IFC
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2015
0
0
http://mme.modares.ac.ir/article_11853_204a98683d23cb4009e9a1b7a2313c04.pdf
Analysis of composite sandwich beam with enhanced nonlinear high order sandwich panel theory
soheil
dariushi
دانشجو/ دانشگاه صنعتی امیرکبیر
author
Mojtaba
Sedighi
عضو هیئت علمی/ دانشگاه صنعتی امیر کبیر
author
text
article
2014
per
A novel geometrically nonlinear high order sandwich panel theory considering finite strains of sandwich components is presented in this paper. The equations are derived based on high order sandwich panel theory in which the Green strain and the second Piola-Kirchhoff stress tensor are used. The model uses Timoshenko beam theory assumptions for behavior of the composite face sheets. The core is modeled as a two dimensional linear elastic continuum that possessing shear and vertical normal and also in-plane rigidities. Nonlinear equations for a simply supported sandwich beam are derived using Ritz method in conjunction with minimum potential energy principle. After obtaining nonlinear results based on this enhanced model, simplification was applied to derive the linear model in which kinematic relations for face sheets and core reduced based on small displacement theory assumptions. A parametric study is done to illustrate the effect of geometrical parameters on difference between results of linear and nonlinear models. Also, to verify the analytical predictions some three point bending tests were carried out on sandwich beams with glass/epoxy face sheets and Nomex cores. In all cases good agreement is achieved between the nonlinear analytical predictions and experimental results.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
1
8
http://mme.modares.ac.ir/article_11699_716ee292ba0801b3220d39d18ae59487.pdf
Experimental Test and Finite Element Analysis of Line Heating Method for Forming of Ship Hull Steel Plates
Ramin
Hashemi
Assistant professor / Iran University of Technology
author
Iraj
Jalili
دانشجوی دکتری، دانشکده مهندسی مکانیک، دانشگاه علم و صنعت ایران ، تهران
author
Mehran
Abdolmohammadi
سازمان تحقیقات و جهاد خودکفائی نداجا، تهران
author
text
article
2014
per
The purpose of this research is to examine and explain the mechanisms of the forming process called ‘line heating’ and to develop numerical tools for efficient calculation and prediction of its behavior. The forming process consists of heating at a (steel) plate in a predetermined pattern of lines by means of a gas torch so that the plate assumes a certain‚ curved shape. Today this method which is widely applied in the production of ship hull shell plate and construction is an alternative or supplement to other forming methods such as pressing and rolling. Considering a rational method for the determination of heating line patterns and heating among would be very beneficial. Much research is carried out in industry and at universities to achieve technology of this method‚ as the potential economic benefit is obvious. In this paper, experimental test and numerical simulation of Line Heating method has been done on naval plate- Grade E. Thermal and mechanical finite element analysis has been done separately. Experimental test results shows that with using Oxy-Acetylene gas heat we can make smooth curvature on plate. Effect of heat input and increasing of heating lines studied in this research. Results shows that increasing two heating lines on plate will increase maximum stress 6% and increasing heat input will enhance bending effect.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
9
16
http://mme.modares.ac.ir/article_11700_32fdfc49c40dde65e89764edea232519.pdf
Nonlinear forced vibration analysis of functionally graded nanobeams in thermal environments with considering surface stress and nonlocal effects
S. Talieh
Pourashraf
university of guilan
author
Reza
Ansari
استادیار دانشگاه گیلان
author
text
article
2014
per
In this investigation, an exact solution is proposed for the nonlinear forced vibration analysis of nanobeams made of functionally graded materials (FGMs) in thermal environment with considering the effects of surface stress and nonlocal elasticity theory. The physical properties of FGM nanobeams are assumed to vary through the thickness direction on the basis of the power law distribution. The geometrically nonlinear equations of motion and corresponding boundary conditions are derived using Hamilton’s principle on the basis of the Euler-Bernoulli beam theory. Using the Gurtin-Murdoch and Eringen elasticity theories, the surface stress and nonlocal effects are taken into account in obtained equations, respectively. For the solution purpose, first, the Galerkin procedure is employed in order to reduce the nonlinear partial differential governing equation into a nonlinear ordinary differential equation. This new equation is solved analytically by the multiple scales perturbation method. In the results section, the influences of different parameters including power law index, surface stress, nonlocal parameter, boundary conditions and temperature changes on the nonlinear forced vibration response of nanobeams are investigated. Also, comparisons are made between the results obtained from the classical, Gurtin-Murdoch and Eringen elasticity theories. It is shown that as the thickness decreases, the surface stress effect moderates the hardening-type nonlinear behavior of nanobeams. This effect is more prominent at low magnitudes of thickness. Moreover, one can find that by increasing the nonlocal parameter, the hardening-type response of nanobeams is intensified.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
17
26
http://mme.modares.ac.ir/article_11691_43988871b1ebe47c6cdf6032cf17e68d.pdf
Study of effective parameters of Parallel Tubular Channel Angular Pressing(PTCAP)
mostafa
ghadiri
university of tehran
author
Mahmoud
Mosavi
استاد/دانشگاه تهران
author
Mahdi
Ghamami
دانشگاه تهران
author
text
article
2014
per
Abstract Various methods have been proposed to produce metallic and bulk form materials.Severe plastic deformation, the ways in which you can set quite a lot of mechanical work applied to the metal. Various methods have been proposed to produce metallic and bulk form materials. However, despite the widespread need for tubes with high strength to weight ratio, few studies and attempts have been done to produce ultra-fine and nano structures.Ultra-fine grain metal created by the process have a high resistance by itself. therefore, these can be as high strength steels are used in harmony with the environment. In this study, optimal design of a cast is done in order to increase the homogeneity of the material microstructure and reduce applied force of the pipe production process.Finite element software is used to design the desired format. Since the framework has been designed based on the pressure in angular channels with parallel tube, the channels angles, corners and curved angles, reshaping and the channel radius ratio, the coefficient of friction between the pipe and the channel and the number of passes are the parameters affecting the process.The effect of the above parameters in a homogeneous effective strain rate and force of the process has been studied.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
27
33
http://mme.modares.ac.ir/article_11701_6c3c40bbcc6338116dace210b06565d4.pdf
Porous Matrix properties effect on the internal heat generation in a square cavity saturated with Cu-Water nanofluid
Aydin
Zehforoosh
دانشکده مهندسی مکانیک
دانشگاه صنعتی سهند
author
Siamak
Hossainpour
دانشیار دانشگاه صنعتی سهند
author
text
article
2014
per
In this paper, natural convection of Cu-Water nanofluid inside an enclosure which is partially filled with porous media, with internal heat generation has been studied numerically. Cu-water nanofluid was used where Maxwell and Brinkmen models determine its properties. Due to the low velocity of nanofluid, Darcy-Brinkman equation used for the modeling of porous media. In order to gain the maximum energy from the temperature dependent heat source, different parameters such as Rayleigh number, volume fraction of nanoparticles, porosity of porous matrix and heat conduction ratio has been investigated. The results show that increasing the volume fraction of nanofluid increases Nusselt number at all porosities and Nusselt will further increases at lower porosities. Changes of thermal conductivity ratio were effective only at low porosities and causes to fast conduction of generated heat and two-fold increase in Nusselt number. Moreover the porosity changes at different thermal conductivity ratio Cause to minimum Nusselt at the porosity of 0.4 to 0.6. Increasing Rayleigh number will lead to nanofluid penetration increase into the porous matrix and with further matrix cooling more increase in Nusselt number in all porosity ranges will be achieved.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
34
44
http://mme.modares.ac.ir/article_11702_c99e6bbb264cbc0256cd512508ada151.pdf
Effects of Preload on Nonlinear Dynamic Behavior of Noncircular Aerodynamic Journal Bearing
Mohammad Mahdi
Jalili
هیأت علمی
author
Mahdi
Zare Mehrjardi
دانشگاه یزد
author
Reza
Rashidi
هیأت علمی/دانشگاه پیام نور
author
text
article
2014
per
In this article, using finite element method the effects of the preload on the nonlinear dynamic behavior of the noncircular two lobe aerodynamic journal bearing have been investigated. Assuming that the rotor is solid, the governing Rynolds equations for both the gas lubricant and rotor equation of motion in static and dynamic conditions have been derived and performance of the noncircular aerodynamic journal bearing in different conditions has been evaluated. Rung Kutta method has been used to solve the time dependent equations of motions of noncircular aerodynamic journal bearing and its gas lubricant. Using the numerical results, to investigate the motion of the center of the rotor in dynamic conditions, the graphs of frequency response, power spectrum, dynamic trajectory, Poincare map and bifurcation diagram have been plotted. The results show periodic, quasi periodic and chaotic rotor behavior for different bearing preload. It is concluded that appropriate selection of rotor parameters like its preload and suitable design and fabrication of rotor and its bearing can prevent any undesirable perturbed motions of the shaft and both the collision and wear of the rotor and bearing.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
45
56
http://mme.modares.ac.ir/article_11704_cd0467283b879dd743e2207eaf6b87f2.pdf
Dynamics modeling and active vibration control of a satellite with flexible solar panels
Abdolmajid
Khoshnood
استادیار دانشگاه خواجه نصیرالدین طوسی
author
Hooman
Moradi
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2014
per
Flexible solar panels of a satellite during a maneuver get excited and vibrate. Such vibrations will cause some oscillatory disturbance forces that affect the satellite rigid body. Vibrations cause cracks in flexible solar panels and these cracks, because of fatigue, make panels fracture. Moreover, satellite rigid body which does accurate works like capturing picture of earth surface or sending information to earth will be disturbed as a result of vibration. Therefore it needs to be prevented against resonance. In this paper, dynamic equations of a satellite including cubical rigid body are extracted, then with combination of ANSYS and ADAMS softwares, the model is simulated and its responses has been compared with analytical model. New control strategy for reducing the vibration of flexible bodies of the multi body system, includes rigid and flexible bodies, is proposed. With eliminate oscillation from rigid body angular velocity, vibrations amplitude of flexible parts will be reduced. For this purpose, an adaptive control system and a notch filter is used to eliminate the oscillation of measurement procedure caused by the vibration of flexible solar panels. Adaptive control system responses with considering resonance and without resonance, is shown and merits of this method is evaluated.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
57
66
http://mme.modares.ac.ir/article_11705_bf217435d48263d53e61f1cf9e2d2125.pdf
Cutting of Ti6Al4V titanium alloy using abrasive water jet and multiobjective optimization of geometry features
Hossein
Amirabadi
استادیار گروه مکانیک دانشگاه بیرجند
author
Abolfazl
Foorginejad
عضو هیات علمی دانشگاه صنعتی بیرجند
author
Milad
Ahmadi Mojavery
کارشناس ارشد
author
text
article
2014
per
Abrasive water jet cutting process can produce tapered edges on cutting kerf. This problem can limit the applications of abrasive water jet cutting process and in some cases it is necessary another edge preparation process. In this paper, an experimental investigation kerf characteristics of Ti-6Al-4V titanium alloy under abrasive water jet cutting is presented. In this regards, it is shown how to use the hybrid approach of Taguchi method and principal component analysis to optimize abrasive water jet cutting are used in this paper. The abrasive water jet cutting process input parameters effect on material removal rate and the characteristics of the surface. A considerable effort was made in understanding the influence of the system operational process parameters such as water jet pressure, traverse speed, abrasive flow rate, and standoff distance. Due to appropriate selecting abrasive water jet cutting process parameters leads to optimizing of kerf characteristics include top kerf width, kerf tapper and kerf deviation, therefore it is important to select appropriate input parameters. The obtained results from this method show that the hybrid approach of Taguchi method and principal component analysis is a suitable solution for optimizing of abrasive water jet cutting process.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
67
75
http://mme.modares.ac.ir/article_11703_b28c459a07f10a663521ea9199afeb04.pdf
Experimental investigation of nanoclay and nanosilica particles effects on mechanical properties of glass epoxy composites
Mohammad Hossein
Pol
عضو هیات علمی/دانشگاه تفرش
author
GHolam Hosein
Liaghat
استاد / دانشگاه تربیت مدرس
author
Erfan
Mehrabani Yeganeh
دانشجوی کارشناسی ارشد / دانشگاه تربیت مدرس
author
Ali
Afrouzian
دانشجوی کارشناسی ارشد / دانشگاه تربیت مدرس
author
text
article
2014
per
In this paper, the tensile properties of 2D woven glass epoxy composite reinforced by two different nanoparticles have been investigated and compared. Hand lay-up method has been used to manufacture nanocomposites with 12 layers of 2D woven glass fibers with 40% fiber volume fraction. The nano-epoxy resin system is made of epon 828 resin with jeffamine D400 as the curing agent. The composites were reinforced by adding organically modified montmorillonite nanoclay (Closite 30B) and nanosilica (SiO2) particles. The nanoclay particles were dispersed into the epoxy system in a 0%, 3%, 5%, 7% and 10% ratio in weight with respect to the matrix, while the spherical nanosilica particles were dispersed into the epoxy system in a 0%, 0.5%, 1% and 3% ratio in weight with respect to the matrix. The results show that low loading of nanoclay decreases the mechanical properties of nanocomposite, while significant improvements of nanocomposite mechanical properties are shown in low loading of nanosilica. Tensile strength and toughness of nanocomposite increase by 7% and 10% after adding 5 wt.% nanoclay. Loading of 0.5 wt.% nanosilica cause 10% and 27% improvement in tensile strength and toughness of nanocomposite.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
76
82
http://mme.modares.ac.ir/article_11706_e1fd7d6dd7ad08714519886d7a2e0e9a.pdf
Adaptive Flight Control Systems in Presence of Actuator Failures
Mohammad
Navabi
دانشگاه شهید بهشتی
author
Mohammad
Radaei
دانشگاه شهید بهشتی
author
text
article
2014
per
Actuator failures can cause control system performance deterioration and even lead to instability and catastrophic accidents and incidents. Therefore, the adaptive control of damaged aircraft in designing flight control systems to enhance safety level has recently become the subject of research. Damage causes structural changes and parametric uncertainties which need a new modeling and control approach. In this paper, firstly, a nominal control design based on linear quadratic regulator design is used and shown that the linear quadratic regulator design is not capable of coping with the unknown actuator failure and cannot achieve satisfactory performance. Then, a feedback adaptive signal is designed based on direct approach to handle uncertain actuator failures in linearized system. The adaptive control scheme is applied to the linearized model of a large transport aircraft in which the longitudinal and lateral motions are coupled as the result of using engine differential thrusts. The type of damage which is considered for actuators in this paper is lock-in-place which means control surfaces are fixed in an uncertain value after damage. Analytical stability analysis and simulation results are presented to demonstrate the effectiveness of the proposed approach.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
83
93
http://mme.modares.ac.ir/article_11719_4e1847c3b5e79ac951080fceee8bb17b.pdf
An experimental study of fluidization of solids particles in a bubbling fluidized bed
hasan
amini
دانشگاه آزاد اسلامی واحد علوم و تحقیقات تهران
author
Hojjat
Ghasemi
دانشگاه علم و صنعت ایران
author
Morteza
Khayat
دانشگاه آزاد اسلامی واحد علوم و تحقیقات
author
text
article
2014
per
For the experimental study of fluidized bed`s hydrodynamics and investigating of several effective parameters on this hydrodynamics, a fluidized bed is designed and manufactured. This bed is a cylindrical transparent column with internal diameter as 14 cm. Bed particles are silica sand in the size ranged from 200 to 750 micrometers. In this study, first the Minimum fluidization velocity ("Umf" ) of Different sieve particles is determined and the effect of particle size and bed height on this velocity is investigated. Then, influence of particle size and bed height on the bed pressure drop is studied. Then experimental results are compared with calculated values from current prediction correlations to determine the deviations of the prediction values from experimental data. As a result, by increasing the particle size in the equal bed height, Minimum fluidization velocity is increased but the pressure drop does not significantly change. Also, by increasing bed height, the Minimum fluidization velocity and pressure drop increased. But for Minimum fluidization velocity, this increase is insignificant and it can be ignored. Also bed pressure drop changed linearly with bed height
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
94
100
http://mme.modares.ac.ir/article_11720_8da1f8161af6b47b07186ba86daa2f0c.pdf
Aerodynamic investigation and optimization of airfoil geometry and oscillation parameters in the plunging motion using RSM
Mohammad Hasan
Javareshkian
دانشیار دانشگاه فردوسی
author
Amir
Baghri
دانشگاه فردوسی مشهد
author
Ali
Esmaeli
دانشگاه لیسبون
author
Abdolmajid
Zamanifard
دانشگاه فردوسی مشهد
author
text
article
2014
per
In this research, the plunging motion of an airfoil by a numerical method based on finite volume in different Reynolds numbers is simulated and the thickness effect, amplitude and reduced frequency on the aerodynamic coefficients are investigated. In this process, SIMPLEC algorithm, implicit solver, high order scheme and dynamic mesh method is used in unsteady simulation and the flow is supposed viscous, incompressible and laminar. Simulations are in three Reynolds 1000, 11000 and 50000, respectively, in accordance with the flight of the insects, small birds and pigeons are done in two amplitudes and three reduced frequencies. The simulation results are compared with published data to confirm the validity of research. This comparison shows comprisable agreement. Pressure distribution and Vortex shedding around airfoils show that the thickness of the airfoils delays vortex shedding and changes time-averaged thrust coefficient. Reduced frequency and amplitude of oscillation are two important parameters in this simulation, but the reduce frequency is more effective than amplitude. The response surface methodology (RSM) was used to optimize the plunging airfoil. Optimization shows that airfoil with 0.29% thickness, 3.08 reduced frequency and 0.5 dimensionless oscillating amplitude produce maximum trust coefficient.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
101
111
http://mme.modares.ac.ir/article_11721_a9335bdb339baee886839eac13f63d83.pdf
Standard and Robust Backstepping Control of a Spacecraft with Inertial Uncertainty
Mohammad
Navabi
استادیار مهندسی هوافضا -دانشکده فناوریهای نوین -دانشگاه شهید بهشتی
author
Sina
Soleymanpour
دانشجوی کارشناسی ارشد مکانیک پرواز و کنترل
author
text
article
2014
per
از آنجا که معادلات سینماتیک و دینامیک وضعیت فضاپیما، معادلاتی غیرخطی هستند، برای کنترل در حالت واقعیتر باید از روشهای کنترل غیرخطی استفاده شود. روش پسگام یک تکنیک سیستماتیک بر پایه لیاپانوف برای طراحی کنترلهای پایدار سیستمهای دینامیکی غیرخطی میباشد. از آنجایی که در عمل شاهد حضور اغتشاشات و عدم قطعیتهای مختلف در سیستم هستیم، نیاز است که کنترلر طراحی شده قابلیت مقاومت در برابر این عدم قطعیتها و اغتشاشات را داشته باشد. بنابراین در اینگونه موارد، از روش بهبود یافتهای به نام پسگام مقاوم استفاده میشود که در آن یک ترم دمپینگ غیرخطی به کنترلر اضافه میشود تا بتواند در برابر اغتشاشات و عدم قطعیتهای پارامتری سیستم مقاومت کند. در این مقاله، پس از استخراج معادلات سینماتیکی و دینامیکی فضاپیما بر حسب پارامترهای اصلاح شده رودریگز، با استفاده از روش پسگام استاندارد یک کنترلر پایدار وضعیت برای سیستم غیرخطی فضاپیما طراحی و پایداری آن توسط تئوری لیاپانوف اثبات میشود. سپس به منظور ایجاد مقاومت در سیستم در برابر عدم قطعیت در ماتریس اینرسی فضاپیما، با اضافه نمودن ترم دمپینگ غیرخطی به روش پسگام استاندارد، پسگام مقاوم بر روی سیستم معادلات فضاپیما پیادهسازی میشود. نتایج شبیهسازی، دقت تعقیب وضعیت و همچنین موفقیتآمیز بودن روش پسگام مقاوم برای مقاومت در برابر عدم قطعیتهای پارامتری را نشان میدهند.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
112
124
http://mme.modares.ac.ir/article_11722_22fba94e39039f74075e11a24e66d4ec.pdf
Investigating the effect of return air vent height on energy consumption, thermal comfort, and air quality in under floor air distribution system
Ghassem
Heidarinejad
Tehran, Ale Ahmad Ave, Tarbiat Modares University, Department of Mechanical Engineering, Room 309
author
Mohammad Hassan
Fathollahzadeh
دانشگاه تربیت مدرس
author
Hadi
Pasdar Shahri
دانشگاه تربیت مدرس
author
text
article
2014
per
In this study, by cooling coil load calculation in under floor air distribution systems, the effect of separate location of the return and exhaust vents and return vent height on energy consumption, thermal comfort conditions and indoor air quality have been investigated. Based on the results obtained from this study, when the height of return vent is equal to 2.0, 1.3, 0.65 and 0.3 m, the amount of energy usage reduction compared to no return vent is equal to 10.9, 15.3, 18.9 and 25.7 percent respectively. Limiting factors in the amount of this reduction are thermal comfort of occupants and indoor air quality. To this end, thermal comfort indices (Predicted Mean Vote and Predicted Percentage of Dissatisfied), local thermal discomfort index (Temperature gradient in vertical direction), and indoor air quality index (Mean Local Air Age) have been probed with changing return vent height by CFD methods (AirPak software with SIMPLE algorithm by using Indoor Zero Equation turbulence model). Based on the results, by reducing the height of return vent from ceiling to floor, the exhaust air temperature increased, which causes to temperature gradient increase in vertical direction. The survey was conducted that choosing the location of 1.3 m(upper boundary of occupied space in seated mode) for return vent, causes to 15.3 percent reduction in the amount of energy consumption while maintaining the states of thermal comfort conditions and indoor air quality.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
125
133
http://mme.modares.ac.ir/article_11723_24d7c5325402c0b6d0e1a4fc1893a92f.pdf
Frequency analysis of rectangular holed FG plates using three dimensional elasticity theory and meshless method
reza
pilafkan
عضو هیئت علمی/ دانشگاه محقق اردبیلی
author
Seyed Javid
Zakavi
عضو هیئت علمی/دانشگاه محقق اردبیلی
author
Soudeh
Bakhshi
دانشجو/دانشگاه محقق اردبیلی
author
text
article
2014
per
In this paper, three dimensional frequency analysis of moderately thick plate with considering the effect of a circular hole is presented by using of Three Dimensional theory of Elasticity and a numerical mesh-less method with radial point interpolation functions. Using this numerical method, the field variable (such as displacement) is interpolated just using nodes scattered in the plate domain. Because there is no relation between nodes, they can be scattered arbitrarily in the problem domain. The plate is made of a functionally graded material that is consists of two different phases of metal and ceramic. Mechanical properties of the plate change independently in the length, width and thickness directions of it using (according to) Mori-Tanaka model. The effects of radius of holes, different volume fraction exponents of functionally graded plate in three directions and different boundary conditions on natural frequencies of the plate is investigated by using of the code written in MATLAB and simulation in ABAQUS. The results have been compared with results in available papers and it shows the high accuracy of the method used in this present work.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
134
142
http://mme.modares.ac.ir/article_11724_432c6a521a2cc837b9d4636ef01a5966.pdf
Stress intensity factor for a longitudinal semi-elliptical crack in a thick-walled cylinder under hyperbolic thermal loading
Mohammad Bagher
Nazari
دانشگاه شاهرود
author
Omid
Asemi
دانشگاه شاهرود
author
text
article
2014
per
In this paper, the stress intensity factor for a longitudinal semi-elliptical crack in the internal surface of a thick-walled cylinder is derived analytically and numerically. The cylinder is assumed enough long and subjected to the axisymmetric cooling thermal shock on the internal surface. The uncoupled thermoelasticity governing equations for an uncracked cylinder are solved analytically. The non-dimensional hyperbolic heat equation is solved using separation of variables method. The weight function method is implemented to obtain the stress intensity factor for the deepest and surface points of the crack. Results show the different behavior of the crack under hyperbolic thermal shock. At a short time after the thermal shock, the stress intensity factor at the deepest point –especially for shallow cracks- for hyperbolic model is significantly greater than Fourier one. The stress intensity factor at the deepest point is greater as the crack is narrower for both models. Unlike mechanical loading, the greatest stress intensity factor may occur at the surface point. According to the results, assumption of adequate heat conduction model for structure design under transient thermal loading is critical.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
143
151
http://mme.modares.ac.ir/article_11725_607ae437a312e9d5d068c8e0ff7ab37f.pdf
Nonlinear Mechanic Model of Asymmetric Structure- Base Isolator Interaction under Harmonic and Earthquake Loads and Study of its Nonlinear Phenomena-Revised
Majid
Amin Afshar
عضو هیئت علمی دانشگاه بین المللی امام خمینی قزوین
author
Sepehr
Aghaei Pour
دانشجوی کارشناسی ارشد دانشگاه بین المللی امام خمینی (ره)
author
text
article
2014
per
Today, base isolation of buildings is a conventional approach to earthquake resistance. The prominent goal is to reduce displacement of structure by movement of elastomeric bearings installed on the base of structures on the ground. Considering widespread construction of asymmetric buildings well as the intensity of damages to such types of structures resulting from earthquake, the present research covers study of interaction mechanics of asymmetric base-isolated structures, where motion equations are presented in two coordinates, one fixed on the building base (global coordinate) and the other on the torsional isolation level (local coordinate). In this conventional approach, the motion equations are calculated on linear form in the initial coordinate system, whereas in the new approach proposed in this research, motion mechanics analysis in the secondary coordinate system will lead to non-linear equations. Three types of structures are proposed with ratio of torsional-lateral correlated natural frequency on asymmetric natural frequency. Responses of both linear and nonlinear methods for the three types of structures under harmonic effects and earthquake are compared while analyzing time history and frequency. Some differences are observed between the linear and nonlinear methods. Then, some non-linear phenomena such as saturation, energy transfer between modes, and rigid displacement in such structures are also analyzed.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
152
162
http://mme.modares.ac.ir/article_11726_cc39ec62158e0851f23502c848f0ba6c.pdf
Optimal Design, modeling and manufacturing of the eddy current damper by arrangement permanent magnet
Yousef
Hojjat
دانشیار دانشگاه تربیت مدرس گروه ساخت و تولید،
author
Ali Asghar
Maddah
دانشگاه تربیت مدرس
author
Mojtaba
Ghodsi
دانشگاه تربیت مدرس
author
Soheil
Talebian
دانشگاه تربیت مدرس
author
Mohammad Reza
Ashoori
دانشگاه سمنان
author
text
article
2014
per
The purpose of this paper is obtaining an optimal arrangement of permanent magnets in a non-contact eddy current damper in order to achieve the maximum damping coefficient (c) among dampers with the same dimension. Magnetic theory and eddy current equations have been employed and solved by finite element numerical method. The dominant damping parameters and the optimum ratio of the ferrite core and the permanent magnet for the specific dimension have been achieved. A damper with the dimensions obtained from design is manufactured in order to verify the result of simulations. A setup also is designed and manufactured to verify the damping coefficient. The damping coefficient of simulation and experimental setup is 69.50 and 68.37 respectively which shows a close correlation between simulation and experiment results. The damping coefficient of the designed damper has been increased by 22.5% compared with a same dimension damper. Furthermore, frequency response is obtained by MATLAB software and a decrease of vibration amplitude in eddy current damper has been investigated. The result showed 20 dB reduction in the peak amplitude of frequency response in the designed damper.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
163
169
http://mme.modares.ac.ir/article_11745_3337b445ea10daae33d3d12d0b9b2260.pdf
Pareto discrete- continuous optimization of Sikorsky ASH-3D helicopter main gearbox
Farid
Vakil-Tahami
Associate professor, University of Tabriz
author
Reza
Hassannejad Qadim
Assistant professor, University of Tabriz
author
Akbar
Rasoulian
Student, University of Tabriz
author
text
article
2014
per
Nowadays, optimization is becoming one of the most important techniques in engineering and industry to provide competing products in design and manufacturing. Therefore, it is a necessity to search for optimum designs with productibility. In aerospace industry reducing weight and improving reliability of the products are major concerns. As regards the gearbox is one of the most important parts in the helicopter propulsion system, these objects should be more considered. However, most of the existing designs consider only one object, hence, it is vital to implement optimization techniques to include different objectives to improve the existing designs and provide optimum products. In this paper, optimum design parameters including module and face width of gears for the main gearbox of Sikorsky ASH-3D helicopter have been determined (modified) using single and multi-objective mixed discrete- continuous optimization method to minimize weight of the gearbox, increase the safety factor and reduce the difference between safety factors of different gears. The results show that the weight of the gears can be reduced by 27.24% comparing with the existing gearbox. The results of the multiobjective optimization have also been presented as Pareto front diagram wich can be used by the manufacturers to satisfy the prefered requiments.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
170
180
http://mme.modares.ac.ir/article_11746_35bc430d569f2c339368dab18ccde803.pdf
Tool wear condition monitoring using time- frequency marginal integral of motor current signal
khalili
khalili
دانشیار هیات علمی- دانشگاه بیرجند
author
Mehdi
Danesh
دانشگاه بیرجند
author
text
article
2014
per
The condition of a cutting tool is an important factor in any metal cutting process. Several different methods have been developed to monitor the condition of tools in turning. Motor current measurement is one of the indirect tool wear monitoring methods in machining processes. The advantage of motor current measurement method over other methods for detecting malfunctions in the cutting process is that the measuring system has an acceptable cost and the measurement apparatus does not disturb the machining process. In this paper, the effect of tool wear and tool breakage on the harmonics of the AC spindle motor is investigated. Finally a method based on time-frequency marginal integral of current signal is proposed for indirect measurement of tool wear in turning. In order to validate the proposed tool monitoring system, an accelerometer was attached to the shank of the cutting tool to measure vibrations resulting from tool wear in feed direction. A vision system was also used to measure tool wear and traces tool state by observing the surface texture of the workpiece. Performance of the proposed system was validated against different experiments. The results showed improved robustness of the proposed system with high potential for practical application in detecting tool wear.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
181
189
http://mme.modares.ac.ir/article_11747_6ca9aa981fab9c835003b48fd0d5aa4e.pdf
Shape optimization of free form shells under stress constraint
Forogh
Abasi
دانشجوی کار شناسی ارشد
author
Behrooz
Hassani
Professor, Ferdowsi University of Mashhad
author
Hossein
Ghasemnejad
دانشجوی دکترای دانشگاه صنعتی شاهرود
author
text
article
2014
per
Shape optimization of free form shell structures with different objective and constraint functions including the stress constraint is the subject of this article. To construct the geometry B-Splines are employed that allow generating smooth free form geometries with a small number of parameters which are considered as the design variables of the optimization problem. For analysis, the finite element method by using the Wilson’s quad shell element is employed. For shape optimization, in each step of the optimization process the mesh generation, finite element analysis, sensitivity analysis and geometry update steps are repeated until convergence. Maximization of the stiffness of structure with volume constraint and the minimization of the weight of structure with the von Misses stress constraint are the addressed problems of this article. In both kinds of problems, the applicates of the control points are considered as the design variables of the shape optimization problem and the sequential quadratic programming (SQP) is employed to solve the optimization problem. Since in this approach, the derivatives of the objective and constraint functions are needed, the sensitivity analysis is carried out in each step by the finite difference method. The quality and smoothness of the obtained results together with the convergence graphs of the presented examples are indicative of the usefulness and efficiency of the proposed approach for shape optimization of shell structures.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
190
200
http://mme.modares.ac.ir/article_11748_234fa9f2fb9f936e921e50a171b4ffbb.pdf
Prediction of Bursting in Warm Tub Hydroforming using Modified Ductile Fracture Criteria
Seyed Jalal
Hashemi
استادیار/مؤسسه آموزش عالی کار قزوین
author
Hassan
Moslemi Naeini
استاد دانشکده مکانیک دانشگاه تربیت مدرس
author
Gholam Hossein
Liaght
استاد دانشکده مکانیک دانشگاه تربیت مدرس
author
Javad
Shahbazi
دانشجوی دکتری دانشگاه تربیت دبیر شهید رجایی
author
Amir Hossein
Roohi
دانشجوی دکتری مکانیک دانشگاه تربیت مدرس
author
text
article
2014
per
Prediction of critical process parameters which causes bursting and its location in warm tube hydroforming is a key factor in hydroforming parts design. In this paper, ductile fracture criteria have been modified so that effect of variation of temperature and strain rate on fracture is considered in forming of aluminum AA6063 tubes. Calibration of modified ductile fracture criteria has been performed using uniaxial tension tests at different temperatures and strain rates. Also, fracture strain and fracture work have been obtained as functions of Zener-Holloman parameter. Tube hydroforming process of a square part has been simulated at high temperatures in Abaqus software and loading curves with various axial feeds have been used to deform the tube. Then, the formed corner radius before bursting has been predicted using modified fracture criteria. A subroutine has been written for using modified fracture criteria. A warm tube hydroforming setup has been fabricated and prediction of modified ductile fracture criteria is compared with experimental results at various temperatures. Results show that modified criteria determine the location of bursting well. Maximum of thinning occurs in transition zone which the tube loses its contact with die cavity. Also, modified Ayada criterion, rather than other criteria, predicts corner radius with little error at high temperatures. Thus, because of its precise prediction, modified Ayada criterion can be used to predict the bursting of aluminum tubes at elevated temperatures.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
201
211
http://mme.modares.ac.ir/article_11749_60351c863002e1f37ffcb3c0089790fe.pdf
Numerical study of the effect of strain rate on damage prediction by dynamic forming limit diagram in high velocity sheet metal forming
Morteza
Saradar
دانشگاه گیلان، دانشکده فنی، گروه مهندسی مکانیک
author
Ali
Basti
Assistant Professor/ University of Guilan
author
Mohammad
Zaeimi
دانشجوی دکترا، دانشگاه سمنان
author
text
article
2014
per
In This paper dynamic forming limit diagram has been investigated as fracture criteria for St13 steel. In fact, effect of various strain rates has been studied. This fracture criterion is based on the Marciniak-Kuczynski (M-K) theory and Solutions of equations have been obtained by applying the Newton -Raphson method. After solution three forming limit diagrams has been created: independent strain rate, dependent strain rate and dynamic forming limit diagram. Dynamic damage criteria investigates forming limit diagram in every strain rate. It is observed that the forming limit is increased by increasing the strain rate, Also for considering the anisotropic and the elastic-plastic behavior of material, the Hill 1948 yield criterion and the Swift hardening rule are used respectively. Also this paper is concerned with the uniaxial tensile properties and formability of sheet metal in relation to the strain rate effects. In order to verification of the results several experiments have been done with a Drop Hammer which is a high speed impact machine. For comparison between quasi static and dynamic damage criterions, all of the stages of experiment were simulated in finite element software Abaqus and results are compared together.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
212
222
http://mme.modares.ac.ir/article_11751_e86a159d4af6c656604edf5680c247cd.pdf
A new algebraic model based on the velocity correlation tensor for DNS of turbulent drag reduction by microfiber additives
Amin
Moosaie
Department of Mechanical Engineering
Engineering Faculty
Yasouj University
author
Kourosh
Goudarzi
Faculty member
Yasouj University
author
Jalil
Abbasi
Yasouj University
author
text
article
2014
per
In this paper, a new algebraic closure model for the DNS of turbulent drag reduction in a channel flow using microfiber additives is presented. This model is an extension of an existing model and cures some the shortcomings of the old model. In the proposed model, using the velocity correlation tensor in the modeling process, more physical conditions of the flow field are taken into account. With this, some of the shortcomings of other models are cured. The proposed model is used to directly simulate turbulent drag reduction in a horizontal channel flow under the action of a constant pressure gradient. For this purpose, time-dependent, three-dimensional Navier-Stokes equations for the incompressible flow of a non-Newtonian fluid are numerically solved. Statistical quantities of obtained by the new model are compared with the results of previous simulations. The good agreement between the results demonstrates the proper accuracy of the new model. Especially, the root-mean-square of velocity fluctuations in the streamwise direction is predicted with high accuracy as compared to previous models. Other statistical quantities are also computed with appropriate accuracy. This model is capable of prediction all properties of a microfiber-induced drag-reduced flow.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
223
230
http://mme.modares.ac.ir/article_11750_b4cf82d8b0d9a6f2c1dd55eafc760490.pdf
Numerical investigation of turbulence characteristics of flow in fixed and oscillating transonic fan cascade
Saleh
Fallah
دانشگاه تربیت مدرس
author
Behzad
Ghadiri
Tarbiat Modares University
author
Ghasem
Heidarinejad
Professor/Tarbiat Modares University
author
text
article
2014
per
Investigations of the phenomena associate with the Fluid-Structure interactionin transonic turbomachines due to the presence of unstable flow behaviors have double significance. Severe restrictions of the experimental methods, has developed researchers approach in this field to Numerical methods. Nevertheless, using simple two-dimensional model to investigate the phenomenon of quality is inevitable because of high computational cost of numerical methods in aerodynamic and aeroelastic simulation of full model of turbomachines. In this paper transonic flow in fixed fan cascade and fan cascade with central blade vibration in Forced harmonic pattern is simulated and variations of turbulence characteristic patterns are studied. In order to prevent divergence of the solution and achieve more accurate results, the step by step algorithm is developed. On the other hand, spring methodology with linear torsional springs is used for movement of dynamic grid around the oscillating blade. Mesh quality is assessed by examining maximum Mach number and y+ variation. Compare the results with the available experimental data indicated a significant difference in the position of the vortices are detached and re-attached. This difference proves need to use a turbulence model is more accurate in terms of the wide separation. In this paper, effect of blade geometry, flow separation and central blade oscillation on flow pattern and turbulence characteristics of transonic flow have been investigated. Obtained results explain the effect of mentioned parameters on the turbulence kinetic energy and dissipation frequency.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
231
242
http://mme.modares.ac.ir/article_11752_f26145d56cf1fa56685b4feb312f948c.pdf
Stability Analysis for Stochastic Piecewise Affine Systems with Verification via Generalized Fokker Planck Equations
Hassan
Salarieh
استادیار/ دانشگاه شریف، دانشکده مکانیک
author
Kaveh
Merat
دانشگاه صنعتی شریف
author
Aria
Alasti
دانشگاه صنعتی شریف
author
Ali
Meghdari
دانشگاه صنعتی شریف
author
text
article
2014
per
In this article, stability analysis for Stochastic Piecewise Affine Systems which are a subclass of stochastic hybrid systems is investigated. Here, additive noise signals are considered that does not vanish at equilibrium points. These noises will prohibit the exponential stochastic stability discussed widely in literature. Also, the jumps between the subsystems in this class of stochastic hybrid systems are state-dependent which make stability analysis more complex. The presented theorem considering both additive noise and state-dependent jumps, gives upper bounds for the second stochastic moment or variance of Stochastic Piecewise Nonlinear Systems trajectories and guarantees that stable systems have a steady state probability density function. Then, linear case of such systems is studied where the stability criterion is obtained in terms of Linear Matrix Inequality (LMI) and an upper bound on state covariance is obtained for them. Next, to validate the proposed theorem, solving the Fokker Plank equations which describes the evolution of probability density function, is addressed. A solution for the problem of boundary conditions that arises from jumps in this class of systems is given and then with finite volume method the corresponding partial differential equations are solved for a case study to check the results of the presented theorem numerically.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
243
251
http://mme.modares.ac.ir/article_11753_e6506bd65774a8a024d2baa6a5dab08f.pdf
Numerical Study of the Effect of Burner Angle on Melting Rate in an Aluminum Rotary Furnace
Mojtaba
Rahimpour
دانشگاه تربیت مدرس
author
Kiumars
Mazaheri
Tarbiat Modares University
author
Seyed Hossein
Seyedein
دانشگاه علم و صنعت ایران
author
text
article
2014
per
Using CFD, the effect of burner angle on an aluminum rotary furnace performance is studied in the present study. Turbulent non-premixed combustion of natural gas and oxygen, radiation, furnace rotation, aluminum smelting and aluminum burn-off are considered in the proposed numerical model. According to the distinct phenomena occurring in an aluminum rotary furnace, the model divides the furnace into three zones: refractory lining, combustion zone and melt zone. Only heat can be transferred through interfaces of zones and mass transfer through them is not considered in such furnace modeling. Numerical simulations regarding burner angles form 0ᵒ to 15ᵒ revealed that the higher burner angles enhance the fuel and oxygen mixing and increases the resident time of combustion gases in the furnace atmosphere, which consequently improve the furnace performance and lower the aluminum melting rate. However, the simulation results also showed that burner angles more than 10ᵒ are not applicable due to refractory lining overheat. It was showed eventually that changing burner angle from 0ᵒ to 10ᵒ decreases furnace operation time by 35 minutes and increases furnace thermal efficiency from 65% to 74.7%.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
252
260
http://mme.modares.ac.ir/article_11754_6304dd7936fdb575040bafd08fad0ec6.pdf
Analytical and numerical study of energy absorption of graded honeycomb structure under in-plane impact
Mehran
Kadkhodayan
استاد/ دانشگاه فردوسی مشهد
author
Ali
Galehdari
دانشگاه فردوسی مشهد
author
Saied
Hadidi Moud
دانشگاه فردوسی مشهد
author
text
article
2014
per
Given the significance of energy absorption in various industries, light shock absorbers such as honeycomb structure under in-plane and out of plane loads are in the core of attention. In this research an analytical equation for plateau stress is represented, taking power hardening model into consideration. The equation of specific absorbed of graded honeycomb structure with the locking strain and strain energy equation is represented. The structure made from five aluminum grades is simulated in ABAQUS/CAE for elastic-perfectly plastic and power hardening model, according to the results; numerical value of absorbed energy is compared to that of analytical method. A drop weight test on a graded honeycomb structure was performed. Based on the numerical simulation results, the experimental and numerical results showed good agreement. Based on the conducted comparisons, the numerical and analytical results are more congruent for power hardening model rather than elastic-perfectly plastic one. In the first step of optimization, by applying SQP method and genetic algorithm, the ratio of structure mass to the absorbed energy is minimized. In the second step, regarding the optimum value of parameters obtained in the first step, the material property of each row is changed. According to the optimization results, while keeping the mass of structure as constant, the structure capacity of absorbing energy is increased by 18% in the first step and 264% in the second model, compared to the primary model.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
261
271
http://mme.modares.ac.ir/article_11755_fe848508cc21ff0dbdffa8426facd741.pdf
Optimal layout design for a space control system modules using a gradient- based method
Maziar
Shafaee
University of Tehran
author
Parviz
Mohammadzadeh
استادیار دانشگاه تهران
author
abbas
Elkaie Behjatie
دانشجوی کارشناسی ارشد دانشگاه تهران
author
Saied
Abbasi
دانشجوی کارشناسی ارشد دانشگاه تهران
author
text
article
2014
per
Abstract This paper focuses on layout modeling and optimization for a space control system. Majority of recent research works consider design components as constant elements over time. A new approach based on variable mass components is proposed in this paper for which the objective function is to minimize mass center variation (MCV) range over time. The proposed approach consists of Human-computer interaction (HCI) and Optimization methods to perform the layout. In the modeling phase, using defined inputs, all system components are determined. In the next step, mathematical model of achieved layout is defined. Mathematical model includes objective function, constraints, variables and parameters, play an important role in choosing appropriate optimization method. Based on mathematical model and design space, a gradient optimization method is selected. By applying this algorithm, optimum layout is proposed. Results of optimization and HCI design are compared. Comparison of the results shows that the optimization technique can significantly improve the results of the layout problem. At last, the results have analyzed and validated with similar research works. The results comparison show more efficiency and accuracy for the proposed method.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
272
282
http://mme.modares.ac.ir/article_11756_3cbf076b72796182161cc34d338ec7f1.pdf
Comparison of Aeroelastic performance base and optimized blades of
Horizontal Axis Wind Turbine
Mohammad Hassan
Javareshkian
دانشیار دانشگاه فردوسی
author
Mohammad Reza
Saber
دانشگاه فردوسی مشهد
author
text
article
2014
per
In this study, the results of two optimized and base blades of a horizontal axis wind turbine with aeroelastic point of view are compared . In order to optimization, the chord length and the twist angle of the blade at various radiuses have been calculated by BEM. The Results which are obtained from 2D Computational Fluid Dynamics (CFD) have been utilized to train a Neural Network (NN). In the process of airfoil optimization, Genetic Algorithm (GA) is coupled with trained NN to attain the best airfoil shape at each angle of the attack. Finally, the optimized blade is derived. In order to simulate the flow on two blades and obtain the aerodynamic forces, the blades and their surrounding regions are organized by unstructured grid. The SIMPLE algorithm and second order upwind scheme are used in numerical fluid flow simulation. The aerodynamic forces on the blades have been used for stress and strain analysis. At this point, in addition to the aerodynamic forces, inertia forces resulting from the rotation of the wind turbine blade is also considered. The aerodynamic results show that optimized blade has high efficiency. The results of the analysis of the stress - strain showed that maximum stress on optimized blade is less than base blade and optimized blade design is also more reliable than the blade base.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
283
290
http://mme.modares.ac.ir/article_11784_aec39a8b0b698d85b413cd23ef4c500c.pdf
Study the Effects of Oscillation Frequency and Amplitude on Flow Around a Flapping Airfoil via an Improved Immersed Boundary Method
Ali
Ashrafizadeh
استادیار دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Ali Akbar
Hosseinjani
دانشجو
author
text
article
2014
per
In this paper an improved immersed boundary method is used for simulating sinusoidal pitching oscillations of a symmetric airfoil. Immersed boundary methods because of using a fixed Cartsian grid are well suited for such moving boundary problems. Two test cases are used to validate the proposed method and the effects of oscillation frequency and amplitude on the flow field are investigated. Flow field vorticity and kinetic energy contours are reported in this paper. It is found that the deflected wake start to be appeared for Strouhal number more than 0.4 at a fixed pitching amplitude 0.71. A chaotic flow can be observed at oscillation amplitude 2.80, for a fixed Strouhal number, 0.22. Kintic energy contour shows that for Strouhal number 0.1, the airfoil performs work and transfers momentum to flow but the fluid energy loss due to the enlargement of flow separation zone decreases the momentum and kinetic energy behind the airfoil. Deficit momentum and kinetic energy behind the airfoil results in drag force increasing. By increasing the oscillation frequency and amplitude more momentum transfers to flow filed behind the airfoil which results in drag force decreasing.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
291
301
http://mme.modares.ac.ir/article_11794_c31ade2946b9fc0ea84b8831bd39f8aa.pdf
Modeling of sliding friction with superimposed ultrasonic oscillation
Mahmoud
Salimi
استاد دانشگاه
author
davoud
shahgholian
دانشجو
author
text
article
2014
per
When two bodies slide on each other the asperities are engaged and deformed which causes the dynamic friction. By superposing ultrasonic oscillation to one of the bodies, the friction force is reduced . The experiments show that the friction force may be reduced by about 60 percent depending on material properties and the kinetics of the two bodies. This phenomenon is widely used in metal forming and metal cutting. This phenomenon may be used as a replacement of lubricants in such processes due to its higher efficiency and less pollution effects . In this research an elastic-plastic model for the surface contact is given which is capable of predicting the friction force when ultrasonic vibrations are superimposed to macroscopic motion . The result of this model is compared with that of the experimental values. The differences between these values are shown to be less than 10 percent . The result of the model is also compared with that of the Dong model. The comparison show that the present model has better accuracy of the Dong model .
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
302
310
http://mme.modares.ac.ir/article_11795_933bcce7e20524fe7c053711e865da65.pdf
Experimental Investigation of the Buzz Cycle in a Supersonic Axisymmetric Intake
Mohammad Reza
Soltani
عضو هیئت علمی / دانشکده مهندسی هوافضا دانشگاه صنعتی شریف
author
Mahdi
Abedi
فارغ التحصیل کارشناسی ارشد / دانشکده هوافضا دانشگاه صنعتی شریف
author
Javad
Sepahi Younsi
دانشجوی دکترای تخصصی / دانشکده هوافضا دانشگاه صنعتی شریف
author
text
article
2014
per
An extensive experimental study has been conducted to investigate the performance and stability of a supersonic axisymmetric mixed compression air intake designed for a free stream Mach number of 2.0. Unstable flow conditions, where the self-sustained oscillations of the shocks waves occur, have been studied in this investigation. Aside from the buzz triggering mechanism, the paper describes the flow phenomenon sequences during the buzz cycle by means of the shadowgraph pictures and via high frequency pressure transducers. Results showed that the pressure inside the intake decreases and increases sequently during the buzz cycle. The intake becomes almost empty (its mass flow rate decreases) as the shock wave moves upstream toward the intake tip. When the shock waves stand at its most upstream location, the pressure inside the intake reaches its minimum value. This low pressure condition causes the shock wave to move toward the intake and consequently the intake pressure increases again. As the pressure inside the intake increases, the shock wave moves upstream. The intake pressure reaches its maximum value when the shock wave stands at the intake entrance and the buzz cycle is then completed.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
311
320
http://mme.modares.ac.ir/article_11796_a8d9a6c3aa5a9c91829acc209190458b.pdf
Static Balancing of Parallel Planar 3-DOF Mechanisms, 3-RRR, 3-PRR, 3-RPR and static balancing of variable weights
Mehdi
Tale Masouleh
استادیار مهندسی مکانیک دانشکده علوم و فنون نوین دانشگاه تهران
author
Mohammad
Homayounpour
Student/ University of Tehran
author
text
article
2014
per
Static balancing is one of the most valuable strategies in manufacturing and industrial designing. This paper deals with the static balancing of parallel mechanisms. Using counter-weights and springs, and their combination, are the most popular methods in this procedure. In this article, theories and formulas of static balancing, by considering the end-effector with constant-weight, using counter-weights and springs are addressed. As case studies, three 3-DOF planar parallel mechanisms, namely, 3-RRR, 3-PRR and 3-RPR with constant-weight are investigated. A static balanced 3-RRR is modeled and validated in Adams software and fabricated using a combination of spring and counter-weight. This mechanism is manufactured in Human and Robot Interaction laboratory (TaarLab). Moreover, a cable parallel 3-DOF mechanism using static balancing concept is designed for which variable weight is considered at the end-effector. The crane benefits from static balancing of variable weight that causes the power actuators just use in relocation the counter-weight in XY plane that is obviously less than the power needed to relocate the main load across the gravity direction. The advantages of these kinds of mechanisms consist in reducing manufacturing and operation price, increasing the safety and using less power in actuators.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
321
331
http://mme.modares.ac.ir/article_11797_0e2a3f05749b1e1d01c6f624bbcb917d.pdf
Compare and study of hole quality characteristics in helical milling and drilling
mohamad hosein
saadatbakhsh
MSc. student of Mechanical Engineering, Tarbiat Modares University
author
amir
rasti
PhD. student of Mechanical Engineering, Tarbiat Modares University
author
Mohammad Hossein
Sadeghi
استاد دانشگاه تربیت مدرس
author
hamed
hassanpour
PhD. student of Mechanical Engineering, Tarbiat Modares University
author
ahmadreza
omiddoodman
MSc. student of Mechanical Engineering, Tarbiat Modares University
author
text
article
2014
per
Helical milling has been known as an innovative method for making high quality holes. In this method, milling tool generates efficiently a high quality hole by moving along a helical path. The hole diameter can be adjusted through the diameter of this helical path. Regarding accuracy of hole in industrial parts, it is necessary to compare this method with conventional hole drilling. Therefore, in this study helical milling and conventional drilling, have been compared with each other. Eight experiments were conducted considering two levels of cutting speed and feed rate on the samples made of AISI 4340 steel at 45 HRC. Minimum quantity lubricant system with two nozzles was used. 100 ml/h of Behran-11 mineral oil at air pressure of 4 bar was employed in this system. Machining forces, surface roughness, nominal diameter, roundness, and cylindricity were output parameters. According to the obtained results, cutting speed was the only one with positive effect on all qualitative parameters of the machined holes. On the other hand, independency of cutting parameters, helical milling lessened machining forces, surface roughness, and geometrical tolerances in compare with conventional drilling.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
332
338
http://mme.modares.ac.ir/article_11802_1d676065983bfba9953048e4bd99838d.pdf
Identification of broken needle in single jersey circular knitting machine using neural network on yarn fluctuations signals
Majid
Moavenian
Academic member of Ferdowsi University of Mashhad Mech Eng. FDI
author
Mohsen
Pazhoohiyani
Msc Student, Mech. Eng., Ferdowsi University Of Mashhad, Mashhad, Iran.
author
Mohammad Ehsan
Momeni Heravi
Academic member of Islamic Azad University, Mashhad Branch.
author
text
article
2014
per
The quality of knitted fabric in circular knitting machines is highly sensitive to any undesired changes in the mechanism and components involved. For instance, a broken needle causes defects on the surface of knitted fabric. Consequently in order to increase the quality and reduce production cost, rapid detection and diagnosis of defected needles on industrial circular weft knitting machines is a crucial need. In these machines when the yarn is pulled down by the needles to knit a loop the created yarn tension, causes fluctuations in the feeding yarn flow. The aim of present research is to identify broken needle defects and their numbers, during yarn feeding in a circular knitting machine, employing neural network analysis on yarn fluctuation signals. The experiments procedures were designed so that three needle defected conditions were implemented on an industrial circular knitting machine. The yarn fluctuation signals were captured and saved, then using wavelet the contaminated signal noise was removed. Statistical and wavelet analysis are implemented to produce the required features. Finally the capability of neuro network for classification of four groups of data including healthy, one, two and four broken needles were examined. The results show that 99.43 % accurate distinction of broken needles is achieved in 50 iterations.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
339
348
http://mme.modares.ac.ir/article_11799_7be15e8d3da22300589be46a5309fe23.pdf
Modelling and empirical investigation of micro-electro-mechanical piezo-resisitive pressure sensor based on the requirements of petrochemical industry
Navid
SeyedKazem Viliani
عضو هیات علمی دانشگاه آزاد اسلامی
author
Mehdi
Hashemi
دانشگاه صنعتی شریف
author
Hadi
Vadizadeh
انجمن پژوهشگران جوان دانشگاه ازاد تهران جنوب
author
Hassan
Pourrostami
عضو هیات علمی دانشگاه ازاد اسلامی
author
Seyed Mohsen
Mostafavi
پژوهش و فناوری شرکت پتروشیمی فن آوران
author
Faramand
Hashemizadeh
پژوهش و فناوری شرکت پتروشیمی فن آوران
author
text
article
2014
per
This article presents analytical and empirical studies of a micro-electromechanical package. This micro-electro-mechanical (MEMS) pressure sensor package contains of a printed circuit board (PCB), the capacitance LCD. First of all, mathematical modeling and computer simulation using software COMSOL software which is based on finite element method are presented to compute the sensitivity of the MEMS pressure sensor and output voltage output. It is worth noting that an Xducer resistor type is adopted to measure the diaphragm deflection. In addition to static and modal analyses of the sensor, the effects of geometric parameters on the voltage has also been studied. Simulation results show that by changing the size and position of the resistor and also the size and thickness of the diaphragm, sensor sensitivity can be changed. Then, with the construction and placement of components on printed circuit boards, the package has been prepared and tested in a laboratory. The experimental results of the package show that the error of the devised system in measuring the pressure is less than 0.5 percent. This pressure sensor package is capable of accurately measuring the pressure up to 6 bar in which all the empirical results are presented at the end of the study. The package can be designed according to the requirements of the petrochemical industry in measuring gas pressure of storage tanks and drums in FANAVARN petrochemical company.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
349
357
http://mme.modares.ac.ir/article_11798_e41d2dcc0b9ee82143812ae1403d2661.pdf
A Numerical and Experimental Investigation of Effect of Control Surface Angle on an Autonomous Underwater Vehicle Drag
ehsan
javanmard
پژوهشکده زیردریا دانشگاه صنعتی اصفهان
author
Shahriar
Mansoorzadeh
هیئت علمی پژوهشکده زیردریا دانشگاه صنعتی اصفهان
author
Ahmad Reza
Pishevar
ریاست دانشکده مهندسی مکانیک دانشگاه صنعتی اصفهان
author
text
article
2014
per
In this paper the effect of horizontal control surfaces (stern fins) angle on the drag force of the Subsea R&D Autonomous Underwater Vehicle (AUV) is investigated using both experimental fluids dynamic and numerical fluids dynamic methods. The experiments were conducted in the Subsea R&D towing tank using a 1:1 scale model of the AUV, at various stern angles and in a speed range of 1 to 3 m/s. A pair of Naca shaped struts was used to connect the AUV to the carriage dynamometer. The stern drag force was experimentally calculated at various stern angles and towing speeds. The results obtained by experimental method compared with those obtained numerically by commercial computational fluid dynamics CFX code. Both experimental and numerical results showed that as the stern angle increases, the total AUV drag force increases, and the drag force coefficient can be estimated by a second order polynomial. The results showed that, at a speed of 1.5m/s, as the stern angle increases to 45 degree, the drag coefficient increases up to 174 percent It was also observed that at a specific stern angle, the drag force due to stern fin increases with the AUV speed. Variation of axial force as a function of stern angle was determined by using both experimental and numerical methods. The results obtained by both methods showed that the expensive experiments conducted in towing tanks can be replaced by numerical simulations.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
358
366
http://mme.modares.ac.ir/article_11800_ca9d35cc2c740f5e91e6121661264d9b.pdf
Static analysis of composite box beams by dimensional reduction method
Esmaeel
Ghafari
دانشجو
author
Jalil
Rezaeepazhand
عضوهیات علمی گروه مهندسی مکانیک دانشکده مهندسی دانشگاه فردوسی مشهد
author
text
article
2014
per
This paper presents prediction of static behavior of composite beams with arbitrary anisotropic materials. The procedure is based on decomposing a 3-D nonlinear elasticity problem into a 2-D analysis of cross section and a 1-D analysis across the beam length. This is accomplished by assuming that magnitude of strain is small compared to unity and cross section size is small relative to wave length of deformation, inherent to beam-like structures. In 2-D cross sectional analysis warping functions are calculated in terms of 1-D strain parameters and finally, fully coupled classical stiffness constants are derived which include extension, torsion and bending in two directions. 1-D analysis is modeled by Finite Element Method through calculating beam strain energy. In this article warpings are derived using Rayleigh-Ritz method. The great advantage of using Rayleigh-Ritz is simplifying cross sectional analysis in contrast with the mesh generation in FEM of similar procedures. Different cross section stiffnesses are investigated for ply orientation angle. Calculated results for symmetric and anti-symmetric composite box beams correlate well with 3-D FEM using Abaqus software as well as experimental results. The present solution has more accurate results for anti-symmetric composite box beam. According to costly use of 3-D FEM analysis, the present procedure with high speed and acceptable accuracy, is truly sufficient for preliminary and optimization problems.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
14
v.
شماره 16- فوق العاده
no.
2014
367
374
http://mme.modares.ac.ir/article_11801_29ee34ef063403f55c14654b9e83d35b.pdf