Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
-
0
0
FA
-
-,-
http://mme.modares.ac.ir/article-15-9399-en.html
http://mme.modares.ac.ir/article-15-9399-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Natural Convection in Semi-Ellipse Cavities with Variable Aspect Ratios using Lattice Boltzmann Method
1
13
FA
Mohsen
Nazari
Assistant Prof. of Mechanical Eng.
Shahrood Univ. of Technology
Y
N
Abstract- In this paper, two-dimensional 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 semi-ellipse cavity using second order boundary condition on curved surfaces is among the novelties of the present work.
Natural Convection,Semi ellipse cavity,Lattice Boltzmann Method
http://mme.modares.ac.ir/article-15-1351-en.html
http://mme.modares.ac.ir/article-15-1351-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Experimental studies of training stress effect on NiTi SMA performance in higher and lower stress than training stress
14
24
FA
Mehdi
Ansari
N
Mohammad
Golzar
Y
Amir Hosein
Behravesh
N
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 0-250 MPa.It was found that SMA wires that trained in 30, 150 and 200 MPa showedtow-way 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.
Shape memory alloy,Tow-Way Shape Memory Effect,Training,Unstable Behavior
http://mme.modares.ac.ir/article-15-11939-en.html
http://mme.modares.ac.ir/article-15-11939-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Stability measure for a parallel cable driven robot
25
34
FA
Mahdi
Bamdad
Y
N
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 (Force-Moment) 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, Gibbs-Appell equations and acceleration energy are used. Robot kinematic and dynamic modeling based on Newton-Euler’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.
Parallel Robot,Cable- Driven,stability,Measure
http://mme.modares.ac.ir/article-15-10080-en.html
http://mme.modares.ac.ir/article-15-10080-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Forward Kinematic Investigation of Three 4-DOF Parallel Robots with Prismatic Actuators Performing 3T1R Motion Pattern in Seven-dimensional Kinematic Space
35
50
FA
Y
Mehdi
Tale Masouleh
N
Payam
Varshovi Jaghargh
N
This paper involves the investigation of the forward kinematic problem of three 4-DOF parallel robots, named as 4-PRUR1, 4-PRUR2, 4-PUU, performing 3 translations and one rotation, namely Schönflies motion. The foregoing parallel robots are special cases of 3 parallel robots, named as 4-PR′R′R″R″, 4-PR″R″R′R′ and 4-PR″R′R′R″, respectively, arisen from the type synthesis performed for 4-DOF 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 seven-dimensional kinematic space using the so-called 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.
4-DOF parallel robot,3T1R motion pattern,forward kinematic problem,seven-dimensional kinematic space,Study's parameters
http://mme.modares.ac.ir/article-15-9251-en.html
http://mme.modares.ac.ir/article-15-9251-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Analysis of effective parameters on the buckling of grid stiffened composite shells based on first order shear deformation theory
51
61
FA
N
Mojtaba
Yazdani
Assistant Professor of Applied Mechanics (Solid)
Y
N
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. First-order 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.
Grid stiffened composite shells,Smeared method,Equivalent stiffness,Ritz method
http://mme.modares.ac.ir/article-15-5674-en.html
http://mme.modares.ac.ir/article-15-5674-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Numerical study of natural convection in a square enclosure with a central heat source filled with nanofluid and presenting correlations for Nusselt number
62
74
FA
Y
Hamidreza
Ehteram
University of Kashan
N
Alireza
Aghaei
University of Kashan
N
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 0-0.05. 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 Rayleigh-Benard, 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.
numerical study,nanofluid,Natural Convection,Enclosure,Average Nusselt number
http://mme.modares.ac.ir/article-15-5233-en.html
http://mme.modares.ac.ir/article-15-5233-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Experimental study of ratcheting influence on fatigue life of Ck45 in uniaxial cyclic loading
75
83
FA
Y
Hamed
Mehrabi
N
In this paper, experimental analysis of ratchetting-fatigue interaction and ratcheting behavior of Ck45 steel were investigated by uniaxial cyclic loading under stress-controled tests. Stress-controled tests performed in two steps in order to evaluate ratchetting strain influence on fatigue life of specimens. First, pre-ratchetting 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 stress-control condition, fatigue life of specimens depends greatly on pre-ratchetting stress amplitude and influence of mean stress on fatigue life is limited to a specific mean stress.
Ratchetting,Fatigue,Uniaxial Cyclic Loading,Ck45 steel
http://mme.modares.ac.ir/article-15-5903-en.html
http://mme.modares.ac.ir/article-15-5903-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Generating initial conditions for the simulation of polymer suspensions using the equilibrium PDF
84
93
FA
Amin
Moosaie
Department of Mechanical Engineering
Engineering Faculty
Yasouj University
Y
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.
Brownian dynamics simulation,dilute polymer suspension,initial conditions,equilibrium probability distribution function
http://mme.modares.ac.ir/article-15-41-en.html
http://mme.modares.ac.ir/article-15-41-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Chatter detection in turning process using machine vision
94
104
FA
N
Y
Chatter or self-excited 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 in-process 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.
Chatter vibration,Turning,Image processing,Surface Texture
http://mme.modares.ac.ir/article-15-1416-en.html
http://mme.modares.ac.ir/article-15-1416-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Experimental Investigation of Thermal Necrosis in Conventional and High Speed Drilling of Bone
105
117
FA
Ehsan
Shakouri
Islamic Azad Universiy-tnb/TMU
N
MohammadHosseyn
Sadeghi
TMU
Y
Mehdi
Maerefat
TMU
N
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.
Bone,thermal necrosis,Conventional Drilling,High Speed Drilling,Thrust Force
http://mme.modares.ac.ir/article-15-807-en.html
http://mme.modares.ac.ir/article-15-807-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
The influence of local polyethylene pipe in a steel pipeline system on water hammer phenomenon
118
126
FA
N
Y
N
This note presents a theoretical analysis and numerical simulation of hydraulic transients in pressurized pipeline system made of a local polyethylene pipe-wall 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 pipe-wall 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.
Transient Flow,polyethylene pipe,pressure wave,Viscoelasticity,wave interaction
http://mme.modares.ac.ir/article-15-5136-en.html
http://mme.modares.ac.ir/article-15-5136-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Investigation of the accuracy of SSI-COV method in estimation of Modal Parameters: numerical and experimental case studies
127
139
FA
N
Mohammad Reza
Ashory
Semnan University
Y
N
N
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 (SSI-COV) 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 SSI-COV method. The results show the applicability of SSI-COV method in practical cases.
Operational modal analysis,Natural frequency,Mode Shape
http://mme.modares.ac.ir/article-15-5550-en.html
http://mme.modares.ac.ir/article-15-5550-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Pore scale study on the reacting flow in porous media including flow turbulence
140
151
FA
Y
N
N
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.
Numerical simulation,Porous Burner,Pore scale,turbulence
http://mme.modares.ac.ir/article-15-12006-en.html
http://mme.modares.ac.ir/article-15-12006-en.pdf
Tarbiat Modares University
Modares Mechanical Engineering
1027-5940
2476-6909
13
10
2014
1
1
Effect of moisture content of building materials on thermal performance of exterior building walls
152
156
FA
Amir
Omidvar
Y
N
http://mme.modares.ac.ir/article-15-10058-en.html
http://mme.modares.ac.ir/article-15-10058-en.pdf