IFC
text
article
2016
per
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
0
0
http://mme.modares.ac.ir/article_14659_856b62f37aecd12966223719ed95bd9e.pdf
Nanomechanics analysis of graphene via development of an MD-based AFEM
Mohammad Mehdi
Malakouti
دانشجوی کارشناسی ارشد
دانشگاه صنعتی خواجه نصیر الدین طوسی
author
Abbas
Montazeri
عضو هیات علمی
دانشگاه صنعتی خواجه نصیر الدین طوسی
author
text
article
2016
per
Due to their accuracy and reliability, atomistic-based methods such as molecular dynamics (MD) simulations have played an essential role in the field of predictive modeling of single layered graphene sheets (SLGSs(. However, due to the computational costs, applications of these methods are limited to small systems. Additionally, according to the discrete nature of SLGSs, conventional continuum-based methods cannot be utilized to study the mechanical characteristics of them. To overcome these issues, here, a new Atomic-scale Finite Element Method (AFEM) based on the Tersoff-Brenner potential has been developed. Efficiency of the proposed method is evaluated through a numerical example analyzed by both of the proposed method and MD simulation. The results show that the computational cost is much reduced (~100 times), while the accuracy of MD simulation is kept. Furthermore, the effects of initial C-C bond length and number of atoms on the speed of the proposed method is investigated. To mimic the MD simulation completely, periodic boundary conditions have been implemented in the extended AFEM. It is demonstrated that there is a noticeable deviation from MD results without considering this type of boundary conditions.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
1
9
http://mme.modares.ac.ir/article_14432_8408906ea172ed4af97f81b705a41cdb.pdf
Variation of Longitudinal Ultrasonic Wave Velocity in the Presence of a Thermal Gradient; Part 2: Experimental Study and Uncertainty Analysis
Ramin
Shabani
دانشجو/ دانشگاه خواجه نصیر الدین طوسی
author
Farhang
Honavar
دانشکده مکانیک دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2016
per
It is essential to inspect manufactured and in-service machines and components in industry. Many different are currently in use for this purpose. Ultrasonic testing is one of the most important nondestructive testing methods. Ultrasonic testing has different applications such as defect detection, assessment of mechanical and metallurgical properties of materials and temperature measurement. In the first part of this paper, theoretical equations and finite element analysis of variation of longitudinal ultrasonic wave velocity in the presence of a thermal gradient were studied. In the second part, the effect of a thermal gradient on the longitudinal ultrasonic waves is investigated by experiments. A specific test rig is designed and fabricated for this purpose. It can provide the desired temperatures and transmit and receive ultrasonic bulk waves simultaneously. Twelve different tests were carried out to study the effects of the work piece length and maximum and minimum temperatures. The experimental results are compared with the theory under similar conditions and very good agreement is observed. Uncertainty analysis is incorporated for determining the uncertainty in measuring the ultrasonic wave velocity in the presence of a thermal gradient and identifying the sources of error. The measurements were found to be quite accurate with an uncertainty of 4.5 m/s.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
10
16
http://mme.modares.ac.ir/article_14436_ef94e63582892df079ff4cc5e4295c5a.pdf
Water conservation in power plant wet cooling tower through changing into hybrid tower using two airflow control systems
Shahed
Taghian Dehaghani
Msc. Graduate Student
author
Hossein
Ahmadi Kia
دانشیار گروه مکانیک دانشگاه اصفهان
author
text
article
2016
per
Wet cooling towers have a high cooling capacity. However, owing to consumption of large water quantities in wet cooling towers, using them in arid regions facing water resource crisis might cause operational problems. In this research, changing the wet cooling tower of unit 5 of Isfahan Islamabad power plant into a hybrid cooling tower, using parallel path wet/dry configuration is studied. The hybrid cooling tower with the recommended configuration causes minimal changes in the other power plant facilities and has a low construction cost. Two different airflow control systems are investigated for the wet and hybrid cooling towers. In the first system, the amount of airflow rate in the cooling tower is adjusted by means of switching tower ID fans on or off. In the second system, an optimum airflow control mechanism with high-tech fans is devised. The results reveal that the optimum airflow control system is more suitable than the other system, due to less water consumption, preventing the sudden fluctuations of airflow and consequently water consumption rates and less fan power consumption. Experimental data and results obtained by the HTFS software are used for validating the simulated results of the wet cooling tower and air-cooled heat exchangers, respectively. The results demonstrate that the annual amount of water conservation due to changing the wet cooling tower into hybrid tower is approximately 343830 and 348718 cubic meters for fan switching and optimum airflow control systems, respectively.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
17
28
http://mme.modares.ac.ir/article_14431_3afccb023e48545d1e0d717e53efd34e.pdf
Investigate the effect of inosculation strategy on promoting vascularization in tissue engineering
Hooman
Salavati
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Madjid
Soltani
عضو هیئت علمی
author
Hossein
Bazmara
عضو هیئت علمی
author
text
article
2016
per
Tissue engineering is a rapidly growing field of research for several decades, which is driven by the human urgent need for tissue substitutes and transplantable organs. Considering the advancements, the clinical applications in the field of tissue engineering have been limited until now. The major reason toward this limitation is the lack of sufficient blood supply for the tissue in the earliest phase after implantation. Time-consuming process of angiogenesis leads to inadequate vascularization and finally, death of cells and destruction of tissue. During recent years, by implementing a strategy called Inosculation, it has been tried to facilitate tissue vascularization by a preformed vasculature network within tissue structure. In the current research considering cellular nature of angiogenesis process, relying on a cell-based mathematical model, the effect of inosculation strategy is investigated through the dynamics of angiogenesis process with respect to extracellular, cellular and intracellular spatio-temporal scales. The results show the advantages of inosculation strategy over angiogenesis strategy in vascularization of tissue constructs. The model demonstrates the capability of inosculation strategy to improve the anastomosis probability, which is providing the crucial requisite for the blood to flow through capillary network. Furthermore, the cellular model was developed in a way that illustrates the effects of extracellular matrix on morphogenesis through branching phenomenon.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
29
40
http://mme.modares.ac.ir/article_14434_1cd094e2bd9ce79e40c477f4cde3de27.pdf
Young’s modulus Estimation of fullerene nano-structure by using molecular mechanics and finite element method
Ali
Nayebi
دانشگاه شیراز
دانشکده مهندسی مکانیک
خیابان ملاصدرا
شیراز
دورنگار: 07136473533
author
Esmaeal
Ghavanloo
عضو هییت علمی
author
Nastaran
Hosseini
دانش آموخته
author
text
article
2016
per
In this paper, a three-dimensional finite element model is proposed for estimating Young’s modulus of fullerene nanostructures. The model is based on the assumption that the fullerenes, when subjected to loading, behave like space-frame structures. The bonds between carbon atoms are considered as connecting load-carrying members like beams under axial, bending and torsion loadings, while the carbon atoms as joints of the members. To create the finite element models, nodes are placed at the locations of carbon atoms and the bonds between them are modeled using three-dimensional elastic beam elements. The elastic modulus of beam elements is determined by using a linkage between molecular mechanics and continuum mechanics. In order to evaluate the Young’s modulus, the spherical shell theory is also utilized. Compression loading on the fullerene is considered and the load – displacement variation is obtained. The effect of diameter on the elastic modulus of fullerenes nanostructures has been studied and it is observed that by increasing the radius of fullerenes, their elastic modulus decreases. After studying the properties of perfect fullerenes, the Young’s modulus of different defective fullerenes is also determined.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
41
48
http://mme.modares.ac.ir/article_14435_5f69c6b88bd985e081d82a7599d1be6a.pdf
An experimental investigation of effect of 3D fabric in the amount of energy absorbed in the GLARE composite
Reza
Amooyi Dizaji
دانشگاه صنعتی سهند
author
Mojtaba
Yazdani
Assistant Professor of Applied Mechanics (Solid)
author
text
article
2016
per
This research investigated experimentally the effect of useing of 3D fiberglass fabric in the energy absorption in glass fiber metal laminate composite made by vacuum assisted resin transfer molding (VARTM) method. The prepared GLARE is made of two or three Aluminum 2024 facing sheets and E glass/epoxy as nano composite core. Composite core section for samples of glass fiber plain weave has been composed of plain weave glass fiber 200 g⁄m^2 , 3D fiberglass fabric samples consists of 3D fiberglass fabric to thickness of 5 mm, resin R510 and hardner H515. All panels fabricated using VARTM method in section glass fiber plain weave in fiber volume fraction of 71%. Low velocity impact tests were conducted using by drop weight device at the impact energy of 50 and 80 j. The results of the low velocity impact experiments show that the amount of resistance of impact plain weave samples in comparison to the 3D fabric in various energy levels is more and better. In applications where weight is an effective agent component, the weight of glass fiber plain weave base samples is less than 3D fiberglass fabric samples.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
49
54
http://mme.modares.ac.ir/article_14433_66920b363586f1662e297e4ea8f80ed0.pdf
nonlinear free vibrations analysis of a piezoelectric bimorph nanoactuator using nonlocal elasticity theory
Abbas
Kaghazian
دانشگاه شهید چمران اهواز
author
Hamid Reza
Foruzande
دانشگاه شهیدچمران اهواز
author
Ali
Hajnayeb
استادیار/دانشگاه شهید چمران اهواز
author
Hamid
Mohammad Sedighi
استادیار /دانشگاه شهید چمران اهواز
author
text
article
2016
per
In this paper, the nonlinear free vibrations of a bimorph piezoelectric nanoactuator is studied based on nonlocal elasticity. The Euler-Bernoulli beam theory and Hamilton’s principle are used to derive the equation of motion of the actuator. In order to obtain the reduced-order form of equations, the Galerkin method is used. The mode shapes of a multi-span beam are used for a faster convergence. The nonlinear natural frequencies are obtained by using He’s variational approach. Equations are solved for clamped-clamped boundary conditions, and the effects of values of DC voltage, actuator length and thickness, length of piezoelectric layers and nonlocal parameter on the nonlinear natural frequencies are studied. The results show that applying a DC voltage induces a static deflection and an increase in the stiffness of the actuator. Therefore, the natural frequency increases. Moreover, increasing the nonlocal parameter decreases the rate of change in frequency variation. An increase in the nonlocal parameter or the length of the actuator increases the nonlinear to nonlinear natural frequency ratio. Finally, the effect of the middle layer material of the actuator on the frequency ratio is studied.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
55
66
http://mme.modares.ac.ir/article_14428_d49d44d0e50a5adfae0e07f5a5e4112b.pdf
Electro-thermo-mechanical behavior modeling of short CNT reinforced piezo-polymeric composite
MohammadJavad
Mahmoodi
دانشگاه شهید بهشتی، پردیس فنی مهندسی شهید عباسپور، دانشکده مهندسی مکانیک و انرژی
author
Mohammad
Vakilifard
دانشکده مهندسی مکانیک و انرژی، دانشگاه شهید بهشتی، تهران
author
text
article
2016
per
A three-dimensional analytical micromechanical model based on unit cell is extended and presented to extract the electro-thermo-mechanical properties of short Carbon Nano-Tube (CNT) reinforced piezo-polymeric composite. Representative volume element (RVE) of the piezonanocomposite consists of three phases including CNT, piezo-polymeric matrix and interphase region. The presented model considers the CNT as a transversely isotropic solid fiber and CNT/matrix interphase region possessing van der Waals’ interaction as an isotropic hollow cylindrical solid that its mechanical properties are derived using the equivalent continuum model. Both phases are considered linear elastic. Also, the matrix is a piezoelectric material that is mechanically isotropic and elastic, and polarized along the perpendicular direction to CNT axis. The state of CNT arrangement within the matrix is assumed to be regular and square. First, the results obtained from the model are compared with available researches. Then, the effects of CNT volume fraction and aspect ratio and interphase effective thickness on the overall properties of the nanocomposite are investigated. In this study, despite the prior works, all the piezo-electro-thermo-mechanical properties of the nanocomposite are studied. The results show that even small amount of FVF has significant effect on improving the composite properties. Furthermore modeling of interphase region includes a great effect on the most of the composite properties, thus its modeling is necessary for more actual prediction about the nanocompite response.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
67
76
http://mme.modares.ac.ir/article_14445_87496e87789f23799a8724a12a129952.pdf
Three dimensional investigation of gas turbine cooling techniques on a flat plate and presentation a method with maximum cooling effectiveness
Mojtaba
Kazemi Kelishami
دانشگاه حکیم سبزواری
author
Esmail
Lakzian
Assistant Professor of Mechanical Engineering,
Hakim Sabzevari University
author
text
article
2016
per
Cooling of high temperature systems such as gas turbine blades is one of the most important systems in industrial. In this paper, three dimensional cooling performance on a flat plate is calculated by a 3D finite-volume method and the realizable k-ε turbulence model which is the improved of the standard k-ε turbulence model and it can generate data more appropriate for fluid injections and jets. In this investigation, 4 different cases have compared together to find the best cooling case with maximum effectiveness. These cooling cases are including 2 cases of film cooling with console and cylindrical holes, one case of impingement cooling and one case of transpiration (with porous wall) cooling. For validation, the adiabatic cooling effectiveness for the console has been compared with the experimental data. These comparisons have been shown a good agreement between experimental and numerical data. The adiabatic cooling effectiveness, the effects of density ratio (by air and CO2 as a coolant) (DR) and blowing ratio (M) are studied in all cases. The adiabatic cooling effectiveness for console and transpiration cooling cases have compared together for studying the penetration of coolant fluid in the main stream (hot fluid) and showing the temperature and effectiveness distribution . The main purpose of this paper is finding the best cooling techniques with maximum effectiveness and the results have been shown which the designed transpiration cooling model has the best effectiveness respect to other cooling techniques.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
77
87
http://mme.modares.ac.ir/article_14446_55aaa6a1fcd2034e5c9e238f7b39545e.pdf
Leader-follower flexible formation control of wheeled mobile robots based on an integrated bio-inspired neurodynamics approach and backstepping scheme
Maryam
Asgari
مهندسی مکاترونیک گرایش اتوماتیک و کنترل تولید، دانشگاه آزاد اسلامی، قزوین
author
Mohammad Reza
Jahed Motlagh
مهندسی کنترل، دانشگاه علم و صنعت ایران، تهران
author
Khalil
Alipour
Assistant Prof./University of Tehran
author
text
article
2016
per
This paper investigates the leader-follower formation control problem of nonholonomic mobile robots based on backstepping technique composed with the bio-inspired neurodynamics while avoiding collision with obstacles. Kinematics model of robot and nonholonomic constraint are introduced and formation control scheme is formed based on backstepping technique. In order to solve velocity jump in backstepping kinematics model, the bio-inspired neurodynamic approach is used. In most of the previous studies, researches are used separation-bearing approach and also supposed that desired separation and bearing are constant. In this paper this assumption is relaxed and desired separation and bearing are considered to be time varying. Error dynamics equations are derived and a new controller is proposed. Also an auxiliary reference angular velocity control law is proposed to guarantee global asymptotic stability of the followers and local asymptotic stability of the entire formation according to direct method of Lyapunov. A common example of changing the formation is obstacle avoidance, when an obstacle is located within a follower path and is not in its leader path. Time varying functions for desired separation and bearing are chosen and the new controller is developed with its proof of stability. Simulations results reveal that each follower robot can track its real time leader employing the proposed kinematic controller while avoiding obstacles. Furthermore control inputs at the start moment and also while avoiding obstacles, do not contain impractical jumps and are reasonable thanks to integrating bio-inspired neurodynamic with backstepping technique.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
88
98
http://mme.modares.ac.ir/article_14475_22d45a602411e3f856dc0b4b81e778b4.pdf
Investigation of wire drawing parameters on interlayer pressure at Copper clad Aluminum wire
Saeed
Rahnama
دانشگاه بیرجند
author
Fariborz
Fatehi Sichani
دانشگاه بیرجند
author
Mehdi
Raghebi
دانشگاه بیرجند
author
text
article
2016
per
Copper clad aluminum composite wire used in wire and cable industry is an applied product. This product must be manufactured according to standard ASTM B566. According to this standard the connection between the layers is one of the quality parameters. Interlayer pressure during the production process, plays an important role in the quality of connection between two layers. The effects of important wire drawing parameters, including a half-angle dies, reduction ratio and coefficient of friction on the interlayer pressure were discussed by slab methods. After samples making, test of wire drawing process was conducted to determine the force with three modes of dry friction, oil lubrication and grease lubrication. There was good agreement between experimental and analytical methods. With Increase in friction coefficient of interlayer the interlayer pressure will increase. With increase in half angle of die, the interlayer pressure was increase significantly. So that, by increasing the half angle of die from 5 to 75 degree, the interlayer pressure increases about 3 times. Also, with increase in reduction of area the interlayer pressure was increase. But, it was found that the friction coefficient of die does not have a role in interlayer pressure changes.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
99
108
http://mme.modares.ac.ir/article_14447_8b62b283f3e339181e8befe10b78a649.pdf
Path planning of cable driven parallel robots in the presence of dynamic obstacles via potential field using computed torque control method
Ali
Aflakiyan
آزمایشگاه تعامل انسان و ربات، دانشکده علوم و فنون نوین، دانشگاه تهران
author
Mehdi
Tale Masouleh
استادیار مهندسی مکاترونیک دانشکده علوم و فنون نوین دانشگاه تهران-آزمایشگاه تعامل انسان و ربات
author
Hassan
Bayani
آزمایشگاه تعامل انسان و ربات، دانشکده علوم و فنون نوین، دانشگاه تهران
author
Rasoul
Sadeghian
آزمایشگاه تعامل انسان و ربات دانشگاه تهران
author
text
article
2016
per
In this paper, kinematic and dynamic model of planar cable-driven parallel robots are introduced in general form which are verified for a constrained cable-driven parallel robot in Sim-mechanics. Path planning based on artificial potential field approach is considered to prevent collision between dynamic obstacle, end-effector and cables in order to achieve collision-free path. As well as to reduce energy consumption, cable tension constraints have been involved in optimization of path planning. This method is proposed to control a cable robot. Therefore, obstacles are distributed randomly in order to have a complex environment. By this way, cable tension constraint is studied as one of the most crucial challenges for cable driven robots. Moreover, Fmincon function of Matlab is applied in order to take into account the required constraints and maintain the limits for cables tension. The latter leads to solve the redundancy resolution which is a definite asset in controlling a cable-driven parallel robot. Finally, a four-cables driven parallel robot is controlled by using the so-called computed torque method for tracking the desired and optimized path. The method is explained and obtained results indicate the efficiency of the proposed approach.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
109
118
http://mme.modares.ac.ir/article_14451_ea0aa599ce68b4a6109ca51a7095c69d.pdf
A modified shape function for calculating stable configurations and natural frequencies of bi-stable [0/90]T composite laminates
Ahmad
Firouzian-Nejad
دانشگاه صنعتی اصفهان
author
Saeed
Ziaei-Rad
دانشگاه صنعتی اصفهان
author
Masih
Moor
دانشگاه علوم و فنون دریایی خرمشهر
author
text
article
2016
per
In this paper, thermal and vibration response of cross-ply bi-stable composite laminated plates were studied using semi-analytical, finite element and experimental method. In order to evaluate the semi-analytical and finite element results, a bi-stable composite plate was manufactured using a special procedure. Next, geometrical characteristics and displacement of different paths on the plate were measured experimentally at room temperature. In semi-analytical approach, the two stable states and the first natural frequency of cross-ply laminates are calculated based on Rayleigh–Ritz approach combined with Hamilton’s principle. In this study, a modified shape function was introduced that allows the curvatures to vary in both longitudinal and transverse directions. Using the modified shape function, the displacement of the plate in its stable configuration and the first natural frequency of the plate can be more accurately predicted in compared to the Hyer’s shape functions. The obtained results from the proposed shape function are in good agreement with the finite element and experimental data. The proposed shape functions can also be used in dynamic and vibration analysis to determine the snap-through load of the cross-ply laminates.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
119
128
http://mme.modares.ac.ir/article_14476_763a903503d11dbc3aef67480118da56.pdf
Effective parameters on variation of wall shear stress in microvessels
Mina
Alafzadeh
جهاد دانشگاهی یزد
author
Ebrahim
Shirani
استاد-موسسه آموزش عالی صنعتی فولاد
author
Effat
Yahaghi
دانشگاه بین المللی امام خمینی
author
Nasser
Fatouraee
دانشگاه صنعتی امیرکبیر
author
text
article
2016
per
The variation of wall shear stress (WSS) in the microvessels may damage the endothelial layers. It also changes the mass diffusion and sediment and may be considered as an important factor in the formation of the fatty plaques and causing heart disease. According to the importance of the issue, the aim of this paper is to study the effective parameters on the wall shear stress in microvessels. In this paper, the hybrid method, combined lattice Boltzmann and immersed boundary methods is used to simulate the red blood cell (RBC) motion in the plasma flow. It should be mentioned that red blood cell has significant effect on WSS, in this regard; the present results show that the blood rheological behavior has the important effect on WSS. The results also demonstrate the effect of stenosis severity and RBC location in different regions on wall shear stress and consequently causing heart, coronary disease. It should be noted that the presented results have been evaluated by previous numerical results for microvessels and the results show the ability of lattice Boltzmann method to simulate complex problems especially for modeling the deformable solid objects suspended in the fluid.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
129
134
http://mme.modares.ac.ir/article_14477_c50f620626ff295868e046907963ee5d.pdf
Approximate solution of zero-effort-miss under gravitational acceleration inversely proportional to the cubic distance
Mohsen
Dehghani Mohammadabadi
Tarbiat modares university
author
Sayed Hamid
Jalali Naini
Tarbiat modares university
author
text
article
2016
per
In this paper, an approximate solution of zero-effort-miss distance in spherical earth model is obtained in Earth-centered inertial (ECI) coordinates. In this approach, the gravitational acceleration is assumed to be inversely proportional to the cubic distance of space vehicle from the earth center. The present solution gives an explicit formula in terms of initial conditions and flight time. Moreover, the piecewise solution, i.e., the connection of solutions, is utilized in order to increase the accuracy of the algorithm. For this propose, the total flight time is divided into several interval using middle points. In each interval, the gravitational acceleration is taken to be inversely proportional to the cubic distance, but the correction constant is updated for each interval. The accuracy of the proposed method and its computational burden are calculated for various numbers of time intervals. For comparison purpose, the piecewise solution is also applied to the linear gravity approximation. The simulation results and calculation of computational burden show that the presented method has better accuracy than linear solution in ECI reference and linearized solution for relative motion with the same computational burden.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
135
144
http://mme.modares.ac.ir/article_14486_ba12af2c5ed373a718ac1836925b776c.pdf
A new severe plastic deformation technique based on simple and pure shear
Soheil
Nakhodchi
عضو هیات علمی/استادیار دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Mohammad
Mahmoudi
دانشجوی کارشناسی ارشد
author
Ali
Shokuhfar
عضو هیئت علمی/ استاد دانشگاه صنعتی خواجه نصیر الدین طوسی
author
text
article
2016
per
Combined shear extrusion (CSE) is a new severe plastic deformation (SPD) technique to produce bulk ultra-fine grained materials. CSE is obtained by the combination of simple and pure shear extrusion. This technique is based on definitions of pure and simple shear. In the present work, the nonlinear (large) deformation elasticity theory is used for obtaining the shear strain applied to the sample under pure shear extrusion with various angles of distortion. Also plastic deformation characteristics of CSE method were analyzed with finite element analysis using commercial Deform 3D software. Shear strain and effective strain applied to the sample, the load required to carry out the process and the final shape of the cross-sectional area were studied for different angles of distortion. Analytical results and finite element analysis shows by increasing the angles of distortion, shear strain and increased rate of shear strain applied to the sample increased so the effective strain and load required to carry out the process increases. Analysis of finite element and geometry of the die shows that distribution of shear strain and effective strain is inhomogeneously and symmetrical in specimen’s cross section which increases from the center to the corners and by increasing the angles of distortion, distribution of strain becomes more inhomogeneously, also the final shape of the cross-sectional area deforms more.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
145
154
http://mme.modares.ac.ir/article_14487_ade9a5d73b50fa52c250c915b24d204e.pdf
Hydroelastic coupled vibrations in spherical containers of membrane bottom, partially filled with frictionless liquids
Behnam
Cheraghi
فارغ التحصیل/ دانشگاه تهران
author
Babak
Mirzavand Boroujeni
استادیار /دانشگاه تهران
author
Maziar
Shafaee
عضو هیئت علمی/دانشگاه تهران
author
text
article
2016
per
Free hydroelastic coupled vibration analysis of frictionless liquids with a free surface in spherical tanks with a flexible bottom has been performed. The side wall has been considered to treate as a rigid body. The flexible bottom treats as a membrane at a certain distance bellow the center point, and the free surface is considered as a cross cutting at the top of the center point. The spherical coordinate system is adopted to derive the governing coupled equations, and finally a vibration analysis is carried out, using the traditional Galerkin's method, leading to closed-form solutions. Effects of various system parameters, i.e., membrane tension, liquid density, geometric parameters of the system such as the container radius, free surface distance discriminate parameter, and bottom distance discriminate parameter on the vibration behavior are investigated. The novelty of the present work is to obtain direct formulas for hydroelastic coupled vibration analysis of the mentioned system, which can be easily used in engineering design applications. Coupling between two mode numbers can be clearly seen in results, in other words, there is a coupling between vibration modes as interaction in spherical geometry.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
155
162
http://mme.modares.ac.ir/article_14488_4bd24faa339bdb81b9a4977df1c3247f.pdf
Numerical investigation of fluid flow between the impeller and casing on disk friction for a centrifugal pump
Mohammad Amin
Dehghani
دانشکده فنی دانشگاه تهران، دانشکده مهندسی مکانیک
author
Amir Farhad
Najafi
دانشگاه تهران
author
Seyed Ahmad
Nourbakhsh
دانشکده فنی دانشگاه تهران، دانشکده مهندسی مکانیک
author
Hossein
Shokohmand
دانشکده فنی دانشگاه تهران، دانشکده مهندسی مکانیک
author
text
article
2016
per
Pumps consume about 20% of whole electricity power in the world. Centrifugal pump is one of the most common pumps that works by the transfer of angular momentum to the fluid. The behavior of such a fluid flow in the side chamber, may affect the pump performance. The side chamber is defined the free space between the fixed (pump casing) and the rotating (pump impeller) parts. Steady, fully 3D computations of the Reynolds-averaged Navier-Stokes equations using a commercial CFD code are conducted in order to study the flow field in the whole pump including both side chambers. Numerical results are validated by comparison with the existing experiments. The impact of fluid flow in hub and shroud side chambers with the volute is investigated qualitatively by using 2D stream lines. Evaluation of the empirical equations shows that the frictional torque may be decreased more than 10%, by using the proper gap size. Considering this situation, the changes in the flow pattern and the value of power loss resulting from friction in hub and shroud side chamber is studied. It reveals that the variation in friction depends on the initial flow pattern in cavity. Finally, in order to obtain the relationship between the power loss and the flow rate, nondimensional coefficients are derived. These coefficients show that the change in the power loss due to the volumetric flow rate, is the same as its change with the gap changing, but their slopes are not equal.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
163
174
http://mme.modares.ac.ir/article_14489_fbf5f07174932c2f7d9ac85249565cb7.pdf
Effect of material and welding parameters on characteristics of T-shape weld of steel plates using experimental data and numerical model
Farid
Vakil-Tahami
Associate professor, University of Tabriz
author
Ali
Ziaei Asl
Assistant Professor, Department of Mechanical Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran
author
Peyman
Majnoun
Department of Mechanical Engineering, University of Tabriz
author
text
article
2016
per
In this paper, experimental data have been used to develop a semi empirical relationship for double-ellipsoidal heat source to model the welding process of a T-shape fillet weld of carbon steel AISI 1020 and stainless steel 304. This model is used in a finite element based computer code to simulate the three dimensional welding process and obtain the temperature profile around the weldment. Experimental data in the form of temperature for certain points have been recorded during the welding process using a computerized data processing system which has been designed for this purpose. Also, the thickness of the weldment layers has been compared by observing their hardness and crystallography. By comparing experimental data with numerical result, the coefficient of the model has been determined using “model updating” process. The effects of material properties and welding parameters have been studied to insure the generality of the model. This model can be used to evaluate the quality of the welding and thickness of the heat affected zone as well as the risks during the welding process such as burn-through and hot cracking. The main advantage of this model is that the number of coefficients is reduced to only one parameter and the rest have been related to the physical and geometrical characteristics of the weld. Results of the numerical simulation obtained using this model show that the major factors which affect the temperature distribution around the weldment are material conductivity, plate thickness, input heating and welding speed.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
175
186
http://mme.modares.ac.ir/article_14490_eef5f6fb0c82f5d6f738e491510fcf38.pdf
The investigation of structure and mechanical properties Dissimilar joining of aluminum 5052 sheet to titanium alloy by friction stir welding
Hossein
Rostami
دانشگاه صنعتی بابل
author
Salman
Nourouzi
Babol University of Technology
author
Hamed
Jamshidi Aval
دانشگاه صنعتی بابل
author
text
article
2016
per
Friction stir welding (FSW) has many advantages in welding dissimilar joints in comparison with fusion welding methods. In this study, weld ability of butt joint of 5052 aluminum alloy and Ti-6Al-4V titanium alloy by FSW process has been studied and discussed. The welding was successfully performed by using a tool with frustum pin. The influences of both rotational and traverse speed of welding tool on mechanical properties are investigated. The results show that the metallurgical and mechanical properties improve by choosing appropriate parameters. The highest tensile strength of 260 MPa was obtained at rotational speed of 500 rpm and a 40 mm/min traverse speed, which was ~ 94% of the aluminum base metal tensile strength. As a result of increasing the rotational speed from 500 to 1000 rpm, high heat input can forms cracks at joint area. In rotational speed of 1000 rpm, increasing traverse speed from 40 to 56 mm/min leads to a sound joint with 192 MPa of tensile strength. This decreasing in tensile strength can be related to the formation of intermetallic compounds such as TiAl3, along the entire interface between the two alloys
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
187
195
http://mme.modares.ac.ir/article_14491_08ecd422fc46db8d55b2b01cfbe07163.pdf
Influence of indenter nose in quasi-static punch shear penetration of the nanostructured laminated plates
Seyed Abdolvhabe
Hossein
عضو هیات علمی/دانشگاه آزاد واحد شوشتر
author
Mohammad Hossein
Pol
عضو هیات علمی/دانشگاه تفرش
author
text
article
2016
per
In this paper, the effects of the adding of carbon nanotubes on quasi-static punch shear behavior of glass/epoxy laminated composites under penetration of three different indenters has been investigated experimentally. The hybrid laminate nanocomposites have 12 layers is manufactured by Hand lay-up method. Fibers have a plain-weave configuration with density of 200 g/m2, while the epoxy resin system is made of diglycidyl ether of bisphenol A resin (DGEBA), Epon 828, with Epikure F-205 as the curing agent. The multi-walled carbon nanotubes (MWCNTs) modified with hydroxide (-COOH) are dispersed into the epoxy system in a 0% and 1% ratio in weight with respect to the matrix. In order to study of influence of the nose shape, three different indenters, flat, conical and ogival, were used. Moreover, the tensile test was performed on the nanomatrix and the hybrid laminate nanocomposite samples. The tensile test indicated that the addition of nanotubes on the tensile properties of resin were seen a significant increase, but no significant changes were observed in the tensile properties of the hybrid laminate nanocomposites. Results of the quasi-static punch shear test show that the highest contact force is exhibited by flat indenter, while the highest absorbed energy is shown by conical indenter. Totally, the adding of carbon nanotubes reduces the contact force and absorbed energy.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
196
204
http://mme.modares.ac.ir/article_14493_fe23e0680bcbba7f85a14e993baa2560.pdf
Passivity based turning control of 3D biped robot with asymptotical stability
Borhan
Beigzadeh
استادیار، آزمایشگاه تحقیقاتی بیومکاترونیک و مهندسی شناختی، مهندسی مکانیک، دانشگاه علم و صنعت ایران
author
Mohammad Reza
Sabaapour
دانشکده مهندسی مکانیک، دانشگاه تهران
author
Mohammad Reza
Hairi Yazdi
دانشکده مهندسی مکانیک، دانشگاه تهران
author
text
article
2016
per
Once the concept of passive walking was appeared, control of biped robots based on dynamically stable periodic gaits around a stable limit cycle became of interest of many researchers and it has been further accelerated nowadays. The authors have previously shown that in addition to passive walking, a passive, biped walker could interestingly show asymptotically stable turning motion over a novel 3D surface called "helical slope". In this paper, based on passive turning concept, a control method would be offered which is effective for 3D biped robots. The approach is based on potential energy shaping that is usually applied for walking control. In the proposed method, asymptotically stable passive turning motions that are performed on a certain helical slope are projected to 3D motions over flat ground and along a circular path (which is the image of the helical slope on the ground). The biped model used in this study, is a 3D model of compass gait robot with flat feet and flexible ankles that could generated stable passive turning motions. The simulation results show the effectiveness of the proposed method as well.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
205
212
http://mme.modares.ac.ir/article_14492_d9760584a067b956805bfad2f118a962.pdf
Post-buckling of laminated plates using collocation method and Legendre basis functions
Seyed Amir
Ghannadpour
استادیار دانشگاه شهید بهشتی
author
Mohammad Ali
Mehrpouya
عضو هیئت علمی
author
Payam
Kiani
دانشجوی دانشگاه شهید بهشتی تهران
author
text
article
2016
per
In this paper, post-buckling behavior of laminated plates is investigated using mesh-free method. One of the most common powerful numerical methods in recent decades is mesh-free collocation method. Due to wildly oscillating solutions at the endpoints and occurrence of Runge phenomenon in the case of uniform distribution of points, the domain of the problem is discretized with Legendre-gauss-lobatto nodes. In this paper, the classical laminated plate theory is used and different out-of-plane boundary conditions with anti-symmetric cross-ply and angle-ply laminates are investigated. Equations system is introduced by discretizing von-Karman’s compatibility equations and boundary conditions with finite Legendre basis functions that are substituted into the displacement fields. Because of large deformations and nonlinear terms in the strain-displacement relations, the nonlinear system of equations is solved by using Newton-Raphson technique. Since number of equations is always more than the number of unknown parameters, the least square technique is used to solve the system of equations. Some results are obtained and compared with those available in the literature.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
213
220
http://mme.modares.ac.ir/article_14494_38dfd347b4ad62993c1ba25a14935796.pdf
Aerodynamic Modification of High-rise Buildings based on Adjoint Method to Reduce Wind Induced Forces
Mohammad Hassan
Javareshkian
دانشیار دانشگاه فردوسی مشهد
author
Ali
Esmaeli
دانشگاه فردوسی مشهد
author
text
article
2016
per
In this research, a new numerical approach which is capable of modifying the shape of three dimensional massive bodies like tall buildings respect to aerodynamic loads is presented; therefore, the aerodynamic forces are improved; consequently, the comfortability of the buildings is increased. This method is drawn into 2 parts; a numerical simulation of fluid flow and Adjoint method. As a result of it, some modifications are performed in the different parts of the building. In the primarily step, the building shape and its setting position are investigated in different flow conditions as effective parameters on the aerodynamic of buildings. Subsequently, the sensitivity level of each variable is studied on aerodynamic loads. The results illustrate that the building pattern has the highest impressments (76%) on the excited forces. In the next step, the amount of sensitivity of the fluid flow on the various areas of the tower is assessed by solving Adjoint equation in the whole fluid domain. As a result of that, some aerodynamic modifications are performed and it has been proved that the imposed loads on the tower have been declined around 31% whereas this amount of improvement is interested for designing of tall buildings.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
221
229
http://mme.modares.ac.ir/article_14495_fe4f08f3ef1eaff56b34dc3ad1c5e12f.pdf
Static analysis of rectangular plates with variable thickness using a radial point interpolation method method
Reza
Pilafkan
عضو هیئت علمی/ دانشگاه محقق اردبیلی
author
Soudeh
Bakhshi
کارشناس ارشد/دانشگاه محقق اردبیلی
author
text
article
2016
per
In this work static analysis of isotropic rectangular plates with variable thickness are presented using three dimensional electricity theory and for first time using radial point interpolation method. Using this numerical method, the field variables are interpolated just using nodes scattered arbitrarily in the plate domain. As there is no connection between any two nodes, their number can be increased in any area and direction to get more accuracy. It is assumed that, the plate thickness varies linearly in y direction or it has parabolic convex/concave lower surface in the y direction. The horizontal upper surface of the plate is subjected to the transverse uniform load in the z direction. Shape functions in this method have Kroneker delta function property and different boundary conditions can be applied easily using elimination approach. Convergence of results for simply supported isotropic rectangular plates with linearly variable thickness is presented for different thickness ratios and compared with available results. Distributions of the deflections and stresses for the plates with parabolic convex/concave lower surface in the y direction and under different boundary conditions are presented in numerous graphs. It has been showed that this numerical method is so appropriate to analyze such plates and have rapid convergence and high accuracy.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
230
238
http://mme.modares.ac.ir/article_14496_ab65cd7946c85faef8997e49dd86ce29.pdf
Energy-Efficient Position Tracking For Digital Hydraulic Systems Using Fast-Switching Valve
Ahsan
Saeedzadeh
Amirkabir university of technology
author
Seyed Mehdi
Rezaei
Amirkabir university of technology
author
Abdolreza
Rahimi
Amirkabir university of technology
author
Mohammad
Zareinejad
Assistant Professor at Amirkabir University of Technology
author
text
article
2016
per
Hydraulic actuators are widely used where high-magnitude forces are exerted; however, they suffer from low energy-efficiency in many cases. To address this issue, there has been a surge in the volume of researches devoted to improving the efficiency of electro-hydraulic servo systems. Digital Hydraulics is the most recent method, proposed by many researchers to improve the efficiency of hydraulic actuators. Low cost and better energy efficiency are two major advantage of these systems that make them popular among researchers. This paper discusses the possibility of using a fast-switching on/off valve in a novel way, instead of servo valves to improve the efficiency of these systems. For this purpose the flow running through the fast-switching valve controlled, employing proper duty cycle. The excess pump flow is discharged to the tank directly instead of going through the relief valve when the valve is off. Thus the wasted energy, caused by the relief valve, is reduced significantly. A nonlinear backstepping controller is designed to control the duty cycle of the PWM signal of the on/off valve. The effectiveness of this method is tested after conducting experiments on a hydraulic test rig and presenting the experimental results.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
239
247
http://mme.modares.ac.ir/article_14500_e7eeead486263c82ed964b2aee413cc9.pdf
Study of significant factors on magnetic abrasive finishing on freeform surface
Seye Alireza
Rasouli
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Mehrdad
Vahdati
Faculty of Mechanical Engineering
K. N. Toosi University of Technology
author
text
article
2016
per
The attempts of researchers in industries to obtain accurate and high quality surfaces led to the invention of new methods of finishing. Magnetic abrasive finishing (MAF) is a relatively new type of finishing in which the magnetic field is used to control the abrasive tools. Applications such as the surface of molds are ones of the parts which require very high surface smoothness. Usually this type of parts has freeform. In this study, the effect of magnetic abrasive process parameters on freeform surfaces of parts made of aluminum is examined. This method is obtained through combination of magnetic abrasive process and Control Numerical Computer (CNC). The use of simple hemisphere for installation on the flat area of the magnets as well as magnets’ spark in curve form is a measure done during testing the experiments. The design of experiments is based on response surface methodology. The gap, the rotational speed of the spindle and the feed rate are found influential and regression equations governing the process are also determined. The impact of intensity of the magnetic field is obtained using the finite element software of Maxwell. Results show that in concave areas of the surface, generally speaking, the surface roughness decreases to 0.2 µm from its original 1.3 µm roughness. However, in some points the lowest surface roughness of 0.08 µm was measured
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
248
258
http://mme.modares.ac.ir/article_14501_edfb77051fe0f91392e8d17222a5a43f.pdf
LTC achievement in national light duty diesel engine with early and late injection strategies and comparing them to each other
Mohammad Javad
Jafari
Department of Mechanical Engineering, KN Toosi University of Technology, Tehran, Iran
author
Amir Hossein
Shamekhi
هیات علمی دانشکده مهندسی مکانیک
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2016
per
The low temperature combustion (LTC) concept is the groundwork of most recent developments in internal combustion diesel engines in order to match stringent environmental standards and regulations. Although, its basic definition which means reducing the combustion chamber temperature to decrease the emissions sounds easy but practical achievement of LTC strategies which can be feasible in a wide range of loads and speeds has its own difficulties. With attention to different effective parameters in a diesel engine combustion process, various methods have been introduced for the purpose of LTC achievement. Two important types of these methods are based upon early and late injection strategies. In addition to analyzing the both mechanisms, in this paper we are intended to implement two different methods in national light duty diesel engine in order to match EURO VI emission standard. One method named UNIBUS is based upon early injection strategies which is benefited from PPC merits and the other one is Modulated Kinetic (MK) which is based upon late injection strategies. Finally both these methods have been compared and contrasted. The results admit the great potentiality of both methods to make a significant and simultaneous reduction in NOx and Soot emissions.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
259
270
http://mme.modares.ac.ir/article_14502_d7be4459b16534a9b7fb85816ae36b9d.pdf
Design and Development of a Mobile Robot for Implementing Obstacle Avoidance Techniques Based on Fuzzy Logic and Vision
Ali
Ravari
Department of Electrical and Computer Engineering, Semnan Science and Research Branch , Islamic Azad University Semnan
author
Mehdi
Tale Masouleh
استادیار مهندسی مکاترونیک دانشکده علوم و فنون نوین دانشگاه تهران-آزمایشگاه تعامل انسان و ربات
author
text
article
2016
per
This article presents the mechanical design process of a mobile robot which is named TL-PR. Two separate algorithms are applied for obstacle avoidance purpose which are experimentally implemented on the proposed robot. The control board Arduino which is used for the under study robot is an open source board. In order to receive the images which are used for obstacle detecting and obstacle avoidance a Kinect sensor is installed in the proposed robot. The structure of TL-PR is a creative, simple and low cost structure. Two methods are used for obstacle avoidance which are implemented on the proposed robot. The first one is based on ultrasonic sensor. Five ultrasonic sensors are set around the proposed robot structure. The fuzzy control is used to manage the output data of the ultrasonic sensors and the rules of the fuzzy control are set on the MATLAB software. The second method which is used for obstacle detection and avoidance is based on image processing algorithm. A Kinect sensor is set on the top of the robot structure which is used for image processing for detecting the obstacles. The second method consists in processing the Visual Studio software and it run based on the OpenCV library. The proposed robot is a desirable platform for the @home robots. The laptop which is set on the robot made the robot compatible for implementing the various control and image processing algorithms.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
271
280
http://mme.modares.ac.ir/article_14504_a8c6b6b7f7ce777683e6c9beca15efb7.pdf
Experimental and numerical analysis of impact on steel curved panels
Ahmad
Bidi
دانشجوی دکترا مکانیک
author
Gholam Hossein
Liaghat
استاد دانشگاه تربیت مدرس
author
Cholam Hossein
Rahimi
استاد دانشگاه تربیت مدرس
author
text
article
2016
per
The low velocity impact behavior of steel panel with different curvature is investigated experimentally. Numerical analysis is used for test results verification. In experimental method drop impact test apparatus is used so three different height for falling weight is considered. Also three different panel curvatures for experiment are used. Two important parameters measured are maximum acceleration and maximum plastic deformation of panel. A high speed accelerometer is used for measuring the impactor acceleration. Also the permanent plastic deformation is measured with numerical measurement system attached to the drop test apparatus.Experimental analysis with three different radius of curvature is modeled with numerical analysis, the numerical analysis is used for further panel curvatures so the panel behavior is estimated in a wide range of panel curvatures. The results in numerical analysis and test (if available) show good agreement when compared together. the results show that increasing the panel radius of curvature will increase impactor acceleration and will decrease the plastic deformation of panel, but if the radius of curvature is increased more and more, then the impactor acceleration will not increase further and will be nearly constant, on the other hand plastic deformation of the panel will not be increased further, when the panel radius of curvature is increased more.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
281
288
http://mme.modares.ac.ir/article_14503_0834bc3906d02bbdd234fc70d5bf0b44.pdf
Hydrophobic coating of aluminum flake particles and application of these particles to produce superhydrophobic surfaces
Nowrouz Mohammad
Nouri
عضو هیات علمی دانشکده مهندسی مکانیک دانشگاه علم و صنعت
author
Mostafa
Shamsi
کارشناسی ارشد- دانشگاه علم و صنعت ایران
author
Mohammad
Saadat Bakhsh
دانشجوی دکترای مکانیک دانشگاه علم و صنعت ایران
author
text
article
2016
per
Superhydrophobic surfaces are the surfaces with self-cleaning behavior due to surface slip condition. This property is applicable to produce drag reducing, anti-corrosive, and anti-fouling surfaces. Superhydrophobic coatings have been vigorously researched through numerous physical and chemical approaches, including lithography, self-assembly, electrospinning, chemical vapor deposition, plasma or chemical etching, and sol−gel techniques, and so forth. The large-scale fabrication of these surfaces is a challenging issue that restricts employment of these surfaces in industrial applications. Hydrophobic coating of micro/nano particles and deposition of the particles on the surface is a solution that facilitates large-scale fabrication of superhydrophobic surfaces. In this study, rotational vapor phase deposition and immersion method are used to fabricate hydrophobic aluminum flakes. Two reaction times are investigated and the results of two coating method and two particle sizes are presented. The results show that vapor phase deposition method is efficient as well as the immersion method while the latter is not cost effective. Stability test of the prepared samples showed that particle sizes are important in the vapor phase coating and the reaction time of 6 h is better than the 12 h.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
289
296
http://mme.modares.ac.ir/article_14505_10f1360efcce45d811586946b194b5b7.pdf
Prediction of the friction factor of the coil side in shell and coiled tube heat exchangers using numerical method
Ashkan
Alimoradi
دانشجو/دانشگاه رازی
author
Farzad
Veysi
هیات علمی گروه مکانیک دانشگاه رازی کرمانشاه
author
text
article
2016
per
In this work steady flow of fluid in shell and coiled tube heat exchangers has been simulated then analyzed. Effect of pitch, coil’s diameter, tube’s diameter, shell’s diameter, coil’s height, shell’s height and Reynolds number on the friction factor of coil side has been investigated using numerical method. Forty cases have been analyzed in numerical work. The working fluid of both sides is water which its viscosity and thermal conductivity were assumed to be dependent on temperature. The standard K-έ model was used for turbulence. Results indicate the diameter of the coil is the most effective geometrical parameter on the friction factor of the coil side so that by remaining other parameters constant, if the coil’s diameter increases 60%, the friction factor will decrease 30.6%. Also by remaining other parameters constant if the tube’s diameter is doubled the friction factor of the coil side will increase 16.5%, if the shell’s diameter is doubled the friction factor of the coil side will increase 11.7% while the effect of other geometrical parameters on the friction factor of the coil side is much less than the effect of coil’s diameter, tube’s diameter and shell’s height. Also a correlation has been proposed for prediction of the friction factor of the coil side that contains the effect of all defined geometrical parameters in addition to Reynolds number. This correlation is applicable for wide range of Reynolds number (2700< Re< 38000) and has been compared with the correlations proposed in previous works.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
297
306
http://mme.modares.ac.ir/article_14506_78f35a83e2dda3c20a686ae07573b830.pdf
Damage detection in beam using dynamic excitation system by experimental
Mohammad Ali
Lotfollahi Yaghin
عضو هییت علمی دانشگاه تبریز
author
Mehadi
Kouhdaragh
دانشجوی دکتری دانشگاه تبریز
author
Mir Mohammad
Ettefagh
عضو هییت علمی دانشگاه تبریز
author
Alireza
Mojtahedi
عضو هییت علمی دانشگاه تبریز
author
text
article
2016
per
Most of structural failures are because of break in consisting materials. Beginning of these breaks is with crack which extension of them is a serious threat to behavior of structure, so the methods of distinguishing and showing of cracks are most important subjects which are being investigated. In this article, a new smart portable mechanical system to detect damage in beam structures form using fuzzy-genetic algorithm is introduced. Acceleration-time history of the three point of beam is obtained. The signals are then decomposed into smaller components using new EMD (Empirical Mode Decomposition) method with every IMF containing a specific range of the frequency. The dominate frequencies of the structure are obtained from these IMFs using Short-Time Fourier transform. Subsequently, a new method of damage detection in simply supported beams is introduced based on fuzzy-genetic algorithm. The new method is capable of identifying the location and severity of the damage. This algorithm is developed to detect the location and severity of the damage along the beam, which can detect the damage location and severity based on the pattern of beam frequency variations between undamaged and damaged states.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
307
314
http://mme.modares.ac.ir/article_14508_864d5505f2dedacbd836d9f7e284a40a.pdf
Aging effects on atherosclerosis susceptible sites in vertebrobasilar system: studying oscillatory shear index and averaged wall shear stress criteria
Ali
Salari
Ferdowsi University of Mashhad
author
Alireza
Sharifi
Ferdowsi University of Mashhad
author
Hamid
Niazmand
دانشگاه فردوسی مشهد
author
text
article
2016
per
Vertebrobasilar system stenosis is one of the risk factor for deaths caused by stroke, the risk of stenosis in these arteries are highly depend on the people’s age. In the present study, atherosclerosis susceptible sites in vertebrobasilar system at different ages 20, 50 and 70 have been investigated. Numerical method (Fluent software) is employed to solve the equations. Blood flow is simulated in these arteries to investigate probable risky sites (prone to stenosis). To find these locations, critical values of the averaged wall shear stress (AWSS) and oscillatory shear index (OSI) have been studied. By considering the AWSS and OSI criteria in 20 years old person it becomes clear that the risk of stenosis is not considerable at this age, somehow ageing increases OSI figures in the right vertebral artery and in its junction reaching to the critical values, besides at this age, the area of the sites with lower amount of AWSS are stretched significantly. At the age of 70, risky sites are expanded toward right vertebral artery. Furthermore the risk of stenosis in all determined risky sites of age 50 increased at the age of 70.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
315
323
http://mme.modares.ac.ir/article_14507_61659ba3a3f1f5fe5777ef92515b442c.pdf
Experimental study on ratcheting and softening behavior of stainless steel 304L thin-walled shells under cyclic pure bending load
Mahmoud
Shariati
Professor at Ferdowsi University of Mashhad
author
Kamal
Kolasangiani
دانشجوی دکتری دانشگاه فردوسی مشهد
author
Behzad
Jahangiri
دانشجوی ارشد دانشگاه صنعتی شاهرود
author
Amin
Saber
دانشجوی کارشناسی ارشد دانشگاه فردوسی مشهد
author
text
article
2016
per
In this research, softening and ratcheting behavior of SS304L thin-walled shells under cyclic pure bending load were investigated. Experimental tests were carried out by a servo-hydraulic INSTRON 8802 machine under force-control and displacement-control conditions and the effect of different parameters such as mean force, force amplitude, length of the shells existence and position of cutout were examined. Under displacement-control loading, softening behavior was observed and under force-control loading with non-zero mean force, accumulation of plastic deformation or ratcheting phenomena was occurred. Based on experimental results, linear relation was observed between plastic energy and rate of plastic deformation, which shows the rigidity of fixtures used in the experimental tests. It was observed that increase of the force amplitude accompanied with an increase in maximum force and plastic deformation, finally. Also, analyzing the existence of cutout, ratcheting displacement of cylindrical shells with cutout in the middle of shell is higher than that of the shell without cutout and crack propagation occurred in this area. Under displacement-control loading, reaction of thin-walled shells under cyclic pure bending load is divided into four areas, incubation, transition, steady-state and crack propagation.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
324
332
http://mme.modares.ac.ir/article_14509_f0833258720616d76e12b1f49915903c.pdf
Measurement of Mixed-mode Fracture Toughness of Polypropylene using Multi-specimen J-integral Method
Moharram
Shameli
Sahand University of Technology
author
Naghdali
Choupani
Sahand University of Technology
author
Mir Karim
Razavi
Sahand University of Technology
author
text
article
2016
per
For ductile fracture, the toughness can be measured as a single parameter value or in a resistance curve format (J-R curve) and is often characterized by the J-integral for elastic-plastic materials. Because of their effectiveness in measuring toughness, the J-integral and J-R curve have become the most important material parameters in elastic-plastic fracture mechanics, and have been applied widely in practical engineering. Polymeric materials are widely being used for load-bearing structural applications and, therefore, understanding of their fracture properties is becoming more important. In this study, mixed-mode I/II stable crack growth experiments were carried out on a widely used polymeric material, polypropylene, using recently modified fixture. Multi-specimen R-curve method were used for obtaining J-R curves of different states of mixed-mode loading conditions from pure mode-I to pure mode-II by varying the loading angle by 15° steps accordance with the standard ASTM-D6068 and then the resulting R-curves have been evaluated to determine the values of initiation toughness, JIC, following the schemes of the E813 and E1820 standard procedures. Finite-element analyses were done by ABAQUS and mode-I and mode-II non-dimensional stress intensity factors and geometric work factors of elastic-plastic fracture were obtained for different conditions. Results show that for this material the value of JIC is much more than the value obtained for the JIIC. This material also exhibited a greater resistance to ductile crack growth in mode-I.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
333
344
http://mme.modares.ac.ir/article_14534_525ef7497ac6e402811debf139c755d4.pdf
Analysis of the work hardening effect on required force and deformation zone in sheet drawing process
Yousef
Mollapour
Razi university
author
Heshmatollah
Haghighat
دانشگاه رازی
author
text
article
2016
per
In this paper, the drawing process of the sheet metal through the wedge shaped die has been analyzed by upper bound method using stream function. First, a new deformation model has been introduced in which inlet and outlet shear boundaries are considered flexible. Then, the optimized geometry of the deformation zone has been determined through the effect of work hardening of the sheet material depending on the process conditions. According to the suggested stream function, velocity field, strain rates and power terms have been calculated. The analytical results have been compared with the results of the published analytical data and the finite element simulation results. Furthermore, the effect of work hardening exponent has been investigated on the deformation zone, drawing force and optimum die angle. It has been shown that by increasing the work hardening exponent, inlet and outlet shear boundaries of deformation zone are being inclined to the inlet zone of the die and the required drawing stress is decreased. In addition, by increasing the friction factor, inlet and outlet shear boundaries are being inclined to outlet zone of the die, and by increasing reduction in thickness, inlet and outlet shear boundaries of deformation zone are being inclined to the inlet zone of the die. It is shown that the analytical results have been improved up to ten percent in comparison to the published data.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
345
353
http://mme.modares.ac.ir/article_14535_9b7436ba13a58e29a761e8c21f567dfa.pdf
Investigating the performance of piezoelectric energy harvester including geometrical, damping and material nonlinearities with the method of multiple scales
Kamal
Jahani
دانشیار دانشکده مکانیک-دانشگاه تبریز
author
Parisa
Aghazadeh
Tabriz university
author
text
article
2016
per
Employing piezoelectric systems is one of the suitable methods for harvesting energy from mechanical vibrations available in the environment. In this work,single degree of freedom model for cantilever beam with piezoelectric layer is considered. Simulation contains nonlinear coefficients like: stiffness, damping and coupling coefficient. Governing system of equations is solved by multiple scales method. First with assuming one term in approximate response, the effects of all nonlinear parameters on frequency curve are investigated. Results show that assuming only one term in response evaluates the effect of nonlinear damping correctly. Increasing this coefficient leads to reduce the range of excitation frequency and maximum harvested power. But one term assumption couldn’t assess the effects of nonlinear stiffness and coupling coefficient logically. In this case, the peak of frequency response curve is independent of nonlinear coefficients. So for obtaining accurate results assuming at least two terms of response is necessary. Results show increasing nonlinear stiffness coefficient increase the maximum harvested power and the range of excitation frequency. The effect of nonlinear coupling coefficient is decreasing the maximum power because this coefficient increases the stiffness of the system.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
354
360
http://mme.modares.ac.ir/article_14536_fae09b5516f3876a721c1f0da6f9885b.pdf
Modeling and design of dynamic state feedback controller with wind speed estimator, in variable speed wind turbines
Vahid
Fazlollahi
دانشجوی کارشناسی ارشد دانشگاه شهید بهشتی
author
Mostafa
Taghizadeh
هیات علمی دانشگاه شهید بهشتی پردیس فنی و مهندسی شهید عباسپور
author
text
article
2016
per
In this paper, in order to improve the control performance and increase the efficiency of Vestas 660 kW wind turbine, a research based on theory and practice, using real data is done, and a state feedback controller is designed. The actual data obtained from Binalood wind power plant, show that these turbines have a low efficiency. This is due to the poor performance of the classical controller in tracking maximum power in the partial load area, and the significant error in measurement of wind speed. In this research, to solve these problems, a state feedback controller is designed which improves the turbine performance. In this controller, in order to control the generator torque, feedback of generator speed and aerodynamic torque are taken. Also, using the rotor speed and aerodynamic torque, the wind speed is estimated much more accurately than it is measured by an anemometer. Since, an accurate model of the system is needed for controller design and simulation, wind turbine modeling is done in different subsystems, and its parameters are identified using real data. Simulations performed in MATLAB, indicate the improvement of the system performance with the designed state feedback controller, compared to the classical controller in the actual wind turbine
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
361
371
http://mme.modares.ac.ir/article_14537_c4b6d8f04e8c1c6b9c6bcdc64cfd285f.pdf
A new technique for internal fixation of lateral malleolar tip of fracture
Mohammad Hossein
Moghaddam
دانشگاه یزد
author
Mohammad Mehdi
Jalili
هیأت علمی
author
Mohammad
Ayati Firoozabadi
فلوشیپ جراحی زانو، دانشگاه علوم پزشکی و خدمات بهداشتی درمانی تهران، تهران
author
text
article
2016
per
The aim of this study is comparison of three common internal fixation and one new fixation techniques for tip of lateral malleolar fracture using finite element analysis. The common technique uses a third tubular plate with five holes along the five screws for bone fixation. The new technique that is presented in this study, add a tensile wire to the first technique to improve performance of fixation. In the third technique, a long internal screw is used to connect two parts of fractured bone. In the forth technique two mounted pins in the bone are connected to the mounted screw in the top region of the bone be a tension bond. 3D finite element models of fibula and tibia were generated based on computed tomography data are used for analysis. The model of fixation parts has been added to this model. The simulated results indicated that the most stress was created under the axial bending loads and the stress values decreased with the second technique. However, the results show that the displacement at the fracture under axial bending is more than torsion load. Because of high stresses in the holes of the plate in the first technique, it is recommended to use external fixation to improve this technique.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
372
382
http://mme.modares.ac.ir/article_14538_1eaa0241757493436e6a3a96bfb3edd5.pdf
Study the thermophoresis effect on the deposition of nano-particles from diesel engine exhaust after the dilution tunnel
Pouyan
Talebizadeh
PhD student / Amirkabir University of Technology
author
Hassan
Rahimzadeh
استاد دانشگاه صنعتی امیرکبیر
author
Goodarz
Ahmadi
Clarkson University
author
text
article
2016
per
The aim of this paper was to study the thermophoresis effect on the deposition of nano-particles from diesel engine exhaust after the dilution tunnel using a computational modeling approach. Dilution tunnel was used in order to dilute the exhaust gas to the extend that was suitable for the measurement systems. The Lagrangian particle tracking method was used to model the dispersion and deposition of nano-particles. For the range of studied particle diameters (from 5 to 500 nm), the Brownian, thermophoresis, gravity and Saffman Lift forces are considered. After verifying the code, the importance of different forces was evaluated. Due to the temperature gradient between the exhaust gas and the pipe walls, particular attention was given to include the thermophoresis force in addition to the other forces acting on nano-particles. The results showed that for the range of nano-particle diameters studied, the Brownian force was the dominant force for particle deposition. Furthermore, the thermophoresis force was important even for relatively low temperature gradient and cannot be ignorable especially for larger particles. The maximum thermophoresis effect occurred for 100 nm particles. The gravity had negligible effects on nano-particle deposition and can be ignorable for particles with diameter less than 500 nm. The Saffman lift also had negligible effects and its effect was noticeable only for the deposition of 500 nm particles. The results of this paper could provide an understanding of two-phase flow emission from diesel engines especially after the dilution tunnel.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
383
390
http://mme.modares.ac.ir/article_14539_21ae346ad0a199b9f539e84b2624dbdf.pdf
A novel 3- axis attitude stabilization with redundant thruster for a cube-satellite supported by reaction wheels
Mahdi
Fakoor
University of Tehran
author
Alireza
Sattarzadeh
دانشگاه تهران- دانشکده علوم و فنون نوین
author
Majid
Bakhtiari
دانشگاه علم و صنعت ایران
author
text
article
2016
per
In the present study, a new attitude stabilization concept has been investigated for a satellite considering failure in one or more reaction wheels. In this approach control torques could be generated using only one thruster mounted on a two axis gimbal mechanism. In the other word, in the absence of reaction wheel(s), control torques are generated by applying a thruster rotating mechanism which can be turned around two axes by thruster vector. If any failure happened in reaction wheels, gimbal angles mechanisms will be added to the system as input controlling. Controller algorithm based on dynamic and kinematic equations of the satellite’s motion, has been developed in the presence of disturbances. Three-axis stabilization of the attitude in a LEO orbit satellites under disturbances has been executed by applying three reaction wheel actuators to produce torque in each direction. Disturbance torques that are commonly applied to the satellites are gravity gradient, solar radiation pressure and aerodynamics. For training the intelligent neuro-fuzzy controller, PID controller is employed. Numerical simulations show that, the recommend controlled method have acceptable results (in the presence of disturbances) and adding of a thruster actuator to the system as a redundancy, could enhance the space missions reliability and if any fault happened in the operation of reaction wheels, thruster mechanisms come in to control system , accurately, and sustained satellite stability at desirability attitude.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
4
no.
2016
391
402
http://mme.modares.ac.ir/article_14542_dda9210c6ed209e246e3d5ca401f51cc.pdf