is used to approximate the unknown density and internal energy distribution functions of such solid nodes. To examine the accuracy of the presented method, several case studies are considered. From those case studies, natural convection problem between to concentric and eccentric cylinders as well as heat transfer from a cylinder in a cross flow are considered to validate the ghostfluid lattice Boltzmann method used to simulate the hydrodynamic and thermal conditions at the curved boundaries. To test the accuracy of the employed refilling method, sedimentation of a single isothermal cold particle in a vertical channel investigated. The results show that the presented ghost fluidlattice Boltzmann method with refilling is capable of simulating the moving thermal curved boundaries with excellent accuracy.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
263
274
http://mme.modares.ac.ir/article_16261_014e4863ac7f9ffa6d61f68bf0508b90.pdf
Investigating the individual characteristics effects on thermal comfort conditions of occupants in a dense occupancy environment
Mahdi
Afzalian
دانشجوی کارشناسی ارشد
author
Farzin
Davodi
دانشجوی دکتری دانشگاه بیرجند
author
Hassan
Hassanzadeh
دانشگاه بیرجند
author
Seyed Alireza
Zolfaghari
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
Mahdi
Maerefat
دانشگاه تربیت مدرس
author
text
article
2017
per
Thermal sensation evaluation of occupants in a dense occupancy space can be an effective step for designing ventilation systems of these environments. In a dense occupancy environment, because of the presence of a large population and also differences in personal parameters such as age, gender, clothing, weight, and body mass index, providing the appropriate thermal comfort conditions is complicated. In this study, the individual characteristics effects on thermal comfort conditions of occupants in a dense occupancy environment is investigated by individualized threenode model. For this issue, a dense occupancy environment with displacement ventilation and inlet air diffusers on the floor is modeled and thermal sensation index for occupants who seated in middle row has been analyzed. Based on the results, the women are more sensitive than men under cold conditions. Also, effects of mass body index on thermal sensation are significantly noticeable. Compared with a healthy person, the thinner people have a cold sensation and fatter ones feel warmer. For example, in the mentioned case, difference between thermal sensation index of thin woman and obese man is 0.42 for the bare parts of the body, indicating noticeable effects on thermal sensation.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
275
283
http://mme.modares.ac.ir/article_16262_3a1405a7b9f180c39937aa66b5f2d2f8.pdf
Effects of air change rate on comfort, air quality and energy consumption in an amphitheater with underfloor air distribution system
Mahdi
Afzalian
دانشجوی کارشناسی ارشد دانشگاه بیرجند
author
Seyed Alireza
Zolfaghari
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
Ali
Foadadini
دانشگاه بیرجند
author
text
article
2017
per
Nowadays, the building ventilation is an essential process, due to need of improving the air quality and thermal comfort conditions for occupants. Providing the mentioned conditions is more complex for crowded and larger spaces. In this study, the effects of air change rate per hour (ACH) on thermal comfort, indoor air quality and energy consumption in an amphitheater with under floor air distribution system have been investigated by using the computational fluid dynamics and Open Foam numerical solver. For this issue, an amphitheater with 50 occupants has been modeled under the conditions that the air inlet diffusers located in front of seats. Also, the air change rate per hour is assumed to be 5, 10 and 15. For better comparison between the results, inlet air temperature is controlled until the mean of thermal comfort index (TSENS) in the occupied zone equals to zero. The results indicate that for air change rates of 15, 10 in comparison with ACH of 5, the CO2 concentrations in the occupied zone are respectively reduced about 36 and 46 percent and so the indoor air quality is improved. On the other hand, the energy consumption is increased about 28 and 69 percent, respectively. Also, based on the results, by increasing the ACH rate, the draft local discomfort is significantly increased and can be reached at the amount of 15%.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
284
294
http://mme.modares.ac.ir/article_16264_d8612ca9df9d0bdd2c9ddf92fbc3a33a.pdf
Effect of initial impact velocity on dynamics and shape of formed splats of hollow droplets in thermal plasma spraying
Hadi
Safaei
دانشگاه صنعتی اصفهان
author
Mohsen
Davazdah Emami
Isfahan university of technology
author
text
article
2017
per
Applications of hollow spherical particles in industry and in thermal spraying process have been developed in recent years. Despite dense droplets, in hollow droplets, the volume changes of the gas play an important role in the dynamics of impact and the shape of the formed splats. In plasma thermal spraying, impact velocities of particles to the surface is in the range of 50 m/s300 m/s, therefore, changes in pressure and volume of the trapped gas, is important. In this research, impact of hollow droplet on a flat surface and its solidification has been simulated. Volume of fluid model for compressible flows at real thermal spraying condition is used while the impact velocities in the range of 50 m/s300 is considered. In a few moments after the impact of droplet on the surface, a pressure wave is formed in the air. This wave, increase the vorticity in vicinity of interface of two fluid, which has a great effect on shaping the formed splats. Simulations showed that shape of formed splats vary with velocities in the range of 50 m/s300 m/s. In higher velocities, the surface of the formed splat is more porous.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
295
305
http://mme.modares.ac.ir/article_16265_5ad74006f685dc394a321bf9adf272b5.pdf
Investigation of attenuation and acoustic wave propagation path caused by corrosion for reliability assessment of prestressed pipe monitoring using Acoustic Emission technique
Reza
Goldaran
instructor
author
Mohammad Ali
LofollahiYaghin
رییس دانشگاه مراغه
author
Mohammad Hossein
Aminfar
هیئت علمی دانشکده عمران دانشگاه تبریز
author
Ahmet
Turer
عضو هیئت علمی دانشکده سازه METU
author
text
article
2017
per
Catastrophic failures due to corrosion are among the most common phenomena in prestressed concrete pipeline, which has been reported in Iran, as well. Structural health monitoring, quick assessment and timely detection of corrosion in its early stages with active insitu sensors is could prove vital in avoiding such hazards. Acoustic emission is a nondestructive technique that can be used to give a better insight on the structural state of such concrete structures. However, the interpretation of the AE measurements is quite challenging and may actually be even more difficult when the concrete is cracked, which would affect the material and structural properties of concrete pipes. The amplitude distribution of the acquired signals is very sensitive to microcracking. This paper presents the results of an experiment conducted in the laboratory of Middle East Technical University on prestressed concrete pipe for determining the amplitude attenuation and path of acoustic wave propagation and frequency spectrum before and after corrosion using HsuNielsen pencillead break source and applying accelerated corrosion. The results from the laboratory tests indicate that since the changing in amplitude and wave propagation path is negligible before and after corrosion, the AE measurements can be used as an accurate method for tackling the problem mentioned above. Then the performed AE measurements are reported and results discussed.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
306
314
http://mme.modares.ac.ir/article_16267_96934699faa47f23ab1b52c3f330784e.pdf
Propane and Butane Gas Liquefaction Cycle Optimization Considering Compressor Technical Limitations with Genetic Algorithm
Mohsen
Khodaee
MSc student
author
Ali
Ashrafizadeh
دانشیار دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Mostafa
Mafi
Assistant Professor, Department of Mechanical Engineering, Imam Khomeini International University, Qazvin
author
text
article
2017
per
Refrigerant is one of the most important parts in a refrigeration cycle. In many refrigeration cycles, especially in the natural gas processing industry, propane is used as refrigerant due to its desirable thermodynamic properties. There are two ways for transferring propane and butane gases from extraction point to the consumption site: a) Pipeline and b) liquefaction and transport in liquid form. The most profitable method for transporting large quantities of propane and butane gases is liquefaction and transport in liquid form using storage tanks. Liquefaction at atmospheric pressure is the most common method for transporting large quantities of gases using specifically designed refrigerated ships. In this paper, a gas refinery butane and propane liquefaction cycle is described first and then simulated in HYSYS software. Afterwards, Genetic Algorithm is used to minimize the total power consumption of the liquefaction cycle, through connecting HYSYS and MATLAB softwares. There are 13 variables and 13 constraints for compressors and heat exchangers in the formulation of the optimization problem. The results of this constrained optimization problem show that the power consumption can be reduced by 12.49% compared to the base case.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
315
324
http://mme.modares.ac.ir/article_16266_0634389b06579d11e7230c37598221ac.pdf
Comparison between empirical mode decomposition and wavelet transform for unbalance detection on rotating machinery using optimized support vector machine
Mohammad
Rahbar
University of Guilan
author
Ali
Chaibakhsh
Assistant Prof. / University of Guilan
author
text
article
2017
per
In this study, fair comparisons between the empirical mode decomposition, ensemble empirical mode decomposition and discrete wavelet transform with the mother wavelet function of Meyer and Daubechies, were performed for detecting unbalance faults in a rotating machinery. In order to classify the healthy class from the unbalance classes, a support vector machines that was optimized by particle swarm optimization algorithm, was used. A comparison between the performances of optimized and nonoptimized of support vector machines were also carried out. In order to obtained the required data, a rotating machinery fault simulator was developed and vibrational signals were acquired at healthy and unbalance fault conditions by accelerometer sensors. By processing the recorded signals and analysing signal to their frequency components, several statistical features were extracted from each frequency component as input support vector machine for the separation of classes. The obtained results indicated that the discrete wavelet transform with the Meyer mother wavelet, higher success rate than other methods for diagnosing unbalance faults.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
325
332
http://mme.modares.ac.ir/article_16291_fbc7ca0d6d91509f43eec90389437d6a.pdf
Cooling performance evaluation of overhead mixing and floor displacement ventilation systems inside a bus by using 65nodes thermal comfort model
Seyed Alireza
Zolfaghari
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
Hassan
Hassanzadeh
دانشگاه بیرجند
author
Mohammad
Raeesi
دانشگاه بیرجند
author
Morteza
Taheri
دانشگاه بیرجند
author
text
article
2017
per
The aim of this study is to compare the performance of floor displacement and overhead mixing ventilation systems in providing the thermal comfort conditions for bus passengers. For this reason, the flow and energy have been numerically simulated inside a Scania 4212 bus with its 45 passengers. In the case of displacement ventilation, the inlet diffusers have been located under the seats at the floor and for mixing ventilation mode, the inlet diffusers have been established overhead of passengers. In both cases, as mentioned in ASHRAE standard for public transportation, the inlet air rate of 5 lit/s has been provided for each passenger and the inlet air temperature has been controlled until the predicted mean vote index is within the allowable range of thermal comfort standards. In displacement ventilation because of locating the inlet diffusers on the floor and the buoyancy effects, the air temperature in foot region is about 18C, which is lower than other parts of body and vertical temperature difference in overhead mixing ventilation occurred less than floor displacement ventilation and the temperature difference between foot and head region is only 2C. In overhead mixing ventilation, air temperature near the head is about 24C while in floor displacement ventilation the temperature is about 26C that is not in neutral zone. The results of 65nodes thermal comfort model indicate that the temperature difference between skin neutral temperatures of each segment in floor displacement mode is higher than overhead mixing ventilation
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
333
342
http://mme.modares.ac.ir/article_16292_f57adb9c2acd8302abf6126daad316c7.pdf
Bladed Disk Nodal Diameter Extraction by Numerical and Experimental Methods
Aref
Nazari
دانشجوی کارشناسی ارشد مهندسی مکانیک، گرایش طراحی کاربردی، دانشگاه تهران
author
Aghil
Yousefi Koma
رئیس / مرکز سیستمها و فناوریهای پیشرفته دانشگاه تهران
author
Seyed Saeid
Mohtasebi
استاد دانشکده مهندسی مکانیک، پردیس البرز، دانشگاه تهران
author
Saeed
Zohoori
دانشجوی کارشناسی ارشد مهندسی مکانیک، گرایش طراحی کاربردی، دانشگاه تهران
author
Mahdi
Safa
فارغ التحصیل کارشناسی ارشد مهندسی مکانیک دانشگاه تربیت مدرس
author
text
article
2017
per
Rotor dynamics is known as the study of vibrational behavior in axially symmetric linear rotating structures. Devices such as engines, turbines, compressors and generators are located in this category. Study of vibrational behavior of these structures in different rotational velocities yields to recognition of critical points and preventing failures, especially high cycle fatigue. The case study of the present paper is a bladed disk used in the first stage of compressor of a gas turbine engine. The material of machined integrated bladed disk is aluminum alloy. The simulations have been done by ANSYS finite element software. By using the cyclic symmetry module of ANSYS the nodal diameter mode shapes of structure have been obtained. In the next step, experimental modal analysis test has been done by measuring 58 points on the bladed disk and the nodal diameters have been obtained experimentally. Finally, experimental and simulation results have been compared to each other. The novelty of this paper is the experimental procedure of obtaining nodal diameter of a bladed disk, which is so useful in verification of numerical simulation.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
343
349
http://mme.modares.ac.ir/article_16293_8c43fbef14e9bda4ee83e2989498a143.pdf
Numerical simulatoin of poolfire suppression using water mist system
investigating nozzle parameter effects
Ghassem
Heidarinejad
Tehran, Ale Ahmad Ave, Tarbiat Modares University,Faculty of Mechanical Engineering, Room 317
author
Emad
Mousavi
دانشجوی کارشناسی ارشد دانشگاه تربیت مدرس
author
text
article
2017
per
With recent developments in sprinkler technology, water mist system is becoming more and more useful in fire suppressions. The computational method is an efficient way to investigating effect of Nozzle parameter of water mists and optimize them. In this research, a open source fire dynamic simulator (FDS) is used to numerically investigating the different nozzle parameter on the fire suppression and extinguishment mechanism.The range of droplet size was determined based on the NFPA 750 standard. Extinguishing mechanisms in water mist systems and their effect on extingushing time and nozzle parameter such as droplet size, water flow rate and spray cone angle were investigated. The simulation concluded that droplet sizes I hollow cone angle smaller than 121 μm and larger than 600 μm were appropriate for fire extingushment. With a full cone angle nozzle and 1/5 flowrate compared with hollow cone nozzle, fire extingush time reduce from 26 second to 7.4 second. Spray cone angle in fine droplets does not much affect the duration of fire extinguishing, however, for large droplets, the desired result can be achieved by reducing the spary cone angle. So with recognition of nozze parameter and its effects on fire extingushing time could rich the optimum design. Keywords m design.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
350
358
http://mme.modares.ac.ir/article_16310_a85a5749fe31831049a162dc74f91e17.pdf
Experimental Study of the Noise Sources from a Hot Supersonic Jet Impinging on a Flat Plate at Initial Stages of Jet Formation
Iman
Bahman Jahromi
پژوهشگاه هوافضا(وزارت علوم تحقیقات و فناوری)
author
Kaveh
Ghorbanian
استاد تمام گروه مهندسی هوافضا دانشگاه صنعتی شریف
author
Mohammad
Ebrahimi
عضو هیئت علمی پژوهشگاه هوافضا
author
text
article
2017
per
The farfield acoustic signature of this transient impinging jet is experimentally investigated in this study. Feedback loop mechanism which is an acoustic resonance mode generated by the reflection of jet shear layer noise from the impinging plate and affecting jet mixing shear layer, is also investigated. The stagnation temperature of jet is increased by means of a reflected type shock tube up to 950 (K). A convergentdivergent nozzle generates jet with Mach number of 1.4. The farfield mixing layer noise of this quasisteady free jet is compared by the results of steady state generated ones. The acoustic signal of this transient jet is investigated when impinges to a normal plate. It is seen that every specific phenomenon has its most powerful acoustic signature at a distinct angle relative to the impingement point. The timefrequency investigations by the means of wavelet transform and related scalograms reveal that the sound wave generated by feedback loop mechanism is tonal and continuous in time compared to the acoustic signals of the jet shear layer that are seen as the intermittent acoustic events in the farfield acoustic scalograms.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
359
368
http://mme.modares.ac.ir/article_16294_af6545a2fa7f360a363ef6d0384bb6b5.pdf
Exact solutions of flow between two concentric pipes and flow over porous wall by a new couplestress theory
Fatemeh
Karami
دانشگاه شهرکرد
author
Afshin
Ahmadi Nadooshan
استادیار گروه مکانیک دانشگاه شهرکرد
author
Alireza
Shateri
دانشگاه شهرکرد
author
text
article
2017
per
A lot of research has been done to study forcetractions and coupletractions acting on the surface of solid and fluid elements. NaviorStokes equations have been developed based on these researches in the domain of fluid mechanics. However, a number of researchers have emphasized that the NaviorStokes equations are not sufficient and they should be modified because regardless of couplestress effects. In this paper, after presenting couplestress theory, two flow geometry between two concentric pipes and flow over porous wall are considered and the behavior of them are compared with classical case. It has been shown that the forcestress tensor is not symmetric by calculating two components of the forcestress tensor for flow between two concentric pipes. In addition, it can be considered that length scale is an effective parameter on small scale flow by calculating flow velocity profile for these two geometries and by comparing them with classical solution. However, the effects of length scale on the velocity profile and the flow rate decrease with increasing geometrical scales of the problem. These results can be used to study fluid flows with smallscale characteristics such as biofluids, lubrication and microelectromechanical systems
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
369
376
http://mme.modares.ac.ir/article_16309_104a20996ecbaee41c58417d47b98327.pdf
Singlerod electrohydraulic servo system control with sliding mode controller improved by parallel fuzzy compensators
Saeed
Barghandan
هیات علمی دانشگاه آزاد اهر
author
Mohammadali
Badamchizadeh
هیات علمی دانشگاه تبریز
author
Mohammad Reza
Jahed Motlagh
هیات علمی دانشگاه علم و صنعت
author
text
article
2017
per
Sliding mode control technique is one of the wellrecognized nonlinear control methods. This method has an advantage like robustness against uncertainties. However, chattering phenomenon constraints the performance of closed loop system. To increase its efficiency, a fuzzy compensator is used along with this method. The fuzzy compensator weights are updated by using adaptive rules. The adaptation rate acts as a controlling coefficient. Therefore, the bigger amount of it increases the adaptation speed of weights which leads to the improvement of closed loop system performance. As a result, the probability of instability of closed loop system increases, too. In this study, it has been proposed to use a parallel fuzzy system along with the main fuzzy system in order to control its weights' adaptation. Moreover, a nonlinear model of the electrohydraulic system has been introduced as a case study. Finally, the performance of closed loop system and the efficiency of the proposed methods have been investigated by using numerical simulations.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
377
384
http://mme.modares.ac.ir/article_16311_17a1de74e1a307dd2afc2ed97d517594.pdf
Offering an analytical relation for estimation of pollution in enclosed parking lots and expressing the corrective suggestions for improving national building regulations of Iran
Javad
Amnian
فارغ التحصیل دکتری دانشگاه تربیت مدرس
author
Mahdi
Maerefat
هیئت علمی دانشگاه تربیت مدرس
author
text
article
2017
per
The CO concentration is an important parameter for design of ventilation systems in enclosed parking lots. By using the initial estimation of CO concentration and investigating the CO removal effectiveness, the ventilation system with low energy consumption and high indoor air quality could be designed. In this paper, by using the principle of mass conservation and the definition of CO removal effectiveness, an analytical relation for estimation of CO concentration is obtained. This relation is estimate the variation of CO with time by using the main functional parameters of parking lot. In spite to the physics of flow, the increasing of air quality is obtained by reducing the idle cars and the mass flow rate of CO exhausted from this cars and increasing the parking lot volume and the ventilation flow. This trend is consistent with the proposed relation of this paper and so the results of this paper could be used as the criteria for estimation of CO concentration and enhancement of ventilation system design. The comparison between results of the proposed relation and experimental and numerical results are represents good accuracy of proposed relation. Furthermore, the amount of energy reduction by enhancing the flow pattern is expressed by using the proposed relation of this paper. In the last section, the approach of different standards is expressed and the modifying suggestions for enhancement of them are expressed.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
385
392
http://mme.modares.ac.ir/article_16312_4255b7fdec7b48abfe00cd857a35e228.pdf
Modeling of groundwater flow in unconfined aquifer in steady state with meshless local PetrovGalerkin
Ali
Mohtashami
دانشجوی کارشناسی ارشد دانشگاه بیرجند
author
Abolfazel
Akbarpour
دانشیار دانشگاه بیرجند
author
Mahdi
Mollazadeh
استادیار دانشگاه بیرجند
author
text
article
2017
per
The complex behavior of the aquifer system is studied by solving a set of governing equations using either analytical or numerical methods. Numerical techniques like finite difference method (FDM) is being used to solve differential equation in some simple cases. Recently Meshless methods are developed in engineering fields. They are used for solving differential equations in both simple and complex cases. As this methods needs no meshing or remeshing on the domain the shortages of meshing disappeared. Less studies already performed in groundwater flow modeling with meshless method. In this study Meshless local PetrovGalerkin with moving least squares approximation function and spline weight function is used to model groundwater flow in Birjand unconfined aquifer in steady condition. The computed surface of groundwater with meshless local PetrovGalerkin method is compared with the results observation. The results are found satisfactory. The relative mean error and root mean square error of computed groundwater surface from Meshless Local PetrovGalerkin are 0.0002 and 0.483 respectively.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
393
403
http://mme.modares.ac.ir/article_16313_565a479714454ef41f6e1dba4d293430.pdf
Fast determination of system specifications of GEO communication satellites.
Mehran
Mirshams
Associate Professor Faculty of Aerospace Engineering K.N.Toosi University of Technology
author
Ehsan
Zabihian
PHD student Faculty of Aerospace Engineering K.N.Toosi University of Technology
author
text
article
2017
per
This paper has introduced a fast GEO satellite conceptual design method named Statistical Design Model (SDM). The main merit of SDM is to determine parameters involved in the satellite conceptual design phase, such as power and mass, with an acceptable accuracy and time performance. This method implemented by means of a complete database can readily find specifications of GEO communication satellite subsystems. With respect to the application of GEO communications satellites as well as high cost and time required for their conceptual design, a demand has always existed to shorten the duration of the development of such satellites. Herein, we present SDM method for the conceptual design of GEO communications satellites lying in the mass range of 1000 to 7000 kg and amply indicate its effectiveness for reduction of design time. For implementation of SDM and the attaining of reliable relations, we used a database which is constructed from records of over 450 GEO communication satellites launched between years 2000 and 2016. The attained relations demonstrating the subsystems specifications are analyzed. The accuracy of the proposed algorithm is verified through a case study and also through a statistical method. In the various subsystems, mean error of the obtained results was nearly 15.7%, being well acceptable for the conceptual design phase.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
404
412
http://mme.modares.ac.ir/article_16314_65fe7d39284ccb83c6d73f9255a353e5.pdf
Fault detection in nonlinear dynamical systems using multisensor data fusion based on Hybrid Extended Information Filter
Amin
Azarshab
petroleum university of technology
author
Mehdi
Shahbazian
Petroleum university of technology
author
text
article
2017
per
An effective way to enhance the system reliability is to develop a fault detection algorithm to perform the monitoring task instantly. In a dynamic system, fault is defined as any deviation from a desired operating condition. According to system dimensions, there are different architectures to implement fault detection algorithm including centralized, decentralized and distributed. In this paper, a centralized approach is designed using multi sensor data fusion technique based on Hybrid Extended Information Filter (HEIF). This approach has the advantages of both existing algorithms, the Hybrid Extended Kalman Filter (HEKF) and the Information Filter (IF). Similar to HEKF, it has better performance compared to conventional Kalman filter and as the IF, it can be implemented noncentrally. The proposed centralized algorithm is more efficient for loworder nonlinear dynamic systems. It is also important for the highorder systems because it is the basis for performance comparison of noncentral approaches. This approach not only enables us to distribute the algorithm for noncentral schemes, but is also superior to the conventional Kalman filter in precision and computational burden with a same convergence speed which helps to move toward a real time implementation. It also acts more timely in fault detection task. In this work, in addition to improved results, we are going to establish a basis for further investigation in largescale systems.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
413
419
http://mme.modares.ac.ir/article_16338_25e441f449e8906dbf54ecfc4b84b275.pdf
Behaviour analysis of a bistable twisting hybrid composite plate with an external metal layer and effecting factors on stability region
Saeed
Saberi
دانشجوی کارشناسی ارشد دانشگاه صنعتی اصفهان
author
Mostafa
Ghayour
Professor
author
Hamidreza
Mirdamadi
Associate Professor of Mechanical Engineering
author
text
article
2017
per
Bistable and multistable plates are types of smart composite structures that have two or more static equilibrium. In this paper, a bistable hybrid composite plate with an external metal layer is studied. The difference between these plates and conventional bistable composite plates and bistable hybrid composite plate with an inner layer of metal is the deformation of them. In other words, unlike the conventional bistable composite plates, in both stable state, transverse curvatures that they have the same size and sign and but twisted curvature is the considerable. The analytical method for studying the behavior of the plate is Rayleigh Ritz method and minimization of potential energy and finite element used. In order to increase the accuracy of the Rayleigh – Ritz method, out of the plane displacement using is guessed Legendre polynomial. At the frist, states of equilibrium and stable states are determined. To understand better the difference between a bistable hybrid plate with an external metal layer and a CFRP bistable composite plate, a comparison between deform at room temperature, curvature and out of plane displacement are done. In the next part, the moment required to snap through between stable states is achieved. Also, the effect of metal layer thickness on out of plane displacement and stability boundary is investigated. Comparing the results of the proposed shape function and Hyer shape function compared to experimental results and the results of finite element analysis show that the results of the proposed shape function is more accurate.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
420
426
http://mme.modares.ac.ir/article_16339_95d6f69aff68cf8e48b469153a0d2cee.pdf
Buckling Analysis of intelligent Nanoplate under Inplane Loading Based on Nonlocal Elasticity and Shear and normal Deformation Theories
Morteza
Ghasemi Shiri
دانشجوی دکترای گروه مکانیک دانشکده مهندسی دانشگاه فردوسی مشهد
author
Abdolrahman
Jaamialahmadi
استادیار دانشگاه فردوسی مشهد
author
text
article
2017
per
In this paper, the nonlocal buckling behavior of a biaxially loaded graphene sheet with piezoelectric layers based on an isotropic smart nanoplate model is studied. The equilibrium equations are derived with the von Karmantype geometrical nonlinearity by considering the small scale effect. The buckling of multilayer smart nanoplate made of graphene and piezoelectric materials in open circuit conditions is investigated. Based on the nonlocal elasticity and shear and normal deformation theories, the governing equilibrium equations are obtained using the principle of minimum total potential energy and Maxwell’s equation. Using an analytical approach, the governing stability equations of smart nanoplate have been presented in terms of displacement components and electrical potential. In order to obtain the stability equations, the adjacent equilibrium criterion is used. The stability equations are then solved analytically, assuming simply supported boundary condition along all edges. To validate the results, the critical buckling load values have been compared with available resources. Finally, following validation of the results, numerical results for intelligent nanoplate are presented. Also, the effects of different parameters such as nanoplate length, different nonlocal parameter, piezoelectric layers thickness, the graphene thickness to length ratio, the piezoelectric layer thickness to graphene thickness ratio and type of Piezoelectric material on the critical buckling loads of intelligent nanoplate are studied in detail. Furthermore, the effect of the mentioned parameters on the critical buckling loads have been presented in some ﬁgures.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
427
438
http://mme.modares.ac.ir/article_16340_683b9f82eda168086726f0aff921bfee.pdf
Elastic behavior of an edge dislocation in a coreshell nanowire embedded to an infinite matrix within surface/interface theory of elasticity
Camelia
Enzevaee
دانشجو
author
Hossein
Mohammadi Shoja
Sharif University of Technology
author
text
article
2017
per
The elastic behavior of an edge dislocation located inside the core of a coreshell nanowire which is embedded in an infinite matrix is studied within the surface/interface elasticity theory. The corresponding boundary value problem is solved exactly by using complex potential functions and Laurent series expansion. An important parameter socalled interface characteristic parameter which has the dimension of length and is a combination of the interface moduli enters the formulations. The stress field of the dislocation, image force acting on the dislocation, and the dislocation strain energy is calculated by considering the interface effect. The stress field of the dislocation is shown as contour plots and the results are compared with classical case. The image forces acting on the dislocation are studied in details and it is shown that they depend on the interface characteristic parameter, nanowire dimension, dislocation orientation, and dislocation distance from the interface. Moreover, the repelling and attracting effects of the interface parameter on the image force are discussed. The equilibrium position of the dislocation is also studied. The dislocation strain energy in the interface elasticity framework is only slightly different from that of traditional elasticity when the dislocation is placed in the central region of the core and reaches its maximum value when it is located near the core–shell interface.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
439
445
http://mme.modares.ac.ir/article_16341_a27205db4696fccf86f93c6f052488d0.pdf
Proposing of practical relation to estimate amount indoor air pollutants
Danial
Hakimi Rad
M.sc Student, Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran
author
Mehdi
Marefat
هیأت علمی دانشگاه تربیت مدرس
author
Behrouz
Mohammad Kari
هیأت علمی مرکز تحقیقات راه، مسکن و شهرسازی
author
text
article
2017
per
Estimating indoor air pollutants to ensure the air quality is very important. In this study, a conventional residential space is numerically simulated in order to investigate the behavior of pollutants. Using the numerical results and the experimental results of other references, proposed the analytical relation to estimate the concentration of CO2 in term of factors such as CO2 produced by breathing residents or combustion equipment, the volume of space and ventilation rate. The results of the analytical relation are full compliance with experimental and numerical results and it can be used to estimate indoor air quality. Proposed relation can be used in all the same cases.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
17
v.
2
no.
2017
446
450
http://mme.modares.ac.ir/article_16152_706a80024219c5654b9f4e5a5efbcbe9.pdf