Experimental Investigation of the Pulse and Plasma Flushing Efficiency in Electrical Discharge Machining
H
Eivazi-Bagheri
Young Researchers Club, Tabriz Branch, Islamic Azad University
author
M.R
Shabgard
Department of Mechanical Engineering, University of Tabriz
author
text
article
2011
eng
This paper presents a study of the relationship between Electrical Discharge Machining (EDM) parameters on the EDM efficiency factors using a full factorial design, based on pulse on-time, duty cycle and tool polarity parameters in EDM machining of AISI H13 tool steel. The results show that, in positive polarity, the plasma flushing efficiency and pulse efficiency increase according to the pulse-on time, but plasma flushing efficiency decreases over 15(μs) pulse duration only under negative polarity of electrode. Based on the experimental results, the plasma flushing efficiency and pulse efficiency increases when the duty cycle increases in positive tool polarity.
Journal of Solid Mechanics
Islamic Azad University Arak Branch
2008-3505
3
v.
4
no.
2011
315
322
http://jsm.iau-arak.ac.ir/article_514441_d2735e6f44ff5ad16fe90f0fd263f04b.pdf
Optimal Nonlinear Energy Sinks in Vibration Mitigation of the Beams Traversed by Successive Moving Loads
D
Younesian
Center of Excellence in Railway Transportation, School of Railway Engineering, Iran University of Science and Technology
author
A
Nankali
Center of Excellence in Railway Transportation, School of Railway Engineering, Iran University of Science and Technology----
Department of Mechanical and Aerospace Engineering, New-Mexico State University, Las Cruces, USA
author
E
Motieyan
Center of Excellence in Railway Transportation, School of Railway Engineering, Iran University of Science and Technology
author
text
article
2011
eng
Optimal Nonlinear Energy Sink (NES) is employed in vibration suppression of the beams subjected to successive moving loads in this paper. As a real application, a typical railway bridge is dynamically modeled by a single-span beam and a traveling high-speed train is simulated by a series of successive moving loads. Genetic algorithm is employed as the optimization technique and optimal parameters of the NES system are accordingly obtained. It is found that the NES can remarkably suppress the vibration level particularly in vicinity of the critical speeds. A sensitivity analysis is then carried out and robustness of the optimal NES is investigated. A parametric study is performed and performance of the optimal NES is evaluated for different values of the load speeds, load magnitudes, load intervals and mass ratios.
Journal of Solid Mechanics
Islamic Azad University Arak Branch
2008-3505
3
v.
4
no.
2011
323
331
http://jsm.iau-arak.ac.ir/article_514442_54218f21e633f28a4543f2467626b60e.pdf
Theoretical Formulations for Finite Element Models of Functionally Graded Beams with Piezoelectric Layers
J.N
Reddy
Department of Mechanical Engineering, Texas A&M University, College Station
author
S
Doshi
Department of Civil Engineering, Texas A&M University, College Station
author
A
Muliana
Department of Mechanical Engineering, Texas A&M University, College Station
author
text
article
2011
eng
In this paper an overview of functionally graded materials and constitutive relations of electro elasticity for three-dimensional deformable solids is presented, and governing equations of the Bernoulli–Euler and Timoshenko beam theories which account for through-thickness power-law variation of a two-constituent material and piezoelectric layers are developed using the principle of virtual displacements. The formulation is based on a power-law variation of the material in the core with piezoelectric layers at the top and bottom. Virtual work statements of the two theories are also developed and their finite element models are presented. The theoretical formulations and finite element models presented herein can be used in the analysis of piezolaminated and adaptive structures such as beams and plates.
Journal of Solid Mechanics
Islamic Azad University Arak Branch
2008-3505
3
v.
4
no.
2011
332
345
http://jsm.iau-arak.ac.ir/article_514443_503e59620489a8388656e8ead9d633dd.pdf
Third Order Formulation for Vibrating Non-Homogeneous Cylindrical Shells in Elastic Medium
M
Gheisari
Faculty of Engineering, Khomein Branch, Islamic Azad University
author
H
Molatefi
Railway Engineering School, Iran University of Science and Technology, Narmak
author
S.S
Ahmadi
Department of Mechanical Engineering, Iran University of Science and Technology, Arak Branch
author
text
article
2011
eng
Third order shear deformation theory of cylindrical shells is employed to investigate the vibration characteristics of non-homogeneous cylindrical shells surrounded by an elastic medium. The kinematic relations are obtained using the strain-displacement relations of Donnell shell theory. The shell properties are considered to be dependent on both position and thermal environment. A suitable function through the thickness direction is assumed for the non-homogeneity property. The Winkler-Pasternak elastic foundation is used to model the elastic medium. Analytical solutions are presented for cylindrical shells with simply supported boundary conditions. From the numerical studies, it is revealed that, the natural frequencies are affected significantly by the elastic foundation coefficients and environmental temperature conditions.
Journal of Solid Mechanics
Islamic Azad University Arak Branch
2008-3505
3
v.
4
no.
2011
346
352
http://jsm.iau-arak.ac.ir/article_514444_80a6852e62a1c3d008778cb4c21e704e.pdf
Constrained Multi-Objective Optimization Problems in Mechanical Engineering Design Using Bees Algorithm
A
Mirzakhani Nafchi
Department of Mechanical Engineering, Payame Noor University
author
A
Moradi
Department of Mechanical Engineering, Chamran University
author
text
article
2011
eng
Many real-world search and optimization problems involve inequality and/or equality constraints and are thus posed as constrained optimization problems. In trying to solve constrained optimization problems using classical optimization methods, this paper presents a Multi-Objective Bees Algorithm (MOBA) for solving the multi-objective optimal of mechanical engineering problems design. In the present study, a satellite heat pipe design, a space truss design and pressure vessel problems are considered. Multi-objective optimization using the bees algorithm which is a new multi-object obtain a set of geometric design parameters, leads to optimum solve. This method is developed in order to obtain a set of geometric design parameters leading to minimum heat pipe mass and the maximum thermal conductance. Hence, a set of geometric design parameters, lead to minimum pressure total cost and maximum pressure vessel volume. Numerical results reveal that the proposed algorithm can find better solutions when compared to other heuristic or deterministic methods and is a powerful search algorithm for various engineering optimization problems.
Journal of Solid Mechanics
Islamic Azad University Arak Branch
2008-3505
3
v.
4
no.
2011
353
364
http://jsm.iau-arak.ac.ir/article_514445_a0e98fe9fd300e291a0844f2f099032e.pdf
Optimization of Functionally Graded Beams Resting on Elastic Foundations
M.H
Yas
Department of Mechanical Engineering, Razi University, Kermanshah
author
S
Kamarian
Department of Mechanical Engineering, Razi University, Kermanshah
author
J.E
Jam
Center for Composite Materials & Structures, MUT, Tehran
author
A
Pourasghar
Department of Mechanical Engineering, Razi University, Kermanshah
author
text
article
2011
eng
In this study, two goals are followed. First, by means of the Generalized Differential Quadrature (GDQ) method, parametric analysis on the vibration characteristics of three-parameter Functionally Graded (FG) beams on variable elastic foundations is studied. These parameters include (a) three parameters of power-law distribution, (b) variable Winkler foundation modulus, (c) two-parameter elastic foundation modulus. Then, volume fraction optimization of FG beam with respect to the fundamental frequency is studied. Since the optimization process is so complicated and time consuming, Genetic Algorithm (GA), a computational algorithm based on Darwinian theories that allow to solve optimization problems without using gradient-based information on the objective functions and the constraints, is performed to obtain the best material profile through the thickness to maximize the first natural frequency. A proper Artificial Neural Network (ANN) is trained by training data sets obtained from GDQ method and then is applied as the objective function in genetic algorithm by reproducing the fundamental frequency for improving the speed of the optimization process. Finally, the optimized material profile for the maximum natural frequency of a FG beam resting on elastic foundations is presented.
Journal of Solid Mechanics
Islamic Azad University Arak Branch
2008-3505
3
v.
4
no.
2011
365
378
http://jsm.iau-arak.ac.ir/article_514446_3e7767fa8826b9ce56b2c9d2327f77ca.pdf
Electro-Mechanical Buckling of a Piezoelectric Annular Plate Reinforced with BNNTs Under Thermal Environment
A
Ghorbanpour Arani
Faculty of Mechanical Engineering, University of Kashan---
Institute of Nanoscience & Nanotechnology, University of Kashan
author
E
Haghparast
Faculty of Mechanical Engineering, University of Kashan
author
text
article
2011
eng
In this article, axisymmetric buckling behavior of piezoelectric fiber reinforced polymeric composite (PFRPC) annular plate subjected to electro-thermo-mechanical field is presented utilizing principle of minimum potential energy. Boron-nitride nanotubes (BNNTs) are used as fibers. Full coupling between electrical, mechanical and thermal fields are considered according to a representative volume element (RVE)-based XY piezoelectric fiber reinforce composite (PEFRC) model. Assuming PFRPC material and its composite constituents to be linear, homogenous, orthotropic, and perfectly bonded with uniform applied field, the basic relation for the axisymmetric buckling of a circular plate subjected to radial compression, radial electrical field, and uniform temperature change are derived. The presented results show that BNNTs can be used as an effective supplement to improve mechanical behavior of polyvinylidene fluoride (PVDF). Also, at normal working conditions, the influence of thermal and mechanical fields is much higher than the electric one on the critical load; hence, this smart structure is best suited for applications as sensors than actuators.
Journal of Solid Mechanics
Islamic Azad University Arak Branch
2008-3505
3
v.
4
no.
2011
379
391
http://jsm.iau-arak.ac.ir/article_514447_470bfc884503a1ab5d1e872bd5d1cb7b.pdf
Magneto-Thermo-Elastic Stresses and Perturbation of Magnetic Field Vector in a Thin Functionally Graded Rotating Disk
A
Ghorbanpour Arani
Faculty of Mechanical Engineering, University of Kashan---
Institute of Nanoscience & Nanotechnology, University of Kashan
author
S
Amir
Faculty of Mechanical Engineering, University of Kashan
author
text
article
2011
eng
In this paper, a semi-analytical solution for magneto-thermo-elastic problem in an axisymmetric functionally graded (FG) hollow rotating disk with constant thickness placed in uniform magnetic and thermal fields with heat convection from disk’s surfaces is presented. Solution for stresses and perturbation of magnetic field vector in a thin FG rotating disk is determined using infinitesimal theory of magneto-thermo-elasticity under plane stress conditions. The material properties except Poisson’s ratio are modeled as power-law distribution of volume fraction. The non-dimensional distribution of temperature, displacement, stresses and perturbation of magnetic field vector throughout radius are determined. The effects of the material grading index and the magnetic field on the stress and displacement fields are investigated. The results of stresses and radial displacements for two different boundary conditions are compared with the case of a thin FG rotating disk with the same loading and boundary conditions but in the absence of magnetic field. It has been found that imposing a magnetic field significantly decreases tensile circumferential stresses. Therefore, the fatigue life of the disk will be significantly improved by applying the magnetic field. The results of this investigation can be used for optimum design of rotating disks.
Journal of Solid Mechanics
Islamic Azad University Arak Branch
2008-3505
3
v.
4
no.
2011
392
407
http://jsm.iau-arak.ac.ir/article_514448_5e4a45850252ceb5d66d934b657766a2.pdf