Cover
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
http://mme.modares.ac.ir/article_12618_da18c8a0c8722e25789569fea68cd5ef.pdf
IFC
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
0
0
http://mme.modares.ac.ir/article_12619_010cba79052e6dfb3b44ab4a63e065c2.pdf
Index
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
0
0
http://mme.modares.ac.ir/article_12620_db78d71f1511cddebb6c1655d6420af3.pdf
Experimental analysis of tensile strength of lateral notched aluminum plates reinforced by the Fiber metal laminate (FML) patches
Faramarz
Ashenai Ghasemi
استادیار دانشگاه تربیت دبیر شهید رجایی، دانشکده مهندسی مکانیک
author
Gholam Reza
Bagheri
دانشگاه تربیت دبیر شهید رجایی
author
Ali
Pourkamali
دانشگاه تربیت دبیر شهید رجایی
author
text
article
2015
per
Since aircrafts are subjected to aerodynamic and structural loads; one common defect in the aircraft fuselage and its wings is crack criterion. In most of the cases, the service life of defective parts can be increased by some sort of repairs. One of the most common types of repairs in this field is using composite patches and pasting them on damaged parts. These patches have significant advantages such as high strength, corrosion and moisture resistance, low weight and also excellent fatigue properties. In this study, base notched plates were fabricated by using of 2024 T4 aluminum alloy. Fiber metal laminate (FML) patches were made of carbonepoxy and Phosphor – Bronze layers. These patches were attached to the base notched plate by using adhesive Arldit 2011. Specimens were subjected to tensile test and results of the tests were compared. The tested variables were chosen as layup, metal layer thickness and composite patch length. The results of current study indicate a dramatic increase in tensile strength of repaired parts by using these patches compared with the repaired notched parts without patches so that tensile strength is increased up to 82.4 % in the best sort of repair.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
1
8
http://mme.modares.ac.ir/article_12008_b4e6b4d7d20daf7378524de2c6a6612a.pdf
Type Synthesis of 3T1R Decoupled Parallel Manipulators based on Screw Theory
Hamid Reza
Mohammadi
دانشیار مهندسی مکانیک / دانشگاه صنعتی نوشیروانی بابل
author
Roghaye
Hasanzadeh
teacher/faculty of faza
author
text
article
2015
per
Decoupled motions in parallel manipulators lead to simpler mechanical structure, larger workspace, lower cost, higher accuracy and easier control as well as designs with lower mobility. One of these manipulators is 3T1R parallel manipulator with general translation in space and a rotation about a fixed direction. Designers used systematic methods to synthesis decoupled parallel manipulators. Screw theory with wide applications has been used to the type synthesis of the parallel manipulators. Moreover, synthesis of uncoupled parallel manipulators has widely studied, while the synthesis of decoupled parallel manipulators has received less attention. One type of decoupled parallel manipulators is a manipulator with groupuncoupling motions whose outputs can be controlled by a series of actuated joints. Here, using screw theory, groupuncoupling motion of 3T1R nonredundant degree of freedoms of the parallel manipulator with the first actuated joints within every four legs is introduced. Upon comparison of the kinematic equations governing the several groups of 3T1R uncoupled parallel manipulators and their Jacobian matrices derived based on screw theory. The geometric conditions of the actuated wrenches are obtained as well as the comprehensive definitions of groupuncoupling motions. Finally, these results have been clarified the related feasible legs of each groups to fulfill the required motions.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
9
18
http://mme.modares.ac.ir/article_12009_436593923192cd96bc161ca6eb8ff758.pdf
Thermal stress analysis of metallic plate with quasirectangular hole
Mohammad
Jafari
استادیار دانشگاه صنعتی شاهرود
author
Mohammad Bagher
Nazari
عضو هیات علمی دانشگاه شاهرود
author
Amir
Taheri Nasab
دانشجوی کارشناسی ارشد
author
text
article
2015
per
The main aim of this paper is to present the method to evaluate the stress distribution around quasirectangular hole in infinite isotropic plate subjected to uniform heat flow at infinity. The used method is the development of the Goodier and Florence’s method for the thermoelastic problem of uniform heat flow. Goodier and Florence used their solution for stress analysis of isotropic plates with circular and elliptical holes. In order to expand this method to solve the perforated plates with non circular holes, by means of conformal mapping, the infinite area external to the hole can be represented by the area outside the unit circle. In this paper, thermalinsulated condition along the hole boundary is assumed. Amongst the important parameters in hole geometry are rotation angle of hole, bluntness and aspect ratio of hole size. The results obtained demonstrate the effect of these parameters on stress distribution around quasirectangular hole and the correct selection of these parameters, lowest thermal stress rather than amount of stress corresponding to circular hole can be achieved. This method can be used for study of the stress analysis of plate with various holes.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
19
26
http://mme.modares.ac.ir/article_12010_cd89815b68417e8f212cbd84c527cc0d.pdf
Forced vibration analysis of conveying fluid carbon nanotube resting on elastic foundation based on modified couple stress theory
Reza
Ansari
دانشیار دانشگاه گیلان
author
Amir
Norouzzadeh
دانشجوی دکترا دانشگاه گیلان
author
Raheb
Gholami
دانشجوی دکترا دانشگاه گیلان
author
text
article
2015
per
In this study, the vibrations of carbon nanotube are investigated in which the inner fluid flow with constant velocity and the widespread external harmonic force is applied to it. Also the nanotube is embedded in an elastic viscoPasternak medium and the boundary conditions at two ends of nanotube are simply supported. In order to analyze the system and considering the small scale effects, the couple stress theory is employed and the Timoshenko beam theory is used for modeling the nanotube. The Hamilton's principle is written with taking into account all energies and external works of system and consequently the nonlinear motion equations of the system are achieved. Then with help of generalized differential quadrature method, the obtained partial differential equations are converted to ordinary differential equations and the domain of the beam is discretized. From the MatCont package in MATLAB software, the frequency responses of nanotube are examined. To this aim, the second order differential equations are turned to first order ones with appropriate transformations. So the small scale effect or equivalently the differences between present approach and classical Timoshenko beam theory are presented. Furthermore the effects of the size of nanotube, fluid velocity, applied transverse force and the elastic foundation parameters are studied. It is observed that the dependency of frequency response on each of these parameters is different and it significantly changes with these factors.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
27
34
http://mme.modares.ac.ir/article_12011_5a59737e6e9589351e01ebebccedbb80.pdf
Effects of air curtain’s jet discharge angle on indoor air quality and occupants’ thermal comfort in a positive pressure room
Seyed Alireza
Zolfaghari
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
Ali
Barati Majan
دانشجوی کارشناسی ارشد مهندسی مکانیک
author
text
article
2015
per
In this study, the effects of discharge angle from an air curtain’s jet have been investigated on aerodynamic sealing of a room with positive pressure ventilation system. For this reason, the modeling of flow, heat transfer and species diffusion has been performed by using OpenFoam® numerical solver. The results show that the jet discharge angle has significant effects on the distribution of parameters such as temperature, concentration of pollutants and occupants’ thermal sensation index. So, by varying the jet discharge angle from +10 (towards the indoor space) to 10 (towards the outdoor space), the average temperature difference between two spaces is reduced to 2.5°C. Also, the mentioned varying in discharge angle causes a significant reduction in the mean concentration of pollutants at the indoor space, from 25ppm to 5ppm. On the other hand, the results indicated that for the discharge angle of 10, the average of occupant’s thermal sensation index is shifting to the cool feeling. Therefore, the mentioned discharge angle can reduce the impacts of outdoor warm conditions on the indoor’s. In other words, the discharge angle of 10 demonstrates the best performance of the air curtain device in thermal and aerodynamic separating of two indoor and outdoor spaces.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
35
41
http://mme.modares.ac.ir/article_12004_e32ef449f0123d395f95031e93d89255.pdf
fatigue crack growth in bodies under rolling contact with multiple moving loads
Amir Reza
Shahani
استاد دانشکده مکانیک دانشگاه صنعتی خواجه نصیر الدین طوسی
author
Reza
Davachi
دانشجوی کارشناسی ارشد مهندسی مکانیک دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2015
per
Rolling bearings is one of the important elements in rotating machinery that they are under rolling contact fatigue, so for better estimation of remaining life of these elements a model which is considered multiple moving loads based on the linear fracture mechanics has been proposed. Considering the effect of the multiple moving loads is a key element of this model that is not considered in literature. The contact surface is modeled by a halfplane with an edge crack. Rolling contact is simulated by moving a load distribution on the boundary of a halfplane. The calculation of the crack path and stress intensity factors is carried out by the stepbystep process on the basis of the singular integral equations method. The effect of the friction coefficient and considering two concentrated moving load on the crack growth path for different angles between the initial crack and boundary of the halfplane and remaining life of a surface under the fatigue rolling contact for 75XГCT steel is analyzed. The results of this analysis are compared with results from previous model. According to the results of the remaining life obtained by increasing the numbers of moving loads on the contact surface the remaining life decrease and get closer to the real state. Furthermore, the remaining life decreases with increasing friction coefficient.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
42
52
http://mme.modares.ac.ir/article_12041_a34a918e73dea13468dd0d0e39d564ef.pdf
Simulation of a turbocharged SI engine to investigate autoignition, knock onset and flame propagation by using Kiva code
Ali
Nasiri Tossi
عضو هییت علمی دانشکده خودرو دانشگاه علم و صنعت ایران
author
Arman
Rostampour
دانشگاه علم و صنعت ایران
author
text
article
2015
per
Knock is a random and complex phenomenon in reciprocating engines and engine tests under knocking conditions involve high costs. In this investigation, EF7(TC) engine which is a bifuel spark ignition engine and has relatively high probability of knock phenomena, is used. The simulation is conducted using KIVA3V code to simulate the engine under nonknocking and knocking conditions. ANSYSICEM software is used to generate structured mesh for its geometry which is provided by IPCO. The original KIVA3V code doesn't have an autoignition model; therefore, a knock integral model has been added to the original code. In this paper, the results of simulation are verified using two methods, experimental incylinder pressure and exhaust port gas temperature. The theoretical results proved a good agreement with experimental data. Compare to experimental data, it shows that KIVA3V and Integral Knock method could simulate knock accurately although the code cannot simulate the fluctuations of knock. Finally, development of flame in combustion chamber and formation of second flame front was investigated in numerical simulation. Besides, the simulation results show that second flamefront is created near exhaust valves and propagate onward. The results show that the model can accurately predict autoignition and calculate the effects of Knock, So, it is possible to use this model to investigate the Knock phenomenon and its effects without any experimental tests which engine damages are expected during a knocking cycle.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
53
62
http://mme.modares.ac.ir/article_12042_576b7b2f6db4641ed11c3ead39f8cf5c.pdf
Suitable parameters determination of lamb wave generation source with lowattenuation for threelayer adhesive joints inspection
Pezhman
Taghipour Birgani
‍Ph.D. Student/Shahid Chamran University
author
Khosro
Naderan Tahan
استاد، گروه مهندسی مکانیک، دانشکده مهندسی، دانشگاه شهید چمران اهواز
author
Sina
Sodagar
Assistant ProfessorDepartment of Technical Inspection Engineering, Abadan Institute of Technology, Petroleum University of Technology, Ahvaz, Iran
author
Mohammad
Shishesaz
ProfessorDepartment of Mechanical Engineering, Shahid Chamran University, Ahvaz, Iran
author
text
article
2015
per
In this paper, Propagated modes in a threelayer adhesive joint are investigated regardless of wave generation source influence and also by taking into consideration it and lowattenuation modes are determined. In the beginning, lamb wave propagation in the adhesive joints is investigated using global matrix method and characteristic equation is derived by applying continuity and boundary conditions which are included tractionfree boundary conditions on outer surfaces of the joints and continuity between layers. Phased velocity and attenuation dispersion curves in terms of frequency are obtained by numerical solution of the characteristic equation. Then, the source influence on wave field is investigated using normal mode expansion method. Average power flow of lowattenuation excited mode and its energy percent to the lamb wave total energy curves in terms of source parameters for specific frequency are obtained. These results are used to determine the suitable parameters of the source which are used to generate lowattenuation lamb wave mode. Finally, finite element simulation of lamb wave generation is performed to compare with the results of normal modes expansion method. The results indicate to generate M3 mode with lowattenuation level in the threelayer adhesive joint aluminiumepoxyaluminium at frequency 0.25 MHz, suitable wedge angle is 16 degree and suitable transducer width is 20 mm.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
63
74
http://mme.modares.ac.ir/article_12043_9513ed19fc4c5d69b2b50772eabe89b2.pdf
Design and manufacturing of modified Iosipesque shear test fixture for determine the in layered composite properties
Mohammad Reza
Variri Sereshk
استاد دانشگاه تهران
author
Ali Reza
Araee
استاد دانشگاه تهران
author
Ahmad Reza
Farokhi
کارشناسی ارشد
author
Nabi
Mehri Khansari
کارشناسی ارشد
author
text
article
2015
per
In this paper the design and manufacturing of Iosipesque shear test fixture modification evaluated. This shear test Fixture by applying the shear load in layered of composites specimens can predict the mechanical properties of composite materials in mode II of fracture.In this paper, first, a common traditional Iosipesque shear test fixture according to the standard was manufactured. Then, by applying shear load on polymerbased composites (carbonepoxy) and wood (a natural composite) specimens, bugs of the traditional fixture were found.Finally by 6 fundamental Modification of the fixture structure, the new design was proposed. It was also found that by applying these reforms, both of concentrating the shear force (in the shear zone) and test accuracy has been increased. Accordingly, after the construction and testing of new fixture on wood and polymer based composite specimens and by applying the standard deviation’s equations, the standard deviation of the modified fixture for wood and polymer based composite has ben reduced 82.7% and 48% respectively, that suggesting the accuracy of the fixture. In addition, fluctuations of the fixtures diagram of the new design also significantly reduced.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
75
83
http://mme.modares.ac.ir/article_12044_dda31d990dbdb53218338bbf3e479fab.pdf
Contact Angle Comparison of Droplet Impact on Solid Surface Using VOF
Sahar
Jafari
فارغ التحصیل دانشگاه تربیت مدرس
author
Mohammad Reza
Ansari

author
Nima
Sam Khaniani
دانشجوی دکترای دانشگاه تربیت مدرس
author
text
article
2015
per
In present work, models that predict contact angle of a droplet with a solid surface, are considered and compared with each other. Two phases were assumed to be Newtonian, incompressible and immiscible fluids. OpenFOAM software is applied to simulate the two phases interface by using Color function VOF (CFVOF) method. Different models for contact angle of a droplet as Tanner and Yokoi models are implemented in the OpenFOAM. In addition, the dynamics and statics contact angle models were used to compare with recent models in order to choose the best one. The outcome of study shows, even though the static contact angle model is simple to understand, however, it could be the best model to predict the droplet behavior in a wide range of different conditions. The fluid viscosity effect was also considered in different models of the present study. It concluded that the fluid viscosity affects the type of pattern of droplet impact and as viscosity of fluid increases; more energy is needed to uplift the droplet again from the surface. KelvinHelmholtz instability (KH) was also simulated and explained in details which initiates on the interface of two fluids due to velocity differences of droplet and the surrounded air.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
84
94
http://mme.modares.ac.ir/article_12045_1ec052c0da50f9c87fe58060affdb7fd.pdf
Effects of interphase damage on the elastoviscoplastic behavior of general unidirectional metal matrix composites
MohammadJavad
Mahmoodi
دانشگاه شهید بهشتی، پردیس فنی مهندسی شهید عباسپور، دانشکده مهندسی مکانیک و انرژی
author
Mohammad Kazem
Hassanzadeh
دانشجوی دکتری، مهندسی مکانیک، دانشگاه گیلان، رشت
author
Reza
Ansari
دانشیار، مهندسی مکانیک، دانشگاه گیلان، رشت
author
text
article
2015
per
In this paper, a 3D time dependent micromechanical model is presented to study the elastoviscoplastic behavior of aligned fiber reinforced composites in the presence of interfacial damage subjected to multiaxial loading. The representative volume element (RVE) of the composite consists of three phases including fiber, matrix and fiber/matrix interphase. The interphase is considered as a distinct phase with a definite thickness that covers the outer surface of fibers. The difference between of manufacturing process temperature to room temperature introducing thermal residual stresses is included in the analysis. The fiber and interphase are assumed to be elastic, while the matrix exhibits elasticviscoplastic behavior with isotropic hardening. The BodnerPartom viscoplatic theory is used to model the time dependent inelastic behavior of the matrix. The Needleman model is employed to analysis interphase damage. For metal matrix composites, it is shown that while predictions based on undamaged interphase are far from the reality, the predicted stress–strain behavior including interphase damage and thermal residual stresses demonstrate very good agreement with experimental data. Furthermore, the elastic properties of the composites with various aspect ratios are extracted by the micromechanical model. The elastic behavior predictions of the composite are also very close to experimental data and the other available model.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
95
105
http://mme.modares.ac.ir/article_12046_fda1c8f4e4b7e0aa41216f88d86b5117.pdf
Experimental study of finishing of AISI H13 hot work steel using Abrasive Flow Finishing (AFF) process
Mohammad Reza
Shabgard
دانشیار تبریزدانشگاه تبریز ریاست دانشکده فنی مهندسی مکانیکگروه مهندسی ساخت و تولید محمد رضا شبگرد
author
Behnam
Karamzadeh
دانشگاه مراغه
author
Reza
Alizadegan
دانشگاه تبریز
author
Ahad
Gholipoor
دانشگاه آزاد تبریز
author
text
article
2015
per
In this research the abrasive flow finishing process (AFF) of AISI H13 hot work steel was studied and the effects of various process parameters such as flow pressure (extrusion pressure), abrasive particles densities, abrasive particles sizes and the first quality of surfaces on variations of surface roughness and material removal have been investigated. The results showed that increasing the density of abrasive particles leads to increase in variations of surface roughness and material removal. Increase of extrusion pressure from 4 to 6 MPa causes the increase in variations of surface roughness and material removal and from 6 to 8 Mpa leads to decrease in the two latter. Electron microscopic results showed that increase of finishing process time over 4 hours causes a detrimental effect on the surface of the specimens, as a result of penetration and stabilization of abrasive particles in the form of broken particles. Also according the results of this paper, increasing the size of abrasive particles leads to higher variations of surface roughness and material removal, and this process is more effective in finishing of rougher surfaces.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
106
112
http://mme.modares.ac.ir/article_12048_2fcda9b44878f6c907e474b52dc84be6.pdf
2D Local Imperfect plate Nonlinear Vibration and Aerothermoelastic analysis in Supersonic Flow
Hamid
Moosazadeh
دانشگاه تربیت مدرس
author
Behzad
Ghadiri
Tarbiat Modares University
author
Masoud
Rasekh
دانشگاه تفرش
author
text
article
2015
per
A homogenous 2D plate with simply support boundary conditions and local imperfection is assumed. The effect of nonlinear deformation with Reddy and marguerre plate model has been introduced. The effect of local imperfection in nonLinear vibration analysis with the effect of thermal and inplane load has been investigated for the first time. The plate softening and hardening type with the effect of imperfection size is investigated. Flutter boundary of local imperfect plate with the effect of supersonic aerodynamic, thermal and mechanical load has been studied for the first time. First and third order piston theory aerodynamic (PTA) is employed to model supersonic aerodynamic loading. Equations of motion have been derived by the use of Hamilton’s principle and resultant nonlinear PDEs have been transformed into nonlinear ODEs via Galerkin’s method. Forth and fifth order rangkutta numerical method has been used to solve ODEs and define panel behavior. Results show that, imperfection amplitude increase structural nonlinear frequencie, and change plate softening type to hardening. Also, amplitude of plate vibration increase and flutter speed decrease continuously. Plate amplitude oscillation increase for small imperfection and decrease for larger imperfection versus flow speed.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
113
124
http://mme.modares.ac.ir/article_12047_4f95307b60788b17a06b1dde386ad475.pdf
Experimental and Numerical Study of a VariableSpansweep Morphing Wing on the Aerodynamic Characteristics of a UAV
Abbas
Tarabi
Aerospace Eng. Complex, MalekeAshtar University of Technology
author
Saajad
Gasemloo
Aerospace Research Institute, MalekeAshtar University of Technology
author
Mahmood
Mani
Amirkabir University of Technology
author
text
article
2015
per
In this research, experiment and computational fluid dynamics (CFD) are used to assess the performance of UAV with variablespan and sweep morphing wing under low speed conditions. Both wing area and aspect ratio are changed due to variations in span and sweep, whereas structure of the variablespan and sweep morphing wing remains constant. In this study, the numerical results of Fluent software and experimental data are presented. Results are achieved under a low wind speed (50, 60 and 70 m/s). In this case, full extension represents a 30% (10 cm) increase in wing span and 36% (12 deg.) in sweep angle relative to the original wing, with no extension. The results of this study show that the morphing wing is capable to improved aerodynamic efficiency, increased both range and endurance, reduced induced drag and in general reduced thrust required. According to experimental and numerical results, the use of morphing wing can increase the range by 13.6% and 13.5%, also, endurance of the vehicle by approximately 8.855 and 8.17%, respectively. The results of this study show that the maximum value of lifttodrag ratio occurred at 6 degrees angle of attack and a speed of 70m/s. These results demonstrate that the use of morphing wing improve the lifttodrag ratio by 10% compared to original wing. Finally, the numerical simulations are compared and show good agreement with the experimental results. This research also showed how morphing concept can be used as an alternative method for roll control.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
125
136
http://mme.modares.ac.ir/article_12049_ce0bb5252c559232491d8dbd36aa54d8.pdf
Controllable Workspace Generation for a CableDriven Rehabilitation Robot using Neural Network and based on patient’s Anthropometric Parameters
Behnam
Miripour Fard
Head of Robotics Eng. Dept
author
Tahereh
Padargani

author
text
article
2015
per
Abstract This paper presents the mathematical modeling and simulation of a cabledriven robotic device that can be used in gait rehabilitation of patients with lower extremity disabilities. A parallel cable robot is considered to assist a model of human body during walking. First, a proper pattern of walking is considered and kinematic and dynamic equations are solved to obtain tensions in cables for entire cycle of walking. By exploiting a numerical procedure, the workspace of the robot are explored to find suspension points of the cables in which the model remain in controllable workspace of the robot. Remaining of the model in controllable workspace means that cables always remain in tension and robot can effectively engaged in rehabilitation. The optimum locations are determined based on minimum cable tensions (energy consumption) and a Neural Network is trained to quickly determine suspension points based on anthropometric parameters of patient. The simulation results show the effectiveness of the method in tracking of the desired trajectory of walking. The results of this study can be used for development and fabrication of an efficient cable driven rehabilitation system.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
137
145
http://mme.modares.ac.ir/article_12080_678abd317b8167e2a4946056eec05284.pdf
Active Noise Cancelation in a Reaction Wheel by simultaneous using of dynamical system identification and online wavelet
Habib
Khaksari
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Abdolmajid
Khoshnood
استادیار دانشگاه خواجه نصیرالدین طوسی
author
Jafar
Roshanian
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2015
per
Reaction wheels are angular momentum exchange devices used to stabilize the position of the satellite and maneuvering. This actuator can change the momentum of the satellite to change the attitude of the system. During the process of operation, noise and disturbances arisen from the unbalancing of the wheels lead to inconvenient performance of the reaction wheels. Several works have been presented for active noise cancelation in these devices. But, the practical tools of signal processing such as filter banks and wavelets which used for offline denoising are samples of very useful noise cancellation methods. If these toolboxes are employed for online denoising these signal processing approaches are applicable for noisy systems such as reaction wheels. The main challenge of this strategy is delay arisen from the signal processing and this is inevitable. In this paper, a strategy of online wavelet denoising is designed and proposed for noise cancellation in a reaction wheel. In this regards, for considering the delay compensation the method of Smith predictor is used to lead the delay of the process out of the closed loop control system. The accuracy of this algorithm requires an estimate of the system dynamics and the understanding of the delay system. According to the use of the FIR filter delay can be fully calculated. The recursive least squares used for identification reaction wheel as an estimate of the system.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
146
152
http://mme.modares.ac.ir/article_12081_c8508db8c3487b0e6564d9b6591f3bc1.pdf
Dynamic instability in tapered beams under wind excitation
Hamid
Moeenfard
Vakil Abad BLVD Ferdowsi University of Mashhad
author
Behnam
Moetakef Imani
استاد دانشگاه فردوسی
author
Morteza
Davoudi
دانشگاه فردوسی
author
Amin
Rahimzadeh
پژوهشکده هواخورشید دانشگاه فردوسی مشهد
author
text
article
2015
per
Dynamic modeling of beams under aerodynamic loading is extremely important in many engineering applications. So the objective of this paper is to present a new approach to model and simulate the time domain response of tapered cantilever beams with airfoil cross section to wind excitation. The extended Hamilton’s principles along with the EulerBernoulli assumptions are utilized to derive the Partial Differential Equation (PDE) governing the deflection of the beam. A new finite difference based algorithm is proposed for finding the modeshapes as well as the natural frequencies of the beam. These modeshapes are then used in a Galerkin projection procedure to convert the PDE governing the system’s behavior into strongly coupled nonlinear Ordinary Differential Equations (ODEs). The aerodynamic loadings are modeled using the open source code of XFOIL. The blade of an under developed 100KW wind turbine is considered as a case study. The results reveal that even a single mode approximation is accurate enough in predicting the beam’s dynamic exposed to wind excitation. It was also observed that the instability speed of beams with higher modal damping is considerably higher than those with lower modal damping. The knowledge resulting from this effort is expected to enable the analysis, optimization, and synthesis of tapered cantilever beams for improved dynamic performance.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
153
161
http://mme.modares.ac.ir/article_12082_5eb65ec4da3b461d9ba6450d18880160.pdf
An upper bound analysis of the geometric shape of the deformation zone in drawing process of the metal plates through wedgeshaped die
Seyed Hooman
Kazemi
دانشجوی کارشناسی ارشد دانشگاه رازی
author
Heshmatollah
Haghighat
استاد گروه مکانیک دانشگاه رازی
author
text
article
2015
per
In the present paper, drawing process of metal plates through a wedgeshaped die, by proposing new velocity field, has been analyzed by upper bound method and simulated by finite element method (Abaqus software). Among the important cases in upper bound analysis of the forming processes is selection the appropriate boundaries for the deformation zone and offering admissible velocity field that in addition to satisfy the incompressibility condition and boundary conditions, is consistent by the behavior of metal flow in the deformation zone. The entrance boundary of deformation zone has been assumed exponential curve surface and boundary at exit has been assumed cylindrical surface. In the past analyses, metal flow lines in the deformation zone have been assumed straight but in reality it is not. In the present work, velocity field and also geometric shape of the deformation zone, justify that metal flow lines are nonstraight. Base on proposed velocity field, internal powers, shear and frictional and also total power have been calculated. Then, according to the plate pulling velocity, required drawing force has been obtained. Finally, analytical results have been compared with the obtained results of FEM. In order to validate the present analysis, obtained results have been compared with other researchers. Also, the effect of various parameters, such as percentage reduction in thickness and shear friction constant on the drawing force and die optimum angle have been investigated.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
162
172
http://mme.modares.ac.ir/article_12083_3efa2ed3eeb12aec9a3dd4a3191909b9.pdf
Instantaneous Center of Rotation of Flexure Joints and Velocity Kinematic Analysis of Microhexapod Using Screw Theory
Ehsan
Rouhani Esfahani
هیات علمی/ دانشگاه آزاد نجف آباد
author
Mohammad Javad
Nategh
هیات علمی دانشگاه تربیت مدرس
author
text
article
2015
per
In this article microhexapod robot is introduced as a micromanipulator. First hexapod which is a parallel mechanism is investigated and also modifications that is needed for the improvement of positioning accuracy and eliminating factors such as clearance and friction in the conventional joints. Doing this, spherical and universal joints are replaced with flexural beam type joints after scaling down the hexapod. Then the degrees of freedom of flexure joints are achieved and after that the instantaneous center of rotation of flexure joints is derived for every finite twist of moving platform and it is shown that the kinematic chain of each pod of microhexapod consists of two spherical joints and a prismatic actuator; but it differs from hexapod in a way the location of the instantaneous center changes with the change of the finite twist of moving platform. Thereafter the velocity kinematics of microhexapod is solved using screw theory. In addition, using the analytical formula, the velocity of actuators was calculated for some case studies; linear motion of moving platform with constant velocity and also constant acceleration and also movement with constant velocity in a circular path. The results are verified with the finite element analysis and shown good agreement.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
173
180
http://mme.modares.ac.ir/article_12085_69347b6ee2a32bc079f9616a73693860.pdf
Study of the causes of excessive vibrations in air fans and proposing practical solutions for decreasing the vibration level
Mohamad Hasan
Mazhab Jafari
کارشناس ارشد تعمیرات مکانیک/ پتروشیمی بوعلی سینا
author
Ali
Hajnayeb
استادیار/دانشگاه شهید چمران اهواز
author
Gholamhossein
Massoumi
Engineer/BualiSina petrochemical company
author
text
article
2015
per
The inseparable parts of any industrial unit are usually the rotary machines. Fans are categorized as a common type of rotary machines, which play an important role in the industry. In order to decrease the repairing costs and energy consumption, Fans have to operate without vibration. However, if the fan unit with an acceptable level of vibrations is installed on a huge structure, the vibration caused by the fan can develop complications for the structure as well as serious problems for the fan itself. A longtime operation of a faulty fan can cause failure in the fan motor and fatigue in the structure. Therefore, investigating the root causes of the vibrations of the fan and decreasing the vibrations is vital for increasing the operating time and the efficiency of the fans. This study is focused on identifying the root causes of excessive vibrations of one of the air fans in BualiSina petrochemical company. First, the main frequencies which are responsible for the increase in vibration levels are identified, by using ODS analysis. Then, the natural frequencies of the structure are derived using the operational modal analysis (OMA). Also, the finite element model of the fan unit and the structure is developed based on the most possible compatibility with the experimental data. Finally, a number of suggestions for reducing vibration amplitudes of the fan are proposed.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
181
188
http://mme.modares.ac.ir/article_12086_0b7d1d3aa6e1075d1b2df83acdb72028.pdf
Numerical study of the effect of moisture–induced swelling stresses on damage behavior of adhesive joints under static loading
Hadi
Khoramishad
استادیار دانشگاه علم و صنعت ایران، دانشکده مهندسی مکانیک
author
Zahra
Abbasi
دانشجوی کارشناسی ارشد، دانشگاه علم و صنعت ایران، دانشکده مهندسی مکانیک
author
text
article
2015
per
The main limitation of the use of adhesive joints is weakening the adhesive layer against damaging environmental factors such as humidity. Use of numerical methods for predicting the strength of adhesive joints exposed to moist environment can significantly save time and cost. In this study, first experimental investigation and numerical modeling of the complete process of moisture diffusion into the adhesive layer and its damaging effect on the adhesive joint strength was determined. Then this process was applied for a single lap joint of SBT 9244 pressure sensitive adhesive and AL2024T3 aluminum alloy substrate with two 12.5 and 50 mm overlap of lengths. As the first step, moisture distribution for 30, 60 and 90 days exposure times in environmental condition of 100% relative humidity was obtained. Then single lap joint tensile test was simulated using cohesive zone model for different exposure times. In this simulation cohesive zone model parameters were determined in such a way that numerical failure load and the existing experimental failure load be in good agreement. The cohesive zone model parameters were determined dependent on the moisture content. The first simulation was done without considering swelling and in the second one swelling was considered. Swelling stress was obtained separately at different exposure time periods. It was found that swelling effect was more considerable in the joints with longer overlap length and shorted exposure time.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
189
198
http://mme.modares.ac.ir/article_12087_755a9e3f38ea1186aba3ec716195a638.pdf
Estimation of a centrifugal pump slip factors at offdesign conditions using computational fluid dynamics
Mohsen
Ghaderi
دانشجو دانشگاه تهران
author
Amir Farhad
Najafi
استاد دانشگاه تهران
author
Ahmad
Nourbakhsh
استاد دانشگاه تهران
author
text
article
2015
per
slip factor is one of the most important parameters used in centrifugal pumps performance prediction. Knowing this parameter as a function of flow rate seems essential for offdesign performance prediction. In this paper, it is intended to establish the slip factor dependence upon flow rate for a centrifugal pump using computational fluid dynamics. For this purpose, the full 3DRANS equations in coupled with RNG kε turbulence model were solved for several flow rates ranging from 45% to 120% of rated condition by means of a commercial code, CFX. In the steady state, this simulation is defined by means of the multireference frame technique, in which the impeller is situated in the rotating reference frame, and the volute is in the fixed reference frame. The validity of the numerical model was confirmed by matching the calculated characteristic curves with the associated experimental data. It was found that there is a good coincidence between the numerical results and available experimental data of global performance, local velocity distribution and slip factors. A comparison was performed among the wellknown slip models which reveals, that the slip factor variations can be predicted very well using CFD analysis.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
199
207
http://mme.modares.ac.ir/article_12126_5bf5716ad60d5158f73c9840bd57ec26.pdf
Burning rate Measurement of solid Propellant using Subscale Motors
Mohammad Reza
Ghelichkhani
بنیاد توسعه علوم و فناوریهای هوافضای ایران ، تهران /کارشناس
author
Ali Reza
Mohammadi
استادیار سازمان فضایی
author
Mohammad Mahdi
Heidari
استاد/مجتمع آموزشی دانشگاهی هوافضا دانشگاه مالک اشتر تهران
author
text
article
2015
per
Burning rate is a determinate Parameter in Performance Prediction of Solid Propellant motors. Any error in determining the burning rate directly affects the prediction of thrust and burning time. Smallscale rocket motors are widely used by space and military industries to carry out burning rate measurement. The use of Subscale motors has many advantages over more simplistic, such as strand burners. Effects like: Two phase flow, radiation, and erosive burning effects are present within a subscale test whereas strand burns are not capable of capturing these parameters. The biggest problem with subscale burning rate motors however is determining appropriate times for when the propellant grain has lit and burned out. Accurate and consistent selection of start and end points is crucial to determining the burning rate of a given propellant. Investigation of Developed and modern methods to obtain burning rate from motor test according to the primary methods in Iran's aerospace industries is the main objective of this study. In this study, using designed laboratory solid rocket motor, 26 tests was Performed. Reproducibility of the methods available in universities and defense companies worldwide has been considered and with Common Tangent bisection method has been compared. Results show the high quality of industrial Methods subset the Thicknesstime Method, HesslerGlick, and mass balance method with comparing to low reproducibility of tangent bisection method
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
219
230
http://mme.modares.ac.ir/article_12127_9cc8476dcc571568c929dada50b03fb2.pdf
Investigation of MHD nanofluid flow over a stretching surface with velocity slip and convective surface boundary conditions
Navid
Freidoonimehr
دانشگاه فردوسی مشهد
author
Asghar
Baradaran Rahimi
دانشگاه فردوسی مشهد
author
text
article
2015
per
Present article provides an analytical investigation of the fluid flow and heat and mass transfer for the steady laminar MHD threedimensional nanofluid flow over a bidirectional stretching sheet with convective surface boundary condition using Optimal Homotopy analysis method (OHAM). In contrast to the conventional noslip condition at the surface, Navier's slip condition has been applied. This paper contains twocomponent fourequation nonhomogeneous equilibrium model that incorporates the effects of Brownian diffusion and thermophoresis simultaneously. The governing partial differential equations (PDEs) are transformed into a highly nonlinear coupled ordinary differential equations (ODEs) consist of the momentum, energy and concentration equations via appropriate similarity transformations. The current OHAM solution demonstrates very good correlation with those of the previously published studies in the especial cases. The influences of different flow physical parameters on all fluid velocity components, temperature distribution and concentration as well as the skin friction coefficients in x and y directions, local Nusselt number and local Sherwood number are tabulated graphically and discussed in details. This study specifies that nano particles in the base fluid offer a potential in increasing the convective heat transfer performance of various liquids. The results show that wall temperature gradient decreases with an increase in thermophoresis parameter or a decrease in Brownian motion parameter. Further, local Sherwood number is inversely proportional to the thermophoresis parameter and also directly proportional to the Brownian motion parameter.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
208
218
http://mme.modares.ac.ir/article_12128_9028f0b756b8e410e2d549310e2d75f1.pdf
Numerical investigation of flow and temperature field on the backwardfacing step affected by Electrohydrodynamic actuator
Kamran
Kamran Mostajiri Abid
University of Guilan
author
Nima
Amanifard
Academic Staff
author
Hamed
Mohaddes Deylami
University of Guilan
author
text
article
2015
per
In this paper, the flow and temperature fields affected by electrohydrodynamic actuator are numerically investigated for the incompressible, turbulent, and steady flow over a backwardfacing step. Air is used as working fluid in heated backwardfacing step cooling process. The electric field is generated by the wire electrode charged with DC high voltage. The numerical modeling is based for solving electric, flow, and energy equations with finite volume approach. The computed results are firstly compared with the experimental data in case of rectangular flat channel and the results agree very well. Then the effect of different parameters such as the radius of the wire, applied voltage, Reynolds number, and the wire position on the heat transfer coefficient is evaluated. The results show that the heat transfer coefficient with the presence of electric field increases with the applied voltage but decreases when the Reynolds number and the radius of the wire are augmented. Moreover, reduction of emitting electrode angle can significantly effect on the heat transfer enhancement. In consequence, one may able to find an optimum place for the emitting electrode position.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
231
238
http://mme.modares.ac.ir/article_12129_1b17afb6e1da44ec4bd2e92d5d980bc6.pdf
Experimental Analysis and Simulation of Temperature Contour Generated in the Welding Process of Electrofusion Tapping Saddle Polyethylene Gas Pipes and Relevant Temperature Estimation for Fitting
Ali
Ebrahimpour
Student
author
Nosratollah
Solhjoei
Islamic Azad Univ. of Najaf Abad
author
Ebrahim
Mohseni Homagerani
مدیر بازرسی فنی شرکت گاز استان اصفهان
author
Meysam
Rasooly
کارشناس ارشد بازرسی فنی شرکت گاز استان اصفهان
author
Arash
Karimipour
مدیر گروه مکانیک دانشگاه آزاد اسلامی واحد نجف آباد.
author
text
article
2015
per
Due to the increasing demand for using polyethylene pipes in gas distribution networks and regarding the technical specifications of transmission and suitable service condition as well as ease of implementation and installation, these materials are considered as ideal substitutes for metal pipes. Regarding the safety and economic aspects in PE (polyethylene) pipe networks before and during the operations, technical inspection is highly required. Examinations have a significant role in the safety and proper function of gas distribution PE pipes tests, because of the damage of the products and excessive costs and time are not usually affordable. Consequently, the mentioned tests are nowadays being replaced by nondestructive types and admissibility of various industries gas company in these methods is increasing. Electrofusion is a proper and fundamental technique for connecting PE pipes. In this research, the mechanism of electrofusion tapping saddle polyethylene welding has thoroughly been studied and simulated using ABAQUS software. Thermal equation of electrofusion is investigated and the results of simulation as compared with experimental results have been evaluated based on which the best qualified methods for connection have been determined and presented.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
239
242
http://mme.modares.ac.ir/article_12130_555dfd301d3fe83330d9f37ae805b5a3.pdf
Effect of porosity on microstructure and mechanical properties of Al2O3(p)/AlA356 MMC
Esmaeil
Damavandi
دانشجوی کارشناسی ارشد دانشگاه صنعتی نوشیروانی بابل
author
Salman
Nourouzi
عضو هیات علمی دانشگاه صنعتی بابل
author
Sayed Mahmood
Rabiee
Academic Staff
author
text
article
2015
per
Presence of porosity and gas layers around the Al2O3 particles are one of the most important reasons of decreasing in mechanical properties of aluminum metal matrix composites. In this research, for decreasing of porosity, increasing of wettability and uniformly distribution of particles in matrix three method were used; using inert gas for injection powder with 5 liter/ min flow rate, particles heat treatment in 1100 ̊C for 20 min and mill Al2O3 particles with Al particles in ratio of Al / Al2O3= 1. The effect of these parameters on microstructure and mechanical properties of composite were investigated. The results showed that amount of porosity and agglomeration of particles were high in metal matrix composite with handy injection of particles. While injection with inert gas, using heat treatment and Al / Al2O3 milled Cause improve wettability and uniformly distribution of particles in molten Al. the results showed the maximum value of hardness , compression strength and impact energy have obtained in metal matrix composite reinforced with Al / Al2O3 milled with value of 78.7 BHN, 539.1 MPa and 8.2 Joule, respectively.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
243
250
http://mme.modares.ac.ir/article_12170_72875f4d858ef52035462cf06417da57.pdf
Evaluation of radial expansion behavior of thickwalled cylinder under internal explosive loading with numerical analysis
Seyed Masoud
Bagheri
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Jamal
Zamani
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2015
per
Given the numerous applications of thickwalled cylinders, it is important to know the behavior of these structures. There are so many relationships for cylinders and spheres containing explosives which have been found mainly based on other experimental models. Hence derive an analytical model of the behavior of structures under internal and highrate loading, like explosion in the cylinders, is of great importance. The main objective of this paper is to derive a mathematical model of isotropic thickwalled aluminum cylinder containing TNT in which JWL equation of state is considered for behavior of explosive expansion. The strength model the present analysis is based on the CowperSymonds in which strain rate at each moment is used for calculation of dynamic strength according to that. Therefore, given the instantaneous explosions pressure boundary conditions as well as instantaneous strain rate and its impact on the dynamic strength of the material, is of significant importance in this paper. With employing equations of equilibrium in thickwalled cylinders, the equations of radial and circumferential stresses and radial velocities derived. Given the instantaneous geometric and boundary conditions and correction the dynamic stress of material with respect to the strain rate, radial velocity by solving the differential equation, is calculated. After extraction of radial velocity, other stress equations will be evaluated. Furthermore, with considering the assumptions and in order to assess the overall results of the analytical modeling, computer simulation was done using Autodyn software, which shows good agreement with the analytical results.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
251
259
http://mme.modares.ac.ir/article_12171_e669e2036697d6b3035b6a3d81a2c40d.pdf
Numerical Investigation of Electroosmotic Flow in Heterogeneous Microchannels
Jafar
Jamaati
Department of Mechanical Engineering, Razi University
author
Ali Reza
Farahinia
Department of Mechanical Engineering, Ferdowsi University of Mashhad
author
Hamid
Niazmand
دانشگاه فردوسی مشهد
author
text
article
2015
per
Numerical modeling of electroosmotic flow in heterogeneous microchannels using two different models is presented in this article. For the through modeling of such flows, the coupled equations of NavierStokes, NernstPlanck and the PoissonBoltzmann are solved for the flow field, electric charges transport and electric field, respectively. Numerical solution of these equations for the heterogeneous microchannels is complicated and difficult. Therefore, simple and approximate models such as HelmholtzSmoluchowski have been proposed in which the solution of PoissonBoltzmann, NernstPlanck are neglected and the effect of the electric field on the flow field is applied through a prescribed slip boundary condition at the walls of microchannel. The electroosmotic flow fields within the heterogeneous microchannels are usually complex and contain the vortex region that is ideal for mixing purpose. Hence, in this paper, the microchannels designed so that they are capable to serve as micromixers in the mixing applications. For the microchannels proposed here, the flow fields are obtained both with approximate modeling and the full simulation of electroosmotic flows so that a comparison can be made to discuss the accuracy of the approximate model. The results of this study can be used to model the electroosmotic flow field within heterogeneous microchannels.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
260
270
http://mme.modares.ac.ir/article_12174_50559ba3c8a5761cf9ffc79d888a836a.pdf
Free vibration analysis of FGCNTRC cylindrical shells surrounded by elastic foundation subjected to thermal loading
Reza
Ansari
دانشیار دانشگاه گیلان
author
Jalal
Torabi
PhD Student
Guilan University
author
text
article
2015
per
In this paper, free vibration analysis of functionally graded carbon nanotube reinforced composite (FGCNTRC) cylindrical shells surrounded by elastic foundation and subjected to uniform temperature rise loading is investigated. The material properties of FGCNTRC are assumed to be graded through the thickness direction. Two kinds of carbon nanotube reinforced composites including uniformly distributed (UD) and functionally graded (FG) are considered. The elastic foundation is modeled by twoparameter Pasternak model, which is obtained by adding a shear layer to the Winkler model. The effect of thermal loading is considered as a initial stress. Applying the Hamilton’s principle based on firstorder shear deformation theory and considering Sanders and Donnell straindisplacement relation, the governing equations are obtained. Using the generalized differential quadrature method in axial direction and periodic differential matrix operators in circumferential direction, the equilibrium equations are discretized. The results are compared with those presented in literature. In addition, the effect of various parameters such as thermal loading, boundary conditions, elastic foundation and different geometrical conditions are studied. The results show that increase in the elastic foundation coefficients and initial thermal loading increase and decrease the nondimensional fundamental frequency, respectively.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
271
282
http://mme.modares.ac.ir/article_12172_22035a0201995c4a704eccb902c23f5d.pdf
An experimental investigation on modeII interlaminar fracture toughness of nanosilica modified glass/epoxy fiberreinforced laminates
Hossein
Movahhedi Aleni
دانشجو/دانشگاه تربیت مدرس
author
Gholam Hossein
Lighat
استاد دانشگاه تربیت مدرس
author
Mohammad hossein
Pol
دستیار پژوهش/دانشگاه تربیت مدرس
author
Ali
Afrouzian
دانشجو/دانشگاه تربیت مدرس
author
text
article
2015
per
In this research, effect of adding silica nanoparticles on the mode II interlaminar fracture toughness of epoxy matrix composites reinforced with glass fibers was experimentally studied. Hand layup method has been used to manufacture nanocomposites with18 layers of 2D woven glass fibers with 40% fiber volume fraction. The nanoepoxy resin system is made of diglycidyl ether of bisphenol A (epon 828) resin with jeffamine D400 as the curing agent. Nanosilica particles are dispersed with 0, 0.5, 1 and 3 wt.% (of epoxy resin) to study the effect of nanosilica content on fracture toughness. Also a series of nanocomposites with 1 wt.% nanosilica content and contained 55 vol.% glass fibers were fabricated to investigate the effect of fiber volume fraction on results. End notch flexure (ENF) test was adopted for the measurement of mode II interlaminar fracture toughness. The results show that high loading of nanosilica has no significant effect on the interlaminar fracture toughness of nanocomposites while the addition of 0.5 wt% nanosilica enhanced the interlaminar fracture toughness about 36% compared to the neat composites. Decreasing fiber volume fraction improved interlaminar fracture energy.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
283
290
http://mme.modares.ac.ir/article_12173_49d7d8c87b3ab47d9605d329a5ea3c4b.pdf
Numerical Investigation of the Effects of Geometrical Parameters of a Viscous Micropump on the Flow Rate and Entropy Generation .
Hojat
Khozeymeh Nezhad
دانشگاه فردوسی مشهد
author
Hamid
Niazmand
دانشگاه فردوسی مشهد
author
text
article
2015
per
In this paper, a numerical study has been performed to investigate the effect of geometrical parameters of a viscous micropump on the flow rate and entropy generation. The present research has been carried out for three geometrical parameters of micropump including eccentricity (), sizes (S) of rotors and also their distance from each other (L) in the range of 0.1 to 0.9, 1.5 to 3.5 and 0.85 to 4.5, respectively. The results show that with increasing , the micropump flow rate also increases. On size variation effects, it is observed that decreasing the downstream rotor diameter, while keeping constant the upstream rotor diameter, the flow rate decreases exponentially. By increasing L, a steep increase in flow rate is initially observed, which becomes almost constant, when rotors are sufficiently far apart. With regard to entropy analysis, the effect of above geometrical parameters has been investigated on the entropy generation. The parameter RS indicating the ratio of the gradient of the entropy production rate to the related flow rate is introduced as a tool for entropy analysis. Also in this paper, for obtaining the maximum flow rate at the minimum frictional dissipation, optimal geometrical parameters are extracted. In this regard, the values of L=2, ε=0.5, S_1=1.5 and S_2=2.5 are selected as the optimum geometrical parameters of viscous micropump.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
291
302
http://mme.modares.ac.ir/article_12193_37abbb3f704ef3303eb598ac5e56bd98.pdf
Prediction of Departure from Nucleate Boiling in a mini Channel Using CFD
Ataollah
Rabiee
shiraz university
author
Alireza
Atf
دانشگاه شیراز
author
text
article
2015
per
In order to meet increased demand for dissipating high heat fluxes from electronic chips that are continually shrinking in size, development of new cooling technologies have been considered for the last two decades. Recent research efforts have shown that boiling two phase flow through the minichannels can provide desired heat transfer coefficients. The occurrence of the dryout phenomenon followed by a sudden increase in temperature due to the critical heat flux is one of the most important challenges in this context. In this study, departure from nucleate boiling phenomenon due to the critical heat flux in a minichannel has been examined using computational fluid dynamics. The governing equations solved are generalized phase continuity, momentum and energy equations. Wall boiling phenomena are modeled using the baseline mechanistic nucleate boiling model developed by Rensselaer Polytechnic Institute (RPI). To simulate the critical heat flux phenomenon, the RPI model is extended to the departure from nucleate boiling (DNB) by partitioning wall heat flux to both liquid and vapor phases considering the existence of thin liquid wall film. It was observed that by applying high heat fluxes near to CHF, DNB occurred and a vapor layer formed adjacent to the wall while most of the flow field is still subcooled liquid.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
303
312
http://mme.modares.ac.ir/article_12194_2d6e56022564c8d607bd90f0a4ff4949.pdf
A Nonlinear Predictive PID Controller Design for Spacecraft Formation Flying Control
Adel
Rabie
دانشگاه اصفهان
author
Maryam
Malekzadeh
هیات علمی
author
Majid
Abnili
دانشگاه اصفهان
author
text
article
2015
per
This paper talked about spacecraft formation flying control. Leaderflower structure is used in formation flying. A nonlinear PID controller is designed based on predictive control. The formation relative equation is obtained from nonlinear Hill equation. First, the frequency control is achieved with the using of predictive control algorithm. In control frequency, disturbances have been replaced from disturbance observer. Equations are rewritten in the form of PID gains. Stability of the closedloop system is proven by closedloop error dynamics. Nonlinear PID controller performance in the pursuit of desired arrangement has been tested in simulations. Also effects of various factors on the quality of controller results are studied. It is shown that choosing predictive horizon time and disturbance observer gains have the most effect on system response. It is shown that if predictive time increase the settling time increase and the control effort decrease. if disturbance observer gain increase from a limit, it has no effect on settling time but control effort increase. As shown in simulation, the tracking response show the controller method ability. the simulation show the ability of this nonlinear control method in tracking.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
313
321
http://mme.modares.ac.ir/article_12203_f6a33906f0e4bd87a379d9135416ec39.pdf
Design and analysis of a novel cabledriven backbone for continuum robots
Mahdi
Bamdad
استادیار دانشگاه صنعتی شاهرود دانشکده مکانیک
author
Arman
Mardani
دانشگاه شاهرود
author
text
article
2015
per
In this study, it has been tried to provide a new model for the structure of a backbone arm, to repel the shortcoming in the generation and transmission of the motion for the continuum robots. Backbone arms such as natural structures include continuum backbones with superior properties such as the ability to adapt to the environment. The actuation power is distributed over the robot’s length and makes the shape continuously deformable. In this paper, it has been suggested to add a linkage between the backbones and the branched tendons for power transfer between the drive and backbones. The ratio of the drive torque to backbone torque is introduced as the transfer ratio. The new design is capable to create a variety of transfer ration during a cycle of motion. The state space equations are extracted by Lagrange equations. Dealing the interference of bonebone and bonelinks as geometric constraints are applied to the design and it determines the allowable range of the continuum robot's geometric parameters. This design is examined with planar simulations. To show the effectiveness of the proposed design, several simulation results are illustrated. Optimum geometrical parameters for the constant torque ratio are calculated.In contrast to previous cases with the widely used; the goal is achieved with this novel backbone continuum robot.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
322
332
http://mme.modares.ac.ir/article_12204_02c7abba9cd67b68e267c68fefaa730a.pdf
Comparison between different models of polymer membrane fuel cell using metal foam as a flow distributor
Saber
Heydari
دانشجوی کارشناسی ارشد، مهندسی مکانیک، دانشگاه اصفهان
author
Ebrahim
Afshari
استادیار گروه مکانیک دانشگاه اصفهان
author
text
article
2015
per
The use of metal foam as a distributor flow field in a polymeric electrolyte membrane fuel cells reduces the weight and volume of the fuel cell, causes more uniform distribution of the reactant gases, and in some cases eliminates the machining process required to create the flow channels. In this paper five models of polymer electrolyte membrane fuel cells are simulated including: the model that the bipolar plate consists of two parallel channels (model 1); The model that is similar to model 1 except that in this case channels are filled with metal foam (model 2); The model that the rib between the channels in anode and cathode side are eliminated and in the anode, metal foam is placed (model 3); the model that is similar to model 3 except that the metal foam is placed on the cathode side (model 4); in model 5, both the anode side and the cathode side are filled with metal foam. The results show that the use of metal foam in the anode or the cathode side in addition to decreasing maximum temperature in the models also helps a more uniform temperature distribution. The uniformity index shows that the distribution of current density is much better and more uniform, when the ribs in models 3, 4 and 5 are eliminated. Comparison conducted between different models shows that the pressure drop caused by the presence of the metal foam, due to the high coefficient of permeability and porosity of the foam, is small.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
333
343
http://mme.modares.ac.ir/article_12205_e08f22f2d3d032c8ba99be2f6ad15498.pdf
Uniform Star Catalog Generation and Comparison Criterion Introduction for a Typical Star Tracker
Jafar
Roshanian
دانشگاه صنعتی خواجه نصیر  دانشکده هوافضا
author
Shabnam
Yazdani
دانشگه صنعتی خواجه نصیر دانشکده هوافضا
author
Masoud
Ebrahimi
استادیار دانشگاه تربیت مدرس
author
Mohammad Javad
Hasani Kabotarkhani
دانشگاه صنعتی خواجه نصیر دانشکده هوافضا
author
text
article
2015
per
Processor memory capacity and update frequency are one of the main restricting constraints in star tracker design and development. In order to decrease the volume of the data required onboard, uniforming the star catalog which is eventually used as pattern recognition database is considered. Three different methods of uniforming the star catalog have been applied. Spherical patches, fixed slope curve and charged particles or Thomson’s problem. After generation of a sphere with uniform distribution of points, a star is assigned to each point according to its spherical distance or best magnitude. In order to evaluate the performance of each method, seven evaluation criteria are defined. Point distribution minimum energy, catalog size, minimum star required for pattern recognition, mean and standard deviation of star distribution in each frame, database size and pattern recognition true recognize percentage. These seven criteria are combined in weighted equation of “average” to choose the best star catalog uniforming method with respect to the star tracker mission. After having implemented the average equation it is demonstrated that uniforming the star catalog using charged particle or Thomson’s problem has better results.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
344
352
http://mme.modares.ac.ir/article_12209_18adb648efebcb174a7b3f6c83c75919.pdf
Direct Numerical Simulation of Controlled Transition Scenarios on a Flat plate
Vahid
Esfahanian
Professor /
Department of Mechanical Engineering, University of Tehran
author
Ali Akbar
Dehghan
Associate Professor/
Department of Mechanical Engineering, Yazd University
author
Khoshab
Masih
Yazd University
author
Hossain
Chizari
Research Assistant/
Vehicle Fuel and Environment Research Institute, University of Tehran
PhD Candidate /
Mechanical and Aerospace Department,
University Science Malaysia
author
text
article
2015
per
Transition control is of the great significance in laminar flows since determination of aerodynamics coefficients as well as heat transfer magnitude is strongly affected by accurate prediction and control of this phenomenon. Transition is severely dependent on space and time such that various microscopic and macroscopic scales can convert to each other rapidly. In one side, available uncertainties in RANS turbulence models can lead to inappropriate, or at least expensive, designs. In the other side, considering the growing rate of computational resources along with development of more efficient numerical methods in CFD applications, Direct Numerical Simulation, DNS, has found an applicable role even in industrial applications. In present study, a robust computational code is developed for Direct Numerical Simulation aimed at fundamental purposes. To this end, highorder compact finitedifference for spatial derivatives and highorder RungeKutta time integration are used in the present code as well as a lowpass filter to elucidate spurious oscillations. Also, nonreflecting boundary condition is employed to keep the domain size as small as possible and to improve the numerical accuracy at the boundaries. In present study, Direct Numerical Simulation investigates controlled transition scenarios for flow over a flat plate. Results are in a good agreement with those of previous researches both qualitatively and quantitatively which verify the various parts of the developed solver.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
353
364
http://mme.modares.ac.ir/article_12206_451b940cffab9f99dc3fadd9844261bf.pdf
Investigation of groove and bump effects on transition region and aerodynamic of a low speed UAV airfoil and wing
Alireza
Naderi
عضو هیات علمی دانشگاه صنعتی مالک اشتر
author
Mehdi
Najafi
پژوهشگر
author
text
article
2015
per
At moderate Reynolds numbers, the perturbations may be intensified and laminar flow regime changes to turbulent flow regime. In transition process from laminar to turbulence, the flow tends to separate from a surface and then reattaches with it. As a result, some bubbles are formed which are called laminar separation bubbles. Understanding the physics of the separation bubble phenomenon and controlling of them are needed to proper aerodynamic devices design at moderate Reynolds numbers. This study has tried to enhance the aerodynamic efficiency of a low speed UAV airfoil and wing by using geometric heterogeneity like groove and bump. In this study; firstly, around CLARKY airfoil a proper turbulence model is proposed and effective value of Reynolds numbers on bubbles are obtained; secondly, a geometric heterogeneity is build and moved from leading edge to trailing edge on the airfoil and the performance of this airfoil is evaluated; Thirdly, geometric heterogeneity around the transition zone is changed and its effect on the performance of this airfoil is evaluated; and fourthly, some grooves and bump are arranged on the wing and their aerodynamic performance are compared relative to the clean wing. The results show that, the KKlω turbulence model is more accurate than others, higher Reynolds number lower bubble size, nearby transition point position is a good option for heterogeneity building, grooves enhance aerodynamic performance more than bumps, and a continues groove is obtained higher aerodynamic performance than clean wing but discontinues aligned grooves obtained lower aerodynamic performance than clean wing.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
365
376
http://mme.modares.ac.ir/article_12207_825087162ad9625434842d4f23620568.pdf
Investigating the influence of effective parameters on the residual stresses in circumferentially arc welded thin walled cylinders of aluminum alloy series 5000
Vahid
Karimnia
424 Hafez Ave, Amirkabir University of Technologhy, Tehran, Iran
author
Iradj
Sattari far
424 Hafez Ave, Amirkabir University of Technologhy, Tehran, Iran
author
text
article
2015
per
In this paper, the residual stresses due to circumferential arc weld of the thin walled cylinders have been investigated by using finite element method. The cylinders were of aluminum alloy series 5000. The 3D finite element models have been developed in ABAQUS. The thermalmechanical analysis was considered as uncoupled. The thermal and mechanical material properties have been defined as temperature dependent. The residual stresses were measured by using Hole drilling method. The experimentally measured data have been used to verify the result of finite element model. By using Taguchi method, the effect of eight geometrical, technological and material different factors have been investigated on the maximum residual stresses in the axial and hoop directions. Considering to a number of factors, L12 Taguchi array has been selected. Each factor has been studied in two levels. The result of statistical analyses have shown that increasing the outer diameter, thickness, heat input rate and yield strength in the studied levels caused the axial and hoop maximum residual stresses enhanced. However, the increase of the section number and the interaction between the outer diameter and heat input rate have led to decrease the maximum hoop residual stresses. Also, the yield strength of material was the most effective factor on maximum axial and hoop residual stresses.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
377
386
http://mme.modares.ac.ir/article_12208_313ae87e597c0260a0f9efe9ad2f933b.pdf
Analytical solution based on higher order shear and normal deformation theory for Buckling of functionally graded plates with piezoelectric layers
Morteza
Ghasemi
ferdowsi university of mashhad
author
Abdolrahman
Jaamialahmadi
Ferdowsi University of Mashhad
author
text
article
2015
per
In this article, the buckling of multilayer rectangular thick plate made of functionally graded, transversely isotropic and piezoelectric materials in both closed and open circuit conditions are investigated. Based on the shear and normal higherorder deformation theory, the governing equilibrium equations of plate are obtained using the principle of minimum total potential energy and Maxwell’s equation. Using an analytical approach, the governing stability equations of functionally graded rectangular plates with piezoelectric layers have been presented in terms of displacement components and electric potentials. In order to obtain the stability equations, the adjacent equilibrium criterion is used. The stability equations are then solved analytically, assuming simply support boundary condition along all edges. Finally after ensuring the validation of the results, the effects of different parameters such as different loading conditions, functionally graded power law index, thicknesstolength ratio and aspect ratio, on the critical buckling loads of plates are studied in details. Furthermore, the effect of piezoelectric thickness on the plate critical buckling loads has been studied. The results present better accuracy in comparison with the classic and third order shear theories.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
387
397
http://mme.modares.ac.ir/article_12210_0baabaccae527e19eadac35daecf6004.pdf
Numerical and Experimental Study of splitter blades effect on the centrifugal pump performance
Mir Boyouk
Ehghaghi
Department of Mechanical Engineering, University of Tabriz
author
Mohammad
Vajdi
Department of Mechanical Engineering, University of Tabriz
author
text
article
2015
per
As pumps are used frequently in industrial plants, their performance improvement is important. In this study, performance improvement of centrifugal pumps by application of splitter blades have been investigated both numerically and experimentally. Radial impellers with different length of splitter blades have been manufactured and tested to obtain performance charts. On the other hand, the flow in impeller and volute has been investigated numerically by ANSYSCFX commercial code. Numerical study has been done using Finite volume method and kωSST turbulence model. Rotating and stationary frames have been used to analyze flow in impeller and volute respectively and the results have been coupled by Frozen Rotor. Three impellers with the lengths of splitter blades equal to 0, 33% and 66% of original blades were tested. Results show head increase when the splitter blades added while the amount of increase depends on the splitter blades length. At BEP (Best Efficiency Point) the maximum head increase was reported for impeller type three (the length of splitters equal to 66% of original blades) about 10.5 percent. It should be noted that as the capacity tends to BEP, the effect of splitter blades is more significant.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
398
410
http://mme.modares.ac.ir/article_12211_6aea98f6324f791f8406943c41ec835a.pdf
Reinforcing Effect of Nanoclay on Buckling Behavior of Nanocomposite Grid Shells: Experimental Investigation
Reza
Zamani
دانشگاه تربیت مدرس
author
Gholam Hossein
Rahimi
Tarbiat Modarres Univ
author
Mohammad Hossein
Pol
دانشگاه تفرش
author
Mohammad
Hedayatian
دانشگاه تربیت مدرس
author
text
article
2015
per
The current study represents the influence of nanoclay on buckling behavior of glass fiber reinforced polymer (GFRP) gridstiffened nanocomposite shells. The nanocomposite grid shells were manufactured from continuous glass fiber using a specially designed filament winding machine. The epoxy/clay nanocomposites with different clay content (0%, 1.5%, 3% and 5% of clay) were used as the matrix of the grid stiffened structures. The state of dispersion and mechanical properties of the epoxy/clay nanocomposites were obtained by Xray diffraction (XRD) method and uniaxial tensile test, respectively and also the grid structures were loaded under uniform axial compression test. The results of XRD show that the clay has been further intercalated by the epoxy matrix. The tensile test results represent that the tensile modulus and Strength, strain to break and energy to break of the epoxy/clay nanocomposites increase with adding clay loading into the epoxy resin. Furthermore, it is found that the critical buckling load of the cylindrical grid samples increases continuously with increasing the clay content up to 5 wt. %. The maximum value of improvement in the critical buckling load is about 10% for the samples with 5 wt. % of nanoclay.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
411
418
http://mme.modares.ac.ir/article_12212_10845f84fedd3ec5806f6259afcae069.pdf
Fault detection of the 3PSP parallel robot using the principal components analysis method
Amir
Rezaei
دانشجوی دکترا/دانشگاه فردوسی مشهد
author
Alireza
Akbarzadeh
ProfessorMechanical EngineeringFerdowsi University of Mashhad
author
text
article
2015
per
In this paper, a multivariate statistical method called Principal Components Analysis, PCA, is utilized for detection faults in a 3PSP parallel manipulator. This statistical method transfers original correlated variables into a new set of uncorrelated variables. PCA method can be used to determine the thresholds of statistics and calculate square prediction errors of new observations for checking the system when a fault occurs in the robot. To investigate on the ability of the PCA method for faults detection of the robot, a nonlinear modelbased controller called Computed Torque Control, CTC, is designed. In this control scheme, rigidbody inverse dynamics model of the robot is utilized to linearize and to cancel the nonlinearity in the controlled system. Also, instead of using the robot prototype model, direct dynamics of the robot is used in the robotcontrol system. In this paper, two faults are artificially applied to the robotcontrol system. These two faults consist of faults in servo drive or servo motors and faults in joints clearances or position sensors. Finally, these faults are applied on the robot throughout a desired endeffector trajectory and the resultant outputs are obtained for both with and without faults in the manipulator. Consequently, the desired and faulty outputs are compared and faults detection using PCA method for the robot is performed.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
15
v.
3
no.
2015
419
430
http://mme.modares.ac.ir/article_12213_de9d0fd96f0024dde5ad5b8ac52cc1e1.pdf