On the Vibrational Analysis of Cantilevered Fluid Conveying Micro-Beams Rested
on Various Elastic Foundations
hamed
mirtalebi
Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran
author
Ali
Ebrahimi Mamaghani
Mechanical Engineering department, Tarbiat Modares University, Tehran, Iran
author
text
article
2020
per
In this research, using modified couple stress theory, dynamic stability of a cantilevered fluid conveying beam embedded in several types of surrounded elastic media has been studied. The governing equation for lateral vibrations of the micro-tube conveying fluid is derived using the extended Hamilton’s principle. The numerical results are obtained by employing the extended Galerkin’s method. For the sake of validation, the acquired results for simple cases are compared and outcomes indicate a very good agreement with those of previous studies available in the literature. The stability diagrams of different configurations with different flow velocities are studied and the effects of various factors such as material length scale, external diameter and different elastic properties on the stability of the system are considered. Results indicate that elastic surrounding media may enlarge the stability regions significantly at larger values of mass ratio parameter while decrease it for smaller values of mass ratio parameter. Furthermore, using elastic media mathematically defined by series functions provides the capability to simulate almost any real time operational environment the micro-tube embedded in and results in an optimal stability state of the micro-structure carrying fluid flow.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
3
16
https://mej.aut.ac.ir/article_3134_291f82d565a632cca26c31cfcf09d545.pdf
dx.doi.org/10.22060/mej.2018.14743.5926
State of Charge Estimation for Series-Connected Lithium Battery Pack Using Extended Kalman Filter
Mohsen
Esfahanian
Mechanical Engineering Dept.
author
Mohammad Javad
Esfandyari
Vehicle, Fuel and Environment Research Institute, University of Tehran, Tehran, Iran
author
Vahid
Esfahanian
Vehicle, Fuel and Environment Research Institute, University of Tehran, Tehran, Iran
author
Hassan
Nehzati
Vehicle, Fuel and Environment Research Institute, University of Tehran, Tehran, Iran
author
Haddad
Miladi
Vehicle, Fuel and Environment Research Institute, University of Tehran, Tehran, Iran
author
text
article
2020
per
The battery pack is one of the main components in electric vehicles which is usually composed of many cells connected in series. Battery state of charge estimation is one of the most important functions of the battery management system in electric vehicles. Due to the different manufacturing and operational conditions, all of the cells in a battery pack do not have the same states of charge and therefore, the cell and pack states of charge are not the same. This paper presents a method for battery pack state of charge estimation which benefits rather low computational cost as well as the high precision. First, the coulomb counting method and the open circuit voltage graph, which is obtained from the experimental results, are used simultaneously to estimate the pack average state of charge. Then, the extended Kalman filter method is used to estimate the difference between the pack average state of charge with those of the cells. The proposed method has been evaluated and verified using an experimental test bench for three series-connected lithium cells. Experimental test results indicate good performance of the proposed method in estimating the lithium battery pack state of charge.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
17
26
https://mej.aut.ac.ir/article_2876_301b5a594b900d1d8e432fc4c893e7ec.pdf
dx.doi.org/10.22060/mej.2018.13717.5707
Fault Diagnosis Based on Model and Dynamic Behavior of Vehicle Suspension System
mahdi
shahab
Department of Mechanical Engineering, Ferdowsi University, Mashhad, Iran.
author
Majid
Moavenian
Department of Mechanical Engineering, Ferdowsi University, Mashhad, Iran.
author
text
article
2020
per
This research, proposes a new effective and practical method, based on the model and dynamic behavior of vehicles for accurate and fast fault diagnoses of their suspension system. So far, a variety of complicated and impractical algorithms have been presented to identify the suspension system faults. In this method, there is no need to use special equipment and tests to diagnosis the fault, in the event of fault appearance, whenever the vehicle passes over obstacles with a necessary excitation threshold such as a speed bumper, the user is alerted, accordingly the position and size of the fault are determined. Designing a suitable structure and using neural-fuzzy networks to identify faults plays an important role in reducing the error of fault diagnosis. Reducing the number, type of sensors (using only the accelerometer sensor), not relying on high sample rates, low-cost and easy to use are other advantages of the proposed method. The fault diagnosis system performance and implementation ability is verified and confirmed by designing and conducting different experiments.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
27
42
https://mej.aut.ac.ir/article_3004_6b0d5fe41e1a22f7fd379fe0a7967a12.pdf
dx.doi.org/10.22060/mej.2018.14343.5838
Solving the Forward Kinematic Problem of Under-Constrained Cable Driven Robots for Online Control Purposes
Ali
Aflakiyan
Human and Robot Interaction Laboratory, Faculty of New Sciences and Technologies, University of
Tehran, Tehran, Iran
author
Nima
Karbasizadeh
Human and Robot Interaction Laboratory, Faculty of New Sciences and Technologies, University of
Tehran, Tehran, Iran
author
Mahdi
Tale Masouleh
University of Tehran, School of Electrical and Computer Engineering
author
Ahmad
Kalhor
School of Electrical and Computer Engineering, Human and Robot Interaction Laboratory, University of
Tehran, Tehran, Iran
author
text
article
2020
per
In this paper, a method is proposed which allows computing the position of the endeffector based on neural networks approach by taking into account external forces applied to the endeffector. As in under-constrained robots kinematics and statics are intrinsically coupled together, and they simultaneously should be considered, the forward kinematic problem of the robot can be made equivalent to an optimization problem. Solving the optimization problem is time consuming and not suitable for practical purposes. Therefore, in order to solve the forward kinematic problem a SimMechanics model based on the robot geometry and dynamic is designed and presented. By means of this method, the forward kinematic problem is solved offline and is used for online purpose. Moreover, an analysis of workspace is performed which reveals that the solution of the forward kinematic problem of the underconstrained cable robots can be calculated uniquely. By resorting to a neural network method, a position control is performed and the proposed method is validated. The comparison of the operated and desired path is shown for a helical trajectory. Maximum error in the assumed workspace is 0.4 percent. Finally, the proposed method was implemented experimentally and the results confirm the efficiency of the foregoing method.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
43
56
https://mej.aut.ac.ir/article_2706_95383298f13859ee31541dde3c2d0c49.pdf
dx.doi.org/10.22060/mej.2017.12945.5480
Design, Modeling and Control of a Hybrid Climbing Robot in Manipulation Mode Using Feedback Linearization Control Method
Hami
Tourajizadeh
tehran
author
Vahid
Boomeri
M.S. Student, Mechanical engineering department, Faculty of engineering, Tehran, Iran
author
text
article
2020
per
In this paper, design, modeling and control of a grip-based planar climbing robot is performed which is consist of a triangular plate and three actuating legs. This robot is extremely applicable for many applications in which a human operator should climb through a truss infrastructure and implement some manipulations on the relevant installations. A grip-based climbing robot is designed which has three legs and grippers for climbing through the truss and infrastructures and is able to perform manipulating tasks by locking two legs and its corresponding grippers. This robot is a kind of hybrid robot which has two phase of climbing and operating modes. The control is performed for the operational phase using Feedback Linearization (FBL) in order to overcome the disturbances of operation. Overall kinematics and kinetics of the robot is modeled. All of the modeling are verified by conducting some analytic and comparative simulation scenarios in the MATLAB and the results are also compared with ADAMS software to investigate the correctness of modeling and simulations. Also by the aid of the proposed climbing robot, it is possible to climb and perform a complete operational task through trusses and infrastructures with the best status of safety and accuracy.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
57
84
https://mej.aut.ac.ir/article_3011_21a3b2bedf8b6274d4c9061df9ca49a2.pdf
dx.doi.org/10.22060/mej.2018.13947.5760
Unmanned Aerial Vehicle Formation Flying Path Plan by Combined Algorithm of Potential and Lyapunov
masih
fathi
university of isfahan
author
Maryam
Malekzadeh Varnosfadrani
هیات علمی/دانشگاه اصفهان-دانشکده مکانیک
author
text
article
2020
per
This paper discussed and introduced a new path-planning algorithm, based on improved potential field and Lyapunov guidance vector field. According to the requirements of the unmanned aerial vehicle for tracking and obstacle avoidance mission, a real-time method is proposed by combined algorithm of Lyapunov and potential. The features of this newly introduced algorithm are real-time, fast computing and obstacle avoidance capability which causes the algorithm to perform well in complex environments and applications like coordinated tracking of unmanned aerial vehicles. Improved potential flow field primarily provides obstacle avoidance feature and Lyapunov guidance vector field provides tracking feature for this newly introduced algorithm. To achieve the mission of tracking the target and avoid the obstacle at the same time, the guidance vector field by Lyapunov guidance vector field is taken as the original vector field of improved potential flow field. The results prove that the new hybrid and combined method is applicable to complex environments and complex application like coordinate tracking of moving target.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
85
96
https://mej.aut.ac.ir/article_2913_c6b49dd9f464ece9be0ac939acf5339d.pdf
dx.doi.org/10.22060/mej.2018.14023.5779
Gust Response Analysis of Flexible Aircraft
Javad
Masrour
Researcher/ Malek Ashtar university
author
S.hossein
sadati
Aerospace Engineering -Malek Ashtar University
author
null
null
null
author
text
article
2020
per
Aircraft flexibility causes problems and difficulties which this problems even might endanger health and safety of the aircraft. This phenomena changes dynamic response of the aircraft to surface control and gust inputs with respect to the rigid models. Also, it has diverse effect on flight quality and handling characteristics. As a result, considering flexibility effects on dynamics response of aircraft is significant which requires that coupled dynamic and vibrational equations of aircraft. The present paper, introduce the dynamics of a large aircraft has been developed on base of a six degree of freedom model, which includes two rigid and four flexible degrees. Quasi steady aerodynamics has been used to describe interaction between solid and fluid dynamics. The essence of this model, enhance perdition of dynamic response to gust and other external disturbances, because of its effects of elastic modes. The characteristics of this external disturbances and elastic model, causes more flexible modes to be exited and strain energy ratio in general dynamics of the aircraft, increases. The effects of different parameters, like stiffness, gust length and profile, has been studied in numerical simulation.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
97
108
https://mej.aut.ac.ir/article_3209_eee2efc88d64cc4cd2a21f03f6d4bbb2.pdf
dx.doi.org/10.22060/mej.2018.13788.5717
Control of a Piezoelectric Nano-Actuator based on Flexoelectric Size-Dependent Theory
Hossein
Vaghefpour
Department of Mechanical Engineering, Faculty of Engineering, Shahrekord University , Shahrekord, Iran.
author
Hadi
Arvin
Department of Mechanical Engineering, Faculty of Engineering, Shahrekord University
author
Yaghoob
Tadi Bani
Department of Mechanical Engineering, Faculty of Engineering, Shahrekord University , Shahrekord, Iran
author
text
article
2020
per
In this paper, for the first time feedback control algorithms and fuzzy control are implemented for tip tracking control of a piezoelectric size-dependent cantilever nanobeam as a nanoactuator to a desired path. The governing partial differential equation of motion is obtained based on a size-dependent high-order flexoelectric theory. The equations of motion for an isotropic piezoelectric Euler-Bernoulli nanobeam are derived based on the von-Karman geometric nonlinearity besides employing the Hamilton’s principle and variational approach. In order to reduce the governing partial differential equations into a set of ordinary differential equations the Galerkin projection method is implemented. By introducing a new set of variables, the state space model of nanobeam is derived. The state feedback, integral state feedback and fuzzy control algorithms are employed to achieve a desired output for tip tracking. Regarding to the findings of this paper, it can be concluded that the fuzzy controller, integral state feedback and state feedback controller have the best performance in that order.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
109
126
https://mej.aut.ac.ir/article_3070_4b487cf8babb62ff160cc4a11b5019fc.pdf
dx.doi.org/10.22060/mej.2018.14089.5795
Natural Frequency Analysis of Rotating Thin-Walled Beams with Embedded Shape Memory Alloy Wires Subjected to Uniform Temperature Field
Mohammad
Hosseini
Mechanic, Faculty of Mechanics, Sirjan University of technology, Sirjan, Iran
author
Kazem
Majidi Mozafari
Mechanic, Faculty of Mechanics, Sirjan University of technology, Sirjan, Iran
author
Forud
Mohammadi
Mechanic, Faculty of Engineering Mechanics, Sirjan University of technology, Sirjan, Iran
author
text
article
2020
per
In this paper, free vibration analysis of the rotating thin-walled composite beams with embedded shape memory alloy wires is represented. Pre-strained shape memory alloy wires are embedded in the middle of the cross section of thin-wall composite beam, symmetrically. The onedimensional thermo-mechanical constitutive law suggested by Liang-Rogers is applied to model the thermomechanical behavior of shape memory alloy wires. The differential governing equations are extracted by using the extended Hamilton’s principle based on first-order shear deformation theory. By heating the thin-walled beam, strain recovery operation will produce a tensile force along the longitudinal thin-walled beam. In order to solve the governing equations, the extended Galerkin method is used. The effect of rotational speed, recoverable strain limit, pre-twist angle, number of shape memory alloy wire and temperature difference on the natural frequency in temperature above the austenite finish are illustrated. It is found that the natural frequencies of rotating thin-walled beam increase as the number of shape memory alloy wires and compressive pre-strained shape memory alloy wires increases. In addition, results are in good agreement with those obtained in the literature.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
127
140
https://mej.aut.ac.ir/article_3151_81064269ed7f2350f7c914dc37bcf8e7.pdf
dx.doi.org/10.22060/mej.2018.14340.5837
Vibrations Analysis of a Rotor Supported by Tilting-Pad Journal Bearings with Considering of Geometric Nonlinearity
Seyed Ali Asghar
Hosseini
Kharazmi University
author
A.
Tamadon
Department of Mechanical Engineering, Kharazmi University
author
Mahdi
Zamanian
Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University, P.O. Box 15719-14911, Tehran, Iran
author
text
article
2020
per
Vibrations of a continuous rotor with uniform circular cross section supported by two tilting-pad journal bearings at both ends are analyzed. Since the shaft is slender, shear deformation is neglected, but, gyroscopic effect is considered (Rayleigh beam theory). In addition, geometric nonlinearity due to large deformation of the rotor is considered. Based on short bearing assumption, an analytical model of a tilting-pad journal bearing with laminar and turbulence flows has been derived. Galerkin method is applied to discretize differential equations of motion. By solving discrete rotorbearing system equations, the response is obtained. For further investigation, responses of rotor-bearing system in different situations are presented. Comparing the responses of the linear and nonlinear rotor with two tilting-pad journal bearings at both ends shows that the nonlinear rotor has less amplitude than linear rotor and nonlinear rotor is closer to reality. In addition, nonlinear model has a larger natural frequency in comparison to the linear rotor. Using turbulence flow makes the bearing stiffer and have less amplitude than laminar flow. Reducing viscosity of lubricant leads to increase of amplitude of response and shows that higher viscosity make the bearing stiffer.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
141
154
https://mej.aut.ac.ir/article_3130_277e5cc9c2791227a0c180e208a44496.pdf
dx.doi.org/10.22060/mej.2018.14537.5878
An Analytical Method for Damped Free Vibration Analysis of a Cracked Beam Considering the Coupled Multimode Equations
mousa
rezaee
دانشگاه تبریز
author
vahid
shaterian alghalandis
mechanical engineering department, university of tabriz
author
text
article
2020
per
The multimodal free vibration of a beam with a breathing crack excited by arbitrary initial conditions is investigated. Taking the initial conditions to be arbitrary makes more than one mode of the beam to be excited simultaneously. By considering the bending moment at the crack position, a multi-harmonic function describing the instantaneous opening and closing of the crack is extracted. Since the modal stiffnesses of the beam are dependent on the crack parameters, the extracted crack breathing function will appear in the equations of motion and makes them to be coupled. These equations are solved using the perturbation method. Then, the free response of the beam is extracted under three cases of initial conditions: excitation of the first mode, simultaneous excitation of the first and second modes, and simultaneous excitation of the first three modes. The results show that by exciting the first mode solely, the harmonic components of the response offer very limited information about the crack. However, by exciting the first several modes simultaneously, many other harmonic components appears at the frequency response curves which are more sensitive to the crack and contain more comprehensive information about the crack parameters.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
155
172
https://mej.aut.ac.ir/article_2900_972abd5a17b4127a1202a3b085558d35.pdf
dx.doi.org/10.22060/mej.2018.13957.5762
Free and Forced Vibration Analysis of Kelvin-Voigt Viscoelastic Nanoplate by Using Modified Couple Stress Theory
saber
salehi
Department of Mechanical Engineering, University of Zanjan, Zanjan, Iran
author
Omid
Rahmani
University of Zanjan
author
S. Amirhosein
Hoseini
Buein Zahra Technical University, Buein Zahra, Qazvin, Iran
author
text
article
2020
per
With the development of nanotechnology in the industrial applications and engineering sciences, analysis of the behavior of nanostructures has become important. In recent years, expansion and using of non-classical theories to predict the behavior of nanostracture materials has attracted the attention of researchers. In this paper, free and forced vibration of viscoelastic nanoplate on the Pasternak viscoelastic foundation will be studied. In this study, due to the inability of classical theories to describe the behavior of nano-dimensional structures, the non-classical modified couple stress theory has been used for express the size effect. By using the Galerkin semi-analytic method, free vibrations analysis for six different boundary conditions are discussed; also, forced vibration of rectangular viscoelastic nanoplate is studied by using the Navier method for simply supported boundary condition. Kelvin-Voigt model is used to simulate the behavior of viscoelastic nanoplate. In the results analysis section, the effect of small-scale factor, structural viscoelastic coefficient, linear elastic coefficient of foundation, external damping coefficient of foundation and shear coefficient of foundation on the natural frequency, maximum dynamic deflection and resonance phenomenon are presented.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
173
186
https://mej.aut.ac.ir/article_2922_a133f4e9695737521b94df8b0c5c3366.pdf
dx.doi.org/10.22060/mej.2018.14036.5785
Desired Properties of Disc in Numerical Models and Its Influence on Biomechanical Behavior of Lumbar Spine
ali
orang
Master of Science, Mechanical Engineering Department , University of Tehran, Tehran, Iran
author
Mojtaba
Haghighi-Yazdi
Assistant Professor,Mechanical Engineering Department, University of Tehran, Tehran, Iran
author
Sadegh
Naserkhaki
Assistant Professor, Biomedical Engineering Department, Islamic Azad University, Tehran, Iran
author
Saeed Reza
Mehrpour
Associate Professor, Tehran University of Medical Sciences, Tehran, Iran
author
text
article
2020
per
In this paper, nonlinear finite element modeling has been presented to conduct a parametric study of disc properties on biomechanical behavior of lumbar spine. This model includes vertebrae (cancellous bone and cortical bone), disc (nucleus, annulus fibrosus, and collagen fibers), end plates, and ligaments. 3 dimensions geometry was reconstructed from computed tomography scans of lumber spine. After applying loads (compression, moment and their combinations) and boundary conditions (fixed L5) to the model, finite element analysis was conducted. Experimental tests available in literature indicated that lumbar spine shows a nonlinear mechanical behavior; hence, to consider this nonlinear behavior in this work, ligaments and annulus fibers have been modeled as nonlinear springs. The obtained results of the current study, which include intradiscal pressure and intervertebral rotation, have been compared with previous in-vitro as well as numerical data. The results of this work showed that stiffening the disc leads to decreased intervertebral rotation in different anatomical planes and the intradiscal pressure.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
187
202
https://mej.aut.ac.ir/article_2920_7b68ed05eea61fece93105abceee9135.pdf
dx.doi.org/10.22060/mej.2018.13925.5756
Impact of Flow around Annular Fins on their Thermal Stresses and Strains
mojtaba
Hosseini
Department of Mathematics, University of Sistan and Baluchestan, Zahedan, Iran,
author
ali
hatami
Department of Mathematics, University of Sistan and Baluchestan,zahedan, Iran
author
samira
payan
Department of mechanical engineering, University of Sistan and Baluchestan, Iran
author
text
article
2020
per
This study considers the impact of transient flow around an annular fin on the development of thermal stresses and strains. The fin thermal stress results were solved for two general cases with and without flow around the fin. The investigations are shown that the thermal stresses developing in the fin are initially similar in the two cases (with no flow and with the external flow). Furthermore, the results show that the maximum tangential stress takes place at the same location in the two cases but those are different. In addition, the tangential is not symmetrical in the case with the flow and the maximum stress, although at the base of the fin, is located in the flow front. Moreover, in the case with the flow, the two-dimensional temperature distribution results in a considerable asymmetrical thermal strain and consequently, asymmetrical thermal stress none of which are observed in the case without flow. Therefore, according to the results, the analysis of the flow around annular fins is essential for calculating thermal stresses.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
203
220
https://mej.aut.ac.ir/article_2990_03a879f575bec6f104e5e392139a1a41.pdf
dx.doi.org/10.22060/mej.2018.14158.5811
Prediction of the Critical Buckling Load of Grid-Stiffened Composite Plates Using Vibration Correlation Technique
Davoud
Shahgholian-Ghahfarokhi
PhD candidtae
author
Milad
Aghaei-Ruzbahani
Student
author
Gholam Hosein
Rahimi
تربیت مدرس*مهندسی مکانیک
author
text
article
2020
per
Due to unique properties, grid-stiffened composite plates are used extensively in aviation, marine and automotive industry. In recent decades, several studies are done to predict the critical buckling load of grid-stiffened composite plates without breakdown or failure. One of the most important nondestructive methods, is vibration correlation technique. The aim of this research is the prediction of the critical buckling load of grid-stiffened composite plates using vibration correlation technique. For this purpose, nonlinear vibration analysis of grid-stiffened composite plates is firstly performed in different compressive loads using finite element software ABAQUS. In the next step, critical buckling load of grid stiffened composite cylinder shells is predicted using vibration correlation technique. To validate the results of vibration correlation technique, three grid-stiffened composite plates are fabricated using filament winding and hand lay-up method with same conditions and was placed under axial compression test. Finally, the critical buckling load is measured experimentally. The results show that the difference between the critical buckling load of vibration correlation technique with experimental buckling load is less than 5%. This subject implies that vibration correlation technique is suitable for prediction of critical buckling load of grid-stiffened composite plates with very high accuracy.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
221
232
https://mej.aut.ac.ir/article_3132_565bc54bf7ce94c0af6feb67742c2255.pdf
dx.doi.org/10.22060/mej.2018.14754.5931
Nonlocal Analysis of Chaotic Vibration, Primary and Super-Harmonic Resonance of Single Walled Carbon Nanotube Considering Thermal Effects
Habib
Ramezannejad Azarboni
aDepartment of Mechanical Engineering, Ramsar branch, Islamic Azad University, Ramsar, Iran
author
Hemad
Keshavarzpour
Department of Mechanical Engineering, Rasht branch, Islamic Azad University, Rasht, Iran.
author
Mohammad
Rahimzadeh
Department of Mechanical Engineering, University of Golestan, Gorgan, Iran
author
text
article
2020
per
In this article, a nonlinear elastic Bernoulli–Euler beam model is presented to investigate the chaotic behavior and primary and superharmonic resonance of single walled carbon nanotubes embedded in a visco-elastic medium at an elevated temperature. Using the Galerkin method and fourthorder Runge-Kutta method the governing equation is solved. The bifurcation diagram and largest Lyapunov exponent are employed to detect the critical amplitude of external force of periodic and chaotic response of single walled carbon. Having known the critical values, phase portrait and Poincare maps are presented to observe the periodic and chaotic behavior of the system. Moreover, the amplitude– frequency response for the primary superharmonic resonance of system is derived with the multiple scale method to investigate the feasibility of jump phenomenon. The sensitivity of jump phenomenon are studied for the selected viscoelastic foundation parameters, detuning parameter and external amplitude load. The results show that the amplitude of external force, viscoelastic foundation parameters, detuning parameter and temperature change in the cases of high and low temperature have a significant effect on the frequency response with jump phenomenon of system. In addition, the chaotic vibration of carbon nanotube can be controlled by changing of amplitude of external force.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
233
248
https://mej.aut.ac.ir/article_2968_d5a26c26fbb72492011f099575bdc9ed.pdf
dx.doi.org/10.22060/mej.2018.13950.5761
Developing a Bidirectional Evolutionary Topology Algorithm for Continuum Structures with the Objective Functions of Stiffness and Fundamental Frequency with Geometrical Symmetry Constraint
Mohsen
teimouri
Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
author
Masood
Asgari
صنعتی خواجه نصیرالدین طوسی
author
text
article
2020
per
Topology optimization of structures, seeking the best distribution of mass in the design space to improve the performance and weight of a structure, is one of the most comprehensive issues raised in the field of structural optimization. In addition to the structure stiffness as the most common objective function, frequency optimization is of great importance in automotive and aerospace industries achieved by maximizing the fundamental frequency or the gap between two consecutive eigenfrequencies. The phenomenon of multiple frequencies, mesh dependency of topology responses, checkerboarding, geometric symmetry constraint, and occurrence of artificial localized vibration modes in low-density regions are the most important challenges faced by the designer in stiffness and frequency optimization problems which influence the manufacturability of the design too. In this paper, Bidirectional Evolutionary Structural Optimization (BESO) method which is a successful approach in stiffness problems is applied for a frequency and stiffness problem separately via creating a software package including a Matlab code and Abaqus FE solver linked to each other. Also, in this paper, the effect of geometric symmetry constraint is considered on resulted topologies from stiffness and frequency problems. So the BESO method is applied for modeling a 2D beam and its stiffness and frequency optimization and finally, the optimization results of both objective functions will be compared with the initial structure.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
249
264
https://mej.aut.ac.ir/article_2895_9a1eda2ca81d64b5a40f227d0a2fb1a8.pdf
dx.doi.org/10.22060/mej.2018.13881.5741
Numerical and Experimental Analysis of Damage Evolution and Martensitic Transformation in AISI 304 Austenitic Stainless Steel at Cryogenic Temperature
Seyed Saied
Kazemi
Department of Mechanical Engineering, University of Tehran, Tehran, Iran
author
Milad
Homayoun Fard
PhD Student Department of Mechanical Engineering, University of Tehran, Tehran, Iran
author
Seyed Mahdi
Ganjiani
Department of Mechanical Engineering, University of Tehran, Tehran, Iran
author
Nasser
Soltani
PhD PROFESSOR at Department of Mechanical Engineering, University of Tehran, Tehran, Iran
author
text
article
2020
per
In this research, properties of ductile damage evolution and martensitic phase transformation in an AISI 304 stainless steel at cryogenic temperature has been studied experimentally and numerically. Simple loading-unloading tension tests for specimens floating in liquid nitrogen have been performed. Accordingly, the cryogenic chamber has been designed and constructed to plunge the tensile test samples into the liquid nitrogen. From simple loading-unloading tension tests, the graph of force-deformation and the evolution of damage parameter during elastic unloadings have been determined. Afterwards, the x-ray diffraction tests have been performed on the stretched sample tests to evaluate the evolution of martensite phase in the resultant biphase material. In the numerical analysis, combining the phase transformation model of Garion and Skoczen and isotropic damage model of Lemaitre, a constitutive model for monotonic loadings has been introduced. The Garion and Skoczen model has been developed based on the assumption of small strains (under 0.2) for cryogenic condition. Furthermore, the hardening law for the biphase material has been obtained from the Mori-Tanaka homogenization. The numerical analysis in this study was carried out implementing the combined constitutive model by means of a user-defined material model subroutine in Abaqus/Standard. Finally, comparing the numerical simulation with the experimental data, parameters of the model has been calibrated.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
1
no.
2020
265
278
https://mej.aut.ac.ir/article_3135_3dff7a90f2746f59073abd240b2e606e.pdf
dx.doi.org/10.22060/mej.2018.14482.5868