Numerical Analysis of Rolling Contact Fatigue in Common Turnouts of Iran Railway Track
Majid
Shahravi
علم و صنعت ایران
author
Mohammad
Rezasefat
School of Railway Engineering, Iran University if Science and technology
author
text
article
2018
per
The highest amount of reported failures in railway tracks are due to turnout problems. The main causes of these breakdowns are: high wheel-rail contact forces, creep in the switchblade due to changes in the rail profile, and inconsistency in the rail profile during wheel passage over wing rail and crossing nose causing collision forces. In this paper, a new method for crossing nose fatigue life prediction is presented using the finite element approach. Firstly, a dynamic model containing a complete turnout (switch and crossing panels) is simulated. For a closer look at the crossing, the results of the forces generated by the dynamic model are transmitted to a more detailed static model at specific sections, because of the criticality of this point in track. Then the stress and strain results are extracted to perform the fatigue analysis on the crossing nose in order to calculate fatigue crack initiation life and critical planes. Regarding the importance of fatigue and the necessity of investigating the effect of different variables on fatigue life, a parametric study is conducted considering variables such as velocity, wagon weight, and turnout type. The results indicate that the predicted fatigue life in UIC60 crossings is less than U33. Also, by increasing the wagon weight and speed or the curve radius fatigue crack initiation life have increased.ntrol the lock-in regime.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2018
2029
2044
https://mej.aut.ac.ir/article_3203_b4739b2762ac52353bc5b34416ea2e41.pdf
dx.doi.org/10.22060/mej.2018.14651.5906
Modeling of hyperelastic incompressible behavior of functionally graded material under bending load
Gholam Hosein
Rahimi
تربیت مدرس*مهندسی مکانیک
author
Mohammad Mahdi
Memarian
Tarbiat Modares University
author
Yavar
Anani
Post. Doc. Researcher
author
Shahram
Hosseini Chaleshtari
PhD Student of Mechanical Engineering at Tarbiat Modares University
author
text
article
2019
per
In this paper, the behavior of inhomogeneous functionally graded rubber with large deformations and under bending loading is modeled by assuming an incompressible hyper-elastic material. In hyper-elastic inhomogeneous functionally graded materials, mechanical properties continuously changes from one point to another in the specified direction. In the other words, they gradually become material from material to another. For modeling the nonlinear behavior of material, hyperelasticity theory and strain energy density functions, which are a function of the invariants of the left deformation Cauchy-Green tensor, are used. In order to be able to apply the existing energy functions to inhomogeneous functionally graded materials, they must be changed, therefore, the changes in the constant of the energy functions are assumed power shape and in the direction of the curvature radius after bending, due to the inhomogeneous functionally graded of the material. Since many materials are inhomogeneous, using the assumption of inhomogeneous functionally graded of the material is one of the most practical methods. In this paper, the modeling of the hyperelastic behavior of inhomogeneous functionally graded rubber is done under bending loading and extraction of the Cauchy stress relations governing the cross-section caused by this loading. For modeling, the generalized Mooney-Rivlin energy function is used and the properties change in radial direction are considered and heterogeneity variations are also investigated.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2045
2062
https://mej.aut.ac.ir/article_3253_9ddb17b4cdb1a06ef74e192bc600c38b.pdf
dx.doi.org/10.22060/mej.2019.14773.5936
‘Effect of Initial Temperature and Cooling Practice on Thermo-Mechanical Stress of
Ring Rolling
ali
negahban
Faculty of Aerospace Engineering, Aeronautical University of Science and Technology, Tehran, Iran
author
ehsan
barati
Mechanical and Aerospace Engineering Department, Malek-Ashtar University of Technology, Shahinshahr, Esfahan, Iran
author
Abdolali
maracy
Mechanical and Aerospace Engineering Department, Malek-Ashtar University of Technology, Shahinshahr, Esfahan, Iran
author
Nader
vahdat azad
Faculty of Aerospace Engineering, Aeronautical University of Science and Technology, Tehran, Iran
author
text
article
2019
per
Ring rolling is a metal forming process used to forge precise, seamless, circular, shaped parts. Due to the unique properties of the produced rings, the application in the advanced industries is high. The most important advantage of the process is the uniform flow of material in the ring after the process. Usually, the working temperature of the device is high during the rolling of super alloys. The high temperature could damage the work rolls. In spite of the cooling practice, the work roll temperature is raised. In general, this reduces the work roll strength. In this research, the effect of various temperature and cooling practice on thermo-mechanical stresses in work roll of ring rolling mill has been investigated. The results show that the amount of produced thermo-mechanical stresses on the work rolls is completely different. In the main roll, mechanical stress has a greater effect on thermo-mechanical stresses. However, in the mandrel, thermal stress determines the amount of thermo-mechanical stresses. Unlike the mandrel, the effect of cooling practice on thermo-mechanical stresses of the main roll is negligible. The results show that cooling practice increases the amplitude of equivalent stress and reduces the mean stress in the work rolls.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2063
2080
https://mej.aut.ac.ir/article_3441_684a69d64bc54e371a9cff81031bbc20.pdf
dx.doi.org/10.22060/mej.2019.14764.5938
Estimation of Stress Concentration Factor of Elliptical Cutout in the Composite Sheets
under Tensile Load
Ali
Abbasnia
Department of Mechanical Engineering, Faculty of Mechanics, Shahrood University of Technology , Shahrood, Iran
author
Abbas
Rohani
Assoc. Prof., Bio. Mech., Fac. Agri., Ferdowsi University of Mashhad, Mashhad, Iran
author
mohammad
jafari
Department of Mechanical Engineering, Faculty of Mechanics, Shahrood University of Technology, Shahrood, Iran
author
text
article
2019
per
In this paper, we try to use a multiple linear regression method to explicitly describe the explicit relation between the stress concentration coefficient of plates containing elliptic openings in terms of mechanical properties and the angle of rotation of openness. First, the stress concentration coefficient for a lot of composites was calculated by the analytical method based on the mixed variable method and using different values of the mechanical properties of the composites. Using the obtained data, using the regression method multiple linear the explicit relation was used to estimate the stress concentration coefficient in unbounded composite plates containing elliptic openings under tensile load. It is important to note that several factors affect the concentration of tension around openness. Therefore, by correct selection of these parameters, it can be significantly reduced the stress concentration and increased the structural strength. One of these factors is the angle of rotation of openness, which is discussed in this article. In addition to the ease of use, the proposed relationship, by eliminating complex and complex analytical solutions, saves time and allows the designer to obtain the desired parameters to achieve the desired stress. The results showed that the regression model was able to estimate the coefficient of stress concentration with an error of less than 1 percent.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2081
2092
https://mej.aut.ac.ir/article_3377_6e90346db9e44850be48f6324bf5df30.pdf
dx.doi.org/10.22060/mej.2019.15143.6042
Experimental and Numerical Investigation of Second Mode of Failure in Unlike End
Notch Flexure Samples
Sattar
Maleki
Department of Mechanical Engineering, Quchan University of Technology, Quchan, Iran
author
atieh
andakhshideh
Department of Mechanical Engineering, Quchan University of Technology, Quchan, Iran
author
Alireza
Seyfi
Department of Mechanical Engineering, Quchan University of Technology, Quchan, Iran
author
text
article
2019
per
Localized lamination using composites is one of the effective solutions to repair damaged metallic pipelines. The connection of composite repair to the metal substructure in this method is one of the most important design parameters. Therefore, deriving the important parameters at the junction will help engineers in designing and predicting the interlaminar crack initiation and propagation at the composite/metal interface. In this paper, to investigate the second mode of failure in this method, the strain energy release rate is calculated experimentally and numerically in a steel/composite bond. According to an experimental standard for calculating the second mode strain energy release rate, ASTM-D7905, experimental tests are accomplished for three symmetric and asymmetric unlike end-notched flexure specimens and a relationship for the thickness of each material to have symmetric specimens is proposed. To validate the thickness calculation relationship, the finite element modeling of unlike samples using virtual crack closure technique is used which indicates the good agreement of experimental and numerical results. Comparing the experimental results showed that the strain energy release rate of symmetric samples is more than asymmetric ones and about 1.6 times as large.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2093
2106
https://mej.aut.ac.ir/article_3343_17f5688bc52619caadb53396c50981ad.pdf
dx.doi.org/10.22060/mej.2019.15299.6089
Optimization of Influence Parameters on Thermal Buckling of Hybrid Composite Plates with Cutout Using Genetic Algorithm
sajad
mahdavi
Faculty of Mechanical Engineering, Shahrood University of Technology
author
Alireza
Shaterzadeh
Faculty of Mechanical Engineering, Shahrood University of Technology
author
mohammad
jafari
Faculty of Mechanical Engineering, Shahrood University of Technology
author
text
article
2019
per
Optimization in the design and maintenance of many engineering systems, economic and even social has been used to minimize the cost or maximize profits. In the buckling analysis, the hybrid composite plates with cutout, the effective parameters on buckling are the cutout geometry, fiber angle, cutout size to plate size ratio, bluntness of cutout corners, and rotation angle of cutout. Therefore, in this study, using genetic algorithm method an attempt has been made to introduce the optimum parameters to achieve the Maximum amount of critical buckling temperature of hybrid composite plate with polygonal cutouts in different boundary conditions and stacking sequences, which are subject to uniform temperature rise. The cutouts in this study are circular, pentagonal, and hexagonal. The solving method used to analyze this study is the finite element based on the energy method. Also, the theory used in this paper is the first-order shear deformation theory. The results presented in this case show that by choosing the appropriate shape of cutout and the optimal selection of parameters affecting buckling, the plate’s resistance to thermal buckling can be increased. It was also found that stacking sequences and boundary conditions have a significant effect on the critical buckling temperature of a hybrid composite plate with cutout.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2107
2122
https://mej.aut.ac.ir/article_3418_a7bc28cc5c5902e25cae3b3967d5e5c3.pdf
dx.doi.org/10.22060/mej.2019.15514.6142
Investigation on the Effect of Pressure and Radius of Contact Surface Curvature on the Friction Coefficient in Contact Surfaces of Interference Fit Joints
Kaveh
Abbasi
Department of Mechanical Engineering, Islamic Azad University, Eslam Abad-E-Gharb, Kermanshah, Iran
author
Hazhir
Ehsasi
Department of Mechanical Engineering, Islamic Azad University, Kermanshah, Iran
author
text
article
2019
per
Interference fit joints are widely used to produce tight joints. Interference fit joints could be applied under dynamics and statics design loads, successfully. Interference fit joints are always imperfect and also affected by some parameters which directly affect the operation of these joints. For instance, the contact surface of every manufactured joint part is not a perfect cylinder and always there are some form defects. The variation of these parameters could affect the performance and strength of interference joints, so these parameters should be considered. Some effective parameters on the strength of interference fit joints are friction coefficient, roughness, materials properties, dimensions and geometric irregularities of contact surfaces. In this study, the effect of diameter of shaft and interference value variation on the friction coefficient in contact surface and strength of joints are investigated. Finite element results are interacted with experimental ones to estimate friction coefficients. Also, factorial method, which is a statistical method for design of experiments, is used to analyze the effects of pressure, which is vary by variation of interference, and radius of contact surface curvature on friction coefficient and strength of joints. Results indicate that the friction coefficient changes with diameter of interference surface, inversely and increase of interference and consequently, pressure leads to growth of friction coefficient.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2123
2134
https://mej.aut.ac.ir/article_3447_0d4863e441894fcd8739729eed5830a5.pdf
dx.doi.org/10.22060/mej.2019.15509.6143
Metallic Closed-Cell Foam Filled Tube Uniaxial Crushing Behavior Analysis Using Voronoi Approach
Youssef
Taraz Jamshidi
Mechanical Engineering Department, SRTTU, Tehran, Iran
author
Ali
Pourkamali Anaraki
Mechanical Engineering Department, Shahid Rajaee University, Tehran, Iran
author
Mojtaba
Sadighi
Mechanical Engineering Department, Amirkabir University of Technology, Tehran, Iran
author
Javad
Kadkhodapour
Mechanical Engineering Department, Shahid Rajaee University, Tehran, Iran
author
Seyed Mohammad Hossein
Mirbagheri
Department of Mining & Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran
author
Behnaz
Akhavan
Industrial Engineering Department, Tehran North Branch, Islamic Azad Universitty, Tehran, Iran
author
text
article
2019
per
Porous materials especially metallic foams are novel materials with high energy absorption and strength to weight ratio capability. In the present paper, we investigate quasi-static uniaxial compression and crushing behavior of closed-cell graded aluminum foams and foam-filled tubes, both numerically and experimentally. To model the mentioned specimens, we place cubes with several densities and strengths to generate functionally graded specimens. Specimens are considered to be graded with two and three layers and non-graded single layer, with and without tubes. Various standard uniaxial compression experiences are conducted for numerical model calibration and validation and also for non-linear mechanical properties and hardening characterization. To enhance strength and energy absorption capability and also tailoring purpose, we layout the cubic foams in tubes with square profile. The 3D Voronoi diagrams approach is manipulated to model stochastic foam microstructure. Also Novel unit cell is proposed based upon Kelvin cell. We implement the hybrid finite element analysis and Voronoi diagram using Python script and Abaqus 2017 commercial finite element method based code for more convenient modeling and efficient analysis. Finally, and after numerical model calibrations, numerical and experimental results showed good agreement.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2135
2148
https://mej.aut.ac.ir/article_3401_d6f79730f24b88be6070c1cefbf6d425.pdf
dx.doi.org/10.22060/mej.2019.15661.6176
An Experimental Investigation on Tensile and Impact Properties of Bagasse/Polypropylene Natural Composite
Shahrouz
Yousefzadeh
- Department of Mechanical Engineering, Aligudarz Islamic Azad University, Aligudarz.
author
Mohammad
Kashfi
Mechanical engineering department, Ayatollah Boroujerdi University, Boroujerd, Iran
author
Parviz
Kahhal
Mechanical engineering department, Ayatollah Boroujerdi University, Boroujerd, Iran
author
Abbas
Ansari-asl
Ahwaz islamic azad university
author
text
article
2019
per
Sugarcane bagasse is one of the most abundant types of natural fibers which can be utilized to fabricate natural composite materials. Since bagasse is one of the wastes of Khuzestan province sugarcane factories, recycling might be an opportunity to enjoy its economic and environmental benefits. In the present study, the mechanical and microstructural properties of Bagasse/Polypropylene natural composite fabricated by the injection molding method were investigated. Bagasse fibers after the drying process were mixed up to polypropylene with 10, 30, 40 and 50% weight fraction of bagasse. In order to investigate the mechanical properties, experimental tests consist of tensile test and Charpy impact tests were carried out. The results showed that the maximum material strength was obtained from the sample made of 40% weight fraction of bagasse. The strength of 40% bagasse was found about 10%more than 50% bagasse. The microstructural analysis indicated that the failure mechanism of 40% bagasse was mainly affected by fiber breakage. However, the main failure mechanism of 50% bagasse was changed to fiber pull out. Additionally, impact absorbed energy was significantly decreased by increasing the bagasse weight fraction.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2149
2160
https://mej.aut.ac.ir/article_3435_9210521b28f11c64bba31c9585e9cdf0.pdf
dx.doi.org/10.22060/mej.2019.15715.6197
Damping Modeling in Dual Axis Torsion Micro-Actuators Considering the Bending of the Supporting Beams
Mozhde
Khadembashi
School of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
حمید
معین فرد
Room 214, School of Mechanical Engineering, Department of Eng, Ferdowsi University of Mashhad, Mashhad, Iran
author
text
article
2019
per
Torsional micro-actuators are employed in a variety of applications such as optical switches and biomedical imaging. Squeezed film damping is one of the important energy loss mechanisms in these systems. This kind of damping is a key factor in the performance characterization of micro-electro-mechanical systems and has been paid attention by many researchers. The objective of this paper is modeling the squeeze film air damping in dual axis torsional micro-actuators by considering the bending of the supporting torsion beams. To do so, first, the air inertial effects is neglected compared to its viscosity and the Reynolds equation governing the behavior of trapped air between the actuator and the underneath plate is simplified. The resulting equation is then normalized and solved using the extended Kantorovich method for obtaining the air pressure distribution under the plate. This pressure distribution is then employed for finding the damping force and torques. A parametric study is also carried out to determine the effect of different design parameters on the damping of the system. The results of this paper can be effectively employed for accurate dynamic modeling of dual axis torsional micro-actuators.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2161
2176
https://mej.aut.ac.ir/article_3353_1f8300e668141bbc65232869dce5ee18.pdf
dx.doi.org/10.22060/mej.2019.15181.6060
Nonlinear Vibration and Stability Analysis of Thermally Postbuckled Double-Layered Graphene Sheet
GholamAli
Varzandian
Department of Mechanical Engineering, Yasouj University
author
Sima
Ziaee
Department of Mechanical Engineering, Yasouj University
author
Mehrdad
Farid
Department of Mechanical Engineering, Shiraz University
author
Abbas
Niknejad
Department of Mechanical Engineering, Yasouj University
author
text
article
2019
per
In the present research, the vibration behavior is presented for a thermally postbuckled double layered graphene sheet. For this purpose, the graphene sheet is modeled as a non-classical orthotropic plate. The formulations are based on the Kirchhoff’s plate theory, and the von Karman-type nonlinearity is considered in the strain-displacement relations. Eringen’s nonlocal elasticity theory is employed to incorporate the size effects. The thermal effects, van der Waals forces between layers and chirality are also included and the material properties are assumed to be temperature-dependent. A semi analytical solution is obtained using multiple time scales method. The effects of variation of the small scale parameter to the natural frequencies, deflections and response curve of double layered graphene sheet are analyzed and the numerical results are obtained from the nonlocal plate model. Numerical results are compared with those of similar researches. Effects of various parameters on the postbuckled vibration of graphene sheet in thermal environments such as the scale parameter, length, and thermal load are presented. The stability of vibration modes around a buckled configuration is investigated. The results show that the scale parameter and thermal changes have very important roles on the nonlinear vibrational behavior of the nano scale buckled structures.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2177
2194
https://mej.aut.ac.ir/article_3479_38fd435eba17470911f204dbd0e0ba27.pdf
dx.doi.org/10.22060/mej.2019.15499.6158
Free Vibration Analysis of Doubly Curved Composite Sandwich Panels with Variable Thickness
Mostafa
Livani
Structures, Aerospace Engineering, Air University of Shahid Sattari
author
Keramat
Malekzadeh Fard
Malek ashtar univ.
author
text
article
2019
per
In this research, the free vibration analysis of doubly curved composite sandwich panels with variable thickness is studied using higher order sandwich panel theory. For the first time, considering different radii of curvatures of the face sheets in this paper, the thickness of the core is a function of plane coordinates (x,y). In addition, in the current model, the continuity conditions of the transverse shear stress, transverse normal stress and transverse normal stress gradient at the layer interfaces, as well as the conditions of zero transverse shear stresses on the upper and lower surfaces of the sandwich panel are satisfied, which is unique. The vertical displacement component of the face sheets is assumed as a quadratic one, while a cubic pattern is used for the in-plane displacement components of the face sheets and all displacement components of the core. The equations of motion and boundary conditions are derived using the Hamilton principle. The effects of some important parameters including composite layup sequences, length to width ratio, varying properties of the face sheets materials, Face sheet thicknesses ratio and varying materials of the face sheets were investigated. The results are validated by the latest results published in the literature.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2195
2212
https://mej.aut.ac.ir/article_3408_2a9b06bba055acaaec06d2d7b4d46ad8.pdf
dx.doi.org/10.22060/mej.2019.15404.6115
Stress and Vibrational Analysis of Non-Pneumatic Tire and Study the Effect of the Spoke Curvature and Velocity on the Wheel Vibration Using Finite Element Method
Farzaneh
Baradaran
Department of Mechanical Engineering, Isfahan University of Technology
author
Peiman
Mosaddegh
Department of Mechanical Engineering, Isfahan University of Technology
author
Reza
Tikani
Isfahan University of Technology
author
text
article
2019
per
Tweel is a new type of non-pneumatic tire. The purpose of this research is to simulate the wheel from the beginning of the movement to reach the speed of 60 km/h and study the effect of spoke curvature and vehicle speed on the vibration amplitudes. Spokes curvature has an effect on the vibrational behavior of the spoke and the wheel. For this reason, in addition to the reference wheel with spokes curvature of 5 mm, two other models with spokes curvature of 4 mm and 6 mm are also modeled. This study has shown that with the change in the curvature of spokes, the amplitude of spokes vibration and its frequencies have changed dramatically. Two important disadvantages of this type of wheels are vibrations and making loud noises at speeds more than 80 km/h. For this purpose, the speed of the wheel in the simulation is increased to 100 km/h. It is observed that at speeds of higher than 70 km/h, the spokes of the wheel are highly vibrated. At this moment, spokes vibrational frequencies are as same as their natural frequencies and the resonance occurs. As a result, the designed wheel is useful at speeds lower than 70 km/h.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2213
2230
https://mej.aut.ac.ir/article_3368_131fd33b6703750bd1a05036247cf53a.pdf
dx.doi.org/10.22060/mej.2019.15051.6023
Dynamic Behavior of a Micro-Beam Subjected to Voltage and Fluid Flow as a Micro Vortex Generator
mousa
rezaee
university of tabriz
author
Naser
Sharafkhani
Department of mechanical engineering, university of Tabriz, Tabriz, Iran.
author
Mohammad Taghi
Shervani Tabar
Department of mechanical engineering, university of Tabriz, Tabriz, Iran.
author
text
article
2018
per
The present work investigated the nonlinear vibration of a cantilever cylindrical micro-beam subjected to voltage and fluid flow as a micro vortex generator. As the microbeam is subjected to the fluid with a given velocity, in addition to the load due to fluid added mass, the lift and drag forces as the two basic flow-induced factors affecting the dynamics of the micro-beam were modeled using Van der pol equation. The Euler-Bernoulli beam theory was used to model the cross fluid motion of beam under nonlinear electrostatic force as a result of the applied voltage. The Galerkin method was used to convert the partial differential equation to regular differential equations as well as to solve the coupled nonlinear equations governing the micro-beam motion and the wake oscillation to evaluate the response of the coupled structure to a combined applied voltage and fluid flow. The effect of fluid flow on the Reynolds number and fluid vortex frequency as two main parameters in the creation of the Lock-in phenomenon was studied. In addition to the effect of different fluid velocities, the response of the micro-beam to different input voltages in the presence of fluid flow was investigated and it was shown that for a given flowing fluid, the applied voltage can be used to control the lock-in regime.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2018
2231
2242
https://mej.aut.ac.ir/article_3089_3a1a6bc95994a9312adb5514893997da.pdf
dx.doi.org/10.22060/mej.2018.14469.5881
The Effect of Curvature of Microbeam and Electrode on the Snap-Through and Pull- In Instabilities
Ehsan
Akrami Nia
Mechanical Engineering, Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
hamid
ekhteraei toussi
Mechanical Engineering, Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
text
article
2019
per
Due to the pull-in instability, the sustainability of micro-electro-mechanical systems is vulnerable. One of the proposed mechanism to improve the stability of these systems is the use of curved microbeams. The curvature causes the snap-through phenomenon by which the microbeam moves to its second stable position. Despite the advantages of snap-through, sometimes it leads to unstable conditions. In order to use the merits of curved structure and avoid the snap-through effect, in the present study, the performance of a structure composed of curved electrode is investigated. By assuming the Euler-Bernoulli beam theory and based on the modified couple stress theory, the governing equation is obtained by using Hamilton’s principle. This equation is converted to a nonlinear ordinary differential equation by using the reduced-order model based on Galerkin procedure. The numerical solution is formulated and obtained by using the MATLAB software. The performance of the systems composed of curved microbeam and curved electrode are compared with each other, as well as with the systems made of straight elements. The results show that in cases where snap-through may cause unstable conditions, the use of curved electrode can result in more sustainable behavior in a wider range of position and voltage levels.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2243
2260
https://mej.aut.ac.ir/article_3373_674a2c7cec2c8e59533a596b879afbe9.pdf
dx.doi.org/10.22060/mej.2019.15562.6157
Edgewise Vibration Reduction of a Small-Scale Wind Turbine Blade with Considering Vibration Coupling
Hamed
Biglari
Faculty of Mechanical and Energy Engineering, Shahid Beheshti University, Tehran, Iran
author
Vahid
Fakhari
Faculty of Mechanical and Energy Engineering, Shahid Beheshti University
author
text
article
2019
per
Edgewise vibration in wind turbine blades is one of the important factors that results in reducing the performance of wind turbines. In this paper, an optimally tuned mass damper is proposed to reduce edgewise vibration of a small-scale horizontal axis wind turbine blade (5 kW) with considering the coupling between edgewise and flapwise vibrations. For this purpose, partial differential equations governing dynamics of the system are derived using the Lagrange method. These equations are completely nonlinear and linearization is not performed to avoid possible errors in the analysis and also, the blade is considered as a flexible member. In deriving governing equations, coupling effect between in-plane and out-of-plane vibrations of the blade, and effect of centrifugal forces and gravity are considered. In order to reduce vibration of the blade, a tuned mass damper is used and its parameters are optimized using one of the genetic algorithm methods for a real blade sample. Finally, with applying wind force as a sweep sine excitation, effectiveness of the optimized tuned mass damper in vibration reduction of the blade is investigated and the related results are presented. Results show that the wind turbine blade vibration reduction is achieved properly using the optimally tuned mass damper.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2261
2276
https://mej.aut.ac.ir/article_3508_cd3a45faecc4911dec5294d50dd91686.pdf
dx.doi.org/10.22060/mej.2019.15531.6151
Modeling and Sliding Mode Control of Rotating Helical Pump
Behnam
Miripour Fard
Assistant professor, Faculty of mechanical engineering, University of Guilan, Rasht, Iran
author
Amir Hesam
Sajjadinia
Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, IRAN
author
Farshad
Hashemi Nader
Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, IRAN
author
text
article
2019
per
Two-phase fluids transportation is very important in the industry. Rotating helical pump is a special form that can be used to transfer fluid-gas flows and also to generate pulsatile flows. The structure of this pump differs from conventional pumps and its geometry can be changed during operation. In this paper, while demonstrating a fabricated second version of the rotating helical pump, a dynamic analysis is performed for the first time and the governing equations are extracted based on the input control variables (rotational speed and tilt angle of the pump). In the dynamical analysis, a rotating control volume corresponding to a spiral tube is considered. In order to determine the values of the inputs corresponding to the desired outputs, we use the non-dimensional characteristic curves of the pump that was published in the previous study. Then the control is performed on the basis of two input variables to reach the desired pump head and flow rate. A sliding mode controller is implemented. The results include governing equations of the rotating helical pump that can be used in future studies. Moreover, the results show the success of the sliding mode method in control of the pump.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2277
2292
https://mej.aut.ac.ir/article_3398_fbf05638c98312d9497689041c04ad5e.pdf
dx.doi.org/10.22060/mej.2019.15770.6198
Design of a Hybrid Adaptive Neuro-Fuzzy Inference System Proportional–Integral– Derivative Controller for Vibration Mitigation of a Structure against Earthquake
Seyed Mahdi
Hadad Baygi
dept. of electrical engineering, Khorasan Institute of Higher Education, Mashhad, Iran
author
javad
faraji
Dept.of electrical engineering, Khorasan Institute of Higher Education, Mashhad, Iran
author
Ali
Karsaz
dept.of electrical engineering, Khorasan Institute of Higher Education, mashhad, Iran
author
text
article
2019
per
This paper proposes a new hybrid controller based on combining adaptive neuro-fuzzy inference system method and proportional–integral–derivative controller, for vibration mitigation of structural system. The proposed controller although has the proportional–integral–derivative controller features, create a fuzzy inference system that has fewer bugs and errors than neural networks in calculations. The whale optimization algorithm is used for optimum tuning of the proposed method and also for identification of parameters related to the experimental structure. Considering four well-known earthquake real data the performance of the proposed controller is evaluated. Then the results are compared with two other controllers namely, fuzzy logic control and adaptive neuro-fuzzy inference system, which are designed for a four-degree of freedom building. The simulation results show that the proposed controller performs better than other strategies which are developed. The results obtained from the simulation show the better performance of the suggested method than the other control methods in reducing the displacement and acceleration of all floors. The results show that the maximum acceleration related to the building’s floors while using proposed method has improvement of 36.3% for the El Centro, 35.4% for the Northridge, 27.7% for the Athens and 22.5% for the Mexico City earthquakes regarding fuzzy control and adaptive neuro-fuzzy inference system control.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2293
2316
https://mej.aut.ac.ir/article_3385_83c319da7e95252aa5217b94dd0d5977.pdf
dx.doi.org/10.22060/mej.2019.15513.6141
Vibration Analysis of Cable-Driven Parallel Robots to Define Critical Speeds
Mazhar
Aminpur
Department of Mechanical Engineering- Faculty of Engineering- University of Kurdistan- Sanandaj- Iran
author
Sirwan
Farhadi
دانشگاه کردستان
author
text
article
2019
per
Cable-driven manipulators are a generation of parallel cinematic chain robots which provide important features including wide workspace and cost-effective high speed operations. However, due to wideness of the workspace and the flexibility of the cables, they are susceptible to unwanted vibrations which reduce their precision. Therefore, determination of velocity limits in the operation workspace is of high importance. In this study, stability analysis and critical velocities of a four cable plane robot are considered. Governing equations of the system are extracted by use of finite element method and employing variable length element. The characteristic coefficients of the extracted equations are nonlinear and velocity dependent ones. To provide a stability analysis, the equations are linearized assuming that the end-effector experiences quasi-static movements and the system is subjected to low amplitude vibrations. Afterward, the corresponding eigenvalue problem is analyzed and critical speeds of the robot in whole workspace domain are calculated. Furthermore, vibration frequencies corresponding to the unstable eigenvalues are determined. It is observed that system critical speed reduces as the end-effector moves to the boundaries of the workspace. In contrast to this, the frequency of the corresponding unstable modes increases as the end-effector moves to the borders of the workspace.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2317
2328
https://mej.aut.ac.ir/article_3359_cc0a02aa901f0fcb48948ab8bfd30381.pdf
dx.doi.org/10.22060/mej.2019.15107.6026
Impacts of Social Robots in Education and Rehabilitation of Children with Autism in Iran
Alireza
Taheri
Mechanical Engineering Department, Sharif University of Technology
author
Ali
Meghdari
Mechanical Engineering Department, Sharif University of Technology
author
Minoo
Alemi
Department of Humanities, Islamic Azad University-West Tehran Branch
author
Hamidreza
Pouretemad
Institute for Cognitive and Brain Sciences (ICBS), Shahid Beheshti University, Tehran, Iran
author
text
article
2019
per
In this study, our objective (as one of the pioneers in Iran) is to explore the clinical application of interactive humanoid robots as medical assistants in the treatment and education of children with autism in order to improve their social and cognitive skills. To reach this goal, we have designed and implemented a set of therapeutic games with the following topics: a) Investigation of social robots’ acceptability and effect on improving the fine/gross movement imitation of Iranian children with autism, b) Exploring the effect of a robot-assisted music-education program on children with autism spectrum disorders’ socio-cognitive skills improvement (as an individual clinical intervention program), and c) The impact of humanoid robots on improving the social and cognitive skills of high-functioning autistic children (as a group clinical intervention program). The results indicated that our robots were accepted by 70 percent of the participants as a communication tool from the first interaction. We also observed improvement in joint attention and fine movement imitation skills of both the high-functioning and low-functioning subjects. It was concluded that the high-functioning children’s social skills improved due to the robot-assisted group therapy sessions, while the stereotyped behaviors of the low-functioning subjects decreased during the course of this program.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
8
no.
2019
2329
2354
https://mej.aut.ac.ir/article_3399_d200eb9d9e09ba33fbda0ca623bc822c.pdf
dx.doi.org/10.22060/mej.2019.15434.6121