2021-10-19T08:40:06Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=1121
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Application of AG method and its improvement to nonlinear damped oscillators
M.
Mohammadian
M.
Shariati
In this paper, a new and innovative semi analytical technique, namely Akbari-Ganji’s method (AGM), is employed for solving three nonlinear damped oscillatory systems. Applying this method to nonlinear problems is very simple because in solving process only a trial solution, the main differential equation and its derivatives are required. The analytical solutions obtained by the AGM are utilized to study the impact of amplitude on nonlinear frequency and damping ratio. It is found that the AGM leads to acceptable results for the problems considered in this paper. Also, in order to obtain a more accurate solution, instead of using a trial solution with higher-order terms which may result in complicated and time consuming mathematical calculations, the solution obtained by AGM is improved via variational iteration method (VIM). The usefulness and effectiveness of the approach is demonstrated through comparison of the obtained results with those achieved by the numerical method. Hence, the AGM can be applied to nonlinear problems consisting of significant nonlinear damping terms and, if necessary, can be easily improved.
Nonlinear frequency
Akbari-Ganji’s method (AGM)
Variational iteration method (VIM)
Semi analytical technique
Damped Duffing oscillator
Flexible beam with damping
Transversal vibration
Quintic nonlinear beam
2020
02
01
203
214
http://scientiairanica.sharif.edu/article_21093_b53fffd5af9a2ffb35fb21c8705ad667.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Modeling particle deposition in the respiratory system during successive respiratory cycles
H.
Nemati
M.S.
Saidi
V.
Hosseini
In this study, using a 5-lobe symmetric model, total, lobar and generational particle deposition in the lungs during successive cycles is investigated. It has been found that for the particle size between 0.05 and 2 μm and the tidal volumes greater than 1000 ml, considering the effect of successive cycles predicted more deposition fraction per cycle compared to a single cycle up to about 16 percent. The mentioned range of tidal volume is related to light or heavy physical activities. So, it can be understood that people exposed to particulate matter within the mentioned size range, when acting physically, are at more health risk compared not only to the resting state, but also to the same state calculations based on a single cycle. Finally, total and generational remaining mass fraction suspended in the respiratory tract after the completion of each cycle is calculated. This remaining mass fraction turned out to be negligible except for particles between 0.05 and 2 μm.
particle deposition
respiratory system
lung
lobe
successive respiratory cycles
2020
02
01
215
228
http://scientiairanica.sharif.edu/article_21269_f4b14976134f581bae1f2fda063908fe.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Estimation of mixed-mode fracture parameters by gene expression programming
A.
Khademalrasoul
A.
Adib
The linear elastic fracture phenomenon has been characterized with stress intensity factors (SIFs). In this study a general function is obtained in order to predict the fracture parameters. Numerical calculation of the SIFs in a mixed-mode condition is a cumbersome task. In this research, more than 6800 numerical analyses using extended finite element method are conducted to simulate the fracture problem. States are considered for a plate with an arbitrary edge or center crack. Mixed mode SIFs were calculated using of interaction integral. Then, Gene Expression Programming (GEP) method is utilized to extraction of a function. Results show acceptable correlations between numerical calculations and genetic programming functions. R-square (R2) values are in a range of 0.91 to 0.96 that guarantees the accuracy of the inferred functions.
Fracture mechanics
Genetic programming
Stress intensity factors
Extended finite element method
2020
02
01
229
238
http://scientiairanica.sharif.edu/article_21094_63d40e8d833258a164c0e844b5eb6616.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Improving heat transfer in a triplex tube heat exchanger containing phase-change materials by modifications of length and position of fins
M. M.
Hossieni
A.B.
Rahimi
Heat thermal energy storage is a technique to improve thermal efficiency through reducing discrepancy between energy demand and supply. Latent heat thermal energy storage as a kind of thermal energy storage method has drawn considerable attention from researchers due to its high thermal energy density and constant operating temperature. This study numerically investigates the melting process in a triplex tube heat exchanger containing phase change material (PCM) RT82. A two-dimensional numerical model has been generated using the Ansys Fluent 16 software program to simulate melting process. In this study, conduction and natural convection have been considered. Selected arrangements of rectangular fins, including lengths and positions, were selected according to heat distribution while the total area of fins was kept constant. This new strategy was done to improve heat transfer in PCM which would result in decreasing its melting time. The select optimized model in this article reduces meting time to 28.4% in comparison with the model in Ref. [1]. Numerical results have been validated by numerical and experimental results of this reference and there has been a proper agreement between them.
Phase change material
Triplex tube heat exchanger
Heat transfer enhancement
fins arrangements
2020
02
01
239
251
http://scientiairanica.sharif.edu/article_21143_e09d1004466884eb1ff816795abaef8d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Studying buckling of composite rods made of hybrid carbon fiber/carbon nanotube-reinforced polyimide using multi-scale FEM
M.
Ahmadi
R.
Ansari
H.
Rouhi
In this paper, the buckling behavior of rods made of carbon fiber/carbon nanotube-reinforced polyimide (CF/CNT-RP) under the action of axial load is investigated based on a multiscale finite element method. A dual-step procedure is first adopted to couple the influences of micro- and nano-scale in order to obtain the equivalent elastic properties of CF/CNT-RP for various volume fractions of CF and CNT. The interphase effect between CNTs and the polymer matrix is taken into consideration. Also, dispersion of CF/CNT into the polymer matrix is assumed to be random. Then, rods with square and circular cross sections are considered whose stability characteristics are analyzed. The finite element modeling is performed using two models including a 3D brick model and a 2D beam model. Selected numerical results are given to study the effects of volume fraction of CNT/CF, interphase and geometrical properties on the axial buckling response of multiscale composite rods.
Multiscale composite rod
Hybrid carbon nanotube/carbon fiber reinforcement
Polyimide
buckling
Finite Element Method
2020
02
01
252
261
http://scientiairanica.sharif.edu/article_21120_35229ece51e9f88aebe66a8b0ab32c51.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Intelligent navigation of a self-fabricated biped robot using a regression controller
P.B.
Kumar
C.
Sahu
D.R.
Parhi
With increasing demand towards use of biped robots in industrial automation and other related applications, navigation and path planning has emerged as one of the most challenging research topic over the last few decades. In this paper, a novel navigational controller is designed and implemented in a self-fabricated biped robot. After fabricating the biped equipped with a large set of sensors, a regression controller is implemented in it for obstacle avoidance and path optimization purpose. The obstacle distances detected by the sensory network of the biped are fed as input parameters to the regression controller and the output obtained from the controller is the necessary heading angle required to avoid the obstacles present randomly in the environment. The biped is tested in a simulation environment for obstacle avoidance and target following behaviour. Along with that, to validate the simulation results, a real-time experimental set up is designed under laboratory conditions. The results obtained from both the environments are compared in terms of navigational parameters and a good agreement between them is observed. Being a relatively new area of research, the navigation of bipeds can serve as a pioneer act towards industrial automation.
Biped Robot
Basic Regression
Navigation
Path planning
V-REP
2020
02
01
262
272
http://scientiairanica.sharif.edu/article_21129_c0c1aae339d603979fc7ae95308fc13d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Adaptive control of a cable-actuated parallel manipulator mounted on a platform with differential wheels under payload uncertainty
M. H.
Korayem
M.
Yousefzadeh
Cable-actuated parallel Manipulators (CPMs) are widely employed for object handling applications. In order to displace the carried object along the ground to an unlimited distance, the CPMs can be mounted on wheeled mobile robots (WMRs). The derivation of the dynamic equations of motion for this integrated system is presented using Lagrange method. Since in load carrying task, the inertia of the moving load is the main source of uncertainty, an adaptive control approach is considered for the CPM, whereas the WMR uses a feedback linearized sliding mode approach. In order to maintain the end-effector of the CPM in within its relative workspace in the WMR frame, the convergence rate in the two controllers should be similar. Decentralization of the control law can be accomplished if the inertia of the CPM motors are negligible compared with the other inertias of the system. This assumption is shown to be applicable if an introduced index is small enough to have noticeable effect on the tracking error.
Cable-Actuated Parallel Manipulators
Mobile Robots with Differential Wheels
Non-Holonomic Constraints
Adaptive Control
sliding mode control
2020
02
01
273
286
http://scientiairanica.sharif.edu/article_21046_caedfb69034b101f04c3f167a3c25a88.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Numerical and experimental study of the effect of the process parameters on the void evolution in the cold extrusion of rods
M.
Rajabzadeh Gatabi
H.
Afrasiab
A.
Moazemi Goudarzi
Elimination of defects such as voids and internal cavities is required in metal forming processes to avoid premature failure of mechanical components during service. In this paper, the effect of different parameters on the void closure behavior is studied in the cold extrusion of rods. A three dimensional nonlinear dynamic finite element model is developed for this purpose. Experiments are also performed on aluminum samples to verify the accuracy of the finite element model. Results of the developed model are in good agreement with experimental findings. It is observed that voids contract in all directions during the direct extrusion which is in contrast to some other metal forming processes like forging and rolling. Effect of parameters such as die semi-angle, friction coefficient and void location on the void evolution is systematically investigated and discussed. The results of this study can help industries using metal extrusion for optimized design and control of the process to reduce voids and porosity and increase the strength of their product.
Void evolution
Cold extrusion
Finite Element Method
Die geometry
Void location
2020
02
01
287
294
http://scientiairanica.sharif.edu/article_21206_cf3fc80e2535c3766e386a3b220001d3.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Analysis of change in the state of hydraulic drive of machines in operation according to the diagnostic results
N.G.
Grinchar
P.A.
Sorokin
V.A.
Karpychev
K.A.
Sergeev
Technical diagnostics is a sphere of knowledge embracing theory, methods and means for defining the technical state of the objects. It is necessary for provision of security, functional reliability and efficiency of the technical object operation, as well as for reduction of the costs for its technical maintenance and reduction of the idle time losses caused by failures and premature shutdowns for maintenance. Therefore the objective of the paper is to analyze the change in the state of hydraulic drive of machines while in operation according to the diagnostic results. In order to achieve the set objective the authors used various experimental methods. The paper considers mutual influence of maintenance and technical diagnostics of hydrostatic drives of construction, track and some other mobile machines. It is shown that introduction of technical diagnostics allows transferring from the system of planned preventive repairs to the system of servicing the machines according to their actual technical state, which allows completely using the resource of a series of expensive aggregates. The authors described several main basic characteristics of change in the volume effectiveness of the hydraulic sets while in operation.
Diagnostic parameter
Hours in operation
Hydraulic drive
Economic expenditures
Performance capability
2020
02
01
295
301
http://scientiairanica.sharif.edu/article_20587_1f33547aa3b27d70cf3458d3e127cc77.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Effect of processing time on microstructure of surface and corrosion resistance of coatings resulting from plasma electrolytic oxidation on titanium alloy in hydroxyapatite nano-particles electrolyte
B.
Barooghi
M.
Sheikhi
A.
Amiri
In this study, the effect of coating processing time on microstructure of surface and corrosion resistance of coatings resulted by plasma electrolytic oxidation (PEO) was investigated on substrate of TiAl6V4 alloy. The coating processes in hydroxyapatite nano-powder electrolytic were carried out in same conditions of constant voltage of 600V and three different times of 125, 250 and 350 seconds. Studying the microstructure of coatings identified that the coating formed in 125 (s) had more compact and steady structure with fine surface cavities and less porosity. X-ray diffraction pattern of coating demonstrates that this coating is consists of oxide phases of titanium (rutile and anatase) and hydroxyapatite. Also, the study of corrosion resistance of coatings by Potentiodynamic polarization and electrochemical impedance spectroscopy in corrosive solution of chloride sodium 3.5% showed that the coating formed in 125 s has the most noble corrosion resitance potential and the least ICorr and finally the highest resistance to corrosion.
corrosion resitance
TiAl6V4
Plasma Electrolytic Oxidation
2020
02
01
302
309
http://scientiairanica.sharif.edu/article_21041_11383805a256531347702dcc32ba91f7.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Parameter converting method for bifurcation analysis of nonlinear dynamical systems
H.
Asghari
M.
Dardel
For detecting behavior of a dynamical system, bifurcation analysis is necessary with respect to change in parameters of system. In this work, based on the solution of ordinary differential equations from initial value and parameters, a simple method is presented, which can efficiently reveal different bifurcations of system. In addition to its simplicity, this method does not required to have deep physical and mathematical understanding of the problem, and because of its high precision and the speed of solutions, does not need to reduce the order of models in many complex problems or problems with high degrees of freedom. This method is named parameter converting method (PCM), which has two steps. In the first step the parameter is varied as a function of time and in the second step, time is expressed as inverse of this assumed function. With this method bifurcation and amplitude-frequency diagrams and hidden attractors of some complex dynamics will be analyzed and the sensitivity of the multi potential well systems to initial conditions is studied. With this algorithm, a simple way to find the domain of high-energy orbit in bistable systems is obtained.
Parameter converting method
sweeping parameter
bifurcation
Poincare’ map
continuation
nonlinear dynamics
time continuation method
unlimited steady solution method
2020
02
01
310
329
http://scientiairanica.sharif.edu/article_21074_b586add3f67251a127671742ea16a6e3.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Modeling, control, and simulation of a SCARA PRR-type robot manipulator
M.E.
Uk
F.B.
Sajjad Ali Shah
M.
Soyaslan
O.
Eldogan
In this study, a SCARA PRR-type robot manipulator is designed and implemented. Firstly, the SCARA robot was designed according to the mechanical calculations. Then, forward and inverse kinematic equations of the robot are derived by using D-H parameters and analytical methods. The software is developed according to obtain cartesian velocities from joint velocities and joint velocities from cartesian velocities. The trajectory planning is designed using the calculated kinematic equations and the simulation is performed in MATLAB VRML environment. A stepping motor is used for prismatic joint of the robot, and servo motors are used for revolute joints. While most of the SCARA robot studies focus on RRP-type servo control strategy, this work focuses PRR-type and both stepper and servo control structures. The objects in the desired points of the workspace are picked and placed to another desired point synchronously with the simulation. So the performance of the robot is examined experimentally.
SCARA robot
Real-time control
Modelling
Simulation
PRR
Servo motor
2020
02
01
330
340
http://scientiairanica.sharif.edu/article_21098_78d1e2ef66a1f50e243fc0c00b688f8a.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Comparative study of damage behavior of synthetic and natural fiber-reinforced brittle composite and natural fiber-reinforced flexible composite subjected to low-velocity impact
M.
Vishwas
S.
Joladarashi
S.M.
Kulkarni
In the present study, comparative study on the damage behaviour of Glass-Epoxy (GE), Jute-Epoxy (JE) laminates with [0/90]s orientation and Jute-Rubber-Jute (JRJ) sandwich is carried out using ABAQUS/CAE finite element software. The GE, JE laminate and JRJ sandwich with thickness of 2 mm is impacted by a hemispherical shaped impactor at a velocity of 2.5 m/s. The mechanisms in which the brittle laminate gets damaged are analyzed using Hashin’s 2D failure criteria and flexible composites are analysed by ductile damage mechanism. The energy absorbed and the incipient point of each laminate was compared. It was observed from the results that there is no evidence of delamination in JRJ as opposed to GE and JE. The compliant nature of rubber contributes in absorbing more energy and it is slightly higher than GE. Also it was observed that there is no incipient point in JRJ sandwich which means there is no cracking of matrix since rubber is elastic material. Thus the JRJ material can be a better substitute for GE laminate in low velocity applications. The procedure proposed for the analysis in the present study can serve as benchmark method in modelling the impact behaviour of composite structures in further investigations.
rubber
Damage
Energy absorbed
Glass fiber
Jute fiber
Low velocity impact
Stiff and Flexible Composites
2020
02
01
341
349
http://scientiairanica.sharif.edu/article_21099_fc44c3b694db62bbdc293cd611568fd8.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2020
27
1
Design of mixed flow pump impeller blade using mean streamline theory and its analysis
D.
Zindani
A.K.
Roy
K.
Kumar
Given the importance of blade design in effective performance of the mixed flow pump, the present work demonstrates the designing of the mixed flow pump impeller blade using almost unexplored Mean stream line theory. The Mean stream line theory, though been used sparingly but has found to give comparable results to that of other templates of design. The design process has been carried out in AUTOCAD 2013 and Solid Works Premium 2014 software. The analysis for equivalent stress, equivalent elastic strain, Total deformation and the directional deformation have been carried out in ANSYS 2014 for different construction material of the blade i.e., stainless steel, titanium alloy, bronze, and copper alloy. Total deformation was found to be maximum for impeller blade made from titanium alloy whereas the equivalent stress and strain was least for titanium alloyed impeller blade. Further, a comparison analysis has been carried out for the equivalent stresses in blade designed using mean stream line theory and free vortex theory. It was observed that the equivalent stress in impeller blade designed using free vortex theory was lesser than that designed using mean stream line theory.
Mixed flow pump impeller blade
AUTOCAD
Solid Works Premium
ANSYS
Mean stream line theory
free vortex theory
2020
02
01
350
360
http://scientiairanica.sharif.edu/article_20829_c6ce09db0545e717365b32d512884859.pdf