2018-08-21T03:25:18+04:30
http://journals.modares.ac.ir/browse.php?mag_id=735&slc_lang=fa&sid=15
735-8165
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
IFC
2016
8
01
0
0
http://journals.modares.ac.ir/article-15-8165-en.pdf
735-2684
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Mechanical properties and microstructure evolution of AA1100 aluminum sheet processed by Accumulative Press Bonding Process
Amir
Mostafapour
Vahid
Mohammadinia
Sever plastic deformation process in one of the important methods to produce nanostructures materials that is highly regarded in two past decades. Accumulative press bonding (APB) is a novel variant of severe plastic deformation processes (SPD), which is devised to produce materials with ultra-fine grain (UFG). In the present work, effect of APB technique on mechanical properties and microstructural of AA1100 alloy, were investigated. The study of the microstructure of AA1100 alloy was performed via optical microscopy. This article revealed that the grain size of the produced samples decreased to 950 nm, after six passes of APB process. The yield strength of AA1100 alloy after six passes of the process increased up to 264 MPa, which is three times higher than that of the as-cast material (89 MPa). After six passes, microhardness values of AA1100 alloy increased from 38 to 61 HV. Furthermore, the results showed that the behavior of variations in mechanical properties are in accordance with the microstructural changes and it can be justified by using the Hall-Patch equation. Moreover, the rise in the yield strength can be attributed to the reduction of the grain size and strain hardening phenomenon.
Sever Plastic Deformation
Accumulative Press Bonding
Mechanical Properties
Metallurgical properties
2016
8
01
1
6
http://journals.modares.ac.ir/article-15-2684-en.pdf
735-5470
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Evaluation of the damage detection capability of Inner product vector for LOP and LOSWF defects in a groove weld
Sattar
Mohammadi Esferjani
Mehdi
Salehi
Welding is one of the most popular methods of connection that used across variety of industries to join together materials. Nondestructive testing methods are commonly used to verify that welds are free of defects. Some limitations to common NDT techniques have restricted their use. The new damage detection techniques are in need. This paper presents a study on the new inspection method. The advantage of this method is it's cost and time effectiveness. This study was conducted to investigate the ability of Inner product vector (IPV) method to detect Lack of Root Penetration (LOP) and Lack of side-wall fusion (LOSWF) on 304 stainless steel beam. The IPV method was proposed as a damage detection algorithm which uses cross correlation functions between vibration responses under white noise excitation. The experimental method was the only method of previous research on the IPV method. This will be achieved by the use of finite element modeling combined with a modal dynamic analysis based vibration technique and MATLAB software was used to numerically implement the computational procedure. In this study, an ideal welding is intended, and the effect of the heat-affected zone (HAZ) on the results is ignored. In order to verify the validity of the IPV method simulation, we refereed to the results of previous experimental research. The results obtained from modeling are compared with experimental results that showed good agreement.
Damage detection
Cross correlation functions
Inner product vector (IPV)
Lack of Root Penetration (LOP)
Lack of side-wall fusion (LOSWF)
2016
8
01
7
16
http://journals.modares.ac.ir/article-15-5470-en.pdf
735-8176
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Passive cooling of a stand-alone building with domed roof in hot and arid climate assisted by solar adsorption chiller
Amin
Haghighi Poshtiri
Safura
Bahar
Azadeh
Jafari
In this paper, a natural cooling system composed of domed roof and solar adsorption chiller is presented and its performance to provide the thermal comfort conditions in Yazd, Kerman, and Tehran is investigated based on ISO 7730. Furthermore, the effects of environmental parameters, wind speed, and geometric characteristics on the system performance are studied. To calculate the number of air changes of the room, Ansys Fluent software is used. Additionally, to estimate the room inlet temperature, the governing equations of the adsorption chiller and cooling channel are solved based on the forth order Runge-kutta and finite difference methods, respectively. The results show that increasing the incision diameter of the domed roof as well as the width of the cooling channel causes to increase the number of air changes of the room. Alternatively, increasing the width of the inlet air vent up to a threshold value will cause to increase the number of air changes. However, increasing beyond the threshold value has no significant effect on the number of air changes. Additionally in the aforementioned cities, the room inlet air temperature is almost constant when the chiller operates. Finally, the environmental conditions are determined which accordingly the system is able to provide the thermal comfort conditions in the test room on July 15.
Domed roof
Natural ventilation
Solar adsorption chiller
2016
8
01
17
28
http://journals.modares.ac.ir/article-15-8176-en.pdf
735-1461
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Closed-form solution of circular and annular plates with elastic boundary conditions under non-uniform normal and shear loads
Mohammad
Molla-Alipour
In this study, a simply and efficient closed form solution for bending and stress analysis of functionally graded circular and annular plates with elastic boundary conditions is presented based on the first order shear deformation theory (FSDT). By using the presented solution procedure, functionally graded plates subjected to arbitrary non-uniformly distributed normal and shear loads may be analuzed and all of stresses components may be exactly achieved. Shear loads may be imposed on the top and bottom surfaces of plate. By using the constitutive equations based on the first-order shear deformation theory, the transverse shear stress components cannot be obtained correctly and constant through-the-thickness distributions will be extracted. So, to achieve the transverse normal and shear stresses components in the proposed solution procedure, the three dimensional theory of elasticity is applied. To establish the accuracy and efficiency of the proposed approach, the obtained results are compared with other available published results and results of the three-dimensional theory of elasticity extracted from the ABAQUS software based on the finite element method (as the most exact method). Comparisons show that the obtained results are very accurate, while it is computationally quite more economic than the three-dimensional elasticity approach. Also, transverse normal and shear stresses boundary conditions on the top and bottom surfaces of the plate are exactly satisfied. Even for a complicated loading, when the non-uniform normal and shear loads are imposed simultaneously on the top and bottom surfaces of plate and transverse stresses boundary conditions on these surfaces are non-zero.
Closed-form Solution
Bending
stress
Elastic edges
Functionally graded plate
2016
8
01
29
40
http://journals.modares.ac.ir/article-15-1461-en.pdf
735-7370
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
A Feasibility Study on Performing Rotary Forging Process by Hexapod Table and Estimation of Forming Load for a Cylindrical Workpiece
Seyed Vahid
Hosseini
Mohammad Javad
Nategh
Rotary forging is a forming method in which, the forces exerted on the workpiece can be reduced by using an inclined forming tool. The final shape of workpiece is formed gradually. The conventional machines used in this process, typically have separate rotational and linear (feeding) motions. The rotational motion is applied by an eccentric mechanism; the feeding motion is exerted with a linear actuator. These machines follow forward kinematics which does not consider the geometry of the workpiece to create motion profiles. Hence, having a special profile to be fully compatible with the piece is not possible. Such compatibility is beneficial to applying a more precise control on the material flow and achieving sound forgings. In this study, the feasibility of performing the rotary forging process on a hexapod table has been investigated. A hexapod machine available to the authors has been employed for this purpose. The hexapod table with six degrees of freedom is responsible for all shaping motions. This device can be used to produce different motion profiles for complex workpieces. The appropriate profiles are obtained through the inverse kinematics. The maximum force being applied on the hexapod actuators was calculated. Two circular and linear profiles were examined to practically shape cylindrical workpieces, and forming load was compared with conventional forging for producing lead cylindrical workpieces. Ultimately, the forming load ratios in rotary forging with liner profile to conventional forging and rotary forging with circular profile were obtained 0.27 and 0.49 respectively.
Rotary Forging
Hexapod
Motion Profiles
Forging Force
2016
8
01
41
51
http://journals.modares.ac.ir/article-15-7370-en.pdf
735-2529
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Numerical and experimental investigation of skin/core debonding in composite sandwich structures with corrugated core under bending loading
Hossein
Malekinejad Bahabadi
Gholam Hossein
Rahimi
Amin
Farrokhabadi
Sandwich structures are consisted of two thin skins with high mechanical properties and a thick core with lower mechanical properties and weight. Due to high strength/ stiffness to weight ratio, these structures are used extensively in engineering structures such as aerospace structures, ship hulls, turbines blades, etc. Skin/core debonding is one of the major failure modes in these structures. In this paper, debonding resistance of sandwich panels with composite skins and a core consisted of PVC foam and a corrugated composite laminate is investigated both experimentally and numerically. Square geometry is considered for corrugated composite laminate and obtained results are compared with reference specimen with simple core made of PVC foam. The three point bend test with attached ENS fixture is used to perform the standard experimental test. The results have shown that in square specimen with 3 and 6 layer skin before the separation between skin/core, the specimens are failed from the middle of the upper skin, but for 8 layer skin, the skin/core debonding are accured before other modes of failure. The maximum skin/core debonding resistance for square specimen are increased 269.26 percent. Specimens are modeled in Abaqus and results show a reasonable agreement between experimental and numerical result.
Sandwich structures
Bending loading
Cohesive zone model
2016
8
01
52
62
http://journals.modares.ac.ir/article-15-2529-en.pdf
735-12104
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Investigation of the mechanism of dissociation of P-selectin/PSGL-1 complex under stretching with molecular dynamics method
Hajar
Hassani-Ardekani
Hanieh
Niroomand Oscuii
Molecular Dynamics (MD) method is a computer simulation for studying the physical movements of atoms and molecules of a N-body system by solving classical equations of motion. Here, this method is used to investigate the structural changes of a vital molecular bond in the body. This bond is created by the interaction of P-selectin, expressed on activated endothelium, and its counterpart P-selectin glycoprotein ligand-1 (PSGL-1) which is expressed on leukocytes. Frequent association and dissociation of these bonds allow the leukocyte to roll on the endothelium layer which is a pivotal step in inflammatory responses. Understanding the mechanism underlying the dissociation process of this bond is helpful in pathological researches. Here this process is simulated with MD method using the program NAMD and Visual Molecular Dynamics (VMD). The results indicate that the hydrogen bonds between ion Ca2+ and residue fucose of glycan group of PSGL-1 and also between sulfated tyrosine residues are the most effective bonds in binding.
Molecular Dynamics
NAMD
Leukocyte
P-selectin/PSGL-1 bond dissociation
non-bonded energy
2016
8
01
63
70
http://journals.modares.ac.ir/article-15-12104-en.pdf
735-10500
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Estimation of mechanical properties of hardened cement paste with molecular dynamics simulation method at nano scale
Amir
Tarighat
Davoud
Tavakoli
The cement paste properties as the matrix in concrete are of great importance in specifying its properties. Recent advances in concrete industry have highlighted the need for accurate knowledge about its nano-structure and components. To estimate the important mechanical properties such as Young's modulus, bulk modulus and poisson ratio of the hardened cement paste at the nanoscale, a comprehensive set of crystalline structures that represent the main hardened cement paste constituents (CSH, CH, Ettringite, Hydrogarnet and monosulphoaluminate) is developed for Molecular Dynamics (MD) simulations. Five different force fields (COMPASS, COMPASS II, INTERFACE, Universal and Deriding) were used and compared with each other to be able to measure the mechanical properties of these compounds. Also, the properties of two types of C-S-H with high and low density were determined by using Mori-Tanaka method. Lastly, Simulation results reported by the authors were compared with existing computational and experimental values. The results shown that using molecular dynamics method was suitable in estimating mechanical properties of hardened cement paste. These findings might be applied in larger scales and also multi-scale simulations.
elastic properties
Molecular Dynamics
Hardened cement paste
Simulation
nano scale
2016
8
01
71
78
http://journals.modares.ac.ir/article-15-10500-en.pdf
735-12358
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Implementation of a Trajectory Predictor and an Exponential Sliding Mode Controller on a Knee Exoskeleton Robot
Kaveh
Kamali
Ali Akbar
Akbari
Alireza
Akbarzadeh
In this article, trajectory generation, control and hardware development of a knee exoskeleton robot is provided. The robot aims to help the individuals with lower extremity weakness or disability during the sit-to-stand movement. In the trajectory generation phase, a new method is proposed which uses a library of sample trajectories to predict the sit-to-stand movement trajectory based on the initial sitting conditions of the user. This method utilizes the theory of "dynamic movement primitives" to estimate the sit-to-stand trajectory. The trajectory generation method is tested on a library of human motion data which has been obtained in a laboratory of motion analysis. In the next step, an exponential sliding mode controller is used to guide the robot along the predicted trajectory. The controller and the trajectory generator are implemented on the exoskeleton robot. For the hardware development, the xPC Target toolbox of MATLAB software and a data acquisition card was used. Finally, the robot was tested on a male adult. The subjects were asked to wear the robot while doing several sit-to-stand movements from various sitting positions. According to the results, the average power which is required to be applied by the user’s knee, is less when the exoskeletons assists him.
Exoskeleton Robot
Sit-to-stand Movement
Trajectory Prediction
Dynamic Movement Primitives
Exponential Sliding Mode Controller
2016
8
01
79
90
http://journals.modares.ac.ir/article-15-12358-en.pdf
735-2744
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Numerical and experimental investigation of welding speed effect on fatigue crack growth in friction stir welded 2024-T351 aluminum alloy
Ali
Rastegar
Danial
Ghahremani Moghadam
Khalil
Farhangdoost
Masoud
Tahani
Friction stir welded butt joints were performed on sheets made of AA2024-T351 aluminum alloy at tool rotational speeds of 400, 630, 800 rpm and traverse speeds of 8, 16, 25 mm/min. The fatigue crack propagation rate was investigated according to standard ASTM-E647 in CT specimens. FE simulation of FSW process was implemented for different welding conditions and next the fatigue crack propagation was simulated using XFEM method. In this analysis, to assess the damage in the joints, maximum stress criterion is used. The maximum principal stress in element was the fracture criterion. Numerical results are in good agreement with the experiments so the simulation is reliable. The obtained results show that the tool rotational and traverse speed affect the fatigues crack growth rate. For all welded specimens crack propagation rate was slower than that of the base metal for low values of ∆K (∆K≤13 Mpa) but is much faster at high values of ∆K. Furthermore fatigue properties of specimens that welded with lower speeds are better than base metal and increase in rotational or traverse speeds of the tool will increase the crack propagation rate of the welded specimens.
AA2024-T351
Friction Stir Welding
Aluminum Alloy 2024-T351
Fatigue Crack Propagation
finite element method
Tool Rotational and Traverse Speed
2016
8
01
91
100
http://journals.modares.ac.ir/article-15-2744-en.pdf
735-2844
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
A comparison between two approaches for solving the governing nonlinear equation of vibrations of electrostatic micro-sensors
Mohammad
Fathalilou
Mojtaba
Rezaee
Electrostatic micro-sensors as a part of microelectromechanical systems (MEMS) play an important role in modern technology. So, precise modeling and suitable solutions for solving the governing mechanical and vibrational equations of them are of great importance. Due to the nonlinear nature of the electrostatic excitation, numerical methods are used to solve the governing equations. This paper presents a comparison between two Galerkin-based approaches to solve them. In the first approach, as used by many researchers in the literature, both sides of the equations are multiplied with the denominator of the electrical force term and then the Galerkin method is applied, whereas in the second approach, we apply direct Galerkin method to solve the equation. As a case study the nonlocal elasticity theory has been used to obtain the governing equation. The results show that for a given beam, although the both approaches predict same pull-in voltage in most cases, but the first approach cannot predict the pull-in instability in some cases and also misses some fixed points. So, the bifurcation diagrams and phase portraits have different quality in the two approaches. Also, the results show that the singular point which is the position of the substrate plate, acts as a strong attractor in the phase diagrams which the first approach is unable to predict it.
Micro Sensor
Electrostatic
Numerical solution
Pull-in
Fixed Points
2016
8
01
101
107
http://journals.modares.ac.ir/article-15-2844-en.pdf
735-9125
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Piezoelectric energy harvesting from bridge vibrations under moving consecutive masses
Masoud
Karimi
Reza
Tikani
Saeed
Ziaei-Rad
Harvesting energy by piezoelectric materials is nowadays an efficient way for powering low-power electric devices. Required energy for sensors which are used in condition and health monitoring of bridges and other civil infrastructures can be examples of the energy harvesters. This study aimed to improve the piezoelectric-based energy harvesting on civil infrastructures, especially on bridge structures. In this investigation, harvesting energy from the vibrations of a bridge under moving consecutivemasses is studied. Harvesting energy iscarried out through a cantilever beam with piezoelectric patch which is installed atthe middle of a simply supported bridge. Governing equations for vibration of an Euler-Bernoulli beam under moving consecutivemasses arederived. The effects of inertial, centrifugal and coriolis forces areconsidered. For verifying, the results of the numerical solution of the moving mass problem are compared to the experimental tests data of the litterature. The harvester is modelled by a cantilever beam with piezoelectric patch under base excitations which are calculated from vibrations of the bridge mid-point. The obtained equations are then solved in MATLAB environment by using the forth order Runge-Kutta method. The calculated induced voltages are compared with those obtained from experiment. A good degree of accuracy is observed.
Energy harvesting
Piezoelectric
Bridge vibrations
Moving consecutive masses
2016
8
01
108
118
http://journals.modares.ac.ir/article-15-9125-en.pdf
735-3493
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Fabrication of hybrid nanocomposite Al2024/Gr/ZrO2 via FSP and evaluation effect role of hybrid ratio in mechanical and wear properties
Saeed
Ahmadifard
Masoud
Roknian
Taleb
Tinati Seresht
Shahab
Kazemi
Hybrid ratio of each reinforcement phases in hybrid composite can be defined as proportion of its volume to total reinforcement volume of the composite. The hybrid ratio is an important factor which controls the participation extent of each reinforcement phases in overall properties of hybrid composites. Hence, in the present work, surface hybrid nano composites of Al2024, Graphite average particle size of 100 μm and ZrO2 average particle size of 15 with different. For fabrication of nano composite the tool rotation rate was set to be 1000 rpm, and its advancing speed was 20 mm/min and tilt angle of 3 degree were chosen and all samples were subjected to 2 passes of FSP to obtain more homogeneous dispersion of the reinforcements. Subsequently, effect of hybrid ratio on microstructural, mechanical and tribological properties investigated. Optical microscopy and scanning electron microscopy were utilized to perform microstructural observation on the samples showed that reinforcements are well dispersed inside the Nugget Zone. Hardness value measurements and pin on disk dry sliding wear tests were carried out to investigate effect of hybrid ratio on mechanical and tribological properties of the nano composites.
Friction stir processing
Hybrid nanocomposite
Mechanical Properties
Al 2024
2016
8
01
119
126
http://journals.modares.ac.ir/article-15-3493-en.pdf
735-3918
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Dynamics modeling of open-chain terrestrial and space robots using a form of Boltzmann-Hamel equations
Abdolmajid
Khoshnood
Es'hagh
Azad
Seyed Mohammad Amin
Razavi
In this article, a form of Boltzmann-Hamel equations (Lagrange’s equations in terms of quasi-coordinates), different from the latter’s standard form and avoiding its structurally inherent complexity, is derived based on which a general algorithm for the dynamics modeling of open-chain terrestrial and space robots with an arbitrary number of rigid elements is presented. This form of Boltzmann-Hamel equations is shown to be particularly advantageous in terms of not requiring the determination of the kinetic energy as a function of generalized coordinates and quasi-velocities, representing generalized forces in terms of body basis vectors and offering a panoramic view of the dynamics of the systems. In the act of developing the algorithm, three highly useful kinematic identities are derived via a comparison between the single rigid body equations derived from both the standard and the proposed form of Boltzmann-Hamel equations. These identities are then used to greatly simplify the final dynamics model of both systems. Finally, the equations of motion for a two-link terrestrial robot is derived using the proposed algorithm and simulation results in MATLAB are compared with the model of the system in ADAMS to validate the model.
Boltzmann-Hamel equations
Quasi-coordinates
open-chain robots
space robots
terrestrial robots
2016
8
01
127
137
http://journals.modares.ac.ir/article-15-3918-en.pdf
735-1701
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Using various organic rankine cycles for production of power and hydrogen by incorporating geothermal energy and proton exchange membrane (A comparative study)
Hadi
Ghaebi
Behzad
Farhang
In the current work different organic rankine cycles (base and modified) coupled with proton exchange membrane presented to produce hydrogen and power. Organic rankine cycles used in this work are basic Organic Rankine Cycles (ORC), ORC incorporating regenerator, ORC incorporating feed fluid heater and ORC incorporating both of the regenerator and feed fluid heater. ORC energy demand supplied by geothermal energy. A thermodynamic model (energy and exergy) of systems done. EES software used to model the systems. Also a parametric study done to investigate the effects of the performance parameters (energetic and exergetic) of considered systems. The results showed that ORC incorporating both regenerator and feed fluid heater with PEM electrolyzer had the maximum energy (3.514%) and exergy (68.93%) efficiency in comparison with other systems. Also it can be observed that evaporator and electrolyzer had the most portion of exergy destruction of the system. Energy efficiency, exergy efficiency, hydrogen production and net power increased by pressure growth in all systems. The amount of exergy efficiency, energy efficiency, hydrogen production and net power increased by the evaporator temperature addition in ORC incorporating regenerator with PEM electrolyzer and ORC incorporating both regenerator and feed fluid heater with PEM electrolyzer but their amount marginally decreased by the evaporator temperature addition in basic ORC incorporating with PEM electrolyzer and ORC incorporating feed fluid heater with PEM electrolyzer.
Geothermal energy
Organic rankine cycles
PEM electrolyzer
Hydrogen production
Power production
2016
8
01
138
148
http://journals.modares.ac.ir/article-15-1701-en.pdf
735-4562
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Optimal design and fabrication of a 4-DOF quattrotaar parallel robot with singularity-free workspace by ABC and PSO algorithms
Mehdi
Zamani Fekri
Mojtaba
Zarei
Mehdi
Tale Masouleh
Mojtaba
Yazdani
Simulation of the four degree of freedom parallel robot (Quattrotaar) is subjective of this paper. The mathematical model of the parallel robot is obtained too. The workspace is optimized for Non-singular kinematic type-2. Artificial Bees Colony algorithm and Particle Swarm Optimization algorithm as overall exploring algorithms are implemented and the results are compared to each other. Neglect of any intrinsic complexity of the optimization problem the results show the capability of both methods for this robot parameters design. Comparison of the results indicates the Particle Swarm Optimization algorithm runs faster than Artificial Bees Colony algorithm. The exploring volume consists of a plan with 500 mm x 500 mm dimension which moves in a vertical direction from 500 mm to 1000 mm. One of the important hints of the paper is a 90-degree rotation of end effector around vertical axis Z. This rotation is caused more flexibility and dexterity for the robot. A 3-D model of Quattrotaar parallel robot is created by Computer Aided Design software and finally, Quattrotaar is fabricated in Human and Robot Interaction Laboratory (Taarlab)
Parallel Robot
singularity
Quattrotaar Robot
Artificial Bees colony
Particle Swarm Optimization
2016
8
01
149
158
http://journals.modares.ac.ir/article-15-4562-en.pdf
735-10525
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Free vibration analysis of a horizontal axis wind turbine with movable base
Saeed
Fadaei Naeini
Abbas
Mazidi
In this paper, equations of motion for a horizontal axis wind turbine with movable base are extracted and natural frequencies and vibration of the system is studied. The wind turbine tower is assumed rigid while its blades are modeled as flexible beams. In-plane bending and twisting are considered as two degrees of freedom for blades motion.The shaft connected the tower to blades is assumed rigid and its rotational velocity is considered.In this paper, specifically, a 5-megawattfloating horizontal axis wind turbine, which it’s basehas three angular velocities in different directions,is studied.Due to the complex shape and variation of the properties along the length, the turbine blade properties such as mass and geometric parameters are extracted by curve fitting in MATLAB.The equations of motion and boundary conditions are derived by Hamilton's principle and then are transformed to ordinary differential equations by Galerkin method. By setting the governing equations to standard form (space state), eigenvalues and frequencies are calculated. The numerical results are compared with published results and good agreement is observed.Then the effect of various parameters on turbine blades frequencies and time responses are demonstrated. Results show that the tower base angular velocity and blades rotational speed have considerable effects on turbine blades time response and vibration frequencies.
Horizontal axis wind turbine
Movable base
Natural Frequency
Free vibration
2016
8
01
159
170
http://journals.modares.ac.ir/article-15-10525-en.pdf
735-8382
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Using acoustic emission method for lubrication monitoring in a journal bearing in the time- frequency domain
Mehdi
Ahmadi Najafabadi
Sadegh
Hosseini
Mehdi
Akhlaghi
Poor lubrication is known as an important factor in the bearings failure. Therefore, it is very important to detect the lubrication condition. Hydrodynamic lubrication, mixed lubrication and boundary lubrication are the basic regimes of the fluid film lubrication. In a proper condition, development of hydrodynamic pressure is adequate to support the load and the bearings operate under hydrodynamic lubrication condition. However, in most situations, they operate in mixed lubrication or boundary lubrication regime and have metal-to-metal contact. To establish these regimes, using the so-called Stribeck curve is a useful method. In this curve, the oil film thickness is proportional to the lubricant viscosity and sliding velocity and inversely proportional to the applied load. However, distinguish of the exact range of hydrodynamic lubrication regime from mixed and boundary regime using this curve and relation related to the sliding bearings, due to high number of affecting design factors and operating parameters is difficult. The present study focused on the acoustic emission measuring method in order to monitoring the lubrication conditions in a type of journal bearings. Thus, condition monitoring of the journal bearing lubrication is provided and the numerical value of operating variables of the bearing for lubrication regime change from hydrodynamic to mixed is achieved. Using wavelet method, frequency features for each regime is identified. Then, for each lubrication regime, metal-to-metal contact detection is performed.
Acoustic emission method
Journal bearings
Wavelet transform
Lubrication condition monitoring
Metal to metal contact
2016
8
01
171
180
http://journals.modares.ac.ir/article-15-8382-en.pdf
735-6632
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Adaptive control for position control of a pneumatic actuator under variable loads
Mostafa
Taghizadeh
Seyed Mahdi
Chavoshian
Under a constant loading condition, use of a controller with constant coefficients can be acceptable for servo pneumatic systems. However in variable loads with widespread changes, more advanced control methods should be considered to achieve desirable performance. In this paper, an adaptive controller is designed and implemented to a variably loaded servo pneumatic system with PWM driven switching valve. In the under examination servo pneumatic system, PWM driven fast switching valve is used instead of expensive servo or proportional valves. Real time identification of system parameters is performed using input-output data and controller parameters are adjusted instantaneously. “Self-tuning regulators” algorithm, in which controller parameters obtain from solving a design problem, is applied to design the proposed adaptive controller. The designed controller is applied to the servo pneumatic system via an interface board and its performance is compared with PD and multi model controller. Unlike the proposed method in multi model control method, a number of constant loads should be considered and corresponding to each load a fixed controller is designed. Experimental results demonstrate the high performance of the adaptive controller under variable loads.
Position Control
Pneumatic actuator
Adaptive Controller
PWM
2016
8
01
181
188
http://journals.modares.ac.ir/article-15-6632-en.pdf
735-10059
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Effect of physical parameters on internal flow and thermal performance of a conical Hartmann-Sprenger tube - Case study
Babak
Afzali
Hassan
Karimi
Hartmann-Sprenger tube is a device in which an under-expanded jet enters a closed-end tube which is placed in a specific distance from the nozzle. By producing an intensive heat inside the tube in some specific modes of operation, the device could be used for some important engineering applications such as acoustic igniters. In present study, thermal performances of a set of six different case studies with conical tubes and different physical specifications are investigated. The variable parameters are the pipe material, the pipe length, the gap distance and the end wall condition which could be closed or perforated. The experimental tests in conjunction with numerical analysis are performed to evaluate the effect of changes in physical parameters on temperature rise inside the tube. The oscillatory flow with strong shock waves is the major reason of temperature rise inside the tube. As the gap distance changes, no oscillatory flow and no sensible temperature rise could be observed. Existence of a tiny hole on the tube end wall reduces the temperature rise, as the shorter tube does. The frequency of oscillations is near the tube resonance frequency for longer tubes. Tubes which made of materials with lower thermal conductivity could produce higher temperatures.
Conical H-S tube
Tube Geometry
Shock Wave Oscillation
Temperature Rise
Resonance Frequency
2016
8
01
189
198
http://journals.modares.ac.ir/article-15-10059-en.pdf
735-11978
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Experimental investigation of viscosity of MgO-MWCNTs hybrid nanofluid in Water- EG base fluid
Mohammad
Akbari
Akbar
Zareie
Nano-fluids are prepared by suspending the ultrafine nanoscale particles in the base fluid and can be substantially enhanced the heat transfer rate compared to pure fluids. Because of great importance of dynamic viscosity applications in related applications of nanofluids in heat transfer and energy systems, experimental investigation of the effects of volume concentration and temperature on dynamic viscosity of MgO – MWCNTs/EG-water hybrid nanofluid has been presented in this study. The nanofluids were prepared with solid volume fractions of 0.025%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6% and 0.8% and experiments were performed in the temperature range of 25 to 60⁰C. In addition, by investigating the rheological behavior of nanofluid against shear rate, the Newtonian behavior was observed. Regarding the weakness of the previous correlations for predicting the dynamic viscosity of this nanofluid and according to the experimental data, a new equation was proposed. The results showed that by increasing the solid volume fraction, the dynamic viscosity increased. This increase is more tangible at lower temperatures compared with higher temperatures. Moreover, at the temperature of 60⁰C, the solid volume fraction has no great effect on the dynamic viscosity of the nanofluid which this issue can be considered as an important achievement in the industrial and engineering applications.
nanofluid
dynamic viscosity
temperature
solid volume fractions
2016
8
01
199
204
http://journals.modares.ac.ir/article-15-11978-en.pdf
735-6849
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Optimum design of compression stiffened panel under buckling constraint using Gaussian surrogate model
Morteza
Dezyani
Hossein
Dalayeli
Shahram
Yousefi
Hamid
Farrokhfal
In the present paper, the results of an approximation method named structural index used as the first step, the process of design and optimization of stiffened panel with Gaussian type surrogate model are carried out. Modeling phase is based on the finite element analyses of the structure. Nonlinear buckling load is set as the design constraint. The surrogate model is employed to reduce the number of finite element analyses in the optimization process. Therefore time of design process is reduced. Using infill points in the modeling and optimization process, converging to local optima is ensured. Introducing a novel technique, finding the global optimum of the surrogate model is guaranteed. The approach of surrogate based optimization is illustrated using two test problems. Also the sensitivity of the response to the initial sampling plan is investigated. Convergence criteria usually used in surrogate based optimization is modified to speed the convergence but is not affected the quality of the response. Design optimization process is presented for two types of stiffened panels. In type 1 stiffened panel with 4 design variables, the initial training set is constructed using 55 points. The response is obtained after addition of 5 infill points. For type 2, the initial sampling plan is selected to be 58 points. The optimization process is stopped after adding 173 infill points. Finally, obtained results are compared with the results of structural index method and an approach toward global optimum of the compression stiffened panel is introduced with the characteristics of optimum structure.
Compression stiffened panel
Optimization
Surrogate Model
Nonlinear buckling
Gaussian model
2016
8
01
205
216
http://journals.modares.ac.ir/article-15-6849-en.pdf
735-2869
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Simultaneous Localization and Mapping Using Laser Data and Unscented FastSLAM with Scan Matching
Marzieh
Zamani Alavijeh
Shahram
Hadian Jazi
Simultaneous localization and mapping (SLAM) is a fundamental problem in autonomous robotic. Many algorithms have been exploited to solve this problem, among these algorithms, FastSLAM is one of the most widely used and Unscented FastSLAM is one of the newest. Although in several scientific researches it is stated that Unscented FastSLAM outperforms FastSLAM, there are still unexamined potentials regarding Unscented FastSLAM. Therefore, this paper seeks to improve the overall performance of Unscented FastSLAM. Map accuracy and quality directly depend on the accuracy of localization and observations. In SLAM algorithms, robot pose is predicted using motion model, and then corrected using the difference between map features and recently observed features. Accuracy of pose estimation may improve by comparing two sequential observations and modifying robot pose to result in best match between them. This method is called scan matching and has been successfully combined with FastSLAM algorithm and some other SLAM algorithms not including Unscented FastSLAM. Therefore, this paper seeks to investigate the performance of Unscented FastSLAM combined with scan matching. Simulation results show that combining Unscented FastSLAM with scan match significantly improves accuracy of localization and mapping.
Simultaneous localization and mapping
Unscented FastSLAM algorithm
Laser
Scan Matching
2016
8
01
217
225
http://journals.modares.ac.ir/article-15-2869-en.pdf
735-2838
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
The effect of laminate layers and follower force on optimum flutter speed of composite wing
Mohammad Reza
Fallah
Mojtaba
Farrokh
Saied
Irani
In this article the composite wing aeroelastic instability speed is optimized by genetic algorithm relative to fiber angle for different layers and follower forces. Aircraft wing is modeled as a beam with two degrees of freedom, which is a cantilever, with thrust as a follower force and mass of the engine. For structural modeling of composite wing the layer theory has been used and unsteady flow assuming subsonic and incompressible flow has been used for aerodynamic model in the time domain. Using the assumed mode the wing dynamic equations of the motion have been derived by Lagrange equations. Linear flutter speed according to the eigenvalues of the motion equations has been calculated. The process of flutter speed calculation has been converted to computer code in which the number of layers, angle of fibers in each layer, the mass of the engine, and the thrust are input variables and the flutter speed is its output. Using Genetic Algorithm, optimum flutter speed has been obtained by changing the angle of fibers. Finally, the impact of the number of layers, the mass of the engine, and thrust on optimum flutter speed has been investigated.
Aeroelasticity
Flutter
Composite wing
Optimization
Genetic Algorithm
2016
8
01
226
236
http://journals.modares.ac.ir/article-15-2838-en.pdf
735-3521
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Investigation of the Performance Characteristics of a Steam Jet Ejectors with Various Expansion Ratios
Mohsen
Kazemi
Mojtaba
Tahani
Sasan
Davoodi
Steam jet ejectors are the essential part in refrigeration and air conditioning, desalination, petroleum refining, petrochemical and chemical industries. A greater understanding of flow physic inside an ejector plays an important role in its performance improvement. In this study, analytical algorithm is developed for design of steam ejectors. The algorithm gives the flow ratio (motive to suction flow rate) as a function of the expansion ratio and the pressures of the entrained vapor, motive steam and compressed vapor. The compression ratio and back pressure variations were studied in ejector flow ratio with expansion ratio of 5 and 50. It showed that compression ratio increase by increasing the flow ratio. Also in a similar flow rate, compression ratio for ejector with expansion ratio of 50 is greater than compression ratio in the ejector with expansion ratio of 50, due to more vacuum in the case with expansion ratio 50. Then, the code results were compared with experimental results that showed appreciate agreement with other results. Finally, Mach number variations from nozzle exit to discharge diffuser were obtained by code. Results showed that the pressurized condition causes the lowering of expansion angle, thus resulting in smaller jet core and larger effective area. The expanded wave is further accelerated at a lower Mach number. Therefore, the momentum of the jet core is reduced. However, the enlarged effective area allows a larger amount of secondary fluid to be entrained.
Ejectors
Expansion wave
compression ratio
throat diffuser
Flow ratio
2016
8
01
237
244
http://journals.modares.ac.ir/article-15-3521-en.pdf
735-244
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
A novel vibration-based optimization technique for identifying elastic constant distribution and volume fraction index in functionally graded rectangular plates
Ahmad
Ghasemi-Ghalebahman
Mohammad
Moradi-Golestani
In this paper, a new inverse method has been presented for identifying the distribution of material properties and volume fraction index of rectangular functionally graded (FG) material plates. This method benefits from vibration analysis of FG plates accompanied by a novel and efficient meta-heuristic optimization algorithm called Drops Contact Optimization (DCO) algorithm, being proposed for the first time in this article. The presented algorithm relies on the initial population and mimics the behavior of water drops in different level of contacting successively with a fluid surface. Through using the second shear deformation theory and applying the Hamilton principle, the motion equations are derived and, subsequently, the natural frequencies of the considered FG plates are obtained. The outcomes relevant to considered different material phases and various length to thickness ratios are achieved and compared with those available in the literature. Making a comparative study of the obtained results with five well-known optimization algorithms confirms that the proposed DCO algorithm produces better performance in convergent speed and accurate characterization of FG materials.
Functionally Graded Materials
Vibration analysis
Inverse method
Elastic constants
Drops Contact Optimization algorithm
2016
8
01
245
254
http://journals.modares.ac.ir/article-15-244-en.pdf
735-2123
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Numerical investigation of nanofluid\'s effect on heat transfer in a pipe partially filled with porous material in a turbulent fluid flow
Alireza
Jamarani
Mehdi
Maerefat
Majid
Eshagh Nimvari
In the present study, effect of nanofluid aluminum oxide-water on heat transfer in a pipe partially filled with porous material in a turbulent flow is investigated numerically. In this regard, the heat pipe is studied in four structures: without porous material, filled with porous material, boundary and central arrangement of porous material. The results of numerical solution show that use of nano particles with changing thermo physical base fluid's properties, enhances heat transfer in all of the above structures. However, with using of nanofluid, heat conduction enhancement ratio in porous medium is lower than clear medium (without porous material). As a result, heat transfer enhancement in boundary arrangement is less and in central arrangement is more.
Heat Transfer
Turbulent Flow
Porous Material
nanofluid
2016
8
01
255
258
http://journals.modares.ac.ir/article-15-2123-en.pdf
735-5734
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Exact semi-inverse solutions for the elastoplastic deformation of beam with power law material model
Hassan
Beik MohammadLou
Hamid
Ekhteraei Toussi
Engineering analyses of beams are based on the proper guesstimate of deformation fields. Up until now, the analyses of beams are widely proposed and experienced in elastic region of materials behavior. This paper considers the elastoplastic engineering analysis of beams. In this regard, following the definition of a proper deformation pattern known as classical Euler- Bernoulli model and using the variational calculus principals the governing equations are extracted. In this analysis the behavior of material obeys the Romberg-Osgood model and yielding is based on the von Mises criterion. Different numerical solutions are represented for the solution of these complicated equations in the literature. In this paper the exact solution is provided for a thin beam under the action of uniformly distributed load by using the two analytical methods of homotopy and Adomian for the clamped- clamped boundary conditions. In verification phase, the deformation of beam is compared with the results of Abaqus software. Different graphical representations are provided for the results of the analytical solutions and simulations. Using these data, the level of consistency between the simulated solutions in one side and the Adomian and homotopy techniques on the other side, are assessed. At the end, the validity of applying the classical engineering theory of beams in the elastoplastic analyses is discussed.
Exact Beam Analysis
Elastoplastic Solution
Homotopy Method
Adomian Method
Variational Calculus
2016
8
01
259
270
http://journals.modares.ac.ir/article-15-5734-en.pdf
735-9708
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
A review of the production of ultrafine grained and nanograined metals by applying severe plastic deformation
Hessam
Torabzadeh
Ghader
Faraji
In this article, it is tried to be mentioned the functional structure of production methods of ultrafine-grained (UFG) and nanograined tubes. As well as metallurgical and mechanical effects of these methods on the matter are fully investigated. Ultrafine grained materials contain grains with an average size of 100-1000 nm and if the grain size is less than 100 nm, the material is classified as nanograined material which have a lot of applications in different industries such as aerospace, automobile, military and medical. Generally, the methods presented in this paper has been done on common materials like aluminum and pure copper and magnesium alloy AZ91. Extremely large plastic deformations lead to ultrafine-grain or nearly nanomaterial in the severe plastic deformation (SPD) methods. Most severe plastic deformation methods for producing ultra-fine grain bulk, whereas in the past decade due to the increasing need tube components with high strength and good ductility, The research was conducted to produce UFG tubes. Advances in this field presented formally so that the advantages and disadvantages of each process are clearly comparable. The most important advantage of ultrafine-grain materials is an enhanced mechanical strength in comparison with their coarse grain counterparts. The microstructural reasons are discussed. Furthermore, this article reviews the refinement and deformation mechanisms, e.g. dislocation deformation mechanism, twin deformation mechanism, grain boundary sliding etc. of SPD methods.
Severe plastic deformation
Ultrafine-grain tubes
Nanomaterial
Mechanical Properties
grain refinement
2016
8
01
271
282
http://journals.modares.ac.ir/article-15-9708-en.pdf
735-6026
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Numerical simultion of heat and mass transfer in textile for electrolyte solution
Ghassem
Heidarinejad
Mohammad Reza
Seyednejad
Hadi
Pasdarshahri
Heat and mass transfer in textiles are usually simulated using models that consider sorption and condensation. But in electrolyte solutions, ions existed in fluid passing the textile can cause a phenomenon called electric double layer. Charges on the textile pores will attract the ions with opposite charge which will affect the fluid flow. To investigate this effect, Poisson-Boltzmann equation is solved beside the other governing equations of the phenomenon. Net electric charge density is computed from this equation and is applied to liquid diffusion coefficient. In this research, the influence of electric double layer is shown and then the factors affecting the strength of this phenomenon have been studied. One side of the textile is thoroughly in contact with liquid and other side is in contact with air. To validate the obtained results, temperature variations in the outer side of the textile are computed and compared with the available experimental works. There is a good agreement between the results. According to the results, applying electric double layer effect in equations cause temperature difference to 20 percent in the outer surface of textile to lack of consideration this. In addition, time for textile full saturation when the electric double layer is considered, increased more than fivefold. The results show that by reducing the viscosity of fluid. The effect of electric double layer on the textile's outer surface temperature has increased. Porosity and zeta potential are other influential factors which according to calculations, increasing each effect can be accelerated electric double layer.
Textile
Heat and mass transfer
Electrolyte
Electric double layer
2016
8
01
283
290
http://journals.modares.ac.ir/article-15-6026-en.pdf
735-5433
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Numerical simulation of under-balanced drilling operations with oil and gas production from reservoir using single pressure two-fluid model
Saeed
Ghobadpouri
Ebrahim
Hajidavalloo
Amin Reza
Noghrehabadi
Younes
Shekari
Mohsen
Khezrian
In this paper, gas-liquid two-phase flow in the annulus of a real well during under-balanced drilling operations is simulated numerically. Oil and gas flow from the reservoir in to the annulus is considered due to under-balanced drilling condition. A numerical code based on one-dimensional form of steady-state single pressure two-fluid model in the Eulerian frame of reference is developed and its results are validated using experimental data from two real wells. The results of numerical simulation show better accuracy in comparison with other researches. Given the importance of prediction and control of the bottom-hole pressure and the amount of oil and gas production during the drilling operations, the effects of controlling parameters such as liquid and gas injection flow rate and choke pressure are discussed. Also, the effects of different controlling parameters on the characteristics of two-phase flow pattern, including liquid and gas void fractions, liquid and gas velocities and pressure distribution along with the annulus are discussed. According to the results, the effects of choke pressure and injected liquid flow rate on the production of the oil from the reservoir are independent of the values of each other and are dependent on the injected gas flow rate.
Under-balanced drilling
two-phase flow
Two-fluid model
Bottom-hole pressure
Oil production
2016
8
01
291
302
http://journals.modares.ac.ir/article-15-5433-en.pdf
735-12091
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Experimental and numerical investigation of effect of shape of ribs on flexural behavior of grid composite plates
Vahid
Tahani
Davoud
Shahgholian
Gholam Hossein
Rahimi
With the arrival of composite materials, because of their unique properties, the ideas were presented in order to strengthen and improve their performance. The ideas were causing building of Grid composite structures. These structures have most widely used in the aerospace, missile and Marine industry because have made ideal mechanical properties: special stiffness and high strength against impact and fatigue. Grid composite plates are made from thin composite shell connected by series composite ribs. Ribs network results in a significant increase in stiffness and strength of structure. In this research, experimental and numerical investigations of effect of Shape of ribs have been on flexural behavior of grid composite plates. For this purpose, three types of Grid plates were considered with triangle, square and rhombic ribs. For the building these plates, silicone mold was designed and built and also was used for making plates from hand lay-up and hand-wound layer technique. Samples were subjected to three-point bending test that for this purpose, the fixture was designed and built. From numerical solution of the problem and compared with experimental results was observed that there is very little difference between experimental and numerical results. Experimental results show that special flexural stiffness of plate with square rib is 1.92 and 1.88 plate with triangular and rhombic ribs, respectively. Also, the flexural strength of plate with square rib is 1.58 plate with triangular rib. Thus plate with square rib is the highest stiffness and bending strength Keywords
Flexure
Grid composite plate
Triangular rib
Square rib
rhombic rib
2016
8
01
303
311
http://journals.modares.ac.ir/article-15-12091-en.pdf
735-8950
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Analysis of stable period-one gait of a planner passive biped with elastic links
Mohammad
Yosofvand
Borhan
Beigzadeh
Amir Hossein
Davaei Markazi
Passive bipeds have become an interesting field of research for investigators. Probably all of passive bipeds which have been modeled previously are considered as a rigid model with point-mass. In this paper, 2D planner compass-gait biped with elastic link is modeled and simulated and its period-one gait is investigated. The stance leg of the passive biped is modeled as an Euler-Bernoulli beam and its vibrations are modeled by using Assumed Modes Method and the equations of motion for the swing phase are developed. Then behavior of the elastic biped is simulated by suing numerical methods in MATLAB software and the changes in leg angles and angular velocities of the biped are discussed. Computer simulations showed that when the vibrations of the stance leg are large, angular velocities become oscillating. Vibrations of the stance leg and the effects of Young's Modulus and damping coefficient on the motion of the elastic biped are discussed. Then model is simulated for the small vibrations of the stance leg and the results show that when the vibrations are small the elastic biped behaves like a rigid biped which verifies our simulations. When the vibrations are small, period-one gait can be found for the elastic biped for the ramp slopes of 0<γ≤0.0328 rad. The split in the eigenvalues of the period-one gait happens at the ramp slope of γ=0.029 rad.
Passive biped
Elastic Link
stability
Robot Vibration
Period-one Gait
2016
8
01
312
320
http://journals.modares.ac.ir/article-15-8950-en.pdf
735-1212
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Dynamic modeling and sensitivity analysis of an n-linkage planar serial robot to design parameters based on Sobol and EFAST methods
Behzad
Mehrafrooz
Mohsen
Mohammadi
Mehdi
Tale Masouleh
In this paper, based on the concept of natural orthogonal complement, an algorithm is devised to analyze the inverse and forward dynamics and dynamic sensitivity of n-linkage planar serial robots. The first goal is to derive the governing dynamic equations of a planar serial robot systematically, more precisely, number of the linkages, mass, moment of inertia and the length of the linkages are the inputs of the algorithm and the output will be the dynamics equations of the robot. As a comparison study, a planar serial mechanism, namely, dynamic modeling of 6R serial revolute manipulator is investigated and the results of the proposed algorithm are compared with other methods, i.e, Adams software and MatODE. In the next step, in order to develop a dynamic sensitivity analysis scheme, Sobol and EFAST methods are employed. By the use of the dynamic equations of the robots, the sensitivity of the actuating torques to the design parameters such as mass and length of the linkages is analyzed. Dynamic sensitivity of three planar serial robots namely, 2R-PSM, 3R-PSM and 6R-PSM is studied in two different configurations such as singular and isotropic. At the end, the effects of various angular velocities on the sensitivity of actuated torques to the design parameters are investigated. The obtained results reveal that the tolerance of uncertainty in the design parameters of robot affects the actuating torques significantly and also the Sobol’s method predict the sensitivity of the robot more precisely.
Serial planar robot
Natural orthogonal complement
MatODE
Dynamics sensitivity analysis
2016
8
01
321
332
http://journals.modares.ac.ir/article-15-1212-en.pdf
735-1519
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Analysis and comparison of buckling load of lattice flat structures under axial compression loading
Mahnaz
Zakeri
Abolfazel
Jafari
Thin sheets stiffened with lattice structures are used widely in many engineering industries. Investigation of stability behavior for the grid structures and determination of the buckling load under compressive loads is an issue that has attracted the attention of many researchers; and extensive studies have been done in this field. In this paper, a new grid called Diacube is introduced and its buckling load is examined. For this aim, first, the buckling behavior of 5 common types of stiffened flat lattice panels containing hexagonal, triangular, square, diamond and kagome grid are investigated under compressive axial load; and the results are compared with Diacube grid. The effect of network density used in each structure on the buckling of these structures will be studied under different boundary conditions. In addition to common grids,. Regarding to the mass difference of samples, specific critical load parameter (the buckling load to mass ratio) is used for comparison between the structures. Using the finite element modeling and numerical analysis, the grid that has the highest buckling load in each boundary condition is determined It is found that if unloaded edges in lattice panels are simply supported, this new Diacube grid will have the highest buckling load among all structures. Finally, validity of the numerical result obtained for two samples of the structures including hexagonal and Diacube grid is evaluated experimentally; and the numerical results are confirmed.
Lattice panel
Buckling load
Experiment
Grid density
Boundary conditions
2016
8
01
333
344
http://journals.modares.ac.ir/article-15-1519-en.pdf
735-6482
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Quantification of damage mechanisms in holed composite laminates by acoustic emission and finite element methods
Naeim
Akbari Shah Khosravi
Ali
Gholizade
Reza
Mohammadi
Milad
Saeedifar
Mehdi
Ahmadi Najafabadi
The laminated composites have many advantages such as high specific strength and specific stiffness. Despite of these advantages, they are prone to different damage mechanisms. This paper focuses on quantification of damage mechanisms in standard Open-Hole Tensile (OHT) laminated composites using Acoustic Emission (AE) and Finite Element Method (FEM). These damages include three main mechanisms, matrix cracking, fiber/ matrix debonding and fiber breakage. To this aim, OHT tests were carried out. The specimens fabricated from two types of glass/epoxy composite materials with [0]5S lay-up and [90]5S lay-up. AE accompanied with wavelet-based approach was then used to detect and quantify damage mechanisms of the specimens. FE analysis based on Hashin criteria was then utilized to simulate the damage mechanisms in the specimens and to validate the AE-wavelet based results. The comparison of applied methods show that the results of the AE-wavelet based approach are in very good agreement with the FEM results. Finally, it was concluded that the AE method has a good applicability to determine the damage mechanisms in laminated composite structures and to predict the remaining life-time of the structure.
Damage mechanisms
Acoustic emission
finite element method
Polymer composites
2016
8
01
345
352
http://journals.modares.ac.ir/article-15-6482-en.pdf
735-2307
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Simulation of Waves Propagation via Linear Phased Array Probe with Improved Design
(in Ultrasonic Inspection Tests)
Shahram
Yareiee
Mohammad-Reza
Sayyed Noorani
Ahmad
Ghanbari
Ultrasonic Phased Arrays are an emerging technology in nondestructive testing and evaluation. Some important factors affecting on the performance of these probes include, positioning elements in probe, number of elements, distance between two elements, elements length, and time delays to excite probe elements. The type of linear phased array probes is a prevailing type in which elements placed side by side and longitudinally. In this paper based on analyzing the existent laws in design and performance of the phased array probes related to the propagation of ultrasonic waves, an improved dimensional design for ultrasonic linear phased array probes, as well as improvement of the sequence of time delays to excite the probe elements are done. In order to evaluate the performance of the probe with improved design in comparison with a similar ordinary probe, an ultrasonic phased array test is simulated using FEM-based ABAQUS software. By numerical simulations, the performance of the probe with improved design versus the ordinary probe for propagating the guided waves in a thin square aluminum plate is compared. In first part, the attenuation coefﬁcient of the received signals of reflected wave is evaluated, and in second part, the performance of the probes for radial scanning is compared. Results of both simulations confirm that the performance of the probe with improved design is much better than the similar ordinary one. Specially, the probe with improved design propagates the ultrasonic waves with the maximum head wave energy, and steers them with higher accuracy towards a determined direction.
Ultrasonic Test
Linear Phased Array Probe
Simulation of Wave Propagation
Finite Elements Method
2016
8
01
353
361
http://journals.modares.ac.ir/article-15-2307-en.pdf
735-12074
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
A Method of DNA Sequencing By Using Carbon Nanotube: A Molecular Dynamics Study
Hossein
Nejat Pishkenari
Masoud
Yousefi
DNA is made up of molecules called nucleotides. There are four different nucleotides in DNA which are called Adenine, Guanine, Cytosine, and Thymine, or simply A, G, C and T. Determining the order of these bases is called DNA sequencing. This sequence determines the genes and these genes specify an individual’s unique traits. Therefore, the genetic research plays an important role in detection, prevention and treatment of diseases which are caused by genetic abnormalities and mutations. Common DNA sequencing methods are usually based on chemical reactions. These methods have some disadvantages for example they are expensive and also they cause losing DNA. So, in recent years the progress in molecular scale simulation methods has made various approaches for DNA sequencing. In this paper, a suitable method for DNA sequencing has been presented and its accuracy is investigated by molecular dynamics simulations. In this method, DNA molecule passes through the carbon nanotube first, and then the graphene nanopore, with a specific speed. Different bases are determined by analyzing the required force for passing DNA. In this proposed method, the speed and cost of sequencing are improved.
Molecular Dynamics
DNA sequencing
Carbon nanotube
graphene nanopore
2016
8
01
362
366
http://journals.modares.ac.ir/article-15-12074-en.pdf
735-2941
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Experimental and numerical examination of the effect of geometrical imperfection on buckling load in axially compressed composites cylinder with and without cutout
Fathollah
Taheri-Behrooz
Milad
Omidi
Mahmood
Shokrieh
When a cylindrical shell subject to a compressive load, because of various imperfections happened during processes as manufacturing, handling, assembling and machining, buckling occurs in loads lower than corresponding static failure load. Still many of cylindrical shell structures are designed against buckling based on experimental data introduced by NASA SP-8007 as conservative lower bound curves. In the manuscript, non-linear methods of Modified Linear Buckling Modeshape Imperfections (M-LBMI) and Simple Perturbation Load Imperfections (SPLI) for composite cylindrical shell with and without cutout are investigated. In order to evaluate the numerical results composite cylinder with stacking sequence of [90/+23/-23/90] are manufactured by using filament winding method and buckling tests are performed under axial loading. Non-linear numerical results in cylinder with and without cutout are close together and have good agreement with experimental data. . It was concluded that buckling load predicted by SPLI and modified LBMI method on cylinder with cutout is close to result of case without apply geometric imperfections. In summary, it was concluded that cutout on the cylinder body act as an imperfection to trigger buckling of the structures so there is no need to apply geometrical imperfections.
Buckling
Composite cylindrical shell
Geometric imperfections
2016
8
01
367
377
http://journals.modares.ac.ir/article-15-2941-en.pdf
735-7783
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Design of A Nonlinear Bilateral Teleoperation System coupled with non-passive Environments
Venus
Pasandi
Mahyar
Naraghi
Seyed Mehdi
Rezaei
Mohammad
Zareinejad
Keyvan
Baghestan
Stability and transparency are both very important conditions in bilateral teleoperation systems. For the design of such systems, different methods have been suggested. Among the approaches presented, passivity framework is widely utilized in which human and environment is considered passive. The operator does not make the closed-loop system unstable. In addition, it is passive against an external input. Thus the adoption of this assumption is correct for the human. Nevertheless it is a conservative presumption for the environment and according to some modern applications of teleoperation systems such as cardiac surgery, it is absolutely not acceptable. In this paper a novel control structure for nonlinear bilateral teleoperation systems interacting with active environments is addressed. In this approach, first a criterion for measuring activity of the environment is presented. Then by developing a PD controller, an algorithm that guarantees master-slave position coordination and static force reflection is introduced. The overall stability of closed loop system is proved using passivity concept and Lyapunov-Krasovskii technique. Simulations are performed to verify the performance of the proposed bilateral teleoperation systems in contact with passive and non-passive environments. Experimental results were carried out to validate the theoretical consequences.
Bilateral teleoperation
Active Environment
Passivity
stability
Proportional-Derivative (PD) control
2016
8
01
387
386
http://journals.modares.ac.ir/article-15-7783-en.pdf
735-7572
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Implementation of Attitude Control for an Octorotor Flying Robot in Autonomous Trajectory Tracking
Seyed Jamal
Hadadi
Payam
Zarafshan
An Aerial Robot or Unmanned Aerial Vehicle (UAV) is an aerial vehicle that provides its flight condition using aerodynamic forces. Also, this vehicle can be named as an autonomous robot. This robot is an under-actuated system and it is inherently unstable. Thus, the control of this nonlinear system is a problem for both practical and theoretical interest. So, the goal of this research is to contrast with highly nonlinear dynamic system of Octorotor that its control is difficult in many cases and it causes existence of instability in this Unmanned Aerial Vehicle (UAV). At the first, the structure of Octorotor is studied in this paper in order to increasing power, more carrying and increment of resistance into changing and distribution. Also, the electronic and mechanic of this robot is studied in some sections. Then, in the following, in order to attitude control of robot with introduction of dynamic system, one of the most common implemented controllers is applied on this robot. Initially, this process is done on the dynamic model of robot by Matlab/Simulink software and finally, implementation of this controller is applied on a fabricated Octorotor during a real flight in autonomous trajectory tracking in outdoor environment. At last, the study of sensors results is also shown.
Octorotor
Controller
Attitude controller
Trajectory tracking
Sensor
2016
8
01
387
395
http://journals.modares.ac.ir/article-15-7572-en.pdf
735-3142
2018-08-21
10.1002
Modares Mechanical Engineering
IQBQ
1027-5940
2476-6909
2016
16
6
Experimental and numerical analysis of the effect of immersion depth on the natural frequencies of a bounded circular plate submerged near the water free surface
Amir
Nasseroleslami
Mahmood
Salari
ََAbstract Recognition of the dynamical behavior and vibrations of marine structures, submerged in vicinity of the water free surface, is one of the most important issues in design of the marine structures. It is obvious that physical properties of the ambient fluid have some influences on vibrational frequencies of the structures. For the structures that have exposed under the influences of asymmetric environmental conditions, prediction of their dynamical behaviors is more complicated. In this paper the effects of immersion depth on first natural frequency of a bounded circular plate that was placed parallel in vicinity of the water surface, are studied numerically and experimentally. Based on the author’s knowledge, the techniques used for exciting the plate and measurements of natural frequencies are innovations of this research. Numerical solutions are done by using of the ABAQUS software. Comparisons of the numerical and experimental results show a good consistency. The investigations showed by increasing of the immersion depth, so the ratio of the depth to plate diameter reached to a certain value, the natural frequencies were also decreased. After that it remained constant while the immersion depths of plate were increased.
Natural Frequency
Experimental analysis
Circular plate
Immersion depth
water free surface
2016
8
01
396
402
http://journals.modares.ac.ir/article-15-3142-en.pdf