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Investigation of Dynamic Behavior of Beams with Different Supports under Moving Vehicles
, M.Sc. Thesis Sharif University of Technology ; Vafai, Abolhassan (Supervisor) ; Esmaeil Pourestekanchi, Homayun (Co-Advisor)
Abstract
With the transportation progress and appearance of transit industry, necessity of modern vehicles redounded to appearance of heavier trucks with higher speeds, moving on the roads. In addition, with the progress in mechanical engineering and automobile industry, appearance of such trucks is growing increasingly. So, bridges as one of the structures that civil engineers design and construct, nowadays are subjected to higher moving dynamic loads in comparison with the past. As a result, lots of investigation and researches in the universities and institutions all over the world are being conducting on the effects of the vehicle speeds on the dynamic stresses of the bridges. Bridge codes...
Nonlinear Vibrations of a Circular Plate Using Perturbation and Experimental Methods
, M.Sc. Thesis Sharif University of Technology ; Navazi, Hossein Mohammad (Supervisor)
Abstract
In this thesis, the nonlinear vibrations of the circular plate is examined using multiple scale methods and experimental tests. At first step, the nonlinear equations governing the problem are written using von Karman's assumption. In the next step, to solve nonlinear equations and calculate natural frequency, the problem is solved using multiple scale method and frequency charts are extracted as a function of the amplitude of vibration. . The design of the setup has been done in such a way that it is possible to simulate the boundary conditions. In the first phase, experimental tests was performed on a 0.3 mm thick aluminum sheet, which did not produce the desired results due to the...
Nonlinear vibration of beams under nonideal boundary conditions
, Article Acta Mechanica ; Volume 218, Issue 3-4 , 2011 , Pages 259-267 ; 00015970 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
Abstract
In this paper, we investigate the influence of nonideal boundary conditions on the nonlinear vibration of damped Euler-Bernoulli beams subjected to harmonic loads. These nonidealities allow for small deflections and/or moments at the supports of the beam. Using the iteration perturbation method, analytical expressions for the case of simply supported beams with immovable end conditions are provided. The results reveal that the first order of approximation obtained by the proposed method is more accurate than the perturbation solutions. Moreover, compared with the previous studies, some interesting phenomenon is predicted. We have shown that in some special combinations of the nonidealities...
Application of the homotopy method for the analytic approach of the nonlinear free vibration analysis of the simple end beams using four engineering theories
, Article Acta Mechanica ; Volume 212, Issue 3-4 , 2010 , Pages 199-213 ; 00015970 (ISSN) ; Jafari Talookolaei, R. A ; Sharif University of Technology
2010
Abstract
In this paper, nonlinear vibration analyses of Euler-Bernoulli, Rayleigh, Shear and Timoshenko beams with simple end conditions are presented using homotopy analysis method (HAM). Closed form solutions for natural frequencies, beam deflection, post-buckling load-deflection relation, and critical buckling load are presented. The calculated natural frequencies for all four cases were verified against some available results in the literature and very good agreement observed. Furthermore, obtained results for deflection, buckling, and post-buckling of each beam are presented and the effects of some parameters, such as slenderness ratio, the rotary inertia, and the shear deformation are examined
Free-edge stress analysis of general composite laminates under extension, torsion and bending
, Article Applied Mathematical Modelling ; Volume 36, Issue 4 , 2012 , Pages 1570-1588 ; 0307904X (ISSN) ; Sarvestani, M. Y ; Sharif University of Technology
2012
Abstract
In this study, based on the reduced form of elasticity displacement field for a long laminate, an analytical method is established to exactly obtain the interlaminar stresses near the free edges of generally laminated composite plates subjects to extension, torsion, and bending. The constant parameters being in the displacement field, which describe the global deformation of a laminate, are appropriately calculated by using the improved first-order shear deformation theory. Reddy's layerwise theory is subsequently employed for analytical and numerical examinations of the boundary layer stresses within arbitrary laminated composite plates. Various numerical results are developed for the...
Interlaminar stress analysis of general composite laminates
, Article International Journal of Mechanical Sciences ; Volume 53, Issue 11 , 2011 , Pages 958-967 ; 00207403 (ISSN) ; Yazdani Sarvestani, M ; Sharif University of Technology
Abstract
In this study, based on the reduced from of elasticity displacement field for a long laminate, an analytical method is established to exactly obtain the interlaminar stresses near the free edges of generally laminated composite plates under the extension and bending. The constant parameters, which describe the global deformation of a laminate, are properly computed by means of the improved first-order shear deformation theory. Reddys layerwise theory is subsequently utilized for analytical and numerical examinations of the boundary layer stresses within arbitrary laminated composite plates. A variety of numerical results are obtained for the interlaminar normal and shear stresses along the...
An analytical framework for the solution of autofrettaged tubes under constant axial strain condition
, Article ASME 2008 Pressure Vessels and Piping Conference, PVP2008, Chicago, IL, 27 July 2008 through 31 July 2008 ; Volume 5 , July , 2008 , Pages 71-80 ; 0277027X (ISSN); 9780791848289 (ISBN) ; Farrahi, G. H ; Movahhedy, M. R ; Pressure Vessels and Piping ; Sharif University of Technology
2008
Abstract
Autofrettage is a technique for introducing beneficial residual stresses into cylinders. Both analytical and numerical methods are used for analysis of the autofrettage process. Analytical methods have been presented only for special cases of autofrettage. In this work, an analytical framework for the solution of autofrettaged tubes with constant axial strain conditions is developed. Material behavior is assumed to be incompressible and two different quadratic polynomials are used for strain hardening in loading and unloading. Clearly, elastic-perfectly plastic and linear hardening materials are special cases of this general model. This material model is convenient for description of the...
An analytical framework for the solution of autofrettaged tubes under constant axial strain condition
, Article Journal of Pressure Vessel Technology, Transactions of the ASME ; Volume 131, Issue 6 , 2009 ; 00949930 (ISSN) ; Farrahi, G. H ; Movahhedy, M. R ; Sharif University of Technology
Abstract
Autofrettage is a technique for introducing beneficial residual stresses into cylinders. Both analytical and numerical methods are used for the analysis of the autofrettage process. Analytical methods have been presented only for special cases of autofrettage. In this work, an analytical framework for the solution of autofrettaged tubes with constant axial strain conditions is developed. Material behavior is assumed to be incompressible, and two different quadratic polynomials are used for strain hardening in loading and unloading. Clearly, elastic perfectly plastic and linear hardening materials are the special cases of this general model. This quadratic material model is convenient for the...