Brittle Fracture in Key-hole Notched Polymer Specimens under Combined Compressive-shear Loading
M.R.
Ayatollahi
Fatigue and Fracture Research Laboratory, School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
author
A.R.
Torabi
Fracture Research Laboratory, Faculty of New Sciences & Technologies, University of Tehran, Tehran, Iran
author
H.R.
Majidi
Fatigue and Fracture Research Laboratory, School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
author
text
article
2018
per
In the present study, brittle fracture of the general-purpose Polystyrene (GPPS) is studied experimentally and theoretically under compressive-shear loading by using the Brazilian disk specimens containing a key-hole notch. The notched specimens are specified by different geometric parameters, i.e. the notch length and the tip radius. In this investigation, 84 fracture tests reported recently by the present authors are evaluated to assess the brittle fracture of key-hole notched specimens under compressive-shear loading. Two energy-based fracture models namely, the averaged strain energy density (ASED) and averaged strain energy density based on the equivalent factor concept (ASED-EFC) are proposed to predict the fracture loads of the tested GPPS specimens. The experimental and theoretical results are plotted for each case in the form of the fracture load versus the notch tip radius. Moreover, the analyses based on the finite element method as well as the experimental observations showed that although brittle failure in the test samples under compressive-shear loading takes place from the applied load side of the notch border by local tensile stresses, the notch bisector line and the other side of the notch border sustain compressive stresses. In fact this phenomenon states the concept of compressive-shear loading. Finally, it is shown that a good agreement exists between the experimental fracture load results and the theoretical predictions evaluated by using the two strain energy-based criteria.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
927
942
https://mej.aut.ac.ir/article_936_e38169df4118a50547fbac8dedea5b1c.pdf
dx.doi.org/10.22060/mej.2017.12258.5293
Analytical Calculation of Stress Intensity Factors for Unequal Cracks Emanating from a Circular Hole in an Infinite Plane
R.
Ghajar
Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
author
M.
Hajimohamadi
Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
author
text
article
2018
per
Thin plates are used in marine and aerospace structures. Geometric defects in components and industrial structures usually occur intentionally or unintentionally which hole is one of them. It is common that a crack initiate in the areas of stress concentration. Even if the crack is relatively small, it propagates and can lead to a dangerous situation. Stress intensity factor is one of the important parameters of the crack behavior. In this paper, by using the analytical solution of Muskhelishvili and finding suitable conformal mapping, behavior of two unequal and aligned cracks emanating from a circular hole is investigated. The effect of parameters such as load orientation, crack length and etc. is studied. The hole and the cracks are assumed to be traction free. The infinite isotropic plane is subjected to a uniform tensile loading at infinity in an arbitrary direction. To ensure the accuracy of the method, results are compared with some specific problems. In this paper, an explicit formula based on the geometric parameters of the problem is presented for stress intensity factor. Also and are obtained for various loading and cracks length.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
943
950
https://mej.aut.ac.ir/article_957_4c680170ebf407561d9e5c9d649f63c0.pdf
dx.doi.org/10.22060/mej.2017.11997.5238
Study on Effect of Boundary Conditions in Transient Dynamic Stress Analysis of Thick Cylindrical Shells under Internal Moving Pressure
M.
Mirzaee
Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran
author
H.
Ramezani
Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran
author
text
article
2018
per
This study presents a new analytic solution for transient elasto-dynamic structural response of cylindrical shells to internal moving load under different boundary conditions. The equations of motion of a thick shell are used and the effects of transverse shear and rotary inertia are considered. The general form of the presented formulations and the solution method are applicable to many theoretical and practical problems. However, the formulation is adjusted for gaseous detonation loading. The pressure history of the detonation loading, which consists of a shock wave and a reaction zone, is represented by an exponential approximation to the Taylor-Zeldovich model. The presented analytic solution is validated through comparison with the available experimental data from the literature and finite element simulations. Representative analyses are carried out for an experimental detonation tube subjected to different boundary conditions including simply-supported, clamped-clamped, and clamped-free. Results show that obtained vibrational behavior can be highly affected by the types of boundary conditions especially for locations near the end of the tube, where the interference between the forward traveling waves and the reflected waves is quite significant.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
951
960
https://mej.aut.ac.ir/article_1022_ebec4495aead155bebd248644ab9c378.pdf
dx.doi.org/10.22060/mej.2017.12283.5304
Investigation of Torsional Static Behavior of Nano-rods Embedded in Elastic Medium Considering Surface Energy Effect
R.
Nazem Nezhad
Department of Engineering, Damghan University, Damghan, Iran
author
M.
Aryanpour
Department of Engineering, Damghan University, Damghan, Iran
author
text
article
2018
per
In this paper, the torsional static behavior of nano-rods under external torsional loads and embedded in elastic medium is investigated by considering the surface energy effect (the energy due to the surface shear modulus and the surface stress). For this purpose, surface stress components are obtained using the surface elasticity theory, and three types of external torsional loadings, uniform torque load, linear torque load, and sinusoidal torque load are considered. Then, the governing equation of motion of nano-rod is derived using the Hamilton’s principle. The governing equation of motion is analytically solved for clamped-clamped and clamped-free boundary conditions; and the surface energy effect on torsional static behavior of nano-rod (rotational displacements) is investigated for various values of nano-rod radius and length, and torsional torque. In order to complete the investigations, effects of value and sign of the surface energy components on torsional static behavior of nano-rod are also considered. The obtained results show that the effect of the surface energy can be dependent on the geometrical parameters and the value and sign of the surface energy components. Results of the present study can be useful in design of nano-electro-mechanical systems like nano--bearings and rotary servomotors.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
961
972
https://mej.aut.ac.ir/article_996_c4d207d83080cae667a354afa6f994e2.pdf
dx.doi.org/10.22060/mej.2017.12197.5290
Wave Propagation in Embedded Temperature-dependent Functionally Graded Nano-plates Subjected to Nonlinear Thermal Loading According to a Nonlocal Four-variable Plate Theory
F.
Ebrahimi
Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran.
author
A.
Dabbagh
Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran.
author
text
article
2018
per
In this article, an analytical approach is used to study the effects of thermal loading on the wave propagation characteristics of an embedded functionally graded nano-plate based on refined four-variable plate theory. The heat conduction equation is solved to derive the nonlinear temperature distribution across the thickness. Temperature-dependent material properties of nano-plate are graded using Mori-Tanaka model. The nonlocal elasticity theory of Eringen is introduced to consider small-scale effects. The governing equations are derived by means of Hamilton’s principle. Obtained frequencies are validated with those of previously published works. Moreover, effects of different parameters such as temperature distribution, foundation parameters, nonlocal parameter and gradient index on the wave propagation response of size-dependent functionally graded nano-plates have been investigated.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
973
988
https://mej.aut.ac.ir/article_959_40f9279bd0c6e6c810957344c076bb84.pdf
dx.doi.org/10.22060/mej.2017.11824.5194
Design of a Nonlinear Controller on Quadrotor Drone Using Combined Method of Gradient Particle Swarm Optimization
H.
Shahbazi
Department of Mechanical Engineering, University of Isfahan, Isfahan, Iran
author
V.
Tikani
Department of Mechanical Engineering, University of Isfahan, Isfahan, Iran
author
text
article
2018
per
In the paper a new method of optimal control in presented which is composed of policy gradient reinforcement learning and particle swarm optimization. This method has a lot of applications in the real world. The combined method is implemented on a quadrotor drone to control attitude and position of the drone. Inspired from reinforcement methods, the gradient of the policy is computed for a proportional-integral-derivative controller and used in particle swarm optimization to be used in optimization process in addition to the other factors. To study the performance of Optimal proportional-integral-derivative controller on attitude control of the system, a quadrotor is fixed to the design a test stand. The system consists of an accelerometer and a gyroscope sensors and a microcontroller which is used to design fuzzy proportional-integral-derivative attitude controller for the quadrotor. Considering that the experimental data has lots of errors and noises, Kalman filter is used to reduce the noises. Finally using Kalman filter leads to better estimation of the quadrotor angles and the optimized proportional-integral-derivative controller performs the desired motions successfully. The presented method is implemented and tested on the quadrotor test bench and compared with some old methods. To check the robustness of the proportional-integral-derivative controller to the external disturbances, random disturbances are applied to the quadrotor. The controller stabilized the quadrotor rapidly even with disturbance is applied.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
989
998
https://mej.aut.ac.ir/article_859_1483f94d561b5c83e43ef0ab60f42df7.pdf
dx.doi.org/10.22060/mej.2016.859
Theoretical and Numerical Study and Comparison of the Inertia Effects on the Collapse Behavior of Expanded metal tube Absorber with Single and Double Cell under Impact Loading
H.
Hatami
Mechanical Engineering department, Engineering Faculty, Lorestan University, Khorram-Abad, Iran
author
A.B.
Fathollahi
Mechanical Engineering department, Semnan University, Semnan, Iran
author
text
article
2018
per
The present study provides the theoretical and numerical comparison and study of the dynamic behavior of a four-rod and four-elastic-plastic joint model under the inertia effects in both single and double cell modes. The theoretical study was carried out by solving nonlinear equations in MATLAB with dynamic equations of motion. Numerical analysis was also carried out with ABAQUS. The objective of this study is to derive the equation of energy absorption in terms of the inertia parameter to the expanded metal tube structure under impact loading and also to study the dynamic behavior of effective parameters and collapse mechanism of the structure in both single and double cell modes. Finally, the analysis of the effect of double cell absorber was carried out for the values of effective parameters in dynamic response. The results show that the collapse of the absorber will be symmetric in two directions.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
999
1014
https://mej.aut.ac.ir/article_1049_a041ce6b8bf161b30a1b1cb6b164217f.pdf
dx.doi.org/10.22060/mej.2017.12016.5242
Comparison of the Effects of Shot Blasting and Sandblasting Processes on the Strength of the Aluminum Adhesive Bonded Joints
A.
Safari
Mechanical Engineering department, College of Engineering, University of Tehran, Tehran, Iran
author
M.
Farahani
Mechanical Engineering department, College of Engineering, University of Tehran, Tehran, Iran
author
text
article
2018
per
In this paper, the influences of surface roughness on the strength of the single lap adhesive joints for the prepared adherent with shot blasting and sandblasting processes were examined. Sheets from 2024-T3 aluminum alloy were cut into pieces and then shot blasted at four different durations and sandblasted with four different pressures. Prepared aluminum specimens were jointed using two different adhesives, two-component Araldite 2015 with high viscosity and epoxy HPL1012/HPH112 with low viscosity. The effects of process parameters on the surface roughness of the adherent and ultimate shear strength of the joint were investigated using design of experiments technique. Tensile test was used to determine the ultimate strength of the joints. The obtained results were presented comparatively. It was shown that by increasing the surface roughness of shot blasted and sandblasted samples, the ultimate shear strength of the joints increases continuously. The optimum surface treatment for ductile and brittle adhesives was similar that shown no relation of this optimum roughness to adhesive type in the prepared samples with sandblast and shut blast processes. The highest ultimate shear strength was obtained for the sandblasted specimens at maximum pressure of 6 bar with 0.6 micrometers of surface roughness.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1015
1022
https://mej.aut.ac.ir/article_1030_fe4dd817c0d4ab58cb91bfcc67e44558.pdf
dx.doi.org/10.22060/mej.2017.12413.5326
Static and Dynamic Pull-in Instabilities Analysis of Partially Affected Clamped Nano Actuators: The Substrate Effect
A.
Noghrehabadi
Department of Mechanical Engineering, Shahid Chamran University, Ahvaz, Iran
author
A.
Haghparast
Department of Mechanical Engineering, Shahid Chamran University, Ahvaz, Iran
author
M.
Ghalambaz
Department of Mechanical Engineering, Dezful Branch, Islamic Azad University, Dezful, Iran
author
text
article
2018
per
Many researches have been carried out for modeling of micro/nano electromechanical systems instabilities, in which both movable and substrate electrodes are at the same size; however, there is no research considering the static and dynamic pull-in instabilities of micro/nano actuators with a smaller substrate electrode in the presence of small size effects. In the present study, the static and dynamic behaviors of partially affected clamped micro/nano actuators are investigated and the effects of position and length of the substrate electrode are analyzed. The non-linear Euler-Bernoulli governing equation of the beam motion and the corresponding boundary conditions are derived using the Modified couple stress theory. Finite element method is utilized to solve the governing equations. In order to investigate the accuracy of the utilized finite element method, the obtained results are compared with those available in the literature and a good agreement between them was found. The results demonstrate that a decrease of the substrate electrode length leads to an increase of the required pull-in voltage and the pull-in capillary force. Moreover, a small reduction in the pull-in deflection of the nano-beam is observed because of the decrease of the substrate electrode. Finally, a new parameter, named as balanced size effect-capillary force which changes the trend of the behavior of the nano-beam, is introduced.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1023
1038
https://mej.aut.ac.ir/article_905_358e7e5833098804cf32b18f2111aa5e.pdf
dx.doi.org/10.22060/mej.2017.11917.5216
Bending and Free Vibration Analysis of Functionally Graded Nano-plate Using Trigonometric Higher-Order Plate Theory
A.
Azizi
Department of Mechanical and Aerospace Engineering, Shiraz University of Technology, Shiraz, Iran
author
A.
Setoodeh
Department of Mechanical and Aerospace Engineering, Shiraz University of Technology, Shiraz, Iran
author
text
article
2018
per
In this paper, bending and free vibration analyses of functionally graded nano-plates are investigated using a new trigonometric higher-order plate theory. The governing equations are developed by employing Hamilton’s principle and then a Navier-type analytical solution for bending and free vibration of simply supported rectangular FG nano-plates is obtained. Furthermore, the nonlocal theory of elasticity is used to take into account the small scale effects. The mechanical properties of the functionally graded nano-plates are assumed to vary by a power law function through the thickness. In order to confirm the accuracy of the present theory, the obtained results from the present solution are compared with the existed results, and a very good agreement is achieved. Moreover, the effects of length-to-thickness ratio, aspect ratio and nonlocal parameter on the bending and free vibration solutions are investigated. The results demonstrate that the inclusion of nonlocal parameter in governing equations or increasing the power index, leads to reduction of the natural frequency and increasing of the deflection and in another word the nano-plate stiffness is reduced. Also, the impact of the nonlocal parameter and size effects is reduced by increasing the length of the nano-plate or aspect ratio. Furthermore, the present theory not only provides exact solution for the bending and free vibration of thick and moderately thick functionally graded nano-plates with minimum computational cost, but also exhibits the parabolic distribution of the shear stress through the thickness.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1039
1050
https://mej.aut.ac.ir/article_945_f29f918ff89980720d298463f44688e6.pdf
dx.doi.org/10.22060/mej.2017.12173.5274
A Novel Algorithm for Automatic Parallel Parking a Car Based On Continuous-Curvature Clothoid Path Planning
S.
Farjad Bastani
Mechatronics department, Qazvin Brunch, Islamic Azad University, Qazvin, Iran
author
A.
Khodayari
Mechanical engineering department, Pardis brunch, Islamic Azad University, Tehran, Iran
author
text
article
2018
per
Nowadays making car intelligent consists wide range of their subsystems control. Intelligent Parallel parking without human interposition can be mentioned as an automobile industrial achievement in recent years. It had been tried in this paper with a new algorithm based on specification of continuous curvature clothoid to design a suitable path for parallel parking. Car movement in this smooth path is safe, continuous and with constant velocity. By this algorithm, the system can park the car with single maneuver in a space with 1.6 times of car length. One of the advantages of our new algorithm is control method of car movement to the parking slot. In this method we change the question of controlling car movement in desired path, to question of control the velocity of the car to desired value. So we could reach more precision in car movement from start to goal position. As steering and linear car velocities are constant, car will move in stable speed and smooth path while driving to the parking slot, so our algorithm has more driving comfort in comparison with other path planning algorithms. The results of implementation in real situations shows high accuracy and popper performance compared with other algorithms.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1051
1060
https://mej.aut.ac.ir/article_778_a1ab06e4cdeb52207095dab82640295a.pdf
dx.doi.org/10.22060/mej.2016.778
Free Vibration of Heterostructures of Graphene and Boron Nitride in Thermal Environment via Aifantis Theory with Velocity Gradients and Ritz Method
S.
Ziaee
Faculty of Engineering, Yasouj University, Yasouj, Iran
author
text
article
2018
per
This article aims to investigate the free vibration of mono-/ multi-layered hererostructures of graphene and boron nitride in thermal environment. To this end, at first, the nonlinear model of inter-layered interaction between different layers are estimated based on Lenard-Jones 6-12 potential, then two variable refined plate theory is used to model the vibrational behavior of in-plane heterostructures of graphnme/boron nitride or vertically stacked graphene/ boron nitride hybrid structures. To incorporate the size effect into two-variable refined plate hypothesis, Aifantis’s theory is used to derive potential energy. To formulate the kinetic energy, an additional length scale which adds gradient velocity to kinetic energy is also used. The eigen-frequency equations are obtained based on Hamilton principle and Ritz method. The results show that the layout of graphene and boron nitride layers only affect out-of-phase natural frequency of multilayered nano-plates. Also, the significant impact of number of boron nitride layers used in heterostructures on the reduction of natural frequency of hybrid structure is demostrated. By controlling the area occupied by boron nitride in mono-layered hybrid structures, one can enhance the natural frequency of nano-sheets. The effects of the value of length scale parameter and temperature change on natural frequencies are studied as well.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1061
1078
https://mej.aut.ac.ir/article_902_368a9765fa11f901f617ccdf0a5ce58e.pdf
dx.doi.org/10.22060/mej.2017.11858.5201
Stress Measurement on Carbon Steel Specimen by Consideration of Magnetic-Barkhausen-Noise
R.
Moharrami
Mechanical Engineering Department, University of Zanjan, Zanjan, Iran
author
H.
Alizadeh
Mechanical Engineering Department, University of Zanjan, Zanjan, Iran
author
text
article
2018
per
In general, all manufacturing processes introduce residual stresses in the manufactured component. Residual stresses affect the design and fabrication of engineering structures, and their field service. So, for structural integrity studies, improvement and development of experimental procedures to determine the residual stresses were be considered by many researcher. In this study, design and prototyping of an appropriate system for non-detective residual stresses evaluation by considering of magnetic-Barkhausen noise were be present. The magnetic-Barkhausen noise analysis used in ferromagnetic materials is based on analysis of rapid irreversible magnetization changes called Barkhausen jumps. Developed system were used to obtained noise voltage level on some loaded carbon steel specimen. The magnetic-Barkhausen noise were dependent to stresses magnitude and direction on the specimen. By this, an appropriate relation for calculation of the stresses from measured voltage were be obtained. Relation coefficient were be corrected by presented calibration procedure. According to obtained results, the magnetic-Barkhausen noise techniques is capable to evaluation of some chemical, physical and mechanical character like residual stress on the industrial component.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1079
1084
https://mej.aut.ac.ir/article_935_17abf0f705e0af9c9e8e6fa01ec2c2eb.pdf
dx.doi.org/10.22060/mej.2017.11686.5159
Nonlinear Longitudinal Free Vibration of a Rod Undergoing Finite Strain
B.
Soleimani Roody
Department of Mechanical Engineering, Yazd University, Yazd, Iran.
author
A.
Fotouhi
Department of Mechanical Engineering, Yazd University, Yazd, Iran.
author
M.
Jalili
Department of Mechanical Engineering, Yazd University, Yazd, Iran.
author
text
article
2018
per
Rods are one of significant engineering’s structures and vibration analysis of a rod because of extended application of it in engineering is very important. Therefore, understanding of longitudinal nonlinear vibration of rod with different boundary conditions and large amplitude is very useful. In this paper, vibration of a rod with different boundary conditions undergoing finite strain, without simplification in strain-displacement relations, is investigated. For obtaining governing equation, Green-Lagrange strain, structural damping and Hamilton principle are used and then Galerkin method is employed to convert nonlinear partial differential equation to nonlinear ordinary differential equation. In spite of many papers that only use of cubic term for nonlinearity, the governing equation has quadratic and cubic terms. The equations with and without damping, are solved with multiple time scales method. In order to verify the accuracy of this method, the results are compared with results of Runge-Kutta numerical method, which have good accuracy. Finally sensitivity analysis for understanding of influence of nonlinear coefficients on rod vibration answer is done.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1085
1096
https://mej.aut.ac.ir/article_885_b18dc48a6c16e1734831efcdbd9b31bd.pdf
dx.doi.org/10.22060/mej.2017.11937.5223
Free Vibration of, Functionally Graded Materials Cylindrical Shells on Elastic Foundation under Axial force, Lateral Pressure and Different Boundary Conditions
A.
Hadi
Aerospace Research Institute, Ministry of Science, Research and Technology, Tehran, Iran
author
S.
Shakhesi
Space Transportation Research Institute, Iranian Space Research Center, Tehran, Iran
author
H.
Ovesy
Aerospace Engineering Department, Amirkabir University of Technology, Tehran, Iran
author
J.
Fazilati
Aerospace Research Institute, Ministry of Science, Research and Technology, Tehran, Iran
author
text
article
2018
per
Free vibration characteristics of functionally graded materials cylindrical shells surrounded by elastic medium under axial force, lateral pressure and different boundary conditions using wave propagation method are investigated in this paper. The material properties of functionally graded materials are assumed to be graded in the thickness direction according to the power law. The elastic medium is assumed as two-parameter Pasternak elastic foundation. Governing equations based on the first order shear deformation theory of Sanders-Koiter for the cylindrical shell resting on elastic foundation under mechanical loads are derived by using Hamilton’s principle. By assuming displacement field in wave propagation form, governing equations are solved. Natural frequencies of cylindrical shell under various boundary conditions are obtained and compared with the results in the literature. It is seen that using displacement field in wave propagation form, acts as an effective and reliable method and gives the acceptable results for various boundary conditions. Although it is shown that for different boundary conditions and geometry dimensions, accuracy of the wave propagation approach is different. In addition, based on the developed theory the effects of different boundary conditions, axial force, lateral pressure and elastic foundation parameters on vibration behavior of functionally graded cylindrical shell are investigated.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1097
1112
https://mej.aut.ac.ir/article_1008_8c0d8c848bcff70dfc0cf6a2ae01dd62.pdf
dx.doi.org/10.22060/mej.2017.12362.5319
Design and Construction of an Electronic Tiltmeter Calibrator and Estimation of Calibration Uncertainty
M.
Ghafarzade
Faculty of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
author
A.
Kamali E.
Faculty of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran
author
R.
Abedini
Faculty of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran
author
R.
Rajabi
Faculty of Mechanical Engineering, K. N. T. University of Technology,Tehran, Iran
author
M.
Tavakoli K.
Faculty of Electrical Engineering, Sharif University of Technology, Tehran, Iran
author
text
article
2018
per
Electronic tiltmeter is used as a tool of setting the accurate angles in advanced equipment. The accuracy and precision of tiltmeter should be evaluated by means of precise calibration equipment. This study aimed to calibrate and evaluate the accuracy of a precise dual axis electronic tiltmeter. To this end, a calibration setup with accurate positioning capability was designed and constructed. Then the calibration setup was employed to investigate linear and nonlinear behavior of electronic tiltmeter and extract the corresponding equations. In order to assess the reliability of the tiltmeter sensor, nonlinearity error and repeatability of the tiltmeter at different angles were obtained. Afterwards in an analytic way, arithmetic and geometric means were compared and the factors which affect the calibrator output error were identified to obtain that how much the accuracy and measurement error of each of those factors affect the uncertainty of angle measurement in the calibration process. The results indicate that both introduced methods of averaging can be used to derive relationship of uncertainty propagation accurately. Uncertainty analysis of the constructed base and calibration process demonstrate that the employed equipment correspond with the evaluation of a precise electronic tiltmeter.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1113
1122
https://mej.aut.ac.ir/article_1029_3eac0c96a898f3faa1f380a8ada6f2df.pdf
dx.doi.org/10.22060/mej.2017.12144.5294
Imitation Learning of Complex Behaviors to Humanoid Robots using Evolutionary Optimization of Neural Network of Unit Pattern Generator
B.
Khodabandeh
Department of Mechanical Engineering, University of Isfahan, Isfahan, Iran
author
H.
Shahbazi
1 Department of Mechanical Engineering, University of Isfahan, Isfahan, Iran
author
A.
Monadjemi
Department of Computer Engineering, University of Isfahan, Isfahan, Iran
author
text
article
2018
per
In this paper, a system based on neural structures known as central pattern generator is presented which enables to acquire the required patterns to move a robot based on a demonstration training. Unit pattern generator can be divided to two subsystems, one is a rhythmic system and the other is a discrete system. The first subsystem is responsible to produce short movements and the second subsystem is responsible to produce rhythmic movements. The special learning algorithm is designed to use these unit pattern generators. Joints and limbs of robot were controlled by Kinect sensor in real time by recognition of the human body skeleton. The work steps were done in this way that the motion sequences of teacher’ body were recorded by Kinect sensor, then transmitted to the computer. These motion sequences teach some nonlinear oscillators then they reproduce motions for humanoid robot. As a result, humanoid body joints imitate the teacher movement in a real time. The main contribution of this paper is design of this learning algorithm which is able to simultaneously search for the weights and topology of the network the algorithm synchronize the neural network by coupling the neurons at the last stage.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1123
1136
https://mej.aut.ac.ir/article_1000_5565c7d3fffee78b0a518643a05d7972.pdf
dx.doi.org/10.22060/mej.2017.12221.5282
Imitating Sound Ankle Behavior with a Powered Below-Knee Prosthesis and Validation of its Mechanical Performance
P.
Shokrani
Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran
author
L.
Ghorbani
Engineering Department, University of Isfahan, Isfahan, Iran
author
H.
Sadeghian
Engineering Department, University of Isfahan, Isfahan, Iran
author
text
article
2018
per
Lower extremity amputation constitute high percentage of limb amputation which significantly reduce the motion ability of the amputees. Therefore the most important goal in the design of prosthesis is to restore function of the limb. Most of the commercially ankle-foot prostheses are passive and thus cause many gait pathologies for below knee amputees. Several powered prosthetic devices have been designed to improve amputee’s walking experience by exploiting active elements. However, most of them include heavy and bulky actuators which is used to produce the power of propulsion. The main purpose of the present design is to store energy during stance period and release it at push off using a combination of springs as well as a low power actuator. Therefore, this prosthesis can provide high mechanical power and torque observed in natural human walking, by employing a small and light actuator. Moreover, in the designed mechanism, the ankle stiffness is mimicked properly in each phase of walking based on the characteristics of a sound ankle. The performance of the proposed prosthesis, was verified by MATLAB/SimMechanics simulation. The results indicate that the ankle-foot prosthesis is capable of following the torque-angle and the power-percent gait cycle characteristics of a normal ankle, sufficiently.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1137
1144
https://mej.aut.ac.ir/article_948_473a26211834bc011b4fec45caf99e26.pdf
dx.doi.org/10.22060/mej.2017.12099.5258
Design and Implementation of Intelligent Systems Detect the Driver’s Lack of Concentration
A.
Ghaffari
Department of Mechanical Engineering, K.N.Toosi University Of Technology, Tehran, Iran
author
A.
Khadayari
Department of Mechanical Engineering, Pardis Branch/ Islamic Azad University, Tehran, Iran
author
S.
Abediny
Department of Mechatronics Engineering, South Branch/ Islamic Azad University, Tehran, Iran
author
text
article
2018
per
Today one of the serious challenges which the world faces is the cars accident. Accident poses irreparable damages to humans all across the globe. Many factors like technical bugs, disregarding of driving rules and loss of concentration contribute most car accidents. An experimental perspective over losing concentration proves its vital role in accidents. In this context, it is very important to monitor the driver’s lack of concentration. This article tries to recommend an intelligent algorithm in order to determine driver consciousness based on visual processing, eye state is one of the most important features to detecting driver’s lack of concentration. The algorithm contains two phases: 1- Face components detection, 2- Driver consciousness detection, The algorithm provides with a full-scale database so as to recover the algorithm instantly. Research findings confirm that our recommended intelligent Algorithm is 96% Successful to predict the driver consciousness. Moreover, we invent a concentration lost cautionary that was tested on a prototype that satisfied our expectations. Finally, we conclude that our recommended Algorithm can act as a deterrent against most terrible accidents successfully. We hope this algorithm reduces accident rate and create an advancement in Smart Cars knowledge.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
50
v.
5
no.
2018
1145
1154
https://mej.aut.ac.ir/article_998_456c32d4c8694eaacb19c1c626f6fcf3.pdf
dx.doi.org/10.22060/mej.2017.12098.5257