IFC
text
article
2016
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
0
0
http://mme.modares.ac.ir/article_15402_593e332a85fca0c94d4222c0dff4399e.pdf
The SDRE controller and estimator design for flexible joint manipulators in presence of noise and disturbance
Moharam
Habibnejad Korayem
Prof. of Mechanical Eng. of Iran University of Science and Technology
author
Saeed
Rafee Nako
دانشکده مهندسی مکانیک، دانشگاه علم و صنعت ایران، تهران
author
Naim
Yousefi Lademakhi
دانشکده مهندسی مکانیک، دانشگاه علم و صنعت ایران، تهران
author
text
article
2016
per
Full feedback data is mostly essential in control design. The measurement of the variation of flexible joint robot (FJR) actuators is not easy as the measurement of the changes of FJR links’ angles. The measurement of the states is also affected by noise, and the disturbance in the workspace of the robot is not ignorable. Hence a state observer or a nonlinear estimator is necessary to improve the performance of the dynamic system. The statedependent Riccati equation (SDRE) is one of the most promising nonlinear optimal control methods for estimating variables of systems. Systematic procedure, simple structure, and incorporating wide range of systems (under observability condition) are some advantages of SDRE method. The majority of nonlinear techniques linearize the model, but the SDRE directly uses the nonlinear state space; it is one of the reasons for its precision and flexibility in design with respect to other methods. The goal of this work is to merge the SDRE controller and estimator simultaneously to reduce the state error of the system in presence of external disturbance and measurement noise. So, first, the controller and the observer formulation has been stated. Then, the procedure has been applied to design and to simulate a 3 DOF robot arm with flexible joints. Next, the process has been tested experimentally using Scout robot and the simulation results have been verified. Finally, the proposed method of this paper has been compared with the optimal sliding mode.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
1
12
http://mme.modares.ac.ir/article_15060_7c221eb0729b0c4c217924ee159d9e5b.pdf
Investigation of cross sectional geometry on temperature and properties of welded area in the rotational friction welding process for AL7075T6
Mehdi
Zohoor
University Faculty Member
KNT University of Technology
author
Seyed Masoud
Seyed Amirkhani
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2016
per
In this paper, the effect of different workpiece geometries on the properties of welded Al7075T6 parts in rotational friction welding process has been investigated by using experimental and finite element approaches. Welding process is continuous drive friction welding. In this research, the samples diameter were selected equal to 25 mm and the samples length were selected equal to 75 mm. The process variables such as friction time (t1), forging time (t2), friction pressure (P1) and forging pressure (P2) where assumed to be constant, whereas, rotational speeds were variable and selected equal to 2000 rpm and 2500 rpm. Three cylindrical parts with different cross sectional geometries were adopted as three samples. Finally, to verify the accuracy of numerical analysis, the experimental and thermomechanical simulation results were compared and found a good agreement between them. Since, an experimental test is a time consuming and a costly process activity, it was decided to get more results by using an alternative method such as finite element simulation technique. Results of this study showed that changing in front geometric of workpiece is an effective factor for tensile strength, length of workpiece and generated flash in welded area and by changing this factor, properties of welded area can be improved.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
13
20
http://mme.modares.ac.ir/article_15035_b81ca3cc7f70a0aa401b8854e7c27ac3.pdf
Fuzzy control of an artificial finger robot using shape memory alloy actuators
Mohammad Mahdi
Kheirikhah
عضو هیات علمی دانشگاه آزاد اسلامی قزوین
author
Alireza
Khodayari
استادیار گروه مهندسی مکانیک، دانشگاه آزاد اسلامی، واحد پردیس
author
Maryam
Tatlari
فارغ التحصیل دانشگاه آزاد قزوین
author
text
article
2016
per
Shape Memory Alloy (SMA) wires are currently employed in robotics as actuators of prosthetic limbs and medical equipment due to advantages such as reducing the size in the application, high powertoweight ratio and elimination of complex transmission systems. In this paper, a fuzzy control system has been designed and implemented for an artificial finger using the SMA actuators. This robotic finger has been designed and modeled with three revolute joints and three SMA wires as the tendon in order to adduction each phalange of the finger and torsional springs to restore them to their original positions. The dynamic model of the finger has been simulated in MATLAB/Simulation. Based on the simulation results, optimal choice of parameters and system features has been obtained and a prototype of finger has been built and tested. Gains of the controllers are set so that the current applied to SMA wires has minimum overshoot and the output of the system has minimal time to achieve stability. The comparison between the simulation results and the actual measured data show that the simulated model is accurate.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
21
28
http://mme.modares.ac.ir/article_15059_fbd8cc74f588b89a12aeab689da9e16d.pdf
Moving obstacle detection algorithm using cell decomposition method
Behrooz
Mashhadi
عضو هیئت علمی دانشگاه علم و صنعت
author
Mohammad Amin
Vesal
دانشگاه علم و صنعت
author
text
article
2016
per
In this paper, the algorithm to detect obstacles surrounding an autonomous vehicle and the method to navigate this vehicle on the road are studied. For this purpose, the road is divided into cells in lateral and longitudinal directions. The assumption is that some special tools specify the cells positions and then full and emptycell corresponding matrix is generated. In this matrix, full cells are displayed with digit 1 and empty cells are displayed with digit 0. In the next step, by analyzing the matrix in Matlab, the vehicle is navigated. In this analysis, firstly the position of the vehicle and the obstacles are identified. Then, based on the road conditions and the obstacles positions, required orders to move the vehicle are determined. If a lane change is needed, according to the road’s curvature and the distance between the vehicle and the obstacle, appropriate path for the vehicle will be chosen. In this paper, for the first time in autonomous vehicle navigations, the road is considered as a 1 and 0 matrix. In this method, the road matrix gets updated with time and provides the possibility of analyzing the vehicle’s movement. Also, the algorithm used to solve the problem is very simple.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
29
36
http://mme.modares.ac.ir/article_15061_c0ea42499c6f8573fa405790b26874dc.pdf
Robust Position Control of Piezoelectric Actuator Using Self sensing Actuation
Mohsen
Asghari
فارغ التحصیل
author
Seyed Mehdi
Rezaei
عضو هیت علمی دانشگاه امیرکبیر
author
Mohammad
Zareinejad
دانشگاه صنعتی امیرکبیر
author
text
article
2016
per
Piezoelectric actuators (PA) are widely used in electromechanical system thank to interesting properties such as: high resolution, fast response, wide bandwidth, mechanical simplicity, high stiffness. Despite these unique desirable properties, they suffer from nonlinear behaviors which adversely affect the positioning accuracy. Among them, hysteresis between applied voltage , actuator position is the most important nonlinearity which can lead to significant error if not compensated. In this study, a sliding mode controller associated with an unknown input observer, which uses the position feedback provided by a selfsensing circuit, is suggested to use in micro positioning applications. The selfsensing technique is based on the linear relation between position , charge, which is measured by an active charge measurement circuit. The advantages of proposed scheme could be summarized as follows. It is a sensorless method which does not need an external position sensor. It does not need any operators to model hysteresis or its inverse. It has improved performance in comparison to traditional controllers like proportional integral (PI) controller. Obtained experimental results demonstrate the effectiveness of proposed method to use in micropositioning applications.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
37
46
http://mme.modares.ac.ir/article_15062_00173793bf13b66867dff657c9ed0ba3.pdf
Nonlinear simulation of viscoelastic fingering instability
Mohammad Hassan
Kayhani
دانشکده مهندسی مکانیک دانشگاه صنعتی شاهرود
author
Hosna
Shokri
دانشکده مهندسی مکانیک دانشگاه صنعتی شاهرود
author
Mahmood
Norouzi
Shahrood University of Technology
author
text
article
2016
per
In this study, the viscous fingering instability in miscible displacement of Newtonian fluid by Viscoelastic fluid is investigated. The Criminale–Eriksen–Filbey (CEF) model has been used as the constitutive equation. Simplicity and dependence of rheological functions to shear rate are the advantages of this model. Also, the CarreauYasuda model was used to show this dependency. In nonlinear simulation, using spectral method based on Hartly transforms, the effect of rheological functions of displacing viscoelastic fluid on this instability has been studied. The results are included concentration contours, transversely averaged concentration profiles, mixing length and sweep efficiency. The results show that, by changing the parameters in order to increases of viscosity of displacing viscoelastic fluid, flow becomes more stable. In other word, sweep efficiency is increased and mixing length is decreased. Also, at first, the sweep efficiency increases with changing the parameters in order to increase the first normal stress difference in this type of fluid and then decreases with evolution of fingering. However, this factor will have little effect on mixing length. In addition, as well as viscous fingering, several nonlinear finger interactions such as Spreading, coalescence and tip splitting were observed in simulation of viscoelastic fingering instability.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
47
54
http://mme.modares.ac.ir/article_15063_501c793775e70272fee54526bd7d32b2.pdf
New sampling method of freeform surfaces on coordinate measuring machine equipped with contact probe
Javad
Zahmati
student/university of birjand
author
Hossein
Amirabadi
دانشیار گروه مکانیک دانشگاه بیرجند
author
text
article
2016
per
Freeform surfaces are widely used in engineering applications. These surfaces are complex and without rotational symmetry, and for this reason they are inspected using the coordinate measuring machines equipped with contact sensor require a suitable sampling strategy. Sampling algorithms are one of the most important factors of error creation in the accuracy of substitute geometry. In coordinate measuring machines, the sampling strategy involves the estimation of the number of sample points (sample size) and identification of their positions (how distribution) on the surface. Thus sample points should be distributed on the surface using sampling strategies that are appropriate for the surface. Often it is difficult to establish such pieces of information (number and the way of distributing the points on the surface) owing to the complex nature of freeform surfaces. In the present work for first time, new adaptive sampling strategy by particle swarm optimization algorithm (PSO) for sampling from freeform surface is proposed. The proposed strategy was compared with two conventional strategies and the deviation between substitute geometry and CAD model is extracted. The simulation results showed that in the proposed method the deviation between substitute geometry and CAD model is less than conventional methods by 2 to 3 times (depending on the number of points). Therefore high efficiency of the proposed method over other methods is concluded.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
55
64
http://mme.modares.ac.ir/article_15064_b1e31f3df4dba277629ce580c9d0492a.pdf
Modeling of the effects of progressive anisotropic damage on the elastoplastic behavior of metal matrix composites
Hosein
Mohammad Roknabadi
دانشجوی کارشناسی ارشد، دانشکده مهندسی مکانیک و انرژی، دانشگاه شهید بهشتی، تهران
author
Mohammad Javad
Mahmoodi
دانشگاه شهید بهشتی، پردیس فنی مهندسی شهید عباسپور، دانشکده مهندسی مکانیک و انرژی
author
text
article
2016
per
The aim of this paper is investigation of progressive damage in a metal matrix composite lamina using coupling of micromechanical method and continuum damage mechanics viewpoint. The micromechanical method is a representative volume element based method known simplified unit cell method which possesses the capability of investigating of progressive damage and plastic behavior in the representative volume elements. The studied damage is isotropic and anisotropic based on continuum damage mechanics viewpoint. Under investigation composite system is Carbon/Aluminum composite. The matrix behavior is considered as isotropic and elastoplastic and the fiber behavior is transversely isotropic and elastic. The fiber arrangement within the matrix is regular. The matrix elastoplastic behavior model is included as bilinear behavior and solution method is successive approximation method. According to available previous studies, Siliconcarbide/Titinium composite system is noticed for validation and comparison with experimental data. Also the effect of fiber volume fraction on the damage progression routine is studied. The results show that by increasing the longitudinal and transverse loadings, the damage variable grows in the fiber direction and perpendicular to the fiber direction and the axial and transverse Young's modulus decrease subsequently. Also the results prove that in longitudinal loading, considering anisotropic damage, damage progression in the fiber direction is more than its growth in perpendicular to the fiber direction. Whereas, under transverse loading, damage growth in perpendicular to the fiber direction is faster.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
65
74
http://mme.modares.ac.ir/article_15065_d5cc2d72656328368bbe159579786674.pdf
Numerical investigation of natural convection effects on the melting and solidification of PCM within a rectangular finned container using LBM
Faramarz
Talati
مدیر گروه سیالات دانشکده مهندسی مکانیک دانشگاه تبریز
author
Mohammad
Taghilou
دانشجوی دکتری/ دانشگاه تبریز
author
text
article
2016
per
The use of phasechange material to enhance the capacity of energy storage/release is the subject of many new researches on management of the energy supply. Study of these systems is directly related to the solidliquid phasechange problem, in which the evaluation of temperature distribution, position of phasechange front and liquid or solid fraction becomes a basic problem. Study of freezing and melting process with regard to natural convection in the liquid phase is the main purpose of the present paper. For this purpose, a rectangular finned container of phasechange material is intended. Fins are used to enhance the heat transfer rate. This fact necessitates the use of immersed boundary condition on the solid phase. Hence, the melting process considering the both effects of natural convection and movement of solid phase is studied. The freezing process is also studied taking into accounts the natural convection with no need to impose the immersed boundary condition. Lattice Boltzmann method is used as a numerical method and results are reported based on the dimensionless parameters. Based on the results, the effects of natural convection is negligible during freezing process, while imposing the effects of natural convection provides a significant change in the required time for complete melting of the phase change material.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
75
86
http://mme.modares.ac.ir/article_15067_bd35d8b61131b0fd77b69f022b926c38.pdf
Vibration reduction of flexible solar panel in wheeled mobile robots based on robot trajectory planning
Morteza
Hafezipour
دانشگاه صنعتی خواجه نصیر الدین طوسی
author
Ali Asghar
Jafari
میدان ونک  خیابان ملاصدرا  خیابان پردیس  دانشگاه خواجه نصیر الدین طوسی
author
Seyed Ali Akbar
Moosavian
دانشگاه صنعتی خواجه نصیر الدین طوسی
author
text
article
2016
per
A solarpowered robot is a mobile robot powered completely or significantly by direct solar energy. The sun's energy is converted into electric energy by solar panels mounted on the robot. These solar panels are required to be light, because of the important demands for lowenergy consumption. As a result of the flexibility of elements of the panels, undesirable lowfrequency vibration may occur when the robot moves on a rough terrain. In this paper, a new method for stabilization of solar panels vibration base on trajectory planning for articulated mobile robot is presented. The dynamics of solar panels attached to the robot is derived using Kane’s method. The attitude and configuration of a rover as a function of the terrain on which it moves is determined using inverse kinematics of the robot. The attitude and configuration of a rover is required to approximate the domain of vibration by derived dynamics equations. Base on this approximation, a trajectory planning algorithm is presented that can reduce vibration without significant decrease in the velocity of the robot. The proposed method is simulated for a sixwheeled mobile robot with rockerbogie structure The obtained results show that the algorithm stable the domain of vibration in allowable area and do not decrease the velocity of the robot significantly.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
87
98
http://mme.modares.ac.ir/article_15068_56f3889030bcd3435a8e6a8d0df6a8dd.pdf
The assessment of Elastic Followup effects on strain accumulation due to creep and plasticity
Mahmoud
Shariati
Professor at Ferdowsi University of Mashhad
author
Hamid
Zabihi Ferezqi
دانشگاه فردوسی مشهد
author
Saeid
Hadidi Moud
دانشگاه بیرجند
author
text
article
2016
per
The Assessment of strain accumulation due to nonlinear events like creep, plasticity or ratcheting phenomenon has gained importance, since it causes an increase in creep and fatigue damage of materials. Some factors like the magnitude of loading, constitutive equations or the elastic regions around the nonlinear events have effect on the rate of strain accumulation. The elastic followup can explain the mechanism of strain accumulation. This phenomenon may occur when a mechanical structure with elastic manner is connected to nonlinear events and they are subjected to a displacement load. In these cases, the high rigidity portion of elastic region of mechanical structure may enhance the force to the regions with low rigidity. So in the local nonlinear portion, the strain is accumulated. This phenomenon is proposed as an important instruction in mechanical assessment codes. In this study, the effects of Elastic Followup phenomenon on strain accumulation due to elasticplastic and local creep are investigated. So the Elastic Followup parameter is defined by the methods which are described in high temperature assessment procedures (R5). The results revealed that the strain accumulation depends on the elastic region in structures which is described by the Elastic Followup phenomenon.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
99
108
http://mme.modares.ac.ir/article_15069_a7aa8b244946b3dc0d0b1a471eb05319.pdf
Numerical Analysis of twofluid mixing with various Density and Viscosity in a microchannel with forced oscillating stirrer
Sajad
Ghanbari
فارغ التحصیل
author
Mohammad
Sefid
عضو هیئت علمی دانشگاه یزد
author
Rahim
Shamsoddini
عضو هیئت علمی دانشگاه صنعتی سیرجان
author
text
article
2016
per
In this present study, the mixing of two incompressible miscible fluids with different density and viscosity has been investigated in a twodimensional microchannel equipped with an oscillating stirrer in different excitation frequency. Although most studies in the field of fluid mixing, have been studied the mixer performance when the two fluids were absolutely identical, but the mixing make sense when two fluids has been nonuniformity such as different temperature, concentration or properties. The aim of this study is to evaluating the effect of various properties of the fluids in mixer performance and mixing value. Simulation has been performed in Re=100 and Sc=10, between 0.1 to 1 strouhal number by using element based finite volume method by means of commercial code CFX. Mixer performance has been evaluated in three different modes: mixing of two identical fluids, mixing of two fluids with different density and mixing of two fluids with different viscosity. The results show that, mixing of the fluids with different properties leads to change in mixer performance, and has unique performance in each case. In comparison with similar properties fluids, mixing of fluids with different viscosity and density show lesser inclined in mixing. It has been shown that variation of strouhal number has lesser effect on mixing index changes. The ratio of maximum mixing index changes to base mixing index in the case of different density and viscosity is 54.01 and 51.15 percent, respectively, while the value is 577.94 percent for the mixing of similar fluids.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
109
119
http://mme.modares.ac.ir/article_15070_154ccc295cac185c2353b7d02ef21ac1.pdf
Dynamic modeling of nano/microparticles displacement in multipoint contact based on the Rumpf model
Manizhe
Zakeri
استادیار دانشکده فناوری های نوین دانشگاه تبریز
author
Javad
Faraji
دانشگاه تبریز
author
text
article
2016
per
In this paper, dynamic behavior of a nano particle on a rough surface in pushing based on the atomic force microscopy (AFM) was modeled and simulated by using the multipoint contact model. First, a multipoint contact model was extracted for two different roughness profiles of rough surfaces including the hexagonal and tetrahedral by combination of the Rumpf singular point contact model with JKR and Schwarz contact models, and the equations of the real contact area and adhesion force were proposed for multipoint contact of rough surfaces. Then, the dynamic behavior of particles in pushing on the rough substrate was modeled by using the new multipoint contact model. Additionally, simulation of the particles dynamics with radii of 50, 400 and 500 nm in moving on the different rough substrates was performed and analyzed, by assuming multipoint, singular point contacts, and flat surface contacts. Results showed that the multipoint contact model, especially in small radiuses of roughness has an essential impact on determining of the critical force. Moreover, assumptions of the flatness or the singular point contact leads to a considerable error to estimate the critical force. Results showed profiles of rough surface and roughness distribution are very important factors in determination the numbers of the contact points, and change the estimated amount of the critical force. In general, the obtained critical force based on the new multipoint contact model in comparison with the ones based on the flat surface and the singular point contact models, was decreased and increased, respectively.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
120
130
http://mme.modares.ac.ir/article_15072_53ab86201ec22fd2896c61746f79ff9a.pdf
Experimental study of the effects of abrasive particle size and work piece hardness in Magnetic abrasive flow Machining
Mohammad Reza
Shabgard
دانشیار تبریزدانشگاه تبریز ریاست دانشکده فنی مهندسی مکانیکگروه مهندسی ساخت و تولید محمد رضا شبگرد
author
Farzam
Arabzadeh Tabriz
Department of Mechanical Engineering, Tabriz University, Tabriz, Iran
author
Ahad
Gholipoor
Department of Mechanical Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
author
text
article
2016
per
Abrasive flow machining (AFM) is a relatively new process with low material removal ratio for deburring, removing recast layers and finishing industrial components with complex shapes among nonconventional machining processes. In this process, the finishing is handled by flowing of the composition of viscoelastic and abrasive particles on workpiece surface, under the pressure of piston. In this research, the abrasive flow machining process of H13 tool steel with applied an external magnetic field around the workpiece for improve the material removal ratio and surface roughness has been investigated and the effect of magnetic field intensity, abrasive particles mesh and the hardness of workpiece as the input parameters on the process outputs including surface roughness and material removal ratio was studied. Also the regression model of MRR and surface roughness was developed and variance analysis was performed. Results of experiments indicated that increase in abrasiveparticles mesh leads to decrease surface roughness and material remove ratio and increase in magnetic field intensity causes to increase material removal ratio and decrease surface roughness. Also the material removal ratio is decreased with increasing of workpiece hardness and on the same condition; better surface finish was achieved in the case of harder workpiece.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
131
138
http://mme.modares.ac.ir/article_15071_2a3a00d5fff617ee139270c96582dc08.pdf
Attitude Control of a Rigid Satellite with PulseWidth PulseFrequency Modulation Using Observerbased Modified PID Controller
Sara
Moghadaszadeh Bazaz
دانشگاه تربیت مدرس
author
Vahid
Bohlouri
دانشگاه تربیت مدرس
author
Seyed Hamid
Jalali Naini
دانشگاه تربیت مدرس
author
text
article
2016
per
In this paper, the performance of a singleaxis attitude control with pulsewidth pulsefrequency (PWPF) modulation is enhanced using a modified proportionalintegralderivative (PID) controller for a rigid satellite with onoff thruster actuators. For this purpose, the wellknown observerbased PID approach is utilized. The onoff thruster actuator is modeled with a constant delay followed by a secondorder binomial transfer function. The modulator update frequency is limited to 40 Hz as an input to the onoff thruster actuators. In this study, the design criteria of pointing accuracy, overshoot of the attitude response, fuel consumption, and the number of thruster firings are considered for a step external disturbance (with different values). The parameters of the observerbased PID controller are tuned using parametric search method. Simulation results show that the fuel consumption and settling time of the observerbased approach are considerably decreased with respect to those of PID controller with PWPF modulator. Moreover, the overshoot of the observerbased approach is omitted. Finally, the robustness of the observerbased modified PID controller is investigated in presence of uncertainties in satellite moment of inertia and thrust level of onoff actuators.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
139
148
http://mme.modares.ac.ir/article_15073_62de0d6bcd3748566877ff6b7a9515d4.pdf
Developing threenode model to estimate individual characteristics effects on thermal sensation and human body thermoregulation
Farzin
Davoodi
دانشجوی دکتری دانشگاه بیرجند
author
حسن
حسن زاده
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
Seyed Alireza
Zolfaghari
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
Mehdi
Marefat
دانشگاه تربیت مدرس
author
text
article
2016
per
Differences in the persons’ individual parameters such as age, gender, weight, height and basal metabolic rate have a significant effect on the human body thermoregulation. Therefore, using the human thermal models that developed on the basis of large humanity population cannot lead to accurate results for specific individuals. Because, the individual parameters have not been considered in standard thermal comfort models and also available individual and local models are so complicated in applications; nowadays, the necessity of developing a simple and accurate individualized model is felt. In this study, some physiological parameters such as: body fat percentage, subcutaneous fat layer thickness, body heat capacity coefficient and tissue conductive resistances have been modeled from readilyavailable external measurement of individuals and these parameters are incorporated into three nodemodel algorithm structure to predict individual variations in thermal response between individuals. Threenode thermal comfort model is based on Gagge’s standard model that has been accurately estimated thermal sensation of the bare and clothed parts of the body. The model has been verified against the analytical and experimental results where a good agreement was found. In conclusion, the results indicate that the mean error in prediction of skin temperature is decreased from 1.2℃ for threenode model to 0.4℃ for the new individual model.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
149
158
http://mme.modares.ac.ir/article_15074_520e38292207d3838f33c92367854dc5.pdf
Numerical design and analysis of supersonic exhaust diffuser in altitude test simulator
Nematollah
Fouladi
کارشناس پژوهشی/پژوهشگاه فضایی ایران
author
Alireza
Mohamadi
پژوهشگر، پژوهشگاه فضایی ایران
author
Hadi
Rezaei
پژوهشگر، پژوهشگاه فضایی ایران
author
text
article
2016
per
In this paper, the design algorithm of a second throat exhaust diffuser applicable in altitude tests of large expansion ratio nozzles is presented. In this algorithm, the geometric parameters of the exhaust diffuser are classified into primary and secondary parts. The primary geometric parameters are calculated from normal shock theory incorporating with a correction coefficient. However, the secondary parameters are selected from the previously reported experimental results. Numerical simulation tool is utilized to satisfy the design candidates and to finalize the correction factor. Axissymmetric compressible Navier–Stokes equations incorporated with two equation KωSST turbulence model are solved to extract the supersonic exhaust diffuser flow features. As a first stage of numerical analysis, we use an unsteady pressurebased solver to accelerate the solution procedure. At the second stage, we use steady densitybased solver to enhance the accuracy of our solutions. The current numerical method is properly validated by experimental reported results in the literature. Finally, we focused on simulation results of a designed diffuser and described the flow futures at different boundary conditions. The simulation results are confirmed that the designed diffuser is suitable for proposed altitude test.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
159
168
http://mme.modares.ac.ir/article_15075_a5f01723c01213344c3da4c91b032bb6.pdf
Study the effect of ultrasonic assisted electrical discharge machining process on residual stress and hardness of Ti6Al4V alloy
Mohammad Reza
Shabgard
دانشیار تبریزدانشگاه تبریز ریاست دانشکده فنی مهندسی مکانیکگروه مهندسی ساخت و تولید محمد رضا شبگرد
author
Behnam
Khosrozadeh
دانشجوی دکتری دانشکده فنی مهندسی مکانیک گروه ساخت و تولید دانشگاه تبریز
author
text
article
2016
per
Electrical discharge machining is one of the usual and widely used machining processes for machining hard metals and alloys which has low machinability by traditional machining methods. Due to the thermoelectric nature of this process, changes in metallurgical and mechanical properties of machined surface and development of residual stresses in components are inevitable. In this research machining of Ti6Al4V titanium alloy is conducted by ultrasonic assisted electrical discharge machining process and the effects of ultrasonic vibration of tool on the machining efficiency, surface integrity such as surface microcracks, residual stress and surface hardness has been evaluated. Machined surface were imaged by scanning electron microscopy imaging to study the size and distribution of surface microcracks. Residual stresses along the depth of the machined surface, evaluated using Nano indentation technique and hardness of discharged surface is measured using a micro hardness measuring instrument. The results show that applying ultrasonic vibration increases electrical discharge machining process efficiency (about 90%), reduces the amount and size of surface microcracks, changes residual stress distribution and decreases the amount of it (average 17%); Increases of surface hardness caused by ultrasonic assisted electrical discharge machining process is 13% more than the traditional electrical discharge machining process.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
169
176
http://mme.modares.ac.ir/article_15076_2746ebd0465d9d425449ee7811b903b1.pdf
Aeroelastic response of horizontalaxis wind turbine in sudden wind gusts based on Unsteady Blade ElementMomentum method
Abbas
Ebrahimi
استادیار دانشکده مهندسی هوافضای دانشگاه شریف
author
Mahmood
Sekandari
فارغ التحصیل دانشگاه صنعتی شریف
author
text
article
2016
per
Wind turbines are subject to various unsteady aerodynamic effects. This includes the wind gust and the change of wind direction. In this work, the aeroelastic behavior of a reference horizontal axis wind turbine has been investigated under different wind gusts and yaw conditions. Unsteady blade element momentum (UBEM) theory and EulerBernoulli beam assumption were used to rotor power estimations. To take into account the time delay in aerodynamic loads due to a sudden change in inflow conditions, a dynamic wake model was implemented. The ONERA dynamic stall model was coupled into the BEM theory to improve the aerodynamic loads prediction in the unsteady inflow and yaw conditions. To verify this method, the results in the case of steadystate are compared with the NREL 5 MW wind turbine and in the unsteady case are compared with the Tjaereborg test turbine. The results indicate that sudden change in wind speed causes sharp fluctuations in terms of elastic torsion of the blade and other parameters such as rotor power. Increasing in wind gradient can leads to increasing time delay to a new equilibrium. The increase in yaw angle can be contributed to the rotor power and the periodic loads reduction. The method presented here may facilitate improvements in the controller design for wind turbines.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
177
184
http://mme.modares.ac.ir/article_15115_bdfb630086c6e2fe9524169e84696746.pdf
Nonlinear modal interaction between asymmetric modes of sandwich plates under wideband random excitation
Saeed
Mahmoudkhani
دانشگاه شهید بهشتی/استادیار گروه هوافضا
author
Hassan
Haddadpour
استاد/دانشگاه صنعتی شریف
author
text
article
2016
per
The nonlinear vibration of sandwich viscoelastic plates under wideband random excitation is investigated. The main attention is put on the influence of the onetoone internal resonance, arisen from the close natural frequencies of the asymmetric modes of a nearsquare plate, on the response. The multimodal response and the onoff intermittency phenomenon are especially considered. The mathematical modeling of the midlayer is based on the moderate transverse shear strains and rotations, which have led to both geometrical and material nonlinearities. For the nonlinear constitutive equation of the mid layer, a single integral viscoelastic model is used. The displacement field in the thickness direction is also assumed to be linear for the inplane components and quadratic for the outofplane components. Moreover, the Kirchhoff theory with the vonKarman nonlinearities are used for the outer layers. The solution is initiated by applying the perturbation method along with the Galerkin’s method to obtain integrodifferential ordinary equations in time. These equations are then, solved using the Gaussian and nonGaussian closure methods and the results are used to investigate the occurrence of the bifurcation with the aid of the Pseudoarclength continuation method. Numerical results are presented for the multimodal response and the minimum excitation intensity required for the nonlinear interaction between asymmetric modes.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
185
195
http://mme.modares.ac.ir/article_15116_b2f5ae35936a3ebe37663a39ada970b5.pdf
Improving the mechanical and thermal properties of chemically modified graphene oxide/polypropylene nanocomposite
Mohammad
Gharebiglou
دانشگاه تبریز
author
Mir Shahabeddin
Izadkhah
دانشگاه تبریز
author
Hamid
ErfanNiya
عضو هیات علمی / دانشگاه تبریز
author
Ali Akbar
Entezami
دانشگاه تبریز
author
text
article
2016
per
The aim of present work is the investigation of polypropylene/graphene oxide nanocamposies. In this work, the reinforcing effects of the graphene oxide nanoparticles on the mechanical and thermal properties of the nonpolar polypropylene are examined. There is two main challenges to improve the properties of polypropylene by graphene oxide nanoparticles. First, the nanoparticles have not suitable dispersion in polymer matrix. Furthermore, there is not sufficient adhesion between nanoparticle and polymer chains. In this study, the graphene oxide (GO) surface is modiﬁed by a linear alkyl chain via a bimolecular nucleophilic substitution reaction between the oxygen groups of GO and reactants to promote the homogeneous dispersion of GO in the organic solvent and increasing the interfacial adhesion between the graphene oxide and polymer matrix. The presence of the alkyl groups on the surface of graphene oxide nanoparticles is characterized by FTIR. To prevent the AGO aggregation in the polypropylene, the solutionblending method is used to prepare the nanocomposites with 0.1, 0.3, 0.5 wt% AGO. The SEM images confirmed the appropriate dispersion of the graphene oxide in the composites. The stressstrain analysis, dynamicmechanical thermal analysis (DMTA), and thermal gravimetric analysis (TGA) are performed to investigate the mechanical and thermal properties of nanocomposites. The results demonstrated that the Young’s modulus of the polymer are improved by 20, 30 and 34% with adding 0.1, 0.3 and 0.5% AGO, respectively. Also the 10% mass loss temperature for 0.1, 0.3 and 0.5% AGO nanocomposites compared to neat polypropylene increased by 2, 8, 12 C0, respectively.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
196
206
http://mme.modares.ac.ir/article_15130_68150d2f13ee0a56ddd65355c12e5e9f.pdf
Numerical analysis of free corner effects in angleply composite laminates based on globallocal method
Hossein
Mohammadi Roknabadi
دانشجوی کارشناسی ارشد، دانشکده مهندسی مکانیک و انرژی، دانشگاه شهید بهشتی، تهران
author
MohammadJavad
Mahmoodi
دانشگاه شهید بهشتی، پردیس فنی مهندسی شهید عباسپور، دانشکده مهندسی مکانیک و انرژی
author
text
article
2016
per
The main purpose of this paper is modeling of the free corner effect of crossply and angleply graphite/epoxy composite laminates using finite element method based on globallocal method. The global area is modeled by first order shear deformation theory and the local area, in the free corner vicinity, is modeled by the Reddy's layerwise theory. Using this method provides the possibility of analysis of thick angleply and crossply laminates. The crossply and angleply laminates are subjected to uniform thermal and extension loading, respectively and the effects of the free edge and free corner interlaminar stresses are investigated. The presented results verification is performed via available results in the previous studies which show good agreement. The present study results show that when the crossply laminate is subjected to thermal loading, the interlaminar stresses distribution is uniform in both length and width of the laminate. However, for the uniaxial extension loading, the interlaminar stresses possess different distribution in the two directions of the laminate. Also, results demonstrate that in angleply laminates under extension loading, the free corner effect increases by increasing fiber angle and the maximum interlaminar stresses occur in 30 degree plies in the free corner vicinity. Moreover, results prove that the effects of the free edge and the free corner are almost similar in layers with fiber angle less than 30 degrees. Parametric study on the thickness and stacking of the laminate layers display that both parameters have a significant influence on the interlamianar stresses at the free corner.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
207
217
http://mme.modares.ac.ir/article_15131_7ca78756c49304bee54a9721dda09a32.pdf
Small Satellite Thermal Control SubSystem Conceptual Design Optimization Methodology
Mehran
Mansour Dehghan
دانشگاه تربیت مدرس
author
Masoud
Ebrahimi
استادیار دانشگاه تربیت مدرس
author
Oveis
Negaresh
دانشگاه تربیت مدرس
author
text
article
2016
per
Satellite Thermal Control subsystem has the responsibility of maintaining the temperature of different parts and other subsystems in an allowable range. The purpose of this paper is to optimally design the satellite thermal control subsystem. In order to achieve this goal, at first a software for thermal analysis of satellite was developed and validated. Receiving orbital data and Satellite’s properties, the software simulates the position of the satellite in any desired orbit and calculates input and output thermal flux. Meanwhile, the software calculates the temperature of each sides of satellite in cold case and hot case. At the end, it computs the minimum and maximum temperature of the satellite. Combination of three commonly used thermal control methods for small satellite was used. Insulation thickness, thickness of radiator’s cover, and the power of radiator are considered as design parameter and allowable temperature of surfaces (minimum and maximum allowable temperature) are considered as design constraints. A weighted function of mass, cost, and power consumption of thermal control system are chosen as objective function that can be an indicator of the cost. Sequential Quadratic Programming as a powerful method in nonlinear optimization was used to optimize thermal control properties.The results demonstrated that the objective function improved dramatically comparing to initial design. High speed, appropriate precision, and extensibility of this software to thermal control design of vast majority of small satellites, makes this research superior. Therefore, this software could be cooperated as the thermal control design module in multidisciplinary design optimization of satellites.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
218
228
http://mme.modares.ac.ir/article_15143_f58feef5b647cf7543b5bd5cff10c7cd.pdf
Mode Complexity in a Harmonically Forced String Considering an Asymmetric Local SpringDamper
Saleh
Jomezade Khazarbeygi
دانشجوی کارشناسی ارشد/دانشگاه صنعتی شاهرود
author
Amir
Jalali
عضو هیات علمی دانشگاه صنعتی شاهرود
author
text
article
2016
per
In this study the steadystate dynamic of a linear, homogeneous, undamped string, coupled with a locally connected springdashpot system is analytically investigated. Both ends of the string are assumed to be excited with identical and synchronous harmonic motion. It is shown that the damper introduces mode complexity and leads to frequency shift between the peak amplitudes in different locations of the string. Also it causes phase variations which indicates mode complexity domain. In this study, it is shown that there are different combinations of spring and damper constants in which the mode complexity attains its maximum level. Surprisingly, the combination is unique in each given excitation frequency ratio. In this situation, the damping constant is bounded in a specified range but, the spring constant is increased as the excitation frequency ratio is increased. In such case, all vibration normal modes of the string are completely destroyed and, in turn, traveling waves are formed. Also it is shown that the damping constant which leads to the maximum frequency shift, is not necessarily equal to the one that introduces the maximum mode complexity.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
229
238
http://mme.modares.ac.ir/article_15141_c93e0a4db6bd357a094b5cc42fd37050.pdf
Dynamic stability of power law FG shallow arches: a theoretical approach
Ali Asghar
Atai
دانشیار دانشگاه تهران
author
Mahdi
Alizadeh
کارشناسی ارشد طراحی کاربردی، دانشکده مهندسی مکانیک، دانشگاه تهران
author
text
article
2016
per
One of the remarkable concerns in Shallow arches’ behavior under lateral loading is snap through, a phenomenon which can make the structure collapse or displace to another stable configuration. Introducing functionally graded materials in recent years led to some interesting results, for instance, using functionally graded materials in shallow arches can give structures with favorable stability properties. In this work, we investigate dynamic stability of the pinedpined functionally graded sinusoidal shallow arch under impulsive loading. Material properties vary through the thickness by power law function. Nonlinear governing equations are derived using EulerBernoulli beam assumption and equations of motion are expressed by a nonlinear differentialintegral equation. The solution utilizes a Fourier form of response. The procedure to analyze dynamic stability followed here uses total energy of the system and Lyapunov function in the phase space. We find the stable region against dynamical snap through under material properties’ variation through the thickness of shallow arch. We also proceed to find the sufficient critical load in order to make the dynamical snap through occur. The results are analyzed in detail and illustrated in some diagrams.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
239
248
http://mme.modares.ac.ir/article_15142_6fd40bedea1bdaf6d14aca3d5cc7020c.pdf
Micromechanical modeling for prediction of the creep behavior of fibrous composite materials
Isa
Ahmadi
استادیار دانشگاه زنجان
author
Neda
Ataee
University of Zanjan
author
text
article
2016
per
A micromechanical model based on the representative volume element (RVE) is presented to study the timedependent and creep behavior of fibrous composite material. To this aim a finite element model is presented for analysis of creep behavior of material in multiaxial creep are presented. The generalized plane strain condition is employed to model the behavior of the RVE in axial and transverse normal loading. The governing equations of the problem in the RVE are discretized using the presented finite element method and the stiffness and force matrixes are presented. Appropriate boundary conditions are implied to the RVE in order to consider the transverse and axial loading conditions including creep behavior. The Euler explicit method is employed to solve the discretized equations in the time domain. The distribution of microstresses and the effect of creep in redistribution of the stresses are studied. The steady state creep behavior of composite in macromechanical scale is investigated by analysis of the micromechanical behavior of the RVE. The macromechanical creep behavior of metal matrix composite in axial and transverse loading are predicted from the presented micromechanical model.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
249
260
http://mme.modares.ac.ir/article_15144_40490f3eec41bfc094466ccf14c43d21.pdf
Control vibration of imbalance Jeffcott rotor by magnetic absorber
Hamidreza
Heidari
استادیار گروه مکانیک دانشگاه ملایر
author
Behnam
Monjezi
دانشجو
author
text
article
2016
per
Unbalance mass and imperfect bearings are the main sources of vibration in rotor dynamics systems. One way to decline and control of a rotor vibration is the use of magnetic absorbers. The magnetic absorber is used to control the position of the rotor and reduce its vibration. In this study, by applying the dynamic absorber system force and creating two new natural frequencies, the magnetic absorber brings the system out of the resonance. Moreover, in order to decrease the vibration amplitude, two different types of dynamics absorbers are designed in which they are checked by the magnetic absorber in a specific range of rotational frequency. In magnetic absorber controller system, the continuous force which is applied to the main system by mass absorber is restored in sixteen levels discontinuously. It is seen that the vibration amplitude is reduced 13% in the area of natural frequency in comparison to the magnetic absorber with discontinuous force. In this paper, two different mass ratios are considered for each one of the two absorber systems. It is observed that in the case of dynamic absorbers with higher mass ratio, rotor vibration amplitude and the maximum force amplitude of the dynamic absorber system decrease. This issue can increase the accuracy of magnetic absorber system in the renewal of the dynamic absorber system force and reduce consumption electrical energy of the control system as well.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
261
268
http://mme.modares.ac.ir/article_15146_44175c20c0711a908c9088f9bef3a446.pdf
Effects of different inlet/outlet arrangements on performance of a trapezoidal porous microchannel heat sink
Hossein
Khorasanizadeh
Associate Prof., Uni. of kashan
author
Mojtaba
Sepehrnia
دانشگاه کاشان
author
text
article
2016
per
Effects of different inlet/outlet arrangements on thermal performance of porous microchannel heat sink MCHS of any geometry has not been studied yet. In this investigation, the effects of utilization of four different inlet/outlet arrangements on electronic chip cooling utilizing trapezoidal MCHS with porous microchannels with porosity of 0.88 have been studied numerically. For this purpose, three dimensional simulations of laminar forced convection flow in microchannels and conduction in solid parts of MCHS by applying constant heat flux of 150 kWm2 at its base plate have been performed utilizing the finite volume method and the commercial AnsysCFX code. The results show that the A and Btype arrangements, for wich the inlet and outlet are in direction of flow in the microchannels, have a better heat transfer performance, smaller thermal resistance and provide more uniform temperature distribution in the MCHS base plate. The results indicate that using porous media is effective in reducing the MCHS base plate temperature and in this regard the Dtype arrangement has the best performance among the heat sinks studied. Considering both the positive effect of using porous media on increasing the heat transfer coefficient and its negative effect on increasing the required pumping power, the Atype arrangement has the best performance.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
269
280
http://mme.modares.ac.ir/article_15147_d29186981a287a56ad0351ba31a66705.pdf
Performance study of adsorption cooling system driven by waste heats of heavy trucks diesel engine
Seyyed Behzad
Golparvar
دانشجوی کارشناسی ارشد / دانشگاه فردوسی مشهد
author
Milad
Mohammadzadeh Kowsari
دانشجوی کارشناسی ارشد / دانشگاه فردوسی مشهد
author
Hamid
Niazmand
دانشگاه فردوسی مشهد
author
text
article
2016
per
Large amount of diesel engine waste heats make researchers design systems that utilize the engine waste heat to provide the cooling demand of the heavyduty vehicles and improve the engine efficiency. Considerable advantages of adsorption cooling system lead to be nominated for this purpose. Coolant and exhaust gases are the main sources of waste heats of diesel engines and using each of them to drive the adsorption cooling system requires its own equipment and working pair. In this paper, a detailed numerical model has been developed and to examine the performance of the cooling system driven by the coolant waste heat with working pair of silica gelwater and also driven by exhaust waste heat with zeolite13xwater working pair. An identical absorbent bed and ambient conditions have been employed to compare the performance of both systems to identify the more appropriate system. The results show that exhaust driven adsorption cooling system has more capability to meet the vehicle cooling demand. Moreover, the performance of the both adsorption cooling systems were examined under variable ambient condition. Results indicate that increase in ambient temperature leads to almost a linear performance drop in both systems that is more considerable in the coolant driven adsorption system.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
281
292
http://mme.modares.ac.ir/article_15170_a8b31c48db9ba8e3e782f0d86f446d5f.pdf
Analytical consideration of springback predicting dualphase steels sheets during U form bending process based on anisotropic nonlinear kinematic hardening model
Asghar
Zajkani
استادیار، مهندسی مکانیک، دانشگاه بینالمللی امام خمینی (ره)، قزوین
author
Hamid
Hajbarati
دانشجوی کارشناسی ارشد، مهندسی مکانیک، دانشگاه بینالمللی امام خمینی (ره)، قزوین
author
text
article
2016
per
An undesirable factor that affects the dimensional precision and final shape of metallic parts produced in cold forming processes is springback phenomenon. An analytical model is introduced to predict springback in Ushaped bending process of DP780 dual phase steel sheet. This analytical model is based on the Hill48 yield criterion and plane strain condition. In this model, the effect of forming history, sheet thinning and the motion of the neutral surface on the springback of Ushaped bending process is taken into account. The anisotropic nonlinear kinematic hardening model is used to consider the impact of complex deformation, including stretching, bending and reverse bending. This model is able to investigate the complex hardening behavior of material such as Bauschinger effect, transient behavior and permanent softening. The effect of the sheet holder force, the coefficient of friction, thickness, material anisotropy and hardening parameters on the sheet springback is studied. It can be seen that analytical model which presented in this paper has good accuracy in the springback prediction in comparison with FEM method and results are close to experimental data. The results shows that the sheet holder force, the coefficient of friction, thickness and material anisotropy have great influences on the springback prediction. Since during the forming process the material experience reverse loading, the hardening parameters of material has a significant influence on the springback prediction. It can be seen that the Bauschinger effect has more influence on the springback prediction than the permanent softening and transient behavior.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
293
302
http://mme.modares.ac.ir/article_15171_6a0c4b98e996e13ec54491480666886a.pdf
Dynamic behavior investigation of a rotating system by two methods of nonlinear modeling and finite element
Mohammad Saleh
Sadooghi
دانشجوی دکتری
author
Siamak
Esmaeilzadeh Khadem
تربیت مدرس
author
Saeed
Bab
تربیت مدرس
author
text
article
2016
per
In this paper the dynamic behavior of a rotating system which includes rotor (shaft), ball bearing and disk in stationary condition and different speeds is investigated. There are nonlinear characteristics in these systems which cause the linear modeling is not sufficiently accurate. So, in this paper the nonlinear dynamic equations of the system are derived and solved. To derive the equations of the system, Hamiltonian method is used, and complex coordinate transform is used to reduce the number of equations. After solving the equations, to investigate the vibrational properties of the system, time response diagram, dynamic orbit, frequency response, and mode shape of the rotor is plotted. To validate the analytical results, finite element method by ANSYS (workbench) software is used.There is a good conformity betweenthe analytical results and finite element results in resonance frequencies of the system in the first three modes which indicates the sufficient accuracy in nonlinear modeling. It can be concluded from nonlinear modeling that the decay rate is negative for the all modes which is indicates the stability of the all modes. Also, the maximum vibration amplitude in the bearing and rotor occurs in third and second modes respectively. Unbalance phase difference of 90 degrees in two discs causes the excitation of all three frequency modes, whereas by unbalance phase difference of 0 or 180 degrees in two discs,only the odd modes (first and third) and the even modes (second) is excited respectively.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
303
314
http://mme.modares.ac.ir/article_15172_03f3c667985010b0ee54d077fc3531f5.pdf
Evaluation and selection of the most consistent turbulent model with the slug flow behavior
Mohamadreza
Ansari

author
Mostafa
Zeynalabedini
دانشجوی دوره دکتری
author
text
article
2016
per
Many models have been applied to slug flow using laminar flow condition. The results obtained from these models are not consistent with the physical behavior of slug flow. Furthermore, discussion on the turbulent models is very rare or not related to the such flow regime. The slug regime is a complicated regime with shear flow and high strain in addition to some vorticity at some sections of the flow. In the present attempt at first stage, the turbulent models differences, the initial assumptions to drive, privilages and shorcomings have been considered with details. Then, its consistency with the physics of slug flow was analysed with high accuracy. In the second stage, simulations using different turbulent models were conducted. The obtained results were compared to each other and with the experimental results of other investigators. Finally, the most consistent model with the physics of the slug flow was selected. The turbulent model of RNG kε showed more reliable in compare to other turbulent models. Thus, it was selected and used to obtain slug flow behavior with higher accuracy. The parameters as pressure distribution during slugging, slug mixture velocity, slug initiation time and position from the duct inlet with RNG model conducted and presented with detailed explanations.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
315
325
http://mme.modares.ac.ir/article_15145_f739e3bff59863682615d8dd97c80647.pdf
A Novel Model Based on the ThreeMass Inverted Pendulum for RealTime Walking Pattern Generation of Biped Robots
Mostafa
Eslami
دانشجوی کارشناسی ارشد/دانشکده مهندسی مکانیک دانشگاه تهران
author
Aghil
Yousefi Koma
رئیس / مرکز سیستمها و فناوریهای پیشرفته دانشگاه تهران
author
Majid
Khadiv
دانشجوی دکتری/ دانشکده مهندسی مکانیک دانشگاه خواجه نصیرالدین طوسی
author
text
article
2016
per
In this paper, to improve the accuracy of the onemass and threemass inverted pendulum models, which have been used for generating realtime walking patterns for biped robots, we propose a novel model based on the threemass inverted pendulum. The proposed model employs an approximation of moment of inertia of the swing leg to improve the accuracy of the threemass inverted pendulum in estimating dynamic behavior of the robot. In order to show significance of the proposed model, trajectories for the Center of Mass (CoM) are obtained using the three models, based on a desired ZMP trajectory. The task space trajectories, then, are mapped into the joint space, using inverse kinematics. Having the joint space variables, the actual ZMPs for the three obtained walking patterns are computed and compared. This comparison well shows merit of the proposed model in estimating dynamic behavior of the robot, especially for walking with relatively high speeds. The kinematic and dynamic properties of the models in this paper are based on the humanoid robot SURENA III, which has been designed and fabricated in the Center of Advanced System and Technologies (CAST), university of Tehran.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
326
334
http://mme.modares.ac.ir/article_15209_ddee8007854cbfec613ba916ca8a836e.pdf
Modeling and Simulation of Mechanical Behavior in Knee Joint under Gait
Behrooz
Sepehri
عضو هیات علمی/ دانشگاه ازاد اسلامی مشهد
author
Hojat
Mohammadi Esfahani
دانش اموخته دانشگاه ازاد اسلامی واحد مشهد
author
Faramarz
Firouzi
عضو هیات علمی/ دانشگاه ازاد اسلامی مشهد
author
text
article
2016
per
Mechanical behavior of articular cartilage is affected by many factors. Inhomogeneous distribution of proteoglycans and collagen fibers through the thickness causes some depthwise behavior. Mechanical properties directly affect stress and deformation of the tissue. In previous studies complexities and variation in mechanical properties were ignored. The aim of the present study is to create a model close to real anatomy of articular cartilage in knee joint and to simulate its behavior under dynamic gate in the stance phase. A 3D finite element (FE) model was created. It was constructed considering femur and tibial cartilages as well as medial and lateral meniscus. In the FE model, a nonlinear isotropic viscoelastic material model used for cartilages and a linear anisotropic elastic one was chosen for meniscuses. As well, cartilages assumed saturated . Numerical simulations on the model showed that peak of maximum principal stress occurred in superficial layer. It was decreased through thickness. These expressed why osteoarthritis fall out in the exterior layers such superficial . The present study showed that hydraulic permeability variation in cartilage as a straindependent variable was negligible in dynamic loading. Also, results had a good agreement with experimental ones
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
335
342
http://mme.modares.ac.ir/article_15196_6313fd2888caaf07e08240daf19bf737.pdf
Analyzing the Effect of Particle Rotation on its Heat Transfer Rate while Interacting with a pair of Vortices
Zahra
Talebpour
دانشگاه فردوسی مشهد
author
Hamid
Niazmand
Ferdowsi University of Mashhad
author
text
article
2016
per
The interactions between vortical structures and spherical particles or droplets is of practical issues in twophase flows. The interactions bring major changes in the flow field particularly when coupled with particle rotation. It is observed that the heat transfer rate is significantly influenced during the time that the vortices’ cores are in the vicinity of the particle. In this paper, transient heat transfer of a rotating spherical particle interacting with a pair of vortices in incompressible and viscous flow is studied using numerical solution of the NavierStokes and energy equations in the range of 20≥Re≤100 and nondimensional rotational velocities 0≤Ω≤1, by computational code which has been developed by the authors. In order to ensure the accuracy of the calculation, the results are compared with numerical data reported in the literature and good agreement between results was observed. Then the effect of circulation direction of two vortices interacting with a particle by spin on its heat transfer rate was investigated. Also distribution of heat transfer coefficient at the particle surface with separate rotation around three different axes in two cases of interacting and noninteracting with vortices is given and the results of heat transfer coefficient are presented. The results show that particle rotation for Ω≤0.5, in both presence and absence of vortices in flow field has negligible effects on the particle heat transfer rate; however, with increasing of particle spin significant effects on heat transfer coefficient has been observed that due to the circulation direction of vortices, different amounts are obtained.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
343
354
http://mme.modares.ac.ir/article_15197_d90fb597578bdcc0604835ec004a5969.pdf
Hydrodynamic interaction of multiple flexible membranes and initial position effect of a membrane on its behavior in a microchannel
As'ad
Alizadeh
دانشگاه صنعتی ارومیه
author
Abdolrahman
Dadvand
Academic Staff
author
Mehadi
Bakhshan
دانشگاه صنعتی ارومیه
author
text
article
2016
per
In this paper, motion of a flexible membrane and hydrodynamic interaction of multiple membranes in a microchannel are simulated by developing a computer code written in C. The membranes are considered as flexible boundaries immersed in the fluid. First a single biconcave shaped membrane with high rigidity is considered. Due to the rigidity of the membrane, it experiences tumbling motion and its vertical displacement becomes oscillatory. Then, the effects of initial position of a circular membrane on its deformation, vertical velocity and displacement are investigated. It was observed that as the initial location of the membrane approaches the channel’s central axis, its vertical displacement and velocity decreased, but its horizontal velocity component increased. Finally, the simultaneous motion of multiple membranes in a microchannel and their interaction with each other and with flow are evaluated. The membranes do not collide and hence the collision mechanism is not modeled. It was found that the upstream membrane experienced greatest deformation and the greatest force was exerted on it by the fluid on it. In addition, simultaneous presence of multiple membranes would result in a reduction in the flow velocity. The current numerical results have good agreement with the available valid numerical ones.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
355
364
http://mme.modares.ac.ir/article_15198_90d5e476da92b60aa6c7c0d098d881ed.pdf
Multiobjective optimization of Hexa parallel manipulator based on kinematic and dynamic indicies
Erfan
Mirshekari
shahid chamran university
author
Afshin
Ghanbarzadeh
Shahid Chamran University
author
Kourosh
Heidari Shirazi
Shahid Chamran University
author
text
article
2016
per
In this study, the effects of geometrical parameters of 6DOF Hexa parallel robot on kinematic, and dynamic performance indices are investigated and its structure is optimized using the intelligent multiobjective Bees Algorithm. In this way, after describing the structure and specifying the geometrical parameters of the robot, inverse kinematic relations of the robot are obtained. Jacobian matrix that maps velocity from joint space to Cartesian space is developed. Mass matrix is obtained from calculating the total kinetic energy of the manipulator in terms of the actuated joints vector. Inverse of the homogen jacobian based condition number is considered as a index to evaluate the kinematic dexterity. based on mass matrix as relation between acceleration vector of the end effecter and torque vector of actuated joints, dynamic dexterity index is presented. Using the multiobjective Bees Algorithm and considering dynamic and kinematic performance indices in a predetermined workspace as the objective functions, structure of Hexa parallel robot is optimized. In this way, the proper geometrical constraints such as limitation of universal and spherical joins, and the constraints to singularity avoidance are considered. Pareto front of the multi objective optimization of the robot is drawn. Diagrams of the kinematic and dynamic performance indices variation in the workspace and the effects of geometrical parameters variation on them are presented.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
365
374
http://mme.modares.ac.ir/article_15199_22a51aeabd0b3bc737dee524b88b75cb.pdf
Mechanical behavior of actin monomers under axial tensile loads: A molecular dynamics study
Behzad
Mehrafrooz
Sharif University of Technology
author
Amir
Shamloo
دانشگاه صنعتی شریف
author
Keikhosrow
Firoozbakhsh
Sharif University of Technology
author
text
article
2016
per
This paper deals with atomistic modeling of nanomechanical behavior of actin monomer. The major cytoskeletal protein of most cells is actin, which is responsible for the mechanical properties of the cells. Actin also plays critical mechanical roles in many cellular processes which gives structural support to cells and links the interior of the cell with its surroundings. Based on the accuracy of atomisticbased methods such as molecular dynamics simulations, in this paper, we perform a series of steered molecular dynamics simulations on both ATP and ADP single actin monomers to determine their intrinsic molecular strength. The effect of virtual spring of steered molecular dynamics on the mechanical behavior of actin monomer is investigated. The results reveal increasing the virtual spring constant leads to convergence of the stiffness. The stiffness of ADP actin and ATP actin calculated as 215.16 and 228.24 pN/Å, respectively. The results also show higher stiffness and Young’s modulus for ATP Gactin in comparison to ADP Gactin. In order to compare the behavior of ATP and ADP Gactins, the number of hydrogen bonds and nonbonded energies between the nucleotide and the protein is analyzed. The obtained persistent length is 15.61 µm which is in good agreement with the other reported literature values.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
375
383
http://mme.modares.ac.ir/article_15200_6a2960ce19e850287a7925f1995b9d2a.pdf
Performance of the Multiresolution Multiscale Finite Volume Method for Solving Pressure Equation in Highly Heterogeneous Porous Media
Mehdi
Mosharaf Dehkordi
Faculty member
author
text
article
2016
per
In the present study, the incompressible flow through highly heterogeneous porous media is modeled by the Multiresolution Multiscale Finite Volume (MrMsFV) method. In order to focus on the effects of the absolute permeability structure on the accuracy and performance of the MrMsFV method, the single phase flow is considered and the effects of the gravity and variation of fluid viscosity and density are ignored. The accuracy of the MrMsFV method is examined by comparing its numerical results with those of the standard finite volume method. These permeability fields are extracted from the tenth comparative study problem of the society of petroleum engineering. For the permeability fields in which the permeability varies smoothly, it is shown that the MrMsFV method produces acceptable results. On the other hand, the numerical results along with mathematical analyses show that the MrMsFV method may produce pressure fields with unphysical peaks for channelized permeability fields. In these cases sufficient conditions for the monotonicity and boundedness of the solution are violated. In fact, the coarse scale transmissibilities may be computed in such a way that the coefficient matrix of the coarse scale pressure equation not to be a socalled Mmatrix.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
384
394
http://mme.modares.ac.ir/article_15215_095bbb16cd4d043b1beaecabb9d5499e.pdf
Machining Free Form Surfaces with Hexapod Machine Tool
ALi
Rabbani
Tarbiat Modares University
author
Mohammad Javad
Nategh
Assoc. Prof, Mechanical Engineering Department, Faculty of Engineering, Tarbiat Modares University
author
Davood
Karimi
Iranian Research Organization for Science and Technology
author
text
article
2016
per
A hexapod machine tool with a parallel structure has six degrees of freedom. This machine has a high dexterity unlike traditional machine tools. The hexapod can be used in machining free form surfaces. Free form surfaces are widely used in today industries. These surfaces are much encountered in auto, aerospace and mold design industries. Therefore machining of these surfaces has attracted the attention of researchers. In this field much research has been done in five axis machine tools. In this paper machining free form surfaces with hexapod machine tool has been investigated. The main topic of this paper is the feasibility of using hexapod as a machine tool table and machining with it. First, the interpolation of free form surfaces for parallel structure machines is explained. Then NURBS curves and surfaces are described and its formulation in matrix form is explained. Then extracting information of free form surfaces with NURBS formulation is explained. Subsequently, some explanation about preparation of machining is given. Finally two free form surfaces designed in Catia and have been machined with the developed hexapod machine tool.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
16
v.
8
no.
2016
395
400
http://mme.modares.ac.ir/article_15206_1eb8b01b71300da6488310feefb0ad05.pdf