Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
IFC
0
0
FA
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Identification and Torque Control of Series Elastic Actuator of Lower Limb Extremity Exoskeleton
1
8
FA
Ali
Taherifar
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
Gholamreza
Vossoughi
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
Ali
Selk Ghafari
Sharif University of Technology
Nowadays the exoskeleton, known as a useful device in robotic rehabilitation and elderly assistance, has been attracted the attention of many researches. One of the most important feathers of the exoskeleton robots are the compliant interaction with patient. The Series Elastic Actuators (SEA) not only interact with human compliantly but also provide several advantaged such as torque measurement and torque control. The pervious researches have used an inner position loop and an outer force loop. In this paper, the motor and power transmission model is also integrated in the controller design. In this paper, the parameters of the SEA, motor and links are identified firstly. Then, two model-based torque control is designed and introduced based on the velocity and current commands. In contrast to previous researched, the controller is proposed for the locked and free condition and the Lyapunov stability analysis is presented. Finally, the experimental validation test on the Sharif lower limb exoskeleton is presented for these controller. The experimental results of the controller show that the accuracy of torque control based on the current and velocity is 1.2 and 0.2 N.m, respectively.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Build Time Estimation in Additive Manufacturing Processes based on Part Orientations
9
16
FA
Amir Hossein
Golmohammadi
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
Saeed
Khodaygan
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
The orientation of part in the additive manufacturing process is one of the most important factors should be considered in the additive manufacturing process. In the additive manufacturing process, the part orientation factor can significantly affect the part properties such as the surface roughness, strength, the manufacturing time and amount of support materials. The manufacturing time is a key factor that can influence the total production cost. Therefore, to minimize the manufacturing time, the optimum orientation of parts should be determined. In this paper, a new method is introduced to estimate the built time of the parts through the additive manufacturing process. According to the proposed method, a practical equation is extracted to estimate the built time of the parts with related to the number of layers and amount of the support materials. The method is capable to estimate the built time of a part associated to the part orientations. The efficiency of the proposed method is demonstrated through a case study in two different type of orientation, and the computational results are compared with the obtained results from the simulations in MankatiUM V5.3 and Repetier-Host software. The average of proposed method relative error in the first type of orientation in comparison with MankatiUM and Repetier-Host software results are, respectively, 5 and 10 percent and for the second type of orientation are 7 and 8 percent. Moreover, calculation cost of proposed method is 140 and 100 times faster than MankatiUM and Repetier-Host software, respectively.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Investigation on the effect of period of temperature variation in intermittent drying of clay
17
28
FA
Mohsen
Heydari
Department of Mechanical Engineering, University of Birjand, Birjand, Iran.
khalili
khalili
Professor/Mechanical Eng. Dept-University of Birjand
Seyed Yousef
Ahmadi Brooghani
Department of Mechanical Engineering, University of Birjand, Birjand, Iran.
Drying process is one of the intensive energy operations in many industries such as tile and clay brick manufacturing industries. Cracking as a result of non-uniform deformation is one of defects that may occur during drying making the dried products useless. Intermittent drying is an effective strategy for improving the drying kinetics and the quality of the dried parts. Proper selection of intermittent drying parameters including the period, amplitude and the start time of variation are the main challenge in the drying. The purpose of this paper is to examine the effect of the period of temperature variation on the drying kinetics and induced stresses in the intermittent drying of clay like material. 3D modeling and simulation of continues and intermittent drying has been done by using finite element method. Moisture and thermal stresses are compared with each other. The good agreement between experiments and the simulation results revealed that the model developed is valid and accurate. Simulation results show that the stresses induced by drying heavily influenced by the frequency of variation. The change of the Frequency variations depending on the material properties and sample dimensions can decrease/increase the drying induced stresses. Intermittent drying has a different effect on the different points of the samples. Hence, the points susceptible to crack formation must be investigated simultaneously. The thermal stresses are negligible compared to the moisture stresses and can be neglected in drying modeling.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Effect of Blade Surface Roughness on Performance of a Low-Pressure Steam Turbine Stage
29
37
FA
Hamed
Bagheri
University of Shahreza, Shahreza, Isfahan
Surface roughness of steam turbine blades is increased during operation. This point has harmful effect on the performance of steam turbines. In this paper effects of surface roughness on performance of a steam turbine stage in two-phase flow conditions are investigated for different outlet pressures. To do so a numerical code has been developed to simulate two-phase non-equilibrium flow in 2D steam turbine geometry. An AUSM-van Leer hybrid scheme is used to calculate inviscid fluxes, the SST turbulence model for turbulence viscosity and Wilcox roughness model for implementation of roughness on the surface of turbine blade. To validate the present in-house code the experimental results of Bakhtar has been used. According to the results of the paper, effect of surface roughness variation on the performance loss in subsonic stages is more than that in supersonic outflows. For example, in subsonic outflow case (Pb= 24.25 kPa) when the roughness height increases from 5µm to 800 µm, the value of efficiency decreases by 15%. However, for supersonic outflow case (Pb= 14.55 kPa) the value of efficiency decreases by 10% for this roughness increase.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Thermal analysis, effect of lubricant and fatigue life of spiral bevel gears of main gearbox
38
48
FA
Mojtaba
Mehrabi
Mehdi
Mohammadimehr
Mohammad Reza
Fatehi
Ali
Ghorbanpour Arani
In the present paper, thermal analysis of used spiral bevel gears in main gearbox of helicopter- belong to Iran Aircraft Manufacturing- is investigated. Firstly, with introducing the geometry properties of gears, basic lubrication and thermal analyses are considered based on standards of gear design such as AGMA. Then, in order to create the finite element model, initial and boundary conditions with considering the oil viscosity and calculating the friction coefficient, convection and heat conduction coefficients are determined based on experimental and analytical models in spiral bevel gear. It is noted that, the goal of finite element model is considered to reduce the complex calculation errors and increase the speed of problem solving. Effects of various parameters such as increasing the FLASH temperature and influences of initial temperature on it, contact stresses and heat fluxes, comparison of different mineral oils on the decreasing of temperature and fatigue life are examined. The obtained results of present work show that the FLASH temperature of main gearbox is linear function of initial temperature, so that FLASH temperature increases 56 centigrade in comparison of initial temperature. Also, it is demonstrated that the presence of various mineral oils in this system lead to reduce the solid-solid surface contact and friction coefficient. Moreover, these lubricants cause the cooling in the gearbox and enhancing more temperature, thus the employing these lubricants lead to exceed the system temperature to 90 centigrade.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
A study on the microstructure and mechanical properties of dissimilar joints of copper-nickel alloy and austenitic stainless steel welded by GTAW process
49
58
FA
Hassan
Jafari
salman
nourouzi
Babol University of Technology
Hamed
Jamshidi Aval
Seyed Jamal
Hosseinipour
In the present study, the mechanical and microstructural properties of dissimilar joint of 304 austenite stainless steel and C70600-copper-nickel alloy made by Gas Tungsten Arc Welding process has been investigated. The aim of this joint is using the twin metallurgical properties such as; heat dissipation and corrosion resistance of copper-nickel alloy and mechanical properties of 304 austenite stainless steel alloy. Welding of two dissimilar metal steel to copper-nickel alloy due to differences in melting point, the difference in thermal conductivity, rapid solidification of copper nickel are facing many problems. In this research due to solubility and weldability of nickel with two both alloys, three filler metals Inconel 625, Inconel 82 and 61 were used. According to microstructural investigations welds made by Inconel 625 and Inconel 82 show a finer equiaxed dendrite structure as compare as in Inconel 61 filler metal. The tensile strength of samples welded by Inconel 625, 82 and 61 filler metals was 324, 323 and 293 MPa, while the elongation percent of three samples show small difference. According to mechanical properties of joints, the Inconel 625 and 82 filler metal are appropriate for dissimilar welding 304 austenite stainless steel and C70600-copper-nickel alloy.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Experimental investigation of dynamics of the air-core vortices and estimating the air entrainment rate at a horizontal intake
59
67
FA
Morteza
Monshizadeh
Ph.D. Candidate of Department of Civil and Environmental Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran
Ahmad
Tahershamsi
Hassan
Rahimzadeh
Professor of Department of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran
Hamed
Sarkardeh
Assistant Professor of Department of Civil Engineering, Faculty of Engineering, Hakim Sabzevari University, Sabzevar, Iran
In the present study, free surface vortex dynamic was experimentally investigated in a horizontal intake. Air entrainment rate into the intake due to the air-core vortices was also discussed. The results presented are the relationship between the vortex type and the intake hydraulic parameters, general pattern of surface displacement of the vortex core and its relation with the vortex type, the required time duration to fully development of the vortex core, and finally evaluation of the vortex induced air entrainment rate. In this research by defining intake number as intake Froude number over the intake relative submergence, a relationship was established between the vortex type and the intake number. Moreover, it was shown that while the intake number increases, surface instability of the vortex core decreases, in which, for the intake numbers greater than one, surface movement of the vortex core is limited to an area of the twice of the intake diameter. Then, another relationship was also established between the time requirement of the vortex air-core formation and the intake number, and it was shown that there will be an exponentially decrease in the mentioned time scale, while the intake number increases. In this context, a relationship was suggested and compared with one of previous works. In the last section, the dependency between air entrainment rate due to the air-core vortices and the intake number was considered, and another relationship was also suggested and compared with previous works.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Trajectory tracking of a VTOL aircraft with uncertainty and disturbances
68
74
FA
Meisam
Kabiri
Amirkabir University of Technology
Mohammad Bagher
Menhaj
Professor/Amirkabir University of Technology
Hajar
Atrainfar
Assistant Professor/Amirkabir University of Techonolgy
This paper addresses the trajectory tracking of a Vertical Take-Off and Landing (VTOL) aircraft. Our objective is to design a controller for a VTOL aircraft in such a way that the aircraft tracks a predefined 3d spatial path in the presence of constant disturbances and uncertainty in the inertial matrix. Taking advantage of the extraction algorithm, we separate the design for the translational and rotational dynamics. First a virtual controller is designed for the translational dynamics from which the ideal thrust direction is extracted. To deal with the under-actuation of the translational dynamics, we have exploited an auxiliary system while an estimator is also involved in the design of the virtual controller to compensate for the effect of the translational disturbance. In order to keep our estimation bounded, we utilize the projection operator which is also smooth enough. An adaptive sliding mode control is used for rotational dynamics control such that the ideal thrust is accomplished. Since the inertial matrix and the bound on rotational disturbance is unknown, an adaptive structure is used to estimate the unknown bounds. The stability of the control framework is established through Lyapunov analysis. Finally simulation results are given to test the validity of the proposed control scheme.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Numerical and Experimental Investigation of Optimization of Photovoltaic Thermal System, Using Taguchi Method
75
86
FA
Mohammad
Hosseinzadeh
Ali
Salari
Mohammad
Sardarabadi
Mohammad
Passandideh-Fard
Alireza
Akbarzadeh
In this study, the performance of a photovoltaic thermal system (PVT) is investigated in a numerical and experimental study. In the numerical part, the Taguchi method is applied to determine the optimum place and time of the PVT system. Moreover, the optimum parameters that are independent of the design of the PVT system are obtained to improve the performance of the system in a specific place and time. Using the specified optimum parameters, the performance of the system is investigated from the energy and exergy viewpoints, experimentally. In the experimental study, using the designed setup, the performance of a water based PVT system is compared with that of a conventional photovoltaic unit (PV). The experiments are performed on a selected day in August at the Ferdowsi University of Mashhad, Mashhad, Iran (Latitude: 36° and Longitude: 59°). The numerical results indicate that the most effective parameter on the performance of the PVT system is the coolant inlet temperature and its optimal value is 20 °C. Moreover, the total energy efficiency of the PVT system in the optimum working condition is 69.02 %. The experimental results reveal that the average output electrical energy of the PVT system is 6.27 % more than that of the PV unit. In addition, the average thermal energy and exergy efficiencies of the PVT system are 34.12 % and 0.72 %, respectively.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Identification and control of an active boring bar using VCA actuator
87
96
FA
Pooria
Naeemi Amini
PhD Candidate,Department of Mechanical Engineering, Ferdowsi University of Mashhad
Behnam
Moetakef-Imani
Boring operations due to the large length to diameter ratio and the high flexibility of tool are prone to self-excited (chatter) vibration. This vibration may cause poor surface quality, low dimensional accuracy and tool breakage. In practice, chatter is the main limitation on production rate. The main reason of chatter phenomenon is the dynamic interaction between cutting process and structure of machine tool. By increasing the length of the cutting tool, the vibration tendency in the tool’s structure increases. Improving dynamic stiffness of the tool is the most effective solution for decreasing vibration and increasing chatter stability. For increasing the stability of the tool in long overhang boring operations, passive and active vibration control has been proposed and implemented. In active control methods, vibrations can be effectively damped over a various cutting conditions. The aim of this research is to enhance chatter stability of an industrial boring bar by increasing the dynamic stiffness. A VCA actuator is used for active vibration control. The designed setup can effectively suppress undesirable vibrations in the radial direction. First, modal parameters of the boring bar are determined by experimental modal analysis. Then, the transfer function of the actuator-tool setup is identified with the sweep frequency excitation. In the following, the direct velocity feedback is successfully implemented in the vibration control loop. The results of cutting tests indicate that the actuator has a great performance in suppressing vibrations and increasing the dynamic stiffness. Hence, the developed method can significantly increase chatter stability of boring operations.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Feedback control of temperature distribution in a thick rectangular functionally graded plate
97
104
FA
shojaat
shafie
Yasouj university
Behrooz
Rahmani
Associate professor of mechanical engineering, yasouj university
amin
moosaie
Yasouj university
Hamed
Panahi
Yasouj university
In this paper, a method for distributed control of temperature distribution in a thick rectangular functionally graded plate is proposed. In this way, the linear nonhomogenous conduction which its governing dynamics is a linear partial differential equation (PDE) with spatially varying coefficients is considered and actively controlled. For this purpose, firstly, this PDE is converted into a set of ordinary differential equations (ODEs) using the modified wavenumber methodology. This apporach is based on the combination of the fast Fourier transform (FFT) and finite difference techniques. Secondly, in order to stabilize each of these ODEs, linear optimal state feedback controller is utilized by minimizing a predefined performance index. The proposed controller is modified by adding a feedforward term to have a good tracking performance for the proposed method. The designed control inputs which are in the Fourier domain, are transfers to physical domain using the inverse Fast Fourier transform (IFFT). In order to solve the linear nonhomogenous conduction heat equation, a combination of finite difference and Runge-Kutta methodologies is implemented. Simulation studies show the performance of the proposed method, for example the smaller settling time, overshoot and also steady-state error.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Comparison of some global chemical kinetics effects on methane lifted flame 3D simulation
105
116
FA
amin
jalalian
PhD student/ Mechanical engineering,Tarbiat Modares University,Tehrran, Iran
Kiumars
Mazaheri
Tarbiat Modares University
In the present study, the effects of several global chemical kinetics in 3-dimensional numerical simulation of methane combustion in a horizontal combustion chamber which has lifted flame by a set of open source code OpenFOAM, is compared. The purpose of this comparison is to study the effects of 1, 2 and 4 step global kinetics on velocity, temperature and species distribution. In this simulation, conservation and state equations are solved simultaneously. Partial differential equations are discreted by finite volume method. The effects of turbulence by standard k-e, radiation by P1 model and turbulence-combustion interaction by PaSR are modeled. The results of numerical simulations have been validated by a cylindrical combustion chamber experimental data. The results show that the kinetics have considerable differences in results of velocity, temperature and species in the final third of the chamber where the flame is located, and differently predict locations of the flame. According to these results, 4-step mechanisms were more accurate than the 2-step type. Between 4 step mechanisms, JL is more accurate than Kim in overall; However, its calculation time is higher than the Kim. Single step kinetics were not able to keep the lifted flame.Towards the experimental results, 2-step model predicts the flame in downward and Kim mechanism estimates the flame in the upward.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Hierarchical Position, Orientation and Impedance Control in redundant robots
117
125
FA
Abbas
Karami
Ph. D. student
Hamid
Sadeghian
Engineering Dept., University of Isfahan.
Mehdi
Keshmiri
This paper presents the problem of controlling multiple tasks in a prioritized scheme during accidental external physical interaction with redundant robot. This issue arises when robots are employed in social, unknown, dynamic environments for complex and critical missions. Exploiting robot redundancy to ensure safety and compliance during performing hierarchical tasks is considered in this work. A general approach to control the main task (position/orientation of the end-effector) with allocated priorities beside compliance behavior in the null space of the tasks is proposed. External interactions on the robot body are estimated with an appropriate observer without using any force/torque sensors which is further used to bring compliance in the redundant space. A novel task allocation method is proposed and the convergence of the task space error, interaction estimation error as well as null space velocities are guaranteed. Finally, the performance of the method is investigated through computer simulation and real experiments on KUKA robot arm.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Experimental study of ballistic properties of hybrid aluminum and epoxy matrix composite reinforced with carbon nanotube
126
132
FA
Majid
Khansari
Emam Hossein Univercity
Hossein
Khodarahmi
Abas
Vaziri
One of the recent techniques which has attracted attention from researchers is the use of Nano particles to reinforce composites. While the technique does not make any changes in the weight of the structure, it improves its mechanical and physical properties. One form of Nano particles includes Carbonic Nano Tubes (CNT). Since its discovery, CNT has found wide application in industryIn this article, the response of aluminum hybrid panels and composites made from epoxy-Kevlar and aluminum hybrid panels and Nano-composites made from epoxy-Kevlar to ballistic impact was studied. Four groups of the panels were constructed using 0, 0.5, 1 and 1.5 percent of carbon nanotubes (CNT)s. The hybrid samples constructed and tried out in this experiment has been done using manual layer-making and heated press.The thickness of the panels constructed from two aluminum plates and ten Kevlar 29 plates was consistent. The ballistic impact test using gas gun was implementated by conical bullet 7.6 gr shooting in two avrege velocities (220 m/s and 275 m/s). input and output velocity with each sample was assessed using a laser speedometer. The amount of energy absorption and special energy absorption of passing of the rocket was determined as the criteria for the comparison of the efficiency of ballistic of different panels. The results indicated that among the four samples examined, the panel made up of 1 percent CNTs had the most amount of energy absorption and ballistic resistance.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Investigation of Gas Compression Process inside Oleo-Pneumatic Shock-Absorber with Two-Phase Flow Simulation Method
133
142
FA
saman
hosseinzadeh
Msc student/iran university science and technology
Bijan
Mohammadi
The Oleo-Pneumatic shock absorber has a dual function in suspension systems. Compressibility of gas plays the role of spring and oil passing through the orifice plays damper role. Shock absorber response to various excitation depends on Fluids (gas and oil) and their internal flow. Prediction of the flow behavior inside the shock absorber can reduce cost of experimental during design and optimization process and performance analysis. Numerical Fluids flow has been simulated with assumption of axisymmetric and two-phase flow. Primary phase is compressible and Redlich-Kwang-Soave equation of state has been used to describe the compressible gas behavior. Volume of fluid model (VOF) has been described the relationship between two phases. k-ε model and Scalable wall function has been chosen for modeling turbulence. The piston's movement has been simulated using dynamic mesh (layering method). The way of gas-oil mixing and temperature change during stroke, has been shown an increase in temperature about 50-degree for largest gas bubble because of compressing. However, temperature of small bubbles has been reduced to oil temperature because of higher heat exchange. In polytropic description of gas process, the polytropic expansion has been found to describe with polynomial function of stroke. Polytropic expansion value starts from 1.3, rises to 1.4, and reduces again after mixing two phases.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Static and dynamic tolerance analysis of flexible rotary systems based on the tolerance zone method
143
152
FA
Saeed
Khodaygan
Hamed
Fallahzadeh
Sharif University of Technology
Because of increasing demands for using of rotating systems in high accuracy and high speed applications, in addition of specific condition of rotating systems, it is necessary to analyze these rotating systems characteristics. Tolerance analysis is a useful tool for estimating effects of dimensional and geometrical errors of effective parameters on functional characteristics in a mechanical system. Unlike other mechanical systems, in addition to the dimensional and geometrical errors, the accuracy of the rotary systems performance directly depend on the flexibility of parts and Non Repetitive Run-Out (NRRO) errors. In this paper, a new method is proposed for static and dynamic tolerance analysis of the rotary systems with the dimensional and geometrical errors, the flexibility effects, and the NRRO errors based on the tolerance zone model. First, using the small degrees of freedom concept, the dimensional and geometrical errors and the NRRO error are modeled in the tolerance zone. Then, based on a new strategy, the performance -assembly functions of the system for modeling the error propagation of the rotary system in the static and dynamic conditions are extracted. Then, using the proposed equations, sensitivities of the requirements such as the end of shaft position and the main natural frequency to tolerances are computed. To illustrate applicability of the proposed method, a rotary system is considered as a case study. Monte Carlo simulations are used for validation of the computational results from proposed method.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Crack Depth Profiling in Metallic Structures through ACFM Data using Type-II Fuzzy Logic System
153
163
FA
Saeed
Ahmadkhah
دانشگاه گیلان، دانشکده فنی، گروه مهندسی برق
Reza PR
Hasanzadeh
Associate Professor, Department of Electerical Engineering, University of Guilan
One of the major issues in the industry is inhomogeneity depth profiling in the metallic structures before reaching them to the border of demolition. Fuzzy logic based methodologies, due to their ability to describe the complex issues with empirical nature such as non-destructive testing, are used for this purpose and usually provide acceptable results. But empirical rules and also extracted data from non-destructive testing methods mainly have high degree of uncertainty and therefore Classical fuzzy methods, which are based on exact membership grades and Type-I membership functions, are incapable to deal with them. Therefore, they cannot deal with noisy environments and also cannot represent a good performance for accurate depth estimation of unknown cracks. In this paper, to allocate uncertainty to rules and membership functions, the type-II fuzzy logic system is used to solve the inverse problem of crack profile depth estimation. Also Alternating Current Field Measurement (ACFM) signals are used to sizing the depth of crack profile. Then, experimental results of the proposed method are compared to the other state of the arts in the presence of different level of noise and different type of cracks. The results show the superiority of the proposed method to the other methods.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Study on turbulent flow in a compound channel with shallow overbank using Particle Image Velocimetry
164
172
FA
Mostafa
Nabipour
Seyed Ali Akbar
Salehi Neyshabouri
Seyed Hossein
Mohajeri
Amir Reza
Zarrati
Mohammad
Zabetian Toroghi
In compound channels, in addition to shear flow originated from the bed (boundary layer flow), other forces are generated by momentum transform between the main channel and the floodplain (free shear layer). Due to such special type of momentum transport, a complicated three-dimensional flow structure forms in a compound channel. Previous studies showed that in a compound channel, secondary currents are enhanced for shallow overbank flow and consequently the complexity of flow structure increases. However, this complexity has not be described properly. To explore turbulent structure of a shallow overbank flow, flow field is measured in a compound channel with vertical walls using Particle Image Velocimetry. The results show that in the main channel, the maximum amount of streamwise velocity occurs below the floodplain level. Whereas in previous studies in compound channels with inclined transitional wall, turbulence intensities profiles in the main channel showed two different trends at lower and higher elevations of the floodplain invert, in the present study three different increasing or decreasing trends were observed for Reynolds shear stress and longitudinal turbulence intensity profiles and four different trends was observed for vertical turbulence intensity. Bed shear velocity was approximately constant in the floodplain but it increased near the interaction zone.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Numerical study of delamination in drilling of Glass/Polyester and investigation of mode ΙΙ fracture contribution
173
181
FA
Mehdi
Ganjiani
hossein
Orui
Mahdi
Ganjiani
Delamination is one the most important defect that reduces strength of part. Many researchers have been studied delamination in drilling of composite materials and they tried to formulate this phenomenon by developing of analytical, numerical and experimental models. In this models up to now, only effect of modeΙ and modeΙΙΙ of crack propagation is considered and effect of modeΙΙ is neglected. The goal of this research is determination of modeΙΙ effect on propagation of interlaminar cracks during drilling of multilayered composites by means of finite element analysis (FEA).Thus the numerical analysis of delamination of unidirectional Carbon/epoxy composite during drilling is performed by modification of previous numerical models. The numerical method which is used for determination of strain energy release rates in modeΙ and modeΙΙ is Virtual Crack Closure Technique (VCCT). This analysis is performed for crack propagation under chisel edge when the drill have not come out from the workpiece and for crack propagation under cutting edges when the drill have come out from the workpiece. By determination of strain energy release rates in modeΙ and modeΙΙ and comparing with critical values G_Ιc andG_ΙΙc, the critical thrust force that causes to delamination is determined and contribution of each crack propagation mode in delamination is discussed. At the end of this research, it was found that the effect of modeΙ is more than modeΙΙ in all of cases such that more than 95percent of crack propagation parameter in power law criteria is due to strain energy release rates in modeΙ.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Optimizing the self- healing behavior of hollow glass fibers reinforced epoxy matrix composite
182
190
FA
Hanieh
Eftekhari
Faculty of Materials Science and Engineering, K. N. Toosi University of Technology, Tehran, Iran
Reza
Eslami-Farsani
Seyed Mohammad Reza
Khalili
Faculty of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
Hossein
Ebrahimnezhad-Khaljiri
Faculty of Materials Science and Engineering, K. N. Toosi University of Technology, Tehran, Iran
In this research work, the self-healing behavior of epoxy matrix composite which reinforced by hollow glass fibers as self-healing container was investigated. For doing this, in first step, the hollow glass fibers were filled with the epoxy resin and hardener by creating a partial vacuum. Then, the filled hollow glass fibers with different percent of 1, 3 and 5 vol.% were embedded in the epoxy matrix. In the next step, by applying press, the destruction was created in these composites. Then, these destructed composites were healed at ambient temperature at different times of 2, 4, 7 and 14 days. Then, for accessing to the optimum healing time and percentage of hollow fibers in composite, the flexural test was applied in these composites. In the final step, the mechanical properties of composite with the optimum healing time and percentage of reinforcement were evaluated via tensile, flexural and impact exams. The obtained results show that the optimum percentage of hollow fibers and time for healing process are 3 vol.% and 7 days. Also, the healing efficiency of composite in optimum conditions (3 vol.% hollow fibers and 7 days healing time) at tensile, flexural and impact exams were approximately 77, 54 and 92 % respectively.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Dynamic Modeling and Optimal Adaptive Robust Control of an Omni Directional Mobile Robot Using Harmony Search Algorithm
191
200
FA
mahmood
mazare
school of mechanical engineering. shahid beheshti university
pegah
ghanbari
student
m.ghasem
kazemi
student
Mohammad Rasool
Najafi
Faculty member, University of Qom
In this paper, an optimal adaptive sliding mode controller of an Omni-Directional Mobile Robot (ODMR) is proposed using harmony search algorithm. First, kinematic model of the robot is derived and then, governing equations of dynamic model have been obtained using linear and angular momentum equilibrium. Since the derived model is not an exact definition of the system, it includes some uncertainties. To compensate them, a tracking control method has been offered. The proposed controller consists of an approximately known inverse dynamic model output as the model-based part of the controller, an estimated uncertainty term to compensate for the un-modeled dynamics, external disturbances, and time-varying parameters to enhance closed-loop stability and account for the estimation error of the uncertainties. In order to compare the results of the proposed controller, an optimal feedback linearization and sliding mode controllers are designed and then, a cost function has been defined by combining the variation rate of control signal and the integral error index. This cost function has been minimized using harmony search algorithm, resulting in optimum control parameters. Finally, the performance of the designed controller in different conditions, such as in presence of disturbance and system parameter variation has been simulated and discussed.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Modeling and optimizing lapping process of 440C steel by Neural Network and Multi-objective particle swarm optimization algorithm
201
212
FA
Mohammad
Shafiei Alavijeh
Department of Mechanical Engineering, University of Birjand, Birjand, Iran
Hossein
Amirabadi
The most essential problem in lapping process is low material removal rate which leads to increase in production costs and time. Thus, in this process, it's essential to select a condition that besides producing pieces with required flatness and roughness, has a high material removal rate. In this research, effects of parameters such as abrasive particle size, abrasive particles concentration in slurry, and lapping pressure on material removal rate, flatness and surface roughness were studied by experimental method in single sided lapping of flat workpieces made of 440c steel. In the following, effect of aforementioned parameters on material removal rate, flatness and surface roughness of lapped surface has been modeled using artificial neural network. Finally, by exerting multi-objective particle swarm optimization, simultaneous optimization of material removal rate, surface roughness and flatness of lapping pieces has been conducted and related Pareto front has been obtained. Obtained results show that by using Multi-objective particle swarm optimization algorithm we can produce workpieces with required surface roughness and flatness with high material removal rate. Consequently, by using this method moreover producing workpieces with desired quality, production cost and time would decrease.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Experimental, numerical and theoretical analysis of energy absorption process by aluminum profile with H-shaped thin-walled cross section
213
223
FA
Abbas
Niknejad
Mechanical Engineering Department, Yasouj University
Mojtaba
Firouzi
Mohammad Rahim
Hematiyan
Sima
Ziaee
This article investigates energy absorption capacity and plastic deformation trend of lateral flattening of an aluminum profile with H-shaped cross section under the quasi-static lateral loading by experimental, numerical and theoretical methods. Samples were prepared with different lengths and three different filling conditions including empty, core-filled and perfectly-filled by polyurethane foam. In addition, samples with the same geometry and filling conditions were laterally compressed with loading angles of 0 and 90 degree. Effect of some parameters such as length, three different filling conditions and loading angle were experimentally investigated on lateral force and specific absorbed energy (SAE). The results show that SAE is independent of samples length. At the loading angle of 90 degree, presence of the filler causes increment of SAE by the structure. Using the perfectly-filled profile under the loading angle of 90 degree is the most optimum condition. Based on two different energy absorption mechanisms, a theoretical equation was derived to estimate total absorbed energy (TAE) by empty sample with loading angle of zero; and predicted results were compared with the experimental samples. Due to present limitations in preparing the samples with different geometrical dimensions, nonlinear ABAQUS software was employed. Some samples with different wall thicknesses were modeled and influence of thickness was investigated on TAE. TAE is directly correlated to the second power of wall thickness; and this relationship can be clearly understood from the theoretical equation and numerical results. High correlation of experimental, numerical and theoretical results indicates precision and accuracy of the performed research.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Friction surfacing of AA7075-T6 deposition on AA2024-T351; Statistical modeling using response surface methodology
224
230
FA
Amir
Mostafapour
Associate Professor, Faculty of Mechanical Engineering University of Tabriz, Iran
Hamed
Kamali
Graduate MSC Student, University of Maragheh, Iran
Mahmoud
Moradi
Malayer University
In this research, deposition of AA7075-T6 coatings on AA2024-T351 substrates was studied. In order to investigate the influence of process parameters on the mechanical properties and microstructure, the experiments were performed based on design of experiments using Response Surface Methodology (RSM). Rotational speed (1200-1600 rpm), axial force (320-640 Kg) and feed rate (100-300 mm/min) were considered as input parameters, while coating width (w), coating thickness (t) and hardness of coating (HC), were raised as process outputs. The results reveal that joining of these two materials was done without any porosity at the interface. Hardness of coating showed a 30% decrease compared to the consumable rod in average. Thickness of deposition is decreased by increasing rotational speed, feed rate and axial force. If axial force is excessively increased, it results in development of an arc toward the plate along deposition. Microstructure of deposition turned into a totally fine-grained homogeneous structure in comparison with rod and plate microstructure.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Experimental study on corrosion detection of prestressed pipe using Acoustic Emission method
231
240
FA
reza
goldaran
instructor
mohammadali
lotfollahi-yaghin
professor at civil engineering faculty of tabriz university
Mohammadhossein
Aminfar
Associate Professor- Department of Civil Engineering- Tabriz University- Iran
Ahmet
Turer
Professor- Civil Engineering Department- ME Technical University- Ankara- Turkey
Corrosion in spiral steel prestressed wires tensioned around core are one of the major weaknesses of prestressed concrete pipes which their untimely detection can cause sudden failure and damages. To date, these kinds of pipes are used and produced in Iran and their abrupt failure due to corrosion has been experienced. In this study acoustic emission monitoring in prestressed concrete was used to investigate the corrosion. An approximately full-scale experimental sample pipe is made in Middle East Technical University laboratory. The pipe is loaded by internal water pressure and accelerated corrosion applied to the sample and the resulted acoustic emission signals are recorded using piezoelectric sensors during corrosion. The sample is tested under wetting and drying cycles frequently for corrosion detection in which during the experiment, pipe inside pressure was fluctuated and Kaiser Effect was studied in different conditions. Experimental results show significant changes in some gained acoustic emission parameters as the pipe work pressure increases to higher amounts. It is shown that the changed AE parameters can be used for damage prediction, condition assessment and corrosion detection of prestressed concrete pipelines.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Extraction of optimum design process for satellite solar panel based on reliability and solutions to improve it
241
251
FA
Mahrad
Damircheli
Sara
Mirshekari
mahdi
fakoor
University of Tehran
The purpose of this research is design of solar panels for a satellite which put in to geostationary orbit considering siutable reliability. The process of solar panel design is conducted according to the Design Structure Matrix (DSM) method. In this regard, an initial plan, a subsequent design process improvement, and a final optimized design process are provided. The first level of designed mechanism product tree includes released mechanism, development mechanism, lock and rotation components. Given the importance of ensuring the proper operation of mechanisms in space and reported mission failures due to lack of mechanism’s operation, the reliability network of designed mechanism is constructed and the reliability of designed panel is calculated. The amount of achieved relaiability is then verified according to the mission and system engineering requirements. Nessecary changes are applied on initial design to achieve into the satisfactory reliability for whole solar mechanism. In this regard, the critical paths in reliability network which lead to reduced reliability are investigated, and improvement of the critical path are proposed, to the extend of increasing reliability by discarding redundant components for critical parts.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Design, fabricate and testing the novel Magnetorheologic damper involving stabilizer nanoparticles of silicone
252
258
FA
Hamed
Adibi
Ebrahim
Yarali
AmirHossein
RamezanShams
The aim of this study, design and fabrication a prototype of double-tube magnetorheological damper (MR damper) involving micron sized and soft ferro magnetic of carbonyl iron (CI) particles and stabilizer nanoparticles of silicone (SiO2). Whiles initially magnetorheological fluid as its application and required, designed and fabricated. Then sedimentation and magnetorheometry tests (in mode of shear) was done. That the resulting of sedimentation test, illustrated that after 10 days, the value of sedimentation just was 15% and maximum of shear stress in maximum current was about 20kpa, that was desired. Then the magnetic section of the research, was conducted using the existing relationships and Maxwell software, at the end, using this data, the geometric dimensions of the MR damper, designed and fabricated. appropriate damper, was double tube type damper and at the combination of two valve and shear modes. After fabrication of appropriate damper, damping test was carried out on appropriate damper by damping test machine, that with regard to the receive graphs from test, at currents of 0 ,1 and 2 amps and speed of 0.05m/s, the magnitude of damping force aspect zero current(conventional damper), at saturate magnetic intensity (H_mr) was 5 times conventional damper. That was desired.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Task Control of Minimally Invasive Surgery with Remote Center of Motion Constraint
259
266
FA
fatemeh
zokaei
department of biomedical engineering, faculty of engineering, university of Isfahan, Isfahan, Iran
hamid
sadeghian
shahram
hadianjazi
This paper presents a novel formulation for controlling the task space of the robot with the Remote Center of Motion (RCM) constraint in Minimally Invasive Surgery (MIS). In MIS it is usually required to prevent any lateral motion at the point at which the robot enters the body, called the incision point or the trocar. Therefore, the surgical tool is only allowed to penetrate inside the body or rotate around its axis to avoid more injuries to the patient’s body. The proposed control law considers the RCM constraint at the kinematic level and the convergence of the task space error and regulation of RCM constraint are satisfied, simultaneously. Moreover, the null space of the robot is also exploited effectively within the framework to perform two additional tasks which can limit the RCM movement and optimize the manipulability measure of the robot. A comparative study is finally performed between the proposed approach and a well-known approach used in the literature. To evaluate the efficiency of the approach, a planar robot with 5 degrees of freedom with the trocar constraint is simulated and the results is verified successfully.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Numerical comparison between the impact of a completely molten and a semi-molten hollow droplet on a surface
267
278
FA
Hadi
Safaei
Mohsen
Davazdah Emami
In this research, the impact of a completely molten hollow droplet and a semi-molten hollow droplet on a surface is simulated numerically. At first, the production process of hollow particles from the agglomerated particles is addressed analytically. By this model, one can predict the particle diameter, solid core diameter and shell thicknesses of produced particle. The results of this section show that hollow particle may hardly develop at small initial porosity values (p=0.2). Then, the collected data from analytical model is used as input data for numerical simulation. In the numerical model, the central solid core was assumed to be a fluid with high viscosity. Due to high impact velocity, volume and density changes of the trapped gas inside droplet are important. Therefore the compressible form of governing equations is used. The results show that the hydrodynamic and solidification behavior of a completely molten droplet and a semi-molten droplet during impact process are different. In the semi-molten state, the central solid core prevents the formation of a counter jet. For this reason, a hollow semi-molten droplet is solidified faster than a completely molten hollow droplet. The overall time of solidification in the completely molten state is 35 μs and the corresponding time for semi-molten state, is 12 μs. Moreover the splat of a semi-molten hollow droplet is more continues compared with a completely molten droplet
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Optimal design of a limit cycle walker under the push-off actuation
279
290
FA
mohammad javad
mohammadi
PHD, Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran
Mahyar
Naraghi
Associate Professor of Mechanical Engineering Department, Amirkabir University of Technology (Tehran Polytechnic)
ali
tehrani safa
MSC, Department of Mechanical Engineering, Amirkabir University of Technology
farzad
towhidkhah
Professor, Department of Medical Engineering, Amirkabir University of Technology
Passive limit cycle walking is a special type of walking happening on a flat and slight downhill surface, without any energy injection and control, and in a cyclic manner. Compensation of energy lost through every heel strike by gravity effect, creates the cyclic behavior for the walking. The main advantage of this type of walking is getting higher efficiency, leading researchers to extend their studies in order to make passive dynamic based walkers. These bipeds can walk on level ground surface by little energy injection, instead of the gravity effect. This fact describes the standpoint of this article. In this research, with impulsive push-off actuation in hand and developing the related models, the walking of an actuated planar parametric model on level ground surface is simulated. Also the stability (with respect to the area of basin of attraction) and gait length has been analyzed by changing design parameters such as actuator’s location and foot shape. The results of this investigation indicates increase in relative stability and gait length for larger foot’s radius and of symmetrical shape.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Uncertainty quantification of electroosmotic flow in a microchannel
291
300
FA
Reza
Nouri
Master's student/ mechanical engineering student- university of Tehran
Mehrdad
Raisee
Uncertainty at experimental results usually adds to experimental data in the form of error bound. Since uncertainties at input parameters play an important part at the discrepancy between numerical and experimental results, considering uncertain parameters in comparison of numerical and experimental results would be logical. Electroosmotic flow is one of the cases which uncertainty quantification on its numerical simulation is necessary because of the presence of uncertain parameters. In this study, uncertainty quantification of electroosmotic flow in the micro T-channel has been presented. Numerical method was first validated by comparison between numerical simulation results of electroosmotic flow with certain inputs and experimental data. At the first step of uncertainty quantification, sample generation of the uncertain parameters has been performed by Latin hypercube method. At the next step, governing equation of electroosmotic flow has been solved by finite element method for every sample. Mass flow rate and velocity field have been selected as objective functions and adjoint method was employed for calculating the derivatives of them. At the final stage uncertainty quantification has been performed by enhanced Monte Carlo method. Results of the adjoint method show geometry parameters and fluid viscosity as the most effective factors on the results. While temperature and density of fluid demonstrate the least effect on the objective functions. Results of the Monte Carlo method illustrate 22.4% uncertainty for the results of mass flow rate and 12.6% on average for the results of velocities.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Numerical simulation of the effect of the geometry and boundary conditions on Supersonic flow in 2D MHD channel .
301
312
FA
Mohammad
Pourjafargholi
GhanbarAli
Sheikhzadeh
Reza
Maddahian
In the present work, numerical simulation of steady, compressible and supersonic airflow in a magneto-hydrodynamic (MHD) generator has been studied. This flow considered to be ideal with low magnetic Reynolds number. A two-dimensional channel with four-pair electrodes and with various geometries and boundary conditions were utilized as a MHD Faraday generator model. The computational model consists of the Navier-Stokes equations coupled with electromagnetic source terms, Maxwell's equations and Ohm's law. Implicit based on density solver is used to solve the Navier-Stokes and the electric potential method is used to solve the Poisson's equation. First, the boundary conditions of constant temperature and constant heat flux were compared. Due to the less Joule heating and generation of higher electrical power, constant heat flux boundary condition was selected to continue working.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Failure Mode Characterization and Dominant Mode Determination in Progressive Damage Due to High Velocity Impact on Woven Composite Laminates
313
322
FA
Mohammad
Mir
Hadi
Sabouri
Department of Mechanical Engineering
Engineering Faculty
Kharazmi University
Tehran
Iran
In this research, the finite element method have been utilized for investigation the progressive damage in composite laminates. Governing equations on progressive damage in three dimensional stress and strain filed have been expressed based on Hashin's onset of damage and Matzenmiller's progression of failure. The damage equations were coded to make a material model in LS-Dyna. This model could simulate various damage modes such as fiber breakage due to tension or compression, failure due to in-plane shear, crushing and delamination. High velocity impact on woven composite laminates have been analyzed using this material model subroutine. Damage pattern, ballistic limit velocity and growth of damage parameter in different failure modes have been investigated. Also, the occurrence of multi-mode damage at an element and degradation the elastic modulus of the composite material and its softening were studied. In addition, the effect of impact on damage growth at near filed and far filed of the impact zone as well as complete or partial damage of the composite laminate have been investigated. Based on outcomes, number of plies of composite laminate and its thickness have important role on manner of results. Also, for a damaged element, change of failure mode by growth of the damage parameters was observed.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Simulation and experimental study of severe plastic deformation of 7075 Al alloy processed by repetitive upsetting-extrusion
323
332
FA
Behzad
Binesh
Department of Mechanical Engineering, University of Bonab, Bonab, Iran
Mehrdad
Aghaie-Khafri
Mohammad
Daneshi
Department of Aerospace Engineering, University of Tehran, Tehran, Iran
In this study, severe plastic deformation of 7075 aluminum alloy was investigated using a new method, based on the combination of conventional upsetting and direct extrusion. In this process, which is called repetitive upsetting-extrusion, cylindrical samples were first subjected to upsetting and were subsequently subjected to extrusion at 250 °C with various processing cycles. Die design was carried out considering the possibility of conducting both upsetting and extrusion by using a single die and the maximum of four RUE cycles were successfully performed on the samples. Finite element method was used to simulate the deformation behavior of 7075 alloy during repetitive upsetting-extrusion processing and the strain distribution was obtained for the deformed samples. The finite element simulation results correlated fairly well with the microstructural observations. Based on the simulation results, the maximum effective strain was observed at the central region of the samples. The deformation behavior and the flow pattern were discussed based on the experimental and the simulation results. In addition, the effect of applied strain on mechanical properties of processed samples was studied. Tensile strength and elongation of deformed samples increased with extending the number of repetitive upsetting-extrusion cycles.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Trajectory Tracking of a Quadrotor for Obstacle Avoidance Using Super-Twisting Sliding Mode Controller and Observer.
333
342
FA
Moein
Doakhan
AUT Department of Mechanical Engineering
Mansour
Kabganian
Professor, Mech Eng Dept, Amirkabir U
reza
nadafi
Institute of Space Science and Technology, Amirkabir University of Technology, Tehran, Iran
Ali
Kamali Eigoli
Assistant Professor of Amirkabir University of Technology
Sliding mode control is one of the most common types robust control that can compensate the model structure and parametric uncertainties, but the main disadvantage of this method is chattering phenomenon. Although a boundary layer around the sliding surface can eliminate chattering effect, it reduces tracking performance and robustness in control. The second generation of sliding mode control called Second Order Sliding Modes (SOSM) is a solution to this problem. Super-Twisting Sliding Mode (STSM) is a modified SOSM control that reduces chattering effect naturally and without a defined boundary layer, while maintaining the robustness of the Conventional Sliding Mode (CSM) control. In this paper, the problem trajectory planning is solved in an environment with fixed obstacles by using firefly optimization algorithm and polynomial trajectories, then STSM control is designed for quadrotor in the presence of uncertainties to tracking path trajectory and the performance of this controller is compared against Feedback Linearization (FL) and CSM control. Also, derivative of some of the states calculates by using super-twisting observer in the closed loop control and stabilization while there is no direct access to them through the sensors.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Fabrication of Al 2024-boron carbide surface nano composite by friction stir processing
343
350
FA
saeed
ahmadifard
Buali Sina University
Amir
Momeni
Materials Science and Engineering department, Hamedan University of Technology, Hamedan, Iran.
The purpose of this investigation was the fabrication of surface nano composite composed of aluminum 2024 and boron carbide particles with the average size of 60 nm by the friction stir processing (FSP) method. The primary FSP tests showed that the rotating speed of 850 rpm and traverse speed of 25 mm/min are the optimum conditions which results in sound defect free samples. Then, the effect of nano particles addition and number of passes were analyzed in the fabricated samples. Optical and field emission scanning electron microscopy techniques showed that the average grain size in the stirring zone decreases by adding nanoparticles to the matrix and increasing the number of FSP passes. The hardness and the abrasion tests showed that strength and wear resistance of the fabricated samples increases with increase in number of passes. The improvement in the mechanical properties was attributed to the uniform distribution of the reinforcing particle and grain refinement. However, in the FSPed base metal the hardness was decreased due to the dissolution of primary strengthening particles during the FSP process. The result of electrochemical tests indicated that corrosion behavior of the FSPed samples improves by adding the reinforcing particles and increasing the pass number.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
A finite element analysis for shape memory polymer Timoshenko beams
351
359
FA
Amir Hossein
Eskandari
Department of Mechanics, University of Tehran
Mostafa
Baghani
School of mechanical engineering, University of Tehran
Majid
Baniassadi
University of Tehran
In this paper, employing a thermomechanical constitutive model for shape memory polymers (SMP), a beam element made of SMPs is presented based on the kinematic assumptions of Timoshenko beam theory. Considering the low stiffness of SMPs, the necessity for developing a Timoshenko beam element becomes more prominent. This is due to the fact that relatively thicker beams are required in the design procedure of smart structures. Furthermore, in the design and optimization process of these structures which involves a large number of simulations, we cannot rely only on the time consuming 3D finite element (FE) analyses. In order to properly validate the developed formulations, the numeric results of the present work are compared with those of 3D finite element results of the same authors, previously available in the literature. The parametric study on the material parameters e.g., hard segment volume fraction, viscosity coefficient of different phases, and the external force applied on the structure (during the recovery stage) are conducted on the thermomechanical response of a short I-shape SMP beam. For instance, the maximum beam deflection error in one of the studied examples for the Euler-Bernoulli beam theory is 7.3%, while for the Timoshenko beam theory, is 1.5% with respect to the 3D FE solution. It is noted that for thicker or shorter beams, the error of the Euler-Bernoulli beam theory even more increases. The proposed beam element in this work, could be a fast and reliable tool for modeling 3D computationally expensive simulations.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
The evaluation of friction models to calculate the flow rate in pressure-time method
360
368
FA
SIMINDOKHT
SAEMI
School of Mechanical Engineering, College of Engineering
Mehrdad
Raisee
Faculty member, school of mechanical engineering, university of Tehran
Michel
Cervantes
faculty member of Division of Fluid and Experimental Mechanics, Department of Engineering Sciences and Mathematics
Luleå University of Technology
Ahmad
Nourbakhsh
The pressure-time method is a flow rate measurement technique generally employed in hydropower plants to evaluate the efficiency of hydraulic turbines. The 1D numerical simulation incorporating the finite volume method is employed to evaluate the method. The results are compared with the experimental data. The flow is simulated inside a straight pipe with Reynolds number Re=6.76×〖10〗^6. The flow rate reduction curve is employed for the simulation of the deceleration part of the flow, before valve closure, in the pressure-time method. The effective parameters on the flow rate calculation including the friction losses and the definition of the final time of the valve closure are studied in detail. The increase in the accuracy of the flow rate calculation is a function of the increase in the accuracy of the friction loss calculations. The effect of several friction factors proposed for the evaluation of the unsteady flow is studied on the accuracy of the flow rate calculation. The Pezzinga friction factor shows the least error in the flow rate calculation. The available methods to find out the final time of integration still show a large error. A new method is proposed for the flow rate estimation without any need to have the exact time of the valve closure with an acceptable accuracy.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Experimental investigation of effect of thermal cycling and metal surface treatment on flexural properties laminate composite of aluminium- epoxy/basalt fibers
369
376
FA
Mehdi
Abdollahi Azghan
Reza
Eslami-Farsani
In this work, effect of thermal cycling on the flexural properties of fiber-metal laminate (FML) has been evaluated. FML plates were composed by two aluminium 2024-T3 and a epoxy polymer-matrix composites ply formed by four layers of basalt fibers. For FML samples the thermal cycle times were about 6 min for temperature cycles from 25 °C to 115 °C. Flexural properties were evaluated on samples after 20, 35 and 55 thermal cycles, and compared to non-exposed samples. While the thermal cycling decreased the flexural strength of chemical treated FML (etched aluminium), increasing at first, and then decreasing after a while was observed in electrochemical treated FML (anodized aluminium). The flexural modulus of FML showed irregularly changes for both of FML with anodized aluminium and FML with etched aluminium. The energy absorption of FML with etched aluminium showed a sharp decline with increasing thermal cycling while the energy absorption of FML with anodized aluminium showed a Low and irregular changes. Evaluation optical microscope showed that the mechanism of failure for the FML with etched aluminium after thermal cycling changed from failure of FML to separation between layers of FML, while for the FML with anodized aluminium before and after thermal cycling it was failure of FML and it has not changed.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Design and Parametric Study of Three Stream Plate-Fin Heat Exchangers with Rectangular Fins
377
387
FA
Amir
Farhang Sotoodeh
Mehrangiz
Ghazi
Department of Mechanical Engineering, Takestan Branch, Islamic Azad University, Takestan, Iran
Majid
Amidpour
Department of Energy System, Faculty of Mechanical Engineering, K. N. Toosi University of technology, Tehran, Iran
In contrast with two stream heat exchangers, the three stream ones owns much more complexity in design and rating and a comprehensive rating method has not been proposed, yet. In this paper, a new rating method is presented in order to be used in three stream plate – fin heat exchangers. Rating, in heat exchangers, means finding out the heat load of the heat exchanger or in the other words calculating the outlet temperature of each stream and furthermore, finding out the pressure drops of each stream. In this paper, the differential equations of energy conservation and heat balance of each steam is extracted and a set of differential equations in terms of outlet temperatures in constructed. The general solution of this set of equations is then extracted. In order to expand the general solution to plate – fin heat exchangers, the geometric, thermal and hydraulic modeling are applied based on fin geometric specification which used rectangular type in this paper without losing generality. Based on all of the extracted equation, a comprehensive algorithm of rating of the three stream plate – fin heat exchangers is presented. In order to evaluate the presented algorithm, a case study is used and the results will be shown. Furthermore. A parametric study is applied to the case study to evaluate the effects of the geometric parameters of the fins such as height and frequency on heat load and pressure drop of the heat exchanger.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Multilevel Modeling of an Unmanned Rotorcraft and Robust Controller Design for Trajectory Tracking
388
398
FA
Mohammad Hossein
Khalesi
Mechanical Engineering Department - Sharif University of Technology, Tehran, Iran
Hassan
Salarieh
Mechanical Engineering Department, Sharif University of Technology
Mahmoud
Saadat Foumani
Mechanical Engineering Department, Sharif University of Technology
According to numerous capabilities and increasingly military and commercial applications of radio controlled helicopters, many investigations are being performed on these unmanned aircraft vehicles. Due to nonlinear, complex, unstable and coupled dynamic system and also existing limitations on manual control, the ability of automatic control of these vehicles has gained great importance. In this paper, in addition to investigating different methods of unmanned helicopters dynamic modeling, a multi-level simulator environment has been designed and implemented for flight performance analysis and effects of different parameters have been investigated. The main importance and innovation of present simulator is in possibility of dynamic flight simulation of helicopter using different theories for applications like control system design, performance analysis and real flight simulation. The main difference of the utilized methods is in theories and assumptions applied in main rotor and its flapping dynamics modeling. For each level, Kalman filter and control system design have been performed and preliminary results show the acceptable performance of estimator and controller systems. Considering the complexity of real unmanned helicopter behavior compared to previously performed models, the proposed multi-level simulator can be used as an appropriate tool for the first step before real flight tests.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
The effect of carbon nanotubes on the life of drilled glass / epoxy composite under fatigue loading
399
405
FA
Ali
Gholizade
Naeim
Akbari Shah Khosravi
Reza
Mohammadi
Mehdi
Ahmadi Najafabadi
Hossein
Heidary
Nowadays fiber reinforcement composite are highly regarded, because of their proper mechanical properties and low weight. One of their main ways to assemble is drilling. Drilling causes to many failures such as: delamination, hole shrinkage, fibers pull-out and thermal failures. These failures reduce composite strength specially in fatigue loading. Using of carbon Nano tubes improve mechanical properties such as: hardness, strength, young module and stiffness. This investigation focuses on effect of added carbon Nano tubes Wt% on lifetime of glass/epoxy laminated composites under tensile - tensile fatigue loading. To main this purpose specimens whit different carbon Nano tubes Wt% have been made. They have been drilled by same condition. Then these specimens were subjected to tensile - tensile fatigue loading. AE sensors and microscopic camera were used to validate results. The results indicate that carbon Nano tubes Wt% increase, increase specimens fatigue life.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Investigation of failure mechanisms of notched aluminum plates repaired with composite patches using acoustic emission method
406
412
FA
mir mohammad
mousavi nasab
Phd student of Mechanical engineering of Amirkabir University of Technology
hamid
fotouhi
M.Sc graduate of Malek Ashtar University
Reza
Mohammadi
PhD student Amirkabir University of Technology
Mehdi
Ahmadi Najafabadi
Hossein
Hosseini Toudeshky
Professor, Aerospace Faculty of Amirkabir University of Technology
Structures during their lifetime experience plenty of static and dynamic loads. These loads cause failure or undermine the structures. So, reinforcement or repairing failed parts is one way to repair out of service structures. Composite materials have been used to reinforce structures. These materials enjoy advantages such as the proportion of their strength to their weight. As these structures get exposed to some load a number of failures get introduced. This research investigates the failure mechanisms of a notched 2024-T3 aluminum plate repaired with a composite patch using visual and acoustic emission methods. After constructing the specimens, tensile test has been conducted, and acoustic emission sensors have been stocked on the surface of the plate, so that they can record acoustic data. At the first stage, mechanical data obtained from the specimens in different states based on the number of layering have been analyzed. At the second stage, acoustic data, obtained from recording of acoustic emission signals, have been compared with the mechanical data. Also the images obtained from SEM were used to investigation of damages. According to this research, it is identified that a reasonable correspondence between the results obtained from mechanical and acoustic data and the desired functionality of the acoustic emission method in determining failure mechanism in those specimens that are repaired with composite patches.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Modeling, development, and evaluation of a micro-robot equipped with vibratory actuator
413
422
FA
Marziyeh
Karami
Department of Mechanical and Aerospace Engineering
AliReza
Tavakolpour-Saleh
Department of Mechanical and Aerospace Engineering, Shiraz University of Technology
Ashkan
Norouzi
Department of Mechanical and Aerospace Engineering, Shiraz University of Technology
The aims of this research paper are modeling, control and development of a mobile micro-robot equipped with vibratory actuators and investigating the effect of stiffness of microrobot's bases as well as friction coefficient on the robot dynamics. Accordingly, the motion principle of stick-slip is used and two small vibrating motors are utilized to run this micro-robot. First, the differential equations governing the micro-robotic platform are extracted and analyzed. Then, friction forces are calculated by modeling the micro-robot as a lumped system, consisting of three point masses connected together via stiff springs. Next, using mechanical and electrical coupled equations, an appropriate model for the vibratory actuators is obtained. In the next step, simulation process with SIMULINK and MATLAB is carried out and the simulation results are presented. Afterward, the influences of the stiffness of robot's bases as well as the friction coefficient on the motion of robot are investigated. A proportional-integral-derivative (PID) controller is applied to the micro-robot to precisely control its motion. Finally, the construction process and experimental evaluation of the micro-robot are presented. According to the simulation result, the positioning accuracy of the micro robot is about 17 m at its maximum translational velocity. Furthermore, a translational velocity of about 4mm/s corresponding to the reference voltage of 1 V is acquired using experiment.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Thermodynamic analysis of a new hybrid-ejector heat pump and comparison with the hybrid heat pump
423
432
FA
Saeed
Khalili Sarbangoli
Department of mechanical engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran
Leili
Garousi Farshi
Department of mechanical engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran
In this article the effect of using ejector on the thermodynamic performance of the hybrid heat pump is evaluated. With simulation of the new hybrid-ejector heat pump in the EES software, first the effect of the ejector mixing section diameter on the results is analyzed and it is concluded that a diameter of about 15mm makes the primary energy ratio (PER, the ratio of useful thermal energy output to the total initial heat energy input) and second law efficiency of the heat pump to be maximum and the exit temperature of the compressor to be minimum. Next, PER, second law efficiency and the compressor exit temperature of new heat pump are compared with those of the conventional hybrid heat pump at the same amount and temperature of the input heat. The results showed that the PER and second law efficiency of the new layout is maximum 10 percent and about 18 percent higher than those of the hybrid cycle respectively. It is also observed that with considering the restriction in compressor exit temperature, in new system, it is possible to increase the temperature of input heat 35C more compared to the increase that can be occurred in the hybrid system. Finally, the analysis of the relative exergy losses in the components of the systems revealed that in the new layout, the relative exergy losses of throttling valve, desorber, compressor and absorber were reduced and improved the performance of this cycle.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Investigation the effect of humidification inlet gases on the dynamic response of a PEM fuel cell stack
433
443
FA
Sharif
Gharib
Railway of Iran
Hassan
Hassanzadeh
Member of univesity of Birjand
To get the real answer a PEM fuel cell system to load changing, dynamic modeling is necessary because static modeling independent of time and it shows the system performance in just one or a few points. In this study, the dynamic performance of a PEM fuel cell stack is modeled in the Matlab Simulink and is validated by the data available in the literature. Modeling is done in two parts; in the first part, the input gases to the fuel cell stack are dray and the second part, the gases entering to the stack are humidification. In order to investigate dynamic response of system to rapid changes in electrical current, the variable electrical current is entered into the system step by step then the effect of this change on output voltage, consumption of reactants, temperature and pressure are obtained. Analyzing results of first part indicates that the time delay of system response to electrical current changes. With increasing the electrical current, the temperature of cell body, consumption of reactants and amount of input gases into the anode and the cathode channels are increased. The temperature of anode and cathode channels and fuel cell body are different and with increasing the stack power are more differences. Analyzing the results of second part indicates that with increasing the relative humidity of input gases the ohmic loss and so on the body temperature of fuel cell is decreased.
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
17
8
2017
10
1
Introducing a new thermal comfort model for evaluation of local and overall thermal sensation in non-uniform environments
444
450
FA
negin
moallemi khiavi
department of mechanical engineering/tarbiat modares university of tehran
Mehdi
Maerefat
Prof. Mechanical Eng.
Trabiat Modares Uiversity
Alireza
Zolfaghari
mechanical engineering faculty/university of birjand
The standard and conventional thermal comfort models such as Gagge and Fangar models are only applicable in uniform thermal environments and predict the overall thermal sensation based on mean environmental and individual parameters and are not capable of evaluation of local thermal sensations of different body parts. But Under non-uniform conditions, the human body’s segments may experience a wide range of physical parameters such as air temperature, radiation temperature and air velocity. So the response of the people to non-uniform conditions depends on local thermal sensation not on overall thermal sensation. Nowadays, thermal comfort in non-uniform environments may be predicted using experiments in the climate chambers or in automobiles and the proposed models are based on the regression analysis of the experimental data from different subjects in special conditions. So the propose of this work is proposing a model for evaluation of local thermal sensation of different body segments and overall thermal sensation in non-uniform environments. In the new model, temperature and physiological mechanisms of different body parts are obtained by 16-segment Tanabe model and then the local and overall thermal sensations are evaluated by the University of Berkeley model. The comparison of obtained results by new model with available experimental data shows good agreement between them.