Frequency Analysis of a Cable with Variable Tension and Variable Rotational Speed
Moharam
Habibnejad
Department of Mechanical Engineering,
Irann University of Science and Technology
author
AliAkbar
Alipour
author
text
article
2011
eng
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.
ADMT Journal
Islamic Azad University Majlesi Branch
2252-0406
4
v.
4
no.
2011
http://admt.iaumajlesi.ac.ir/article_534762_0d607fd81ef7d4e6ced3d31938ad8aa8.pdf
Investigating the Effect of Different Boundary Conditions on the Identification of a Cavity Inside Solid Bodies
Mahmud
Khodadad
author
Mohsen
DashtiArdakani
author
text
article
2011
eng
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.
ADMT Journal
Islamic Azad University Majlesi Branch
2252-0406
4
v.
4
no.
2011
http://admt.iaumajlesi.ac.ir/article_534763_eefd8abaca702666d5caf94750c5fe48.pdf
THE ENERGY AND EXERGY ANALYSIS OF SINGLE EFFECT ABSORPTION CHILLER
Farshad
PanahiZadeh
author
Navid
Bozorgan
author
text
article
2011
eng
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.
ADMT Journal
Islamic Azad University Majlesi Branch
2252-0406
4
v.
4
no.
2011
http://admt.iaumajlesi.ac.ir/article_534764_abee9b067bed87e2141719fe4b1b81fb.pdf
Investigation of Process Parameters on Hot Ring Rolling by Coupled Thermo-Mechanical 3D-FEA
AmirHossein
Gheisari
author
MohammadReza
Forouzan
author
AbdolAli
Maracy
author
text
article
2011
eng
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 thermo-mechanical 3D-FEA. 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.
ADMT Journal
Islamic Azad University Majlesi Branch
2252-0406
4
v.
4
no.
2011
http://admt.iaumajlesi.ac.ir/article_534765_d5bb973d560a42e1d093e745055ef825.pdf
Comparative Investigation in a Turbine Blade Passage Flows with Several Different Turbulence Models
Mahmoud
Ebrahimi
author
MohammadHosein
Rouzbahani
author
text
article
2011
eng
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 Spalart-Allmaras and k-ω SST models. Based on the results obtained, that all of these models can simulate the flow with reasonable result but the Spalart-Allmaras model and REALIZABLE k-ε model is better than other models with significant in shock capturing. Based on result, Spalart-Allmaras and k-ω SST models showed a larger boundary layer on suction trailing edge than k- ε models family. Although using REALIZABLE k-ε model leading to savings in computational cost and time.
ADMT Journal
Islamic Azad University Majlesi Branch
2252-0406
4
v.
4
no.
2011
http://admt.iaumajlesi.ac.ir/article_534766_672c2b397830dcfe03f1fdcec8c9714b.pdf
Analysis of Two Dimensional Steady-State Heat Conduction Problems by MLPG Method
GholamHosein
Baradaran
author
MohammadJavad
Mahmoodabadi
author
text
article
2011
eng
Numerical solutions obtained by the Meshless local Petrov–Galerkin (MLPG) method are presented for two-dimensional steady-state 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 initial-boundary-value 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 two-dimensional steady-state heat conduction problems.
ADMT Journal
Islamic Azad University Majlesi Branch
2252-0406
4
v.
4
no.
2011
http://admt.iaumajlesi.ac.ir/article_534767_ce13921167cb42c980bc8e03ae3fcf22.pdf