
text
article
2013
per

Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
0
0
http://mme.modares.ac.ir/article_10162_b152e0fb086391957f61ab144db4c7c4.pdf
Natural Convection in SemiEllipse Cavities with Variable Aspect Ratios using Lattice Boltzmann Method
Mohsen
Nazari
Assistant Prof. of Mechanical Eng.
Shahrood Univ. of Technology
author
حسنی
شکری
دانشگاه شاهرود
author
text
article
2013
per
Abstract In this paper, twodimensional natural convection heat transfer in semi ellipse cavities is investigated using lattice Boltzmann method. The Prandtl number is taken as 0.71 that corresponds to that of air. Heat transfer and flow pattern are predicted at various Rayleigh numbers ranging from 104 to 106 for different aspect ratios. By increasing of the aspect ratio, the heat transfer rate in the cavity is increased for low Rayleigh numbers, but it is decreased for high Rayleigh numbers. The obtained results of the lattice Boltzmann method are validated with those presented in the literature and show that the lattice Boltzmann method can simulate heat transfer and flow pattern in complex cavities. Analysis of heat transfer in a semiellipse cavity using second order boundary condition on curved surfaces is among the novelties of the present work.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
1
13
http://mme.modares.ac.ir/article_10163_feeec7f0ce48ab76ec199311c86a5162.pdf
Experimental studies of training stress effect on NiTi SMA performance in higher and lower stress than training stress
Mehdi
Ansari
دانشجو
author
Mohammad
Golzar
هئیت علمی دانشگاه تربیت مدرس
author
Amir Hosein
Behravesh
هئیت علمی دانشگاه تربیت مدرس تهران
author
text
article
2013
per
SMA training in constant stress causes stabilized response. Since in engineering applications alloy stress isvariant,the aim of this study is to investigate SMAs response in some range of stresses.In this study, six SMA wires were trained in 30, 50, 100, 150, 200 and 250 MPa. At the next step, their recoverable strains were evaluated in 0250 MPa.It was found that SMA wires that trained in 30, 150 and 200 MPa showedtowway shape memory effect (TWSME). Also recoverable strains in stresses higher than 100 MPa are independent of training and in order to have better performance, stresses higher than 100 MPa are required. SMA wires trained in 180 and 200 MPa resulted in unstable behavior.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
14
24
http://mme.modares.ac.ir/article_10164_74084d2c6f1bfc7cbb19300c7122fba4.pdf
Stability measure for a parallel cable driven robot
Mahdi
Bamdad
استادیار دانشگاه صنعتی شاهرود دانشکده مکانیک سرپرست دانشکده مکاترونیک
author
شیرکو
فاروقی
استادیار، مهندسی مکانیک، دانشگاه صنعتی ارومیه، ارومیه
author
text
article
2013
per
A modified measure for the parallel cable driven robots is presented in this paper. These robots have additional advantages compared to other robots and even the parallel structures, but they are readily exposed to disturbances. The presence of external wrench (ForceMoment) may be the cause of violation against the motion constraint. The stability measure proposes a number between zero and one that could be the criterion for the evaluation of the robot's ability while returning to its original equilibrium which was influenced by external disturbances. To offer a stability measure, GibbsAppell equations and acceleration energy are used. Robot kinematic and dynamic modeling based on NewtonEuler’s method calculates the measure. To illustrate the capabilities of the proposed measure, a 6 DOF cable robot with six cables is simulated. The results of the two simulations are presented and analyzed. The stability measure is depended to kinematic parameters and also to kinetics parameters as cables tension at the beginning of motion. Therefore using the proposed measure one can better evaluate the stability within the wider range of parallel cable robots.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
25
34
http://mme.modares.ac.ir/article_10165_2a22e0903342c881488eb169324c47c4.pdf
Forward Kinematic Investigation of Three 4DOF Parallel Robots with Prismatic Actuators Performing 3T1R Motion Pattern in Sevendimensional Kinematic Space
داود
نادری
دانشیار دانشکده مهندسی دانشگاه بو علی سینا همدان
author
Mehdi
Tale Masouleh
استادیار مهندسی مکانیک دانشکده علوم و فنون نوین دانشگاه تهران
author
Payam
Varshovi Jaghargh
دانشجوی دکتری مهندسی مکانیک، دانشگاه بوعلیسینا، همدان
author
text
article
2013
per
This paper involves the investigation of the forward kinematic problem of three 4DOF parallel robots, named as 4PRUR1, 4PRUR2, 4PUU, performing 3 translations and one rotation, namely Schönflies motion. The foregoing parallel robots are special cases of 3 parallel robots, named as 4PR′R′R″R″, 4PR″R″R′R′ and 4PR″R′R′R″, respectively, arisen from the type synthesis performed for 4DOF parallel mechanisms with identical kinematic limb structures. Each robot has 4 identical kinematic chains and each chain consists of one prismatic active joint and 4 revolute passive joints. Due to different direction of revolute joints in each limb, 3 different architectures are considered in this paper. The forward kinematic problem is explored in sevendimensional kinematic space using the socalled Study's parameters and LIA algorithm and eventually, it has been shown that an algebraic expression of degree 4 indicates the forward kinematic of each kinematic chains of parallel robots under study in this paper. Moreover, using homotopy continuation and comparison with resultant method, it reveals that the forward kinematic problem of this robots have up to 236,236 and 2 real solutions, respectively.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
35
50
http://mme.modares.ac.ir/article_10166_9415354a45f28967a76a616ee3023099.pdf
Analysis of effective parameters on the buckling of grid stiffened composite shells based on first order shear deformation theory
محمد امین
قاسمی
دانشگاه صنعتی سهند
author
Mojtaba
Yazdani
Assistant Professor of Applied Mechanics (Solid)
author
سید محمد
حسینی
دانشگاه صنعتی سهند
author
text
article
2013
per
Grid stiffened composite shells are one of the most important structures in aerospace industries. In this study critical buckling load of these structures with diamond shape stiffeners under axial loading based on smeared method is presented. The effect of shell thickness, angle of fibers in shell and the direction of stiffeners into the buckling load is determined. Firstorder shear deformation theory based upon the Ritz method is used to calculation of critical buckling load of these structures. In the use of FSDT theory, transverse shear forces in stiffeners have been considered. The results are compared with FEM solution with clamped boundary condition.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
51
61
http://mme.modares.ac.ir/article_10167_20df6be996c3c8751afa55837d944b79.pdf
Numerical study of natural convection in a square enclosure with a central heat source filled with nanofluid and presenting correlations for Nusselt number
قنبرعلی
شیخ زاده
معاون آموزشی و تحصیلات تکمیلی/دانشکده مهندسی مکانیک دانشگاه کاشان
author
Hamidreza
Ehteram
University of Kashan
author
Alireza
Aghaei
University of Kashan
author
text
article
2013
per
Abstract The present study aims to investigate numerically the natural convection of various nanofluids inside a square enclosure with a central heat source at different aspect ratio. Also, some correlations are presented in order to calculate the Nusselt number in terms of Rayleigh number and volume fraction of nanoparticles. The heat source and cavity walls are kept at constant temperatures of Th and Tc, respectively. The nanofluids are considered to be water as the base fluid and different nanoparticles such as Cu, CuO, Ag, Al2O3, or Tio2. To discretize the governing equations, the control volume method and SIMPELER algorithm have been employed. The study has been carried out for aspect ratios from 0.2 to 0.8, Rayleigh numbers from 1e3 to 1e6 and the volume fractions of nanoparticles ranging in 00.05. The results indicated that the Nusselt number increases with increasing the volume fraction of nanoparticles as well as the aspect ratio. Furthermore, by increasing the Rayleigh number, some eddies, of kind of RayleighBenard, are developed in the space between the heat source and the upper wall of the enclosure. Based on the obtained results, several correlations with high accuracy have been present in order to evaluate the Nusselt number.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
62
74
http://mme.modares.ac.ir/article_10168_34e4b8ebf41308979b835c65f48ee766.pdf
Experimental study of ratcheting influence on fatigue life of Ck45 in uniaxial cyclic loading
محمود
شریعتی
دانشگاه شاهرود
author
Hamed
Mehrabi
کارشناس ارشد دانشگاه صنعتی شاهرود، دانشکده مکانیک
author
text
article
2013
per
In this paper, experimental analysis of ratchettingfatigue interaction and ratcheting behavior of Ck45 steel were investigated by uniaxial cyclic loading under stresscontroled tests. Stresscontroled tests performed in two steps in order to evaluate ratchetting strain influence on fatigue life of specimens. First, preratchetting tests were performed with various loading setups and then, their fatigue life were measured in fatigue test with a constant load for all specimens. In uniaxial cyclic loading for stresscontrol condition, fatigue life of specimens depends greatly on preratchetting stress amplitude and influence of mean stress on fatigue life is limited to a specific mean stress.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
75
83
http://mme.modares.ac.ir/article_10169_dc5c45e24c3be18e783f5ce457ede6e6.pdf
Generating initial conditions for the simulation of polymer suspensions using the equilibrium PDF
Amin
Moosaie
Department of Mechanical Engineering
Engineering Faculty
Yasouj University
author
text
article
2013
per
In this study, a new method for producing initial conditions that are required for the Brownian dynamics simulation of dilute polymer suspension flows is proposed. For this purpose, the equilibrium probability distribution function is employed to generate an equilibrium ensemble of polymers. This approach is programmed and by using it, a polymer suspension in the inception of a simple shear flow is simulated. Also, the results of simulations in a similar flow configuration based on the conventional approach of generating initial conditions are presented. The excellent agreement between the results demonstrates the high accuracy of the proposed method for generating initial conditions. The main advantage of the proposed method is its low computational cost.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
84
93
http://mme.modares.ac.ir/article_10170_436c6df9841cefcc12d2876275f03fcc.pdf
Chatter detection in turning process using machine vision
مهدی
دانش
دانشگاه بیرجند
author
خلیلی
خلیلی
دانشگاه بیرجند
author
text
article
2013
per
Chatter or selfexcited violent relative dynamic motion between the cutting tool and the workpiece is an undesirable phenomenon in machining due to its destructive effects on the product surface quality, machining accuracy, cutting tool life and machine tool life. Because of these reason, there is a need for inprocess detection methods to predict and avoid chatter vibration during machining processes. In this work, Chatter detection in turning process is performed based on analysis of feed marks in surface texture of work piece using image processing techniques. In order to validate the proposed vision based method an accelerometer was attached to the shank of cutting tool for measuring vibrations.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
94
104
http://mme.modares.ac.ir/article_10171_ac9a02f276b4469b4dce0660fd0382be.pdf
Experimental Investigation of Thermal Necrosis in Conventional and High Speed Drilling of Bone
Ehsan
Shakouri
Islamic Azad Universiytnb/TMU
author
MohammadHosseyn
Sadeghi
TMU
author
Mehdi
Maerefat
TMU
author
text
article
2013
per
Internal immobilization of fractured parts of bone depends on the drilling of fracture site and screw fixation of implanted devices to the bone. During drilling, the temperature may rise allowable temperature of 47°C and causes irreversible thermal necrosis. This study is concerned with methods of drilling to determine the best processing condition to minimize the osteonecrosis. Drilling tests were performed with two drilling techniques: conventional, and high speed drilling on the bovine femur and increase of temperature in drilling site, duration of temperature raise and thrust force were measured. The result for conventional drilling shows that in all processing conditions, the generated heat is over the allowable limit, which makes thermal necrosis inevitable. On other hand, it was found that increase of cutting speed of drill bit to 7000 rpm, leads to considerable decrease of thrust force and increase of heat dissipation with chips, simultaneously and leads to decrease of local temperature raise in drilling site. But with more increase of rotational speed of drill bit, because of not sensible change in drilling force and considerable increase of friction between chips, drill bit body and drilled hole, amount of temperature elevation is increased.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
105
117
http://mme.modares.ac.ir/article_10172_f2b156f80032a04bae591f8a695a5562.pdf
The influence of local polyethylene pipe in a steel pipeline system on water hammer phenomenon
محمد
درویش دماوندی
دانشجو
author
حسن
رحیم زاده
استاد تمام دانشکده مکانیک دانشگاه صنعتی امیرکبیر
author
علیرضا
ریاسی
استادیار دانشکده فنی دانشگاه تهران
author
text
article
2013
per
This note presents a theoretical analysis and numerical simulation of hydraulic transients in pressurized pipeline system made of a local polyethylene pipewall located at a steel pipeline system. The continuity and momentum equations are solved by the method of characteristic (MOC) taking into account the viscoelastic effect of the pipewall for polyethylene pipe. The polyethylene pipe length and location at the pipeline and the discharge flow rate are changed and their influence on transient flow is investigated. By comparing this pipeline system with one that is made of polyethylene pipe totally, the possibility of using local polyethylene pipe due to its effect on the pressure wave is investigated.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
118
126
http://mme.modares.ac.ir/article_10173_8b89dfa5885b58cad2d1c5d13dca7847.pdf
Investigation of the accuracy of SSICOV method in estimation of Modal Parameters: numerical and experimental case studies
هدی
سرپرست
دانشگاه سمنان
author
Mohammad Reza
Ashory
Semnan University
author
محمد مهدی
خطیبی
دانشگاه سمنان
author
علی
عسگری طبری
دانشگاه سمنان
author
text
article
2013
per
Conventional modal testing is a powerful tool for dynamic analysis of structures. One of the drawbacks of this technique is the problem of excitation of large structures such as: bridges, towers or trains. However, these structures are excited by ambient forces, such as wind, walking of people or passing the cars on bridges. Operational Modal Analysis (OMA) is the practical tool to overcome this problem. In OMA the structure is excited by ambient forces and only the responses are taken into account. In this article, the accuracy of one of OMA methods is investigated. The modal parameters of a cantilever beam are estimated both from Stochastic Subspace Identification–Covariance Driven (SSICOV) method and Finite element method. The effect of noise and damping on the accuracy of modal parameters is investigated. Also, a crankshaft is considered for experimental investigation of the accuracy of SSICOV method. The results show the applicability of SSICOV method in practical cases.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
127
139
http://mme.modares.ac.ir/article_10174_704c9f9366b5feb2fc144d32fb46dc45.pdf
Pore scale study on the reacting flow in porous media including flow turbulence
نیما
فلاح
دانشگاه تربیت مدرس
author
مهدی
معرفت
دانشگاه تربیت مدرس
author
مجید
اسحق نیموری
دانشگاه تربیت مدرس
author
text
article
2013
per
This paper presents pore scale simulation of turbulent combustion of air/methane mixture in porous media to investigate the effects of multidimensionality and turbulence on the flame within pore scale. A porous medium consisting of a staggered arrangement of square cylinders considered here. Results of turbulent kinetic energy, temperature, flame thickness, flame structure and flame speed are presented and compared at different equivalence ratios. The turbulent kinetic energy increases along the burner because of turbulence created by the solid matrix with a sudden jump at the flame front due to increase of the velocity as a result of thermal expansion. Also, it is shown that at higher equivalence ratios, the effect of turbulence within porous burner is highly significant phenomenon. Due to higher turbulence effects in higher equivalence ratios, the flame thickness increases by increasing the equivalence ratio which is in opposite of the trend observed in laminar flow simulation. Also, it is shown that the dimensionless flame speed and excess temperature is higher at lower equivalence ratios due to lower heat loss to the cold upstream environment of burner. Two dimensional structure of flame in the pores of porous medium is shown in the present study via isotherm lines.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
140
151
http://mme.modares.ac.ir/article_10176_4fb5cf5419efad8d5114dd5666c04808.pdf
Effect of moisture content of building materials on thermal performance of exterior building walls
Amir
Omidvar
استادیار دانشگاه صنعتی شیراز
author
بهنام
رستی
دانشگاه صنعتی شیراز
author
text
article
2013
per
Modares Mechanical Engineering
Tarbiat Modares University
10275940
13
v.
10
no.
2013
152
156
http://mme.modares.ac.ir/article_10175_9b4a104edf46f17617e9c801fdfdf9d6.pdf