2011
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Frequency Analysis of a Cable with Variable Tension and Variable Rotational Speed
2
2
In this paper coupled nonlinear equations of motion of a suspended cable with time dependent tension and velocity are derived by using Hamilton’s principal. A modal analysis for a stationary sagged cable is initially carried out in order to identify the dynamic system. The natural solution is directed to compute the natural frequencies and mode shapes of the free vibration of a suspended cable. Natural frequencies and mode shapes are plotted versus a dimensionless parameter l, known as static sag character. In case of moving cable, the tension force and the rotary speed of the pullies are assumed to be sinusoidal functions. Galerkin mode summation approach is utilized to discretize the nonlinear equations of motions. Numerical simulations are carried out in the time domain. A frequency analysis is then carried out and effects of the frequency of tension force and rotary speed on the belt dynamic responses are studied.
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0
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Moharam
Habibnejad
Department of Mechanical Engineering,
Irann University of Science and Technology
Department of Mechanical Engineering,
Irann
Iran
hkorayem@iust.ac.ir


AliAkbar
Alipour
Iran
alipour233@yahoo.com
Investigating the Effect of Different Boundary Conditions on the Identification of a Cavity Inside Solid Bodies
2
2
The effect of boundary conditions on the solution of the inverse problem of identifying the geometry and location of a cavity inside an elastic solid body using displacement measurements obtained from a tension test is investigated. The boundary elements method (BEM) coupled with the genetic algorithm (GA) and the conjugate gradient method (CGM) are implemented in this identification problem. A fitness function which is defined as the squared differences between the computed and measured displacements is minimized. The best initial guess of the unknown shape and location of the cavity is found by the GA, then this initial guess is used by the CGM to achieve convergence. The imposed boundary conditions, i.e. geometrical constrain and specified tractions are kept constant during all iterations. Certainly changes in the boundary conditions can be effective in the correct identification of the shape and location of the cavity. In this study the effect of different boundary conditions on the convergence is investigated and the best and the most suitable boundary conditions which results in the faster and more accurate convergence are found.
1

0
0


Mahmud
Khodadad
Iran
khodadad@yazduni.ac.ir


Mohsen
DashtiArdakani
Iran
mohsen_dashtiardakani@yahoo.com
THE ENERGY AND EXERGY ANALYSIS OF SINGLE EFFECT ABSORPTION CHILLER
2
2
The first and second laws of thermodynamics have been employed to evaluate energy and exergetic efficiency of the single effect absorption chiller which is used for air conditioning purpose. The performance analysis has been carried out by developing a computer program in EES and modeling the chiller and its components. To evaluate entropy of the water/lithium bromide solution at any point, an empirical correlation has been utilized. Exergy destruction and thermodynamic properties at any point in the cycle are evaluated by using related equations or build in property data. The results showed that maximum exergy destruction was occurred in the generator and the absorber at various operating conditions and these components had greater effect on the energy and exergetic efficiency rather than condenser and evaporator. Thus, it can be clearly stated that the generator and absorber are the most important components of the absorption chiller. The results also showed the exergetic efficiency was less than the energy efficiency due to exergy destruction taking place within the absorption chiller. Therefore, it can be concluded that the exergy analysis has been proven to be a more powerful tool in pinpointing real losses and can be used as an effective tool in designing an absorption chiller and obtaining optimum operating conditions.
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0
0


Farshad
PanahiZadeh
Iran
f_panahizadeh@yahoo.com


Navid
Bozorgan
Iran
n.bozorgan@gmail.com
Investigation of Process Parameters on Hot Ring Rolling by Coupled ThermoMechanical 3DFEA
2
2
Hot rolling of a large ring of titanium alloy (LRT) is a highly nonlinear incremental forming process with coupled mechanical and thermal behaviors (MTBs) which significantly affect microstructure and properties of the ring. The feed rate of idle roll and the rotational speed of driver roll have major effects on ovality of the ring. In this paper, the effects of these parameters on the ovality of the ring have been investigated by a coupled thermomechanical 3DFEA. The results show that the ovality of ring blank decreases with the increase of the rotational speed of driver roll or the decrease of the feed rate of idle roll. The results obtained can provide a guide for forming parameters optimization.
1

0
0


AmirHossein
Gheisari
Iran
a.gheisari@me.iut.ac.ir


MohammadReza
Forouzan
Iran
forouzan@cc.iut.ac.ir


AbdolAli
Maracy
Iran
a_maracy@mutes.ac.ir
Comparative Investigation in a Turbine Blade Passage Flows with Several Different Turbulence Models
2
2
In the present work a two dimensional numerical investigation of steam flows in a turbine blade passage is performed. A finite volume approach has been used and the pressure–velocity coupling is resolved using the SIMPLE algorithm. The purpose of this paper is to find that one of the used turbulent models is better for this kind of studies. A structured mesh arrangement with boundary layer mesh was adopted to map the flow domain in the blade passage. Pressure profiles around the blades for all models results are compared with the experimental data and good agreement is observed. The three models results of k–ε turbulence models (standard, Realizable and RNG) have compared with SpalartAllmaras and kω SST models. Based on the results obtained, that all of these models can simulate the flow with reasonable result but the SpalartAllmaras model and REALIZABLE kε model is better than other models with significant in shock capturing. Based on result, SpalartAllmaras and kω SST models showed a larger boundary layer on suction trailing edge than k ε models family. Although using REALIZABLE kε model leading to savings in computational cost and time.
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0
0


Mahmoud
Ebrahimi
Iran
ebrahimi@iust.ac.ir


MohammadHosein
Rouzbahani
Iran
rozbahani@mecheng.iust.ac.ir
Analysis of Two Dimensional SteadyState Heat Conduction Problems by MLPG Method
2
2
Numerical solutions obtained by the Meshless local Petrov–Galerkin (MLPG) method are presented for twodimensional steadystate heat conduction problems. The MLPG method is a truly meshless approach, and neither the nodal connectivity nor the background mesh is required for solving the initialboundaryvalue problem. The penalty method is adopted to efficiently enforce the essential boundary conditions, the moving least squares approximation is used for interpolation schemes and the Heaviside step function is chosen for test function. The results show that the present method is very promising in solving engineering twodimensional steadystate heat conduction problems.
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0
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GholamHosein
Baradaran
Iran
bara02002@yahoo.com


MohammadJavad
Mahmoodabadi
Iran
mahmood_1985_mj@yahoo.com