Cover
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
http://mme.modares.ac.ir/article_12995_39697c35ff07da3ea6d5e30f33927c4b.pdf
IFC
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
0
0
http://mme.modares.ac.ir/article_12993_dba040c072d027d1f7d51cda51a84c83.pdf
Content
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
0
0
http://mme.modares.ac.ir/article_12994_c7367f793be1fb91f7bc7b4a76a5a36e.pdf
Investigation of Dynamic behavior of Unidirectional Plies Using One Parameter Plastic Model
Behnam
Davoodi
دانشیار گروه مهندسی ساخت و تولید/ دانشگاه تبریز
author
Ashkan
Mahmoud Aghdami
دانشجوی دکتری/ دانشگاه تبریز
author
text
article
2015
per
In this article constitutive equations on dynamic behavior of off axis polymer matrix composites in different strain rates were investigated. Using the Hill Anisotropy and assumptions governing in fiber composites, a model was developed to express the dynamic behavior of polymer matrix composites. Using the flow rules and effective stress and assumptions in fiber composites like non plastic behavior of composites in fiber direction, the Hill parameters were omitted and reduced to one namely a_66 parameter. This model was called2D one Parameter Plastic Model (also it can be developed for 3D composite layers). This model was developed for off axis composites as well. For each composite with different fiber directions, effective stress effective strain was introduced. With choosing the right value for parameter a_66 by try and error, all the stress strain curves were collapsed in to one single curve. Using this model and the experimental static and quasi static results gathered from different authors (in range of〖 0.01s〗^(1)), a viscoplastic model was obtained which can predict the polymer composite respond both in static and high strain rate tests (between 400 s^(1) and 700s^(1)). Constant parameters in high strain rates in this model were calculated through extrapolating the data in the static test rang. The accuracy of this model was investigated and approved by Split Hopkinson Pressure Bar test. The results showed that the visco plastic model can predict the dynamic respond of composite fibers in high strain rates very well.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
1
6
http://mme.modares.ac.ir/article_12634_f97fd7efb10b060e0ed33fb727914fad.pdf
Experimental and Numerical study of Runback ice accretion effects on aerodynamic performance of NACA23012 airfoil
Mohammad Mahdi
Nazemi
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Masoud
Mirzaei
دانشیار تهران پارس,دانشکده هوافضا دانشگاه خواجه نصیر
author
Sohrab Gholamhosein
Pouryoussefi
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2015
per
In this paper, Effects of runback ice accretion on NACA 23012 airfoil have been studied experimentally and numerically. For this purpose, experiments were applied on runback ice within Reynolds number of 0.6×〖10〗^6 over the angle of attack from 0 degree to 20 degree and then results were compared with the results of clean airfoil. Generally, Having examined behavior of the flow pattern and aerodynamic coefficients of the iced airfoil the results of which were compared to that of the clean airfoil, it can be concluded that icing phenomenon affects aerodynamic performance of the airfoil in two ways; in the first way that occurs at low angles of attack prior to stalling of the airfoil the effect is local .In this case ice accretion on the airfoil contributes to formation of a flow separation bubble behind the ice ridge on the upper surface of the airfoil. After numerical simulation of flow field, flow separation bubble behind the ice ridge was observed. The main effect of icing which is related to the second way occurs at angles of attack close to stall and poststall. In this case flow pattern around the airfoil as well as aerodynamic coefficients undergo a fundamental change. In addition, it was made clear that runback ice causes stall angle decreases 2 degree and maximum lift reduces about 8 percent.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
7
15
http://mme.modares.ac.ir/article_12635_e9431829bd33e01bf1a4732d454a4279.pdf
Modeling and Forecasting of Energy Consumption in Food and Processing Industry using Artificial Neural Networks
Bahram
Hosseinzadeh Samani
دانشگاه شهرکرد
author
Hamed
Hourijafari
هیات علمی/ مرکز مطالعات بین الملل انرژی
author
text
article
2015
per
In all societies and countries, in order to plan to provide the required energy for various sectors, it is necessary to accurately predict the demand, type of energy carriers and energy supply method. Considering the importance of food industries in each country, in this study, modeling of required energy for food industries sector was investigated. Modeling of energy consumption was performed using artificial neural networks. In the first step, the input data to the model was calculated according to statistics, balance sheets and input method proposed in this paper. Two methods, namely multiple neural network and single neural network were tested and the results showed that multiple neural network has a higher accuracy. For each of the energy carriers (gasoline, kerosene, fuel oil, natural gas, electricity, gasoline and LPG) the best neural network was selected by taking the average of 20 times per program for each network characteristic. Finally, the network was implemented in the form of final model using Simulink environment of MATLAB 7.0 software. Data analysis showed that daily consumption of natural gas in the industry is increasing, while the consumption of fuel oil and LPG is going to be decreased.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
16
22
http://mme.modares.ac.ir/article_12637_d0d0cf78e08606523497f360af0fbf64.pdf
Numerical investigation of the plasma actuator effects on the flow field and heat transfer coefficient in a flat channel
Ali
Rafi
Department of Mechanical Engineering, University of Guilan, Rasht, Iran
author
Nima
Amanifard
Academic Staff
author
Hamed
Mohaddes Deylami
Faculty of Technology and Engineering, East of Guilan, University of Guilan, Rudsar, Iran.
author
Farid
Dolati
Department of Mechanical Engineering, University of Guilan, Rasht, Iran.
author
text
article
2015
per
Plasma actuator is one of the newest ways in vortex generation and flow control techniques which can enhance heat transfer rate by inducing external momentum to the boundary layer of the flow. In this paper, a 2D numerical approach was implemented to analyze the presence of plasma actuator on the incompressible, turbulent, steady flow in a flat channel. In this approach, the flow field and heat transfer characteristics such as the stream function and heat transfer coefficient were evaluated through the variety of Reynolds number, at the presence and absence of applied voltages. The present computed results are firstly compared with the numerical data in case of rectangular flat channel and the results agree very well. The numerical results indicate that at a constant Reynolds number with the presence of a plasma actuator, the heat transfer coefficient will be increased but in a constant applied voltage the heat transfer coefficient will increase to the Reynolds of 250 and then will be decreased respectively. In addition, the size of generated vortexes significantly depends on the applied voltage and the upstream flow speed. On the other hand, according to the results, the flow speed affects the size of generated vortex and vanish the actuator effect at high Reynolds. According to the results, there is an optimized point for the applied voltage and flow speed.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
23
30
http://mme.modares.ac.ir/article_12636_7b17a8e38b5f3aee30aa9decc8e9a7e2.pdf
Analysis and Assessment of Installing Blocks on Performance of Stilling Basins
Mohammad
Mardani
Post Graduate student, Department of Mechanical Engineering/Amirkabir University of Technology
author
Hasan
Rahimzadeh
استاد دانشکده مهندسی مکانیک/ دانشگاه صنعتی امیرکبیر
author
Hamed
Sarkardeh
Assistant Professor, Department of Civil Engineering, Faculty of Engineering/ Hakim SabzevariUniversity
author
text
article
2015
per
One of the most frequently encountered cases of rapid varied flow is the hydraulic jump. Stilling basins are used to dissipate the excess kinetic energy of flow to ensure the safety of overflow spillway, chutes, sluices, pipe outlets etc. in this study the topic of block in stilling basins is investigation in a general approach and it’s effect on energy dissipation and downstream scouring are analyzed. In the present research, the energy dissipation and scouring phenomenon were studied in different hydraulic and geometric conditions. Moreover, the present paper was focused on the effect of presence of blocks as an effective parameter on energy dissipation on stilling basin performance. To analyze and assessment of formed hydraulic jump in the stilling basins, the experimental data of many recent researches were achieved and compared. It was concluded that presence of blocks has significant effect on energy dissipation from 1% to 34%. It is also shown that with increasing the Fr Number, the secondary depth increases and the using a rough bed causes reducing the secondary depth between 18% to 37% in comparison with smooth one. Moreover, installing a rough bed also reduced the length of hydraulic jump between 27% to 67%. Using block in the stilling basins, reduces the scouring depth from USBR standard recommendation. Finally, it was concluded that using blocks increased the efficiency of the stilling basin performance.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
31
41
http://mme.modares.ac.ir/article_12638_915d65a25e5cf848554747da1ad7d3bf.pdf
Investigation of inlet guide vanes and return channel angle effects on twostage compressor performance with onedimensional simulation
Mohammad Reza
Ali Goodarz
دانشیار دانشگاه تربیت دبیر شهیدرجایی
author
Hamid
Azimi Kivi
کارشناسی ارشد از دانشگاه تربیت دبیر شهید رجایی
author
text
article
2015
per
In the present paper, flow field in all components of a twostage centrifugal compressor are simulated using onedimensional method. Internal flow simulating is performed by solving basic equations of corrected empirical relations of geometry, thermodynamics and dynamics with an algorithm with iterative solution was in MATLAB. The purpose of simulation is to obtain the effect of inlet guide vanes and return channel intake angle changes on performance maps. The inputs include stagnation temperature, stagnation pressure and mass flow. The solution is done by calling the primary geometry and inlet thermodynamic and ambient conditions at the nominal speed and 70, 90 and 105 percent of the nominal speed, by applying a continuous flow with convergence of mass flow rate and Rothalpy conservation. Then in performance stability range the results of onedimensional model are validated by empirical and threedimensional modeling results. Then the effect of incidence angles of inlet guide vanes and return channel on compressor performance at performance maps are expressed and analyzed. This model can be used to design inlet guide vane and return channel and estimate optimized angle of guide vanes to gain maximum performance and pressure ratio.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
42
50
http://mme.modares.ac.ir/article_12639_f0300b5c480a18402864f7bf1984f99f.pdf
Analytical solution of stress and displacement in axisymmetric inhomogeneous half space under normal concentrated surface loading
Ali Asghar
Ataee
استادیار دانشگاه تهران
author
Mohammad
Bayat
دانشجوی کارشناسی ارشد
author
text
article
2015
per
In this paper, an analytical solution for stress and displacement in an inhomogeneous half space under the action of concentrated normal surface loading is investigated. The Young modulus is considered to vary with the spherical radius R in a power law form of order n, while the Poisson’s ratio is taken to be constant. The problem is solved analytically using an elasticity approach and considering a semiinverse method in which, based on equilibrium equations on the surface of an arbitrary hemisphere in the halfspace and centered at the point of application of load, some stress components are assumed to be proportional to 1/R2. It is then shown that this assumption is valid and all stress components in this axisymmetric problem are proportional to 1/R2, while displacements are proportional to 1/R(n+1). and their variation with azimuthal coordinate φ is in the form of a special function called hypergeometric function. Illustrative examples are presented, which show variations of stresses and displacements both in R and φ directions. It is seen that the inhomogeneity parameter has a significant effect on both of these field variables.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
51
57
http://mme.modares.ac.ir/article_12640_e552421e68c8b6d6ba7f4e41836b29d9.pdf
Evaluation of FEM instability loads of stiffened cylindrical shells and comparison them with analytical results
Amir Reza
Shahani
استاد دانشکده مکانیک دانشگاه صنعتی خواجه نصیر الدین طوسی
author
Roohollah
Mohammadjani
M. Sc., Department of Mechanical Engineering, K.N.T. University of Technology
author
text
article
2015
per
The instability behavior of stiffened cylindrical shells and determination of the corresponding buckling loads under axial compression, according to the extended range of structural applications of them in various fields of engineering, has been paid a lot of attention from researchers and extensive amount of studies have been performed on it so far. Because of a lack of the general closed form responses due to complexity of the governing equations and analyses process, using the FE software codes as the main technique of the stiffened shell's buckling load determination is inevitable. Accordingly the present paper has been studied the reinforcement effects of ring and stringer and also compared the buckling loads which are evaluated by analysis of the FE numerical modeling in ABAQUS software with instability results that obtained from a general analytical equation derived by other references via applying the simplifying assumptions to the governing equations. Furthermore an attempt has been performed for extraction of the finite element instability load vs. structure reinforcement correspondence that enables the designers to accurately determine the instability load of structure for other values of structure's stiffening volume without performing additional FE analyses which are much more expensive in term of computer time.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
58
68
http://mme.modares.ac.ir/article_12643_cb3877e0384c51f81da6b8b631e26a7f.pdf
Optimal Gait Planning for a Biped Robot by employing Active Toe Joints and Heels
Mahdokht
Ezati
Master student of mechanical engineering in K. N. Toosi University of Technology
author
Majid
Khadiv
PhD candidate of mechanical engineering in K. N. Toosi University of Technology
author
Seyed Ali Akbar
Moosavian
استاد دانشگاه خواجه نصیرالدین طوسی
author
text
article
2015
per
In this article, the significance of utilizing active toe joints in biped robots feet is examined. The main goal of this research is to employ active toe joints and heels to improve gait performance from two points of view: actuating torques of knee joints and total consumed energy. Considering the effectiveness of toes and heels in walking, a new walking pattern is fully addressed and compared with another walking pattern which does not exploit toes and heels. In order to develop a verified dynamics model for considered humanoid robot with 22 DoFs, two analytical methods i.e. Lagrange and Kane are adopted and the obtained results are compared. To reduce calculation burden, an iterative method for dynamics model development is proposed, based on Kane approach. Furthermore, to verify the obtained ground reaction forces and moments, ZMP is computed and compared using two methods. In the procedure of gait planning, first the pelvis trajectory is planned. Then, the feet trajectory planning process is done. After designing trajectory in task space, all joint trajectories except the trajectories of toes are obtained, using closedform inverse kinematics solution. Toe joints trajectories are planned separately, considering the sole trajectories. Consequently, the significant parameters in gait planning are considered as design variables in optimization procedure in order to reduce the maximum torque of knees and total consumed energy as cost functions. Finally, it is demonstrated that which walking pattern is highly appropriate for walking with large step length on flat terrain, under joint torque and velocity limitations.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
69
80
http://mme.modares.ac.ir/article_12641_264659bd24fe4c97ec4305236ec08bcc.pdf
Numerical and experimental investigation ofeffect of vortex generators on flowover suboff bare hull model
Mojtaba
Dehghan Manshadi
استادیار دانشگاه صنعتی مالک اشتر اصفهان
author
Kazem
Hejranfar
استاد تمام دانشکده هوافضا دانشگاه شریف
author
Amir Hamzh
Farajollahi
دانشجوی دکتری
author
text
article
2015
per
The fThe flow field around the axisymmtric stream lined bodis which forms the main body of the airplaines and submarines has been the subject of several researches. Turning maneuvers of submarines result in cross flow separation that generates large hydrodynamic forces. The separation of a simple axisymmetric body is very complex in nature. Understanding these vortical flows is paramount to improving vehicle performance and design. A suitable way to reduce the effects of this separated flow is to use vortex generators. The main goal of the present study is to investigate the flow field around a Suboff standard underwater model employing the vortex generator by using the oil flow visualization method and CFD method (OpenFOAM code) at 0° ≤ α ≤ 30° angles of attack. The novelty of the this study is the application of oil flow visualizing method and CFD simulation which can help us to precisely study the structure of threedimensional vortical flow field. The results show that Vortex Generators placed along the submarine do indeed significantly reduce cross flow separation, size of vortices and drag forces.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
81
90
http://mme.modares.ac.ir/article_12642_631bd8b79bf21bc8b39d3ba9458181fd.pdf
Numerical modeling of internal convection heat transfer of magnetic fluid in the pulse magnetic field and different time frequencies
Hadi
Kargar Sharifabad
گروه مهندسی مکانیک، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران
author
Mohammad
Falsafi
گروه مهندسی مکانیک، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران
author
text
article
2015
per
This numerical study forced convective heat transfer ferrofluid within a circular copper tube includes portions of the electromagnetic isolation under an alternating magnetic field is performed. Laminar flow through a tube under uniform and thermal flux passes. Intensifying transfer of particles and velocity increase in the boundary layer using nanoparticles to increase the effect of magnetic field onto more heat transfer, the main goal is. Convection regimens resulting from complex interactions between magnetic nanoparticles were studied under different conditions, with the concentration and volume of different the heat transfer process under different frequencies of the applied magnetic field were studied. Magnetic field effects on the convective heat transfer coefficient at different Reynolds numbers and volume percentages have been studied. Also when the electromagnetic is insulated pipe parts of have been studied and have been compared with the modes without insulation. Increase the frequency and volume fraction of magnetic field, resulting in increased heat transfer were better. Magnetic field at low Reynolds numbers have shown a greater impact. For prove the numerical results evaluated in this research work has been studied experimentally. The results showed that the modeling data were in very good agreement with experimental data.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
91
98
http://mme.modares.ac.ir/article_12644_bfd7f58ae89abfeb4843d6d8a68f5063.pdf
Experimental study of transient cooling of fluid inside a closed reservoir by using CuO/water nanofluid
Mohsen
Nazari
Assistant Prof. of Mechanical Eng.
Shahrood Univ. of Technology
author
Nasibe
Babazadeh
دانشگاه شاهرود
author
Mohammad Mohsen
Shahmardan
دانشگاه شاهرود
author
Mojtaba
Ashouri
دانشگاه شاهرود
author
text
article
2015
per
Transient heat transfer from a storage fluid around a central tube is experimentally investigated in a wide range of Reynolds number, i.e. 700
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
99
106
http://mme.modares.ac.ir/article_12621_b9568cf794a21f8d9d38ed5582318578.pdf
Experimental Formability Investigation of Titanium Alloy in Hot Incremental Sheet Forming Process
Ali
Barani Shooli
MSc. Student, Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran
author
Saeed
Amini Najafabadi
Instructor of Mechanic Institute, Technical and Vocational University (Mohajer center), Isfahan, Iran
author
Mahmoud
Farzin
استاد، دانشکده مهندسی مکانیک، دانشگاه صنعتی اصفهان، اصفهان، ایران
author
text
article
2015
per
Incremental forming of sheet metals is a new method to produce parts in small batches. Since no die is used, relatively cheap equipment and also reduction of forming forces, parts with different sizes can be produced with lower cost in comparison with conventional methods like deep drawing. Due to low formability of Ti6Al4V at room temperature, forming of these sheets should performed at high temperatures. Simultaneous effect of heat generation and deformation can be realized in Electric Hot Incremental Forming of sheets. In this method, because of passing electric current through a closed circuit including voltage supply, spherical tool and sheet, local heat is produced at tool and sheet interface and by incremental movement of tool on the sheet, the desired geometry is formed. In this research Ti6Al4V sheet is experimentally formed by Electric Hot Incremental Forming method and effect of influencing parameters, namely initial sheet thickness, feed rate, spindle speed, tool vertical step size and amount of current passing circuit on formability and maximum forming angle of a frustum with varying wall angle is investigated. Amount of current entering the circuit has a significant effect on sheet formability and with increasing sheet thickness, amount of current required for deformation increases. Passing very high current through the circuit causes sheet burning and reduction of formability. It will be shown that a decrease in feed rate, step size and spindle speed and an increase in sheet thickness can increase maximum forming angle.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
107
114
http://mme.modares.ac.ir/article_12654_f349d9c56ef81e06c339f10f8010ff3e.pdf
Simulation of steam condensation on the plate by LBM method
Mojtaba
Abbasi Hatani
دانشجوی کارشناسی ارشد دانشگاه تهران
author
Mohammad Hasan
Rahimyan
دانشیار مهندسی مکانیک دانشگاه تهران
author
text
article
2015
per
In this paper, based on latticeBoltzmann method (LBM), the steam condensation and growth of a droplet on the horizontal cold wall and falling down on vertical wall has been simulated. The Lee’s LBM model which is stable in the high density and viscosity ratios is used. This method is accompanied with solving the temperature equation and adding a phase change source term. The Lee model is based on CahnHilliard theory which is assumed to be incompressible flow and therefore the velocities of the flow are divergencefree. when phase change occurs this condition will not be satisfied. A phase change source term is added on the interface of gas and liquid phase. Solution of temperature field in a passive scalar method of solving the flow field is separated and Boussinesq assumption would be influence the flow field of the temperature field. The density ratio of 25 is considered to be in this paper which is density ratio of steam and water. The model is extended to two dimensions (D2Q9) to simulate droplet condensation. The simulation results are compared in various grids. The effects of gravitational acceleration, equilibrium contact angle, the cold wall and also the mass conservation, have been investigated separately. Finally the stream field for the different time step has been analyzed.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
115
122
http://mme.modares.ac.ir/article_12655_65502ee5768257414404d37b71588089.pdf
Numerical and experimental investigation on effects of the primary and secondary overlaps on the performance of Savonius wind turbine
Maryam
Amiri
دانشگاه فردوسی مشهد
author
Mohsen
Kahrom
استاد دانشگاه فردوسی مشهد
author
Ali
Kianifar
دانشیار دانشگاه فردوسی مشهد
author
text
article
2015
per
Due to simplicity of design and manufacture, selfstarting characteristics and operating independently of wind direction, Savonius wind rotors have been considered by many scientists. In the present study, the effects of the primary and secondary overlap ratios on the performance of Savonius wind rotors have been investigated, by means of numerical simulation and wind tunnel tests. Eight different rotor structures were analyzed numerically; three of them were also studied by experimental methods. The effects of the primary and secondary overlap ratios, Reynolds number and the number of the blades on the power and torque coefficients were examined. For all investigated rotors, the maximum value of the power coefficient occurred at a tip speed ratio between 0.8 – 1.0 (blade tip speeds close to the wind speed). Additionally, the maximum power coefficient was found at a dimensionless primary overlap ratio of 0.2; however, increasing or decreasing the secondary overlap ratio caused a reduction in the maximum value of the power coefficient. Also, it was shown that an increase in Reynolds number resulted in the increase of the maximum and average values of power coefficient. Moreover, although adding more blades could produce a more uniform torque, it causes the maximum value of the power coefficient to decrease. By increasing the positive secondary overlap ratio, torque coefficient was increased while the negative overlap ratio reduced the torque coefficient.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
123
131
http://mme.modares.ac.ir/article_12656_3c8fae34053a25d36ca4a342a5fc0786.pdf
Thermodynamic Modeling of an Auxiliary Power Unit Equipped to a Tubular Solid Oxide Fuel Cell with Application in Aerospace Power System
Jamasb
Pirkandi
استادیاردانشگاه صنعتی مالک اشتر  مجتمع دانشگاهی هوافضا
author
Mostafa
Mahmoodi
عضو هیات علمی / دانشگاه صنعتی مالک اشتر
author
Farhad
Amanlo
کارشناس ارشد / دانشگاه صنعتی مالک اشتر
author
text
article
2015
per
Solid oxide fuel cells competence in combination with gas turbine cycle has caused the obtained synthetic system to become as a new power production system in consideration of different researchers. One of the important applications of this type of hybrid systems is to use them in UAV propulsion systems and in airliners as an APU. The main purpose of this research is design of a hybrid APU equipped to solid oxide fuel cell that would be one of the basic requirements for electric power generation in larger aircrafts in the future. Design parameters and decisionmaking variables in analysis of this system are the compressor pressure ratio, gas temperatures entrance to turbine and the number of selected cells. The results show that the system’s increasing pressure causes decrease in the temperature of outlet gases from the turbine and the cell’s operating temperature; and this problem severely affects the productivity and efficiency of the electrical system. At 1000 ° C for entrance gases to the turbine, electrical efficiency of system is about 49 percent. Also, the maximum electrical efficiency of the system in fuel cell is estimated to be about 55 percent. The obtained result shows that in case of controlling the generated heat in the cell and effective usage of it, the overall system efficiency will be augmentable about 84 percent. On the other hand, increasing the number of cells will cause increasing electrical efficiency and reducing the overall efficiency of the fuel cell hybrid system.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
132
144
http://mme.modares.ac.ir/article_12659_6f9ccef75404fe9c6d1439e77df42efa.pdf
An Experimental, Analytical and Numerical Investigation of Static Performance of an Electromotor Driven Propeller with Application in UAVs
Jamasb
Pirkandi
استادیاردانشگاه صنعتی مالک اشتر  مجتمع دانشگاهی هوافضا
author
Mostafa
Mahmoodi
عضو هیات علمی / دانشگاه صنعتی مالک اشتر
author
Mostafa
Rezvandoost
دانشجوی کارشناسی ارشد / دانشگاه صنعتی مالک اشتر
author
text
article
2015
per
Because of various applications of UAVs, research in this field has been developed increasingly in recent years. Propeller has considerable importance as a key factor in producing propulsion in such vehicles. Having information about a propeller’s performance variations in different operational conditions is very important in order to choose a suitable propeller for a predefined mission of the flying vehicle. For this aim, in this research a test stand was designed and fabricated to evaluate the static performance of electromotor driven propellers with application in UAVs. After collecting data by performing experimental tests, the results were compared to those obtained from the numerical and analytical techniques. In order to verify the results, a propeller was modeled and a computational method was applied based on kε, RNG turbulence model. The comparison of experimental, analytical and computational results shows an acceptable agreement between them. According to the results, the difference between analytical and empirical results is 0.4%, the difference between computational and empirical results is 0.3% and the difference between analytical and computational results is about 1.23%. Also in the range of the rotational speed of the propeller, the difference between computational and empirical results became less than 10% in most cases, implying the validity of the applied computational method and correctness of experimental test procedure.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
145
156
http://mme.modares.ac.ir/article_12657_dd0f81588f37938a415649e99b756d5e.pdf
Effect of workpiece cross section on the mechanical properties of commercially pure titanium produced by Equal Channel Angular Pressing
Mehran
Kadkhodayan
استاد/ دانشگاه فردوسی مشهد
author
Mahmoud
Shariati
هیات علمی دانشگاه فردوسی
author
Reza
Naseri
دانشگاه فردوسی مشهد
author
text
article
2015
per
Equal channel angular pressing is one of the most effective severe plastic deformation processes for fabrication of ultrafine grained or even nanostructured materials. Among the metallic biomaterials, commercially pure titanium exhibits the best mechanical properties, compared with other alloys. In this study, the effect of workpiece cross section on the mechanical properties of commercially pure titanium produced by this process has been investigated. The workpieces in two types of cross section(square and circular) are pressed one pass in the square channel with angle 120° at room temperature and effects of cross section on the forming load, grain size, hardness, strength and toughness was studied. Finite element simulation by using the ABAQUS software has been performed for forecasting the forming load, equivalent plastic strain and investigation of effects of geometry parameters of die channel on these. The simulation results have shown good agreement with experimental results. Through analysis of results, it is found that by using the workpiece with circular cross section at equal channel angular pressing process, not only decreased the required pressing load, but also significantly improved the mechanical properties of the materials such as hardness and strength as compared to using the workpiece with square cross section.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
157
166
http://mme.modares.ac.ir/article_12658_792b299e32ac1f7a0bf423bc6a3c4b77.pdf
Computational Simulation of Effects of Nanofluidicity and Flow Boundaries on Natural Heat Transfer In presence of Magnetic Field, Using LBM
Pouyan
Ramian
Student
author
Mohammad
Taeibi Rahni
Professor
author
Armen
Adamian
Assistant Professor
author
text
article
2015
per
In this paper, natural convective heat transfer of nanofluids in a uniform magnetic field between the square cavity and inner cylinder, was simulated via Lattice Boltzmann Method. The inner cylinder in square shape, diamond, and circular has been examined. Square cavity walls and inner cylinder surfaces are at a constant cold and warm temperature, respectively. The flow, temperature, and magnetic field is calculated with solving flow, temperature, and magnetic distribution functions simultaneously. D2Q9 lattice arrangement for each distribution function is used. The results clearly show the behavior of fluid flow and heat transfer between the cavity and the cylinder. The results have been validated with available valid results showing relatively good agreement. The effects of Rayleigh number, Hartmann number, void fraction and type of nanoparticles on natural convective heat transfer are investigated. This study shows that for all three geometries used with the same void fraction, type of nanofluid, and Rayleigh number, natural convective heat transfer decreases with Hartmann number. Also, when Hartmann number was had fixed, natural convective heat transferwas increased with Rayleigh number. Thus, to select the right geometry for optimum natural convective heat transfer, our needs to pay special attention to Hartmann and Rayleigh numbers. In addition, viod fraction and type of nanofulid can affect heat transfer directly.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
167
178
http://mme.modares.ac.ir/article_12680_dfaf1ea51a4f94f3037f921869fcea12.pdf
Variable Thickness Supersonic Airfoil Post flutter With plunging and pitching free play and Nonlinear Damping and Stiffness
Hamid
Moosazadeh
تربیت مدرس
author
Behzad
Ghadiri
Tarbiat Modares University
author
Puria
Zarifian
امیر کبیر
author
text
article
2015
per
The application of wing and stabilizer in aerospace vehicle is most important to stability and flight motion. Nonlinear 2D wing is estimated. Nonlinear damping and stiffness with freeplay in plunging and pitching motion is assumed. 2nd order Damping nonlinearity and 3rd order stiffness nonlinearity in pitching and plunging motion is assumed. Fully nonlinear structure with nonlinear 3rd order piston theory aerodynamic is assumed for the first time and result evaluated with different references. The equations are defined with Hamilton principle with the use of kinetic and potential energy and virtual work. They are solved in the state space via the rugekuta numerical method to determine chaotic and limit cycle oscillation motion of supersonic airfoil. The result show that as the speed increases, the behavior of 2D wing is softening type with the use of nonlinear rotational stiffness. But, It shows hardening type with the use of transversal nonlinear stiffness. The effect of transversal and rotational freeplay is more complicated than other parameters and increases instability in low speed. In other hand the stability increases with freeplay in high speed. As shown, increase velocity decrease damping effect in post flutter behavior.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
179
189
http://mme.modares.ac.ir/article_12681_f40c0521c07e7e16918fb6e6575a50b2.pdf
Sound Localization in Plates Using Low Cost Acoustical Sensors
Seyed Amir
Hoseini Sabzevari
دانشگاه فردوسی مشهد
author
Majid
Moavenian
دانشگاه فردوسی مشهد
author
text
article
2015
per
The necessity to meet ongoing needs of industry, considering theoretical progress achievements and availability of costeffective equipment, has encouraged numerous researchers to investigate the application of monitoring systems. In this paper the sound localization is implemented to find the impact position on the surface of a plate. As an experimental example the sound caused by ball impact on a ping pong table is used. For this purpose, a database is gathered. These sound's signals were recorded 25 times at 5 different points along the length of the table by a low cost microphone, attached to the surface. In the proposed method, first the data related to the ball impacts are detected and isolated from the whole pc recorded signals sent by the microphone. Then, the above 125 impacts are clustered based on the impact point locations, using a 4 dimensional space feature extracted from statistical signal moments. Furthermore in order to specify sound localization, a second space feature based on energy of wavelet transform coefficient signals was extracted. Ultimately for clustering the impact point locations, an artificial neural network was designed and applied to the above data. The results show average values of sensitivity Se=91.20% and positive predictivity P+=91.18%. Also, sensitivity Se=91.97% and positive predictivity P+=93.45%, correspondingly for impact localization.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
190
196
http://mme.modares.ac.ir/article_12683_ce4166cd72eb9a78d3c7ea64311d9dfe.pdf
A Scaled Boundary FiniteElement Solution to TwoDimensional Steady State Reaction–Diffusion Equation
Mohammad Hossein
Bazyar
Faculty Member of Yasouj Univesity
author
Hadi
Arjmand Karkazloo
دانشگاه یاسوج
author
Ali Reza
Yaseri
دانشگاه شیراز
author
Amin
Moosaie
دانشگاه یاسوج
author
text
article
2015
per
A semianalytical method socalled the Scaled Boundary FiniteElement Method (SBFEM) is employed for solving twodimensional steadystate reactiondiffusion equation with constant diffusion and decay coefficients which is widely used in contaminant transfer, chemical engineering and heat transfer problems. This method has been successfully applied to various problems of engineering such as elastodynamics, fracture mechanics and seepage. This method has advantages of both boundary element method and finiteelement method. Only the boundary is discretized reducing the spatial dimension by one. Unlike the boundary element method no fundamental solution is required. Interpolation over the boundaries is approximated using shape functions same in the finiteelement method. Singularities, anisotropic problems, nonhomogeneities satisfying similarity and radiation condition at infinity used in modeling unbounded domains are simply modeled by this technique. In this study, after derivation of the scaled boundary finiteelement formulations for reaction–diffusion equation, solution procedures based on dynamicstiffness matrix are proposed. The accuracy and performance of the SBFEM is evaluated using numerical examples. There are a reasonable agreement between the results of the scaled boundary finiteelement method, the analytical solutions and the popular numerical approaches.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
197
208
http://mme.modares.ac.ir/article_12682_91cf019877735b593883c4b22278f662.pdf
The analysis of natural convection flow with radiation for a medium inside an triangular enclosure using natural element method
Hassan
Hadadi
دانشجوی کارشناسی ارشد دانشکده مهندسی مکانیک دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Cyrus
Aghanajafi
استاد دانشکده مهندسی مکانیک دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Farschad
Torabi
Assistant Professor, K. N. Toosi University of Technology
author
text
article
2015
per
In this paper the natural element method is employed for study conductive, convective and radiative heat transfer for laminar ﬂow in a triangular enclosure. The natural element method referred to as natural neighbor Galerkin method is a new technique in the ﬁeld of computational mechanics and considered as a meshless numerical method. The shape functions used in natural element method, which are based on the Voronoi diagram of a set of nodes, are attentively interpolant and the essential boundary conditions can be imposed by directly substituting the corresponding terms in the system of equations. In this paper for solving radiative transfer equation used P_1 approximation. Effects of different parameters such as Rayleigh number for nonradiation and Planck number and mean temperature for radiation are considered. revealed that increasing the Rayleigh number, increases the strength of free convection regime and consequently increases the value of convective heat transfer rate. It is also revealed that decreasing the Planck number and mean temperature, increases the strength of Radiation regime and consequently increases the value of radiative heat transfer rate. Results for natural element method are compared with the another studys reported in the literatures. By comparison, it is shown that natural element method is efﬁcient, accurate and stable, and can be used for heat transfer and fluid flow.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
209
220
http://mme.modares.ac.ir/article_12684_33afd057a6d21ff1b92bab0031760c60.pdf
Numerical study of different models of an Agnew micro hydro turbine
Mohammad Hasan
Shojaeefard
استاد دانشکده مهندسی مکانیک و رئیس دانشکده مهندسی خودرو
author
Ammar
Mirzaei
دانشکده مهندسی مکانیک دانشگاه علم و صنعت ایران
author
Mohamad Sadegh
Abedinejad
دانشکده مهندسی مکانیک دانشگاه علم و صنعت ایران
author
Yousef
Yassi
پزوهشکده مهندسی مکانیک سازمان پژوهشهای علمی و صنعتی ایران
author
text
article
2015
per
In this study, a threedimensional fluid field of an axial flow type micro hydro named Agnew has been investigated. The turbine installed at the Hydrulic Machines Laboratory (HML) of Iranian Research Organization for Science and Technology has been designed to generate 1 kw output power.All numerical simulations were performed using ANSYS CFX, a Computational Fluid Dynamic code, to investigate the performance parameters, such as efficiency and power, and results are validated against experimental data. Four different grid sizes are studied in accordance with the Grid Convergence Index (GCI) to investigate mesh independency of the solution. Results of several turbulence models were also examined to find out the Shear Stress Transport (SST) model in order to take into account the turbulence in the flow. Several turbulence models were also examined together with wall function in order to take into account the turbulence in the flow. A mixing plane interface plane was used to pass the disturbance of rotary domain to stationary domain. The obtained results show that a high resolution advection scheme, mixing plane to model the rotorstator interaction together with a turbulence intensity of I=6% at the inlet, best matches with the experimental results. The difference between the efficiencies computed from both numerical approaches and experimental values may be ascribed to a numerical error, a model error or a systematic error.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
221
230
http://mme.modares.ac.ir/article_12687_21aa703c054bf1031ae6030153f66c98.pdf
Analytical study of high velocity impact on sandwich panels with foam core and aluminum facesheets
Ali
Alavi Nia
دانشیار دانشگاه بوعلی سینا دانشکده مهندسی گروه مکانیک
author
Mehdi
Kazemi
دانشجوی دکترای مهندسی مکانیک دانشگاه بوعلی سینا
author
text
article
2015
per
Sandwich panels due to high strength to weight ratio and energy absorption properties, are widely used in various industries including aerospace industries, marine and automotive industries. Analysis of ballistic resistance of sandwich panels is mainly numerical and experimental, and there are a few analytical models in this field due to mathematical complexities. Hoo Fatt et al. have studied analytically high velocity impact on sandwich panels with composite skins and foam core. Because of the widespread use of sandwich panels with metal facesheets and foam core in aerospace industry, by modifying the analytical method provided by Hoo Fatt et al. the ballistic resistance of the foam core sandwich panels with metal surfaces impacted by high velocity cylindrical projectile is analytically investigated in this paper. Two types of panels with polymeric and metallic foam cores and aluminum surfaces have been used to assess the accuracy of the analytical method. Results show that the proposed analytical method can predict the residual velocity of the projectiles impacted at high velocities on the foam and metallic core panels with different relative densities of the core.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
231
239
http://mme.modares.ac.ir/article_12685_d4d6ac034e28890b39c2ed6cfda841cc.pdf
Solution of nonlinear nearly incompressible hyperelastic problems by isogeometric analysis method
Behrooz
Hassani
هیئت علمی/دانشگاه فردوسی مشهد
author
Seyed Mehdi
Tavakkoli
هیات علمی دانشگاه صنعتی شاهرود
author
Mehdi
Ardiani
مهندس عمران
author
text
article
2015
per
This article is devoted to the derivation of formulation and isogeometric solution of nonlinear nearly incompressible elastic problems, known as nearly incompressible hyperelasticity. After problem definition, the governing equations are linearized for employing the NewtonRaphson iteration method. Then, the problem is discretized by using concepts of isogeometric analysis method and its solution algorithm is devised. To demonstrate the performance of the proposed approach, the obtained results are compared with finite elements. Due to large deformations in this kind of problems, the finite element method requires a relatively large number of elements, as well as the need for remeshings in some problems, that results in a large system of equations with a high computational cost. In the isogeometric analysis method, using BSpline and NURBS (NonUniform Rational BSpline) basis functions provides us with a good flexibility in modeling of geometry without any need for further remeshings. The examples studied in this article indicate that by using the isogeometric approach good quality results are obtained with a smaller system of equations and less computational cost. Also, influence of different volumetric functions for the nearly incompressible materials are investigated.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
240
248
http://mme.modares.ac.ir/article_12709_ffca6fcb96d4a6b9a7e7700faeb5c946.pdf
Study of the stress distribution around a circular hole in a heterogeneous plate subjected to inplane loads
Mehdi
Ghannad
Assistant Professor
author
Mohammad
Jafari
عضو هیأت علمی/دانشگاه شاهرود
author
Amin
Ameri
مهندس مکانیک/دانشگاه شاهرود
author
text
article
2015
per
Because of the continuous changes of mechanical properties of functionally graded materials and therefore reducing the effects of stress concentration, many researchers are interested in studying the behavior and use of these materials in various industries. For the correct design of perforated inhomogeneous plate is needed to know the accurate information about the deformation and stress distribution in different points of the plate especially around the hole. In this paper, is tried to present the analytical solution to calculate the 2D stress distribution around the circular hole in long FG plate, by using the complex potential functions method. The plate subjected to constant uniaxial or biaxial stress. One of the most important goal of this research is to study the effect of compression load applied to the hole boundary on stress distribution around the hole. The variation of material properties, especially Young's modulus is in a radial direction and concentric to the hole. The special exponential function is used to describe the variation of mechanical properties. The finite element method has been used to check the accuracy of analytical results for homogeneous and heterogeneous plates, also for all loading cases. In the presence of applied load at the boundary of circular hole, amount of radial stress in addition to hoop stress is considerable. Therefore the Von Mises stress is used to study the stress around the hole. The results showed that inhomogeneous plate with increased modulus of elasticity has greater load bearing capacity with respect to homogeneous plate.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
249
256
http://mme.modares.ac.ir/article_12710_6bcb450f5d1093bdfb77014a427c7f4b.pdf
Admittance Control Stability Analysis of a Lower Limb Rehabilitation ServoPneumatic System
Morteza
Fathi
هیأت علمی دانشگاه
author
Farid
Najafi
عضو هیأت علمی گروه مهندسی مکانیک و رئیس دفتر ارتباط با صنعت دانشگاه گیلان
author
text
article
2015
per
In this study, a vertically placed doubleacting pneumatic cylinder controlled by two On/Off solenoid valves is applied for the purpose of the lower limb rehabilitation. Because of the different physical conditions and degrees of disability of patients and changes of the system dynamic parameters, admittance control strategy is used to compliantly interact between users and actuator. To analyze the stability, a linear model of the servopneumatic system is developed and its continuous transfer function is derived. Due to the exponential functions in the continuous transfer function of the system, the necessary transformations are used to achieve the discrete closedloop transfer function of the system. In this way, the determination of the stable performance boundaries of the admittance control parameters related to changes in other dynamic parameters of the system is possible by root locus analysis of the discrete closedloop system. These dynamics parameters include equivalent mass, damping and stiffness of the actuator and leg impedance and the proportional and differential gains of the inner loop position controller. Good correspondence is observed between the analytical and experimental stability limits of the system. Analytical results for appropriate choice of the admittance control and other dynamic parameters of the servopneumatic system are applicable to get smoothly and stable performance during the rehabilitation process.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
257
268
http://mme.modares.ac.ir/article_12711_ed92f5dd8a5cf9fc2ada8f973f918cfa.pdf
Investigation and improvement effectiveness of sound wall geometry for decrease airport noise
Rouhollah
Talebitooti
استادیار/دانشگاه علم و صنعت ایران
author
Akbar
Eshraghi
دانشجو
author
Mansour
Torabi
دانشجو
author
Mohammad Reza
Gheibi
دانشجو
author
text
article
2015
per
The different factors such as material, height, thickness, installation status, and geometry of the wall's head can influence on the efficiency of the sound walls to decrease the noise pollution of theairports. This paper is presented to improve the effective geometry of the wall's head as well as finding the best wall's head to maximize the noise reduction in an airport. To investigate the performance of the sound wall, the boundary element method is used. Then, in order to modeling the sound walls with different dimensions and sizes, PATRAN software is utilized. In the next step, the models are meshed and finite element method is used to analyze the vibrations of the models. Consequently, the natural frequencies and the mode shapes of sound's walls are predicted and finally the insertion loss via modeling of sources of noise and sound receivers are calculated. The design method of Taguchi experiments is applied to decrease the total numbers of the different models of Y shape geometries. Lastly,the governing equations with approximately fitted over the test cases are determined by neural network. Finally, the genetic algorithm is used to obtain the ideal head's wall.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
269
277
http://mme.modares.ac.ir/article_12712_cd4492b516d6b1706212ad5304a75c5e.pdf
Introducing a proper definition of the Nusselt number for fluid flow in a pipe partially filled with porous media
Alireza
Jamarani
دانشجوی کارشناسی ارشد
author
Mehdi
Maerefat
استاد دانشکده مکانیک دانشگاه تربیت مدرس
author
Majid
Eshagh Nimvari
دکترای تخصصی مهندسی مکانیک
author
text
article
2015
per
In the present study the validity of two conventional Nusselt number definitions were investigated using analytical and numerical methods for convection heat transfer in a pipe partially filled with porous media. The first definition is denoted as Nu_1 (x)=(2R(∂T/∂r)_(r=R))⁄((T_wT_m (x)) ) and the second one follows: Nu_2 (x)=(2Rq_cond^'')⁄(k_ref (T_wT_m (x)) ). The Nusselt number resulted from these two definitions was investigated analytically in a pipe for different porous configurations. The results show that the calculated Nusselt numbers using these two definitions, are different in porous media boundary arrangement. In the first definition, the heat transferred to the fluid flowing thorough the porous media is not considered, so the Nusselt number which is calculated via this definition cannot demonstrate the physics of heat transfer phenomenon properly. The boundary arrangement of porous in a pipe with turbulent flow is simulated numerically and the Nusselt number was calculated by the two definitions. The calculated Nusselt from the first definition shows that the Nusselt number increases as the heat conduction coefficient of porous grows which is not a proper expression of physics of this problem. So, the first definition of the Nusselt number is not proper for porous boundary arrangement in a pipe. However, with investigating of the second definition, it is seen that with increasing the porous heat conduction coefficient, the Nusselt number increases which this result is physically valid; therefore the second definition is more appropriate for the porous media boundary arrangement.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
278
286
http://mme.modares.ac.ir/article_12719_2debce1664e85e5773f66ce3f1886270.pdf
Sensitivity analysis of peakshaving natural gas liquefaction cycles to environmental and operational parameters
Amirhossein
Moradi
دانشجوی کارشناسی ارشد گروه مهندسی مکانیک
author
Mostafa
Mafi
عضو هیآت علمی دانشگاه بین المللی امام خمینی (ره)
author
Mansour
Khanaki
استادیار دانشگاه بین المللی امام خمینی قزوین
author
text
article
2015
per
Existence of huge reserves of natural gas in the country and also the extent of its distribution lines has caused the use of natural gas as the main energy carrier. Seasonal fluctuations in gas consumption in domestic sector and giving priority to this sector has led that the gas supply to other sectors such as thermal power plants is faced with many problems in the cold season. One way to deal with this issue (shortage of natural gas) is the liquefaction and storage of surplus natural gas in the summer, using peakshaving gas liquefaction plants. In this study, SMR and N2expander processes have been evaluated. Changing in operational and environmental parameters (such as changes in flow rate, pressure, temperature and composition of the feed gas and working fluid of the cycle) are the main problems that peakshaving plants will be permanently encountered with them, thus low sensitivity to changing conditions is the one of the important criteria in the selection of suitable process for peakshaving. In this study, the sensitivity of liquefaction processes has been investigated using normalized sensitivity analysis. The results indicate that SMR process, despite lower power consumption is more sensitive to changes of the environmental and operational parameters and even, in some cases, the applied perturbation in the probable error range of measurement devices (such as 20 kPa uncertainty or fluctuation in compressor suction pressure), causes malfunction of the liquefaction process (wet entering the compressor).
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
287
298
http://mme.modares.ac.ir/article_12713_187df77b20286b2ce1f28f824e63252b.pdf
Static analysis of composite beams with shear deformation effect using polynomials based dimensional reduction method
Esmaeel
Ghafari
دانشگاه فردوسی مشهد
author
Jalil
Rezaeepazhand
عضوهیات علمی گروه مهندسی مکانیک دانشکده مهندسی دانشگاه فردوسی مشهد
author
text
article
2015
per
This paper, presents the static analysis of composite beams with transverse shear effects using polynomials based dimensional reduction method. In dimensional reduction method, a three dimensional elasticity problem is split into a two dimensional cross section analysis and a one dimensional beam analysis. FEM is commonly used to analyze beam cross section in the literature. In this study, polynomial functions and RayleighRitz method are used to present an analytical procedure for two dimensional cross section analysis. Variational Asymptotic Method (VAM) is employed considering shear stiffnesses of composite beam cross section. VAM, asymptotically generates fully coupled cross section stiffness matrix. VAM benefits small parameters, related to characteristic length of cross section, to find stationary values of beam energy functional. By minimizing the energy functional with respect to warpings, in and out of plane warping functions are acquired. In this article, isotropic beams with different cross section geometries and symmetric as well as antisymmetric composite box beams are investigated. Presented results show appropriate correlation of the present study with theoretical and experimental results, as well as 3D Finite Element analysis. Using dimensional reduction method reduces the computing time and empowers researchers to design and optimize composite beamlike structures.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
299
308
http://mme.modares.ac.ir/article_12714_a27e5626f8bc37204fc1a0a79021174c.pdf
TimeOptimal Rendezvous of the Space Debris USING Electrodynamic Tether System (EDT)
Hamid
Gazerpour
دانشگاه تهران
author
Mohamad Ali
Amiri Atashgah
استادیار دانشگاه تهران  دانشکده علوم و فنون نوین
author
text
article
2015
per
In this paper, simulation and timeoptimal control of an electrodynamic tether system as a new and inexpensive form of space propulsion system are investigated. The EDT, can provide desired acceleration by interaction between a current in the tether wire and earth’s magnetic field, without any fuel consumption, for any orbital maneuvering. For this reason, it is an appropriate choice for space debris mitigation missions. In this work, firstly, dynamics of the EDT, together with the earth’s magnetic field are simulated. Secondly, exploiting the developed simulation toolset, variations of classical orbital elements are observed and then feasibility studies of nonimpulsive orbital maneuvers are conducted. In this manuscript, distinctly, relative motion and rendezvous by means of the EDT, adoption of appropriate coordinate system, problem conditions and also the method of solution are discussed. Simulation results demonstrate that the EDT can perform a wide range of inplane and outofplane orbital maneuvers in lowearthorbits (LEO). Eventually, an inplane rendezvous problem with space debris, is solved by implementation of Direct Collocation method in Matlab by developing a solver program and resolving its limitations with respect to optimal rendezvous problem using electrodynamic tether, and then optimal control in a minimumtime condition, and also optimal trajectory are obtained.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
309
317
http://mme.modares.ac.ir/article_12720_0538642dfa99f4ee639b765fe2ddba9b.pdf
Tool wear estimation in turning by the use of nonstationary time series method
Behrang
Hosseini Aghdam
K.N.Toosi University of Technology
author
Mehrdad
Vahdati
K.N.Toosi University of Technology
author
Morteza Homayoun
Sadeghi
Mechanical Engineering Department, University of Tabriz
author
text
article
2015
per
In the present paper, vibration signals recorded during a turning process are used for tool wear estimation. During the cutting process, tool acceleration signals are recorded with the use of an accelerometer installed on tool holder, for different wear values. Since the measured acceleration signals have time dependent variance and are nonstationary, time series with time dependent coefficients were used for modelling them and extraction of wear sensitive features. The extracted wear sensitive features are residual variance of different signals and are used as distance between the signals associated with worn tools and the baseline model. Based on analysis of distance between worn tools’ acceleration signals in different cutting directions and the baseline signal, a correlation was found. By the use of this correlation, a criterion was obtained for detection of critical wear stage. Such that the distance curves for feed and main cutting directions possess a minimum in the vicinity of critical wear level. Investigation of results revealed that the curves obtained through this method are more accurate than the ones obtained from stationary modelling method. The results obtained here can be used in online realtime algorithms of tool wear estimation.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
318
326
http://mme.modares.ac.ir/article_12721_e6ed6794789d20700cfde22ec48c1192.pdf
Experimental investigation of velocity and roughness effects on subcooled flow boiling
Bagher
Soleimani
دانشجوی کارشناسی ارشد دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Ali
Keshavarz Valian
دانشیار دانشگاه خواجه نصیر الدین طوسی
author
Touraj
Malek Pour
دانشجوی کارشناسی ارشد دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2015
per
The subcooled flow boiling occurs when the bulk temperature is less than saturation temperature of the liquid at that pressure while the surface temperature is higher. The most importance of boiling phenomenon is related to the high latent heat of fluid which could removes high heat flux at relatively low temperature difference between liquid and the hot surface. In this study, the impact of velocity and roughness on the subcooled flow boiling were investigated experimentally for pure water. An experimental setup was designed and manufactured. The experimental setup consists of a plexiglass channel with cross section 20×30 mm and the length of 120 cm. A cylindrical heater with diameter 12 mm made of copper is located on the bottom surface of the plexiglass channel. All the experiments were conducted for the surface roughness of 0.65, 2.5 and 4.4 µm at velocities of 0.5, 0.7 and 0.9 m/s. The experimental results show that the surface heat flux increases as the surface roughness and velocity increases. However, this affect of velocity enhancement was only observed for lower boiling surface temperature and opposite trend has taken place for higher boiling surface temperature. This is due to the simultaneous consideration of the convection and boiling terms along with the interaction between them which has not been presented experimentally yet. It appears that this kind of experimental study has not been carried out for copper type surfaces.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
327
334
http://mme.modares.ac.ir/article_12723_99fb65c99d784380fca01ac8f0d4037c.pdf
Applications of the Incremental HoleDrilling Method for Measurement of NonUniform Residual Stresses in Fiber Metal Laminates
Ahmad Reza
Ghasemi
استادیار / دانشکده مهندسی مکانیک/ دانشگاه کاشان
author
Mohammad Mehdi
Mohammadi
دانشجوی دانشگاه کاشان
author
text
article
2015
per
In this paper, the incremental holedrilling method is used to measure experimentally with accuracy nonuniform residual stresses in each ply of fiber metal laminate (FML) composites. Integral method was used for the approximation of residual stress. This method, considered a constant and uniform residual stress analysis at each holedrilling depth increment. At the first, finite element method is used to calculation of the calibration coefficients matrix of the incremental hole drilling process. The calibration coefficients matrix determined by a finite element analysis can be used directly in the experiment. Calibration coefficients matrix used to relate the measured strain relaxation field with the existing residual stresses prior to the holedrilling process. Also, for the experimental determination, released strains induced by high speed drilling process on FML composites with a stacking sequence of [AL/02/902]S have been quantified. At the end, the experimental measurements are compared with the theoretical predictions of the classical laminate theory. The good agreements between the experimental and theoretical results show that, incremental holedrilling technique can be improved to be successfully applied for measuring nonuniform residual stresses in FML composites.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
335
345
http://mme.modares.ac.ir/article_12722_f63f125788e24b62cda516b7d0a10639.pdf
Theoretical and Experimental Investigation of the Effective Parameters on the Microstructure of magnesium Wire Produced by Friction Stir Extrusion
Mohammad Ali
Ansari
دانشگاه تهران
author
Emadoddin
Sadeqzadeh Naeini
دانشگاه تهران
author
Mohammad Kazem
Besharati Givi
دانشگاه تهران
author
Ghader
Faragi
استادیار دانشگاه تهران
author
text
article
2015
per
Friction Stir Extrusion (FSE) is a modern one step process with high efficiency for conversion and recycling of materials which capable of producing Nanoengineered material via production with good deformability, mechanical and physical properties. Novelty of this production technique is utilization of frictional heat and severe plastic deformation for material flowing, mechanical alloying and finally amendment of powder, chips and other recyclable scraps directly to useful products. Sample’s microstructure was revealed and average grain size was gained for 18 samples. Experimental parameters by use of design of experiments for two factors and analysis of variance were investigated and by the use of experimental results were validated. In this study, the effect of rotational speed in 3 levels and plunge rate in 2 levels were examined on microstructure of produced wires via FSE process. Based on process parameters, there is an equation for grain size prediction was presented by using full factorial design of experiment. Furthermore, normal possibility diagram and residual versus order based on residual theorem were evaluated for systematic error entry and reliability to experimental results. The efficient region on contour diagram reveals that suitable condition of minimum grain size and maximum strength occurred at 250 rpm for rotational speed and 14 mm/min for feed rate. It should be noted that analysis of variance showed that rotational speed, feed rate and interaction of rotational speed and feed rate respectively have a meaningful effect on the grain size of produced wire.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
346
352
http://mme.modares.ac.ir/article_12730_3b14ca91063ef73c09e83bed07bf8704.pdf
A robust active roll control system for improving roll stability of an articulated vehicle carrying liquid
Reza
Kazemi
K. N. Toosi University of Technology
author
Mohammad Amin
Saeedi
K. N. Toosi University of Technology
author
text
article
2015
per
In this paper, to improve the roll stability of an articulated vehicle carrying liquid an active roll control system using a robust nonlinear controller is presented. First, a sixteendegreeoffreedom nonlinear dynamic model of an articulated vehicle is developed next using TruckSim software in a standard maneuver, the vehicle model is validated. Then, the dynamic interaction between the fluid cargo and the tractor semitrailer vehicle, by integrating a quasidynamic slosh model with sixteendegreeoffreedom of a tractor semitrailer model is investigated. Also, for rollover prevention of an articulated vehicle carrying liquid, a novel nonlinear robust control including combination of sliding mode control and feedback linearization control is proposed. Control system performance for two different fill volumes in Jturn and lane change maneuvers is shown. Next, to investigate the rollover stability of an articulated heavy vehicle carrying liquid, load transfer ratio is considered as an important factor. Moreover, in order to study the performance of the robust control system, a linear controller has been used. The simulation results confirm the excellent performance of the proposed robust control system in critical lane change maneuver due to increase of longitudinal velocity and a reduction of road friction coefficient.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
353
364
http://mme.modares.ac.ir/article_12731_617fff6a22749f85e9aa176c6c2c8106.pdf
A Laboratory Study of Penetration Depth and Distribution of Bubbles Formed by a Translating Vertical Fluid Jet
Mohammad Reza
Tavakoli
دانشگاه صنعتی اصفهان
author
Pouriya
Bayat
Isfahan University of Technology
author
text
article
2015
per
Air entrainment in liquids via a fluid jet, is a complex phenomenon that has important applications in industry and the environment. The impact of a vertical laminar water jet translating over the quiescent pool of water at constant velocity was studied empirically, and the penetration depth as well as distribution of the bubbles formed by this jet was measured for both fresh and sea water with two different optical methods. This experiment was conducted at different flow rates (corresponding to different vertical velocities). In each case, the jet was moved at different horizontal velocities relative to the pool surface. As the jet started its horizontal translation, air began entering the pool from the bottom of the point of impact. Bubbles penetration depth was measured through a highspeed imaging technique, and pulse shadowgraphy was used for measuring the bubbles distribution. Increasing the vertical velocity of the jet while simultaneously decreasing the horizontal velocity of the same led to increased bubble penetration depths, and similar results were obtained for fresh water and sea water. This result was obtained in spite of the fact that the number and size of the bubbles formed in sea water were dramatically different from those formed in fresh water. Moreover, the significant role of buoyant forces in the distribution of the bubbles was obvious. The penetration depth and distribution of the bubbles were measured and reported for various jets with different diameters at different vertical and horizontal velocities.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
365
375
http://mme.modares.ac.ir/article_12732_b39f07886248611158cee74f9bf7e985.pdf
Study on the percolation behavior of the mechanical properties of nanoparticle reinforced polymer nanocomposites using threedimensional micromechanical modeling
Reza
Ansari Khalkhali
دانشیار دانشگاه گیلان
author
Mohammad Kazem
Hassanzadeh Aghdam
دانشجوی دکتری، مهندسی مکانیک، دانشگاه گیلان، رشت
author
Ali
Mashkor
دانشجوی دکتری، مهندسی مکانیک، دانشگاه گیلان، رشت
author
text
article
2015
per
Significant improvements in mechanical properties of polymers reinforced with nanoparticles at relatively low volume fractions, is caused that the use of polymer nanocomposites increase. The main reason for the increase in mechanical properties of nanocomposites is the presence of an interphase region between the nanoparticles and polymer matrix. In this work using a unit cellbased micromechanical model, the percolation behavior of the mechanical properties of nanoparticle reinforced polymer nanocomposites is investigated. The Representative Volume Element (RVE) of nanocomposites consists of three phases including nanoparticles, polymer matrix and interphase. The RVE is extended to c×r×h nanocells in three dimensions and the state of dispersion of nanoparticles into matrix is random. Effects of interphase region including its thickness and elastic modulus and nanoparticle geometry on the percolation behavior of the nanocomposite are studied. Results show that with decreasing the nanoparticle size or increasing aspect ratio of nanoparticle, critical volume fractions decreases. The predicted results of the present micromechanical model are in good agreements when compared with results of the other micromechanical model. The herein reported results could be useful to guide the modeling and optimal design of nanocomposite reinforced by nanoparticles with the highest economic interest.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
376
382
http://mme.modares.ac.ir/article_12733_beacfd78c4463539f1d7b589f8ffbfe0.pdf
Experimental Investigation on GasLiquid TwoPhase Flow Regimes in Upward CoCurrent Vertical Tubes with Intermediate Diameter
Mohammad Reza
Ansari

author
Reza
Azadi
فرهیخته کارشناسی ارشد
author
Sahar
Kiani Haghgu
فرهیخته کارشناسی ارشد
author
text
article
2015
per
In the present research, twophase flow is studied adiabatically in vertical plexigalss tubes with inner diameters of 40 mm and 70 mm in heights of 1.73 m and 3.22 m. Flow pattern maps are presented for both tubes and effect of diameter and height on the transition curves between flow patterns is investigated. Air and water are used as working fluids. Superficial velocities of air and water for 40 mm tube are 0.0549.654 m/s and 0.0150.877 m/s; and for 70 mm tube are 0.03820.44 m/s and 0.0361.530 m/s, respectively. By changing the tube diameter from 40 mm to 70 mm, slug pattern region shrinks considerably. Inlet is designed to be "annular" for which bubbly flow in 70 mm tube is not observed in low water superficial velocities. However, this pattern is observed in higher water and lower air superficial velocities. For both tubes, the main flow regimes observed are bubbly, slug, churn and annular. The results obtained using image processing technique show that bubbly regime in 40 mm can be divided into three subpatterns called dispersed, agitated and agglomerated bubbly. In addition, two subpatterns are recognized in slug regime as large slug and small slug. Also semiannular pattern is observed as an independent flow pattern in tube with inner diameter of 70 mm which has not been analyzed accurately up to now.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
383
392
http://mme.modares.ac.ir/article_12734_64832b8ae41bcd763ee774666bd9e9c7.pdf
Dynamic Stall Control of a Low Reynolds Number Airfoil with a Separation Bubble Control Blade
Seyed Erfan
Salimipour
Quchan University of Advanced Technology
author
Shima
Yazdani
faculty member / Quchan University of Advanced Technology
author
text
article
2015
per
In the present paper, a two dimensional numerical analysis of the dynamic stall phenomenon associated with unsteady ﬂow around the NACA 0012 airfoil at low Reynolds number (Re ≈ 130000) is studied. For this purpose, a thin blade with height of 0.005 chord length was placed vertically on the airfoil to control the bursting of the laminar leading edge separation bubble. The numerical simulation of flow is based on discretization of convective flaxes of the turbulent unsteady Navierstokes equations by secondorder Roe’s scheme and an explicit finite volume method in a moving coordinate system. Because of the importance of the time dependent parameters in the solution, the secondorder time accurate is applied by dual time stepping approach. Three oscillating patterns with different frequencies and angular amplitudes were used to study the dynamic stall phenomenon. In order to validate the operation of computer code, some results for static and dynamic stall are compared with experimental data. The results of this study showed that the burst control blade had the acceptable effects on the dynamic stall control; so that these effects were increased while the oscillation frequency was raised. The best result occurs in 5 deg angular amplitude and reduced frequency of 0.15; so that the lift stall reduced 50% and there was not any obvious stall in drag coefficient.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
393
401
http://mme.modares.ac.ir/article_12735_35cb731cd270624193a85c563ffa2be9.pdf
Identification effects of hybrid fibers in composite properties and Acoustic Emission parameters by Fuzzy C Means
Mohammad
Nikmehr
دانشگاه زنجان
author
Ramin
Khamedi
استادیار عضو هیات علمی گروه مکانیک دانشکده مهندسی دانشگاه زنجان
author
text
article
2015
per
Purpose of this study is to identify effects of hybrid fibers in composites properties which has reinforced by carbon and basalt fibers and also effects of hybrid composite in Acoustic Emission (AE) behavior under four point bending test by nondestructive AE testing. One of the main problems for failure mechanisms identification by AE method is discrimination of events due to different types of damage which occurs during loading of composite material. Fuzzy C means clustering algorithm is a tool which is used in this paper to separate acoustic events. The results show that the method of clustering provides a better correlation between the acoustic signals, damage mechanisms and also time of these mechanisms. For analyzing the AE signals, some of the descriptors like amplitude, duration, count, acoustic energy and rise time were used to identify the micro mechanisms of failure. In the first steps of the hybrid composite loading, it is noisier than the last steps and it shows the progressive damage mechanisms. Scanning Electron Microscope (SEM) observation was verified the results of tests and analysis.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
402
408
http://mme.modares.ac.ir/article_12759_7ebc3b1742fe6123c69ed8dc31d4a599.pdf
Application of nonlinear asymmetrical damper in the optimal design parameters of passive suspension under random excitation
Reza
Hassannejad
Assistant Professor of Mechanical EngineeringFaculty of University of Tabriz
author
Abolfazel
Seifi
دانشجوی کارشناسی ارشد رشته مهندسی مکانیک گرایش طراحی کاربردی
author
Mohammad Ali
Hamed
استادیار گروه مهندسی مکانیک دانشکده مهندسی مکانیک دانشگاه تبریز
author
text
article
2015
per
Passive suspension system is used in most vehicles due to its low energy consumption and low cost in most vehicles. Therefore, today there is a challenge in order to enhance the suspension system. The aim of this study is to present a new method for MultiObjective design of vehicle suspension based on the use of asymmetrical dampers (Nonlinear). Hence, It is shown that using these type of dampers with a choice of two type coefficient by which one of them is in compression and another one in expansion, will lead to a more optimal design compared to those in the literature. For this purpose, vehicle was modeled using full model with eleven degree of freedom under random road excitation. Then, since the tasks of suspension system are reduction of vertical acceleration exerted on passengers, reduction of pitch acceleration of sprung mass, improving road holding and reduction of the change of four wheel work space. Therefore, the problem is defined as a MultiObjective problem with conflicting objectives which formulated and solved by NSGAII algorithm. The obtained results indicated that using asymmetrical dampers leads to more efficient design compared to those methods with symmetrical dampers.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
6
no.
2015
409
418
http://mme.modares.ac.ir/article_12760_5a7c11711556491b19e3393ce3187fb1.pdf