Search for: vibration
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    Forced vibration analysis of laminated rectangular plates using super elements

    , Article Scientia Iranica ; Volume 10, Issue 2 , 2003 , Pages 260-265 ; 10263098 (ISSN) Ahmadian, M. T ; Zangeneh, M. S ; Sharif University of Technology
    Sharif University of Technology  2003
    The implementation of new techniques and design of new elements have been an important issues among finite element researchers. In this regard, a designed super element has been applied to analyze a series of dynamic problems. Findings indicate that in large structure analysis the same results as the conventional method can be obtained when applying a few super elements. The time required for dynamic analysis using a super element is significantly smaller than the regular finite element. In this paper, the forced vibration of laminated composite rectangular plates is analyzed. The dynamic response of the plate, using a four-super element, is obtained. In-plane deformation, as well as bending... 

    Vibration analysis of orthotropic rectangular plates using superelements

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 191, Issue 19-20 , 2002 , Pages 2097-2103 ; 00457825 (ISSN) Ahmadian, M. T ; Sherafati Zangeneh, M ; Sharif University of Technology
    Elsevier  2002
    In recent years, development of the superelements has significantly influenced the analysis of structural dynamics. One of the common implementation of this element has been in the analysis of plates and shells. In this paper, application of superelements in the vibration analysis of orthotropic rectangular plates with different boundary conditions is considered, in which bending and in-plane displacements are also included. Results of this study indicate that there is a good agreement between single superelement and 625 elements using conventional methods © 2002 Published by Elsevier Science B.V  

    Discussion: “Optimum design of vibration absorbers for structurally damped timoshenko beams“ (Esmailzadeh, E., and Jalili, N., 1998, ASME J. Vib. Acoust., 120, no. 4, pp. 833-841)

    , Article Journal of Vibration and Acoustics, Transactions of the ASME ; Volume 123, Issue 4 , 2001 , Pages 548-549 ; 10489002 (ISSN) Rastegar, M. R ; Ghorashil, M ; Sharif University of Technology

    Analytical solution for the free vibration analysis of delaminated timoshenko beams

    , Article The Scientific World Journal ; Volume 2014 , 2014 ; ISSN: 1537744X Jafari Talookolaei, R. A ; Abedi, M ; Sharif University of Technology
    This work presents a method to find the exact solutions for the free vibration analysis of a delaminated beam based on the Timoshenko type with different boundary conditions. The solutions are obtained by the method of Lagrange multipliers in which the free vibration problem is posed as a constrained variational problem. The Legendre orthogonal polynomials are used as the beam eigenfunctions. Natural frequencies and mode shapes of various Timoshenko beams are presented to demonstrate the efficiency of the methodology  

    Free vibration analysis of joined conical shells: Analytical and experimental study

    , Article Thin-Walled Structures ; Vol. 85, issue , December , 2014 , p. 350-358 Shakouri, M ; Kouchakzadeh, M. A ; Sharif University of Technology
    Natural frequencies and mode shapes of two joined isotropic conical shells are presented in this study. The joined conical shells can be considered as the general case for joined cylindrical-conical shells, joined cylinder-plates or cone-plates, conical and cylindrical shells with stepped thicknesses and also annular plates. Governing equations are obtained using thin-walled shallow shell theory of Donnell and Hamilton's principle. The continuity conditions at the joining section of the cones are appropriate expressions among stress resultants and deformations. The equations are solved assuming trigonometric response in circumferential and series solution in meridional directions and all... 

    Crack detection in underground pipelines using piezoelectric sensors

    , Article Advanced Science Letters ; Volume 19, Issue 3 , 2013 , Pages 770-774 ; 19366612 (ISSN) Nozarian, M. M ; Adeldost, H ; Zabihollah, A ; Sharif University of Technology
    Regarding the structural health monitoring of pipelines, early detection of cracks may be one of the possible ways to prevent future failures. Among the detection methods which have been known, one is to measure the vibration signals generated due to the hydraulics of pipe. This article discusses application of thin film piezo sensors mounted directly on the pipe. The vibration induced strain is transuded into electric voltage by the piezoelectric sensor. The recorded signals are used for PSD analysis which indicates that this method can be used as an accurate and cost effective detection. Moreover the promising results from the respective experiments on pipes indicated that second natural... 

    The vibration-rotation kinetic energy operator for sequentially bonded tetra-atomic molecules in internal coordinates

    , Article Molecular Physics ; Volume 105, Issue 17-18 , 2007 , Pages 2269-2278 ; 00268976 (ISSN) Ebrahimi, H ; Tafazzoli, M ; Sharif University of Technology
    An exact vibration-rotation kinetic energy operator for polyatomic molecules has been obtained. Using this Hamiltonian for sequentially bonded tetra-atomic molecules, all rovibrational terms have been derived with internal coordinates as the vibrational variables. The present approach is greatly simplified with less algebra compared with conventional methods. Also, simple and explicit expressions for the vibration-rotation coupling terms in internal coordinates are presented  

    Vibration transfer path analysis and path ranking for NVH optimization of a vehicle interior

    , Article Shock and Vibration ; Vol. 2014, issue , 2014 ; ISSN: 10709622 Sakhaei, B ; Durali, M ; Sharif University of Technology
    By new advancements in vehicle manufacturing, evaluation of vehicle quality assurance has got a more critical issue. Today noise and vibration generated inside and outside the vehicles are more important factors for customers than before. So far several researchers have focused on interior noise transfer path analysis and the results have been published in related papers but each method has its own limitations. In present work, the vibration transfer path analysis and vibration path ranking of a car interior have been performed. As interior vibration is a source of structural borne noise problem, thus, the results of this research can be used to present the structural borne noise state in a... 

    Using a combination of vibration absorber and a classical active controller to suppress the chatter vibration and increase the stability in turning process

    , Article 10th International Conference on Modern Circuits and Systems Technologies, MOCAST 2021, 5 July 2021 through 7 July 2021 ; 2021 ; 9781665418478 (ISBN) Ebadi, Y ; Moradi, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Free, forced, and self-excited vibrations are the three main types of machine tool vibrations. Self-excited vibration is the most important type of destructive vibration in machining. The most important factor in increasing the chipping rate, stability, and tool life is decreasing this type of destructive vibration. In this paper, we aim to introduce a method to control the self-excited vibrations by the means of the combining a vibration absorber as a passive controlling method and a classical active controller such as PID or compensator or the other classical methods. Utilizing the SIMULINK toolbox of MATLAB software, first, we designed and added the vibration absorber to the model... 

    Coupled bending torsional vibrations of viscoelastic rotors with fractional damper

    , Article JVC/Journal of Vibration and Control ; 2022 ; 10775463 (ISSN) Bayat, Z ; Haddadpour, H ; Zamani, Z ; Sharif University of Technology
    SAGE Publications Inc  2022
    The behavior of a Jeffcott rotor with lateral-torsional coupling is investigated in the presence of internal and external damping and eccentricity. The governing equations are derived based on the Lagrange method. Also, the Laplace method and linearization is used to solve the governing equations for free vibrations analysis. For a rotor with unbalance, the instability occurs when the real part of eigenvalues has positive values, and at the same time, it is the intersection point between the lines of natural frequencies. The instability speed increases with increasing the external damping, yet dependent on the internal damping and unbalance. Also, it is demonstrated that the rotor critical... 

    Stream-wise and cross-flow vortex induced vibrations of single tapered circular cylinders: An experimental study

    , Article Applied Ocean Research ; Volume 42 , 2013 , Pages 124-135 ; 01411187 (ISSN) Zeinoddini, M ; Tamimi, V ; Saeed Seif, M ; Sharif University of Technology
    Tapered circular cylinders are employed in a variety of ocean engineering applications. While being geometrically simple, this configuration creates a complex flow pattern in the near wake of the structure. Most previous experimental studies on tapered circular cylinders were dealing with stationary cylinders to explore the wake flow field and vortex shedding patterns past the cylinder. Few studies paid attentions to the vortex induced vibration of the tapered cylinders. This paper reports some results from in-water towing-tank experiments on the vortex-excited vibrations of tapered circular cylinders in a uniform flow. Cylinders with different mean diameters (28 and 78 mm), mass ratios (6.1... 

    Thermo-mechanical vibration of rotating axially functionally graded nonlocal Timoshenko beam

    , Article Applied Physics A: Materials Science and Processing ; Volume 123, Issue 1 , 2017 ; 09478396 (ISSN) Azimi, M ; Mirjavadi, S. S ; Shafiei, N ; Hamouda, A. M. S ; Sharif University of Technology
    Springer Verlag  2017
    The free vibration analysis of rotating axially functionally graded nanobeams under an in-plane nonlinear thermal loading is provided for the first time in this paper. The formulations are based on Timoshenko beam theory through Hamilton’s principle. The small-scale effect has been considered using the nonlocal Eringen’s elasticity theory. Then, the governing equations are solved by generalized differential quadrature method. It is supposed that the thermal distribution is considered as nonlinear, material properties are temperature dependent, and the power-law form is the basis of the variation of the material properties through the axial of beam. Free vibration frequencies obtained are... 

    A Study of the Effects of Ultrasonic Vibration on the Stability of Orthogonal Cutting Process Against Chatter

    , M.Sc. Thesis Sharif University of Technology Yazdian, Mohammad (Author) ; Akbari, Javad (Supervisor) ; Movahhedy, Mohammad Reza (Supervisor)
    Machining chatter is unstable and destructive vibrations that leads to damages to the surface of workpiece and reduces the tool life. These damages have significant effects on surface quality and material removal rate. Many studies have been done on chatter modeling and control in various machining processes. On the other hand, recently, ultrasonic vibrations have been used in many manufacturing processes including cutting to enhance the quality of products. Therefore, it is important to investigate the effect of ultrasonic vibrations on the stability of cutting process. Although a number of advantages such as improved surface roughness of workpiece and reduced machining forces have been... 

    A new method for detection of rolling bearing faults based on the Local Curve Roughness approach

    , Article Polish Maritime Research ; Volume 18, Issue 2 , July , 2011 , Pages 44-50 ; 12332585 (ISSN) Behzad, M ; Bastami, A ; Sharif University of Technology
    Detection of rolling bearing faults by vibration analysis is an important part of condition monitoring programs. In this paper a new method for detection of bearing defects based on a new concept of local surface roughness, is proposed. When a defect in the bearing grows then roughness of the defective surface increases and measurement of the roughness can be a good indicator of the bearing defect. In this paper a method of indirectly measuring surface roughness by using vibration signal is introduced. Several attached examples including both numerically simulated signals and actual experimental data show the effectiveness of the new, easy-to-implement method  

    Vibration effect on electrical resistance fluctuations in electrical connectors

    , Article Engineering Solid Mechanics ; Volume 6, Issue 4 , 2018 , Pages 299-306 ; 22918744 (ISSN) Behzad, M ; Darvish Gohari, H ; Mohammadi Dehabadi, A. A ; Sharif University of Technology
    Growing Science  2018
    Proper functioning of electrical connectors used in high oscillation is of great importance. Vibrations in connector pins cause stress and electrical resistance variations in the contact surface. In the present paper, the impacts of vibrational loads on electrical connectors is being modeled using the finite element method, and the electrical resistance oscillations of the connectors will be examined. Ultimately, the parameters affecting the electrical resistance oscillations of contacts will be determined and their relations with oscillations in electrical resistance are specified as well. © 2018 by the authors; licensee Growing Science, Canada, 2018 Growing Science Ltd. All rights reserved... 

    Corrigendum to "Finite element analysis of machine and workpiece instability in turning". [Int. J. Mach. Tools Manuf. 45 (2005) 753-760] (DOI:10.1016/j.ijmachtools.2004.11.017)

    , Article International Journal of Machine Tools and Manufacture ; Volume 48, Issue 2 , 2008 , Pages 260- ; 08906955 (ISSN) Mahdavinejad, R. A ; Ghorbanian, O ; Movahhedy, M. R ; Sharif University of Technology

    The effect of local muscle vibration on clinical and biomechanical parameters in people with knee osteoarthritis: A systematic review

    , Article Medical Journal of the Islamic Republic of Iran ; Volume 35, Issue 1 , 2021 , Pages 1-9 ; 10161430 (ISSN) Barati, K ; Esfandiari, E ; Kamyab, M ; Ebrahimi Takamjani, I ; Atlasi, R ; Parnianpour, M ; Yazdi, H ; ShahaIi, S ; Bidari, S ; Sharif University of Technology
    Iran University of Medical Sciences  2021
    Background: To identify and synthesize available published studies on the effect of local muscle vibration (LMV) on pain, stiffness, and function in individuals with knee OA.Methods: Five databases were searched to find relevant papers on April 29, 2020, including, PubMed, Scopus, EMBASE (Ovid), Science Citation Index, and COCHRANE Central Register for Controlled Trials (CENTRAL). Randomized controlled trials (RCTs) and nonrandomized-controlled-trials (non-RCTs), such as interrupted time series and prospective cohort studies were included. Two independent reviewers screened articles and assessed inclusion through predefined criteria. Participants' characteristics, study design, intervention... 

    Vibration isolation of a ship's seat

    , Article Smart Structures and Materials 2005 - Damping and Isolation, San Diego, CA, 7 March 2005 through 10 March 2005 ; Volume 5760 , 2005 , Pages 607-617 ; 0277786X (ISSN) Agahi, M ; Bahrami Samani, M ; Behzad, M ; Sharif University of Technology
    Different factors cause vibration. These vibrations make the voyages difficult and reduce comfort and convenience in passenger ships. In this paper, the creating factors of vibration have discussed first, then with mathematical modelling it will be attempted to minimize the vibration over the crew's seat. The modelling consists of a system with two degrees of freedom and by using vibration visolation with passive method of Tuned Mass Damper (TMD) it will be tried to reduce the vibration over personnel. Moreover using active control systems will be compared with passive systems  

    Vibration analysis of three points inside the vehicle due to engine shaking including sub-frame

    , Article Asian Simulation Conference 2005, ASC 2005 and the 6th International Conference on System Simulation and Scientific Computing, ICSC 2005, Beijing, 24 October 2005 through 27 October 2005 ; 2005 , Pages 248-252 Javad, M ; Farhad, M ; Mohammadpanah, A ; Sharif University of Technology
    World Publishing Corporation  2005
    Riding comfort, driving stability and drivability are important factors in good vehicle performance. These factors are heavily subject to low frequency vibration generated by engine. A recent tendency in engine mounting system design is the insertion of a sub-frame. In this paper a complete model of a typical vehicle is simulated with and without sub-frame. An acceleration analysis is studied for three important parts; steering roll, pedals and beneath of the deriver's feet. Also the effect and importance of existence of engine mount is studied by removing one engine mount. The results are presented graphically and show how using sub-frame improve the isolation of body vibration due to the... 

    Dynamics of Timoshenko beams on Pasternak foundation under moving load

    , Article Mechanics Research Communications ; Volume 31, Issue 6 , 2004 , Pages 713-723 ; 00936413 (ISSN) Kargarnovin, M. H ; Younesian, D ; Sharif University of Technology
    The response of a Timoshenko beam with uniform cross-section and infinite length supported by a generalized Pasternak-type viscoelastic foundation subjected to an arbitrary-distributed harmonic moving load is studied in this paper. Governing equations are solved using complex Fourier transformation in conjunction with the residue and convolution integral theorems. The solution is directed to compute the deflection, bending moment and shear force distribution along the beam length. A parametric study is carried out for an elliptical load distribution and influences of the load speed and frequency on the beam responses are investigated. © 2004 Elsevier Ltd. All rights reserved