Loading...
Search for:
vibration-response
0.008 seconds
Identification of nonlinear model for rotary high aspect ratio flexible blade using free vibration response
, Article Alexandria Engineering Journal ; Volume 59, Issue 4 , August , 2020 , Pages 2131-2139 ; Kavyanpoor, M ; Ghalandari, M ; Nazari, M. A ; Bui, D. T ; Sharif University of Technology
Elsevier B. V
2020
Abstract
Nonlinear identification of a narrow cantilever blade undergoing free vibration was studied. In the absence of forced excitation and because of general data deficiency of this system, the current identification methods cannot be applied with sufficient accuracy. A new identification approach was introduced in the present study based on nonlinear free vibration decay. Nonlinear free response of the presented system is determined by the coupling of generalized variation iteration and the modified differential transformation methods. The comparisons between the experiments and calculations is highlighted the good accuracy of the identified nonlinear model. © 2020 Faculty of Engineering,...
Experimental and numerical investigation on the effect of blade number on vibrations of industrial fans
, Article COMADEM 2010 - Advances in Maintenance and Condition Diagnosis Technologies Towards Sustainable Society, Proc. 23rd Int. Congr. Condition Monitoring and Diagnostic Engineering Management, 28 June 2010 through 2 July 2010 ; February , 2010 , Pages 473-480 ; 9784883254194 (ISBN) ; Ebrahimi, A ; Oskouie, S. N ; Massoumi, H ; Sharif University of Technology
Abstract
In this paper, the effect of blade number on the vibration behavior of industrial fans has been studied experimentally and numerically. Two similar industrial fans with similar specifications and only different blade numbers were chosen in a plant. The vibration levels were measured on these fans and the results revealed that the blade passage phenomenon is the main cause of vibrations on both fans. Both fans and their structures were modeled numerically and the performance characteristics, vibratory forces and vibration response of structure were calculated. The results showed that the number of blade has small effect on vibratory forces compared to the performance characteristics. The...
Free vibration analysis of general stepped circular plates with internal elastic ring support resting on Winkler foundation by green function method
, Article Mechanics Based Design of Structures and Machines ; Volume 44, Issue 3 , 2016 , Pages 212-230 ; 15397734 (ISSN) ; Mofid, M ; Sharif University of Technology
Taylor and Francis Inc
Abstract
Natural frequencies are important dynamic characteristics of a structure. Therefore, the exact solution pertaining to free vibration of stepped circular plate elastically restrained against rotation, translation, and internal elastic ring support resting on an arbitrary variable elastic foundation using Green Function is presented in this paper. Thus, an accurate and direct modeling technique is introduced for modeling stepped circular plate on an arbitrary variable elastic foundation with arbitrary boundary conditions and internal elastic ring support. The effect of the translational along with rotational support flexibilities, as well as, the elastic coefficient of Winkler foundation and...
Performing building vibration assessments by acoustic measurements
, Article Building Acoustics ; Volume 27, Issue 1 , December , 2020 , Pages 21-33 ; Peplow, A ; Kasaei, A ; Sharif University of Technology
SAGE Publications Inc
2020
Abstract
This article presents an innovative application of the frequency domain decomposition method based on an acoustic and vibration response. Frequency domain decomposition method has been frequently used for operational modal analysis testing in the last decade to identify modal parameters for in-situ case studies. For these studies, the outputs of the vibration response through accelerometers have been employed in the analysis. In this article, the frequency domain decomposition method is employed, for the first time, to analyze both acoustic and vibration response of the building which is a novel application in building vibration response. As a case study, a cylindrical shaped seven-story...
Free vibrations of functionally graded material cylindrical shell closed with two spherical caps
, Article Ships and Offshore Structures ; 2021 ; 17445302 (ISSN) ; Kiani, Y ; Bagheri, N ; Eslami, M. R ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
Free vibration response of a cylindrical shell closed with two hemispherical caps at the ends (hermit capsule) is analysed in this research. It is assumed that the system of joined shell is made from functionally graded materials (FGM). Properties of the shells are assumed to be graded through the thickness. Cylindrical and hemispherical shells are unified in thickness. To capture the effects of through-the-thickness shear deformations and rotary inertias, first order theory of shells is used. Donnell type of kinematic assumptions are adopted to establish the general equations of motion and the associated boundary and continuity conditions with the aid of Hamilton's principle. The resulting...
Vibration and dynamic analysis of oil well drillstring considering coupled axial and torsional effects using cylindrical superelement
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 14 , November , 2013 ; 9780791856437 (ISBN) ; Ghorbani, Sh ; Firoozbakhsh, K ; Barari, A ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2013
Abstract
In this paper axial and torsional vibrations of a drillstring are studied using cylindrical superelement. Drillstring vibration equation is derived by calculating kinetic and potential energy and work done by external forces on drillstring, and utilizing Hamilton's principle. The model is analyzed by implementing finite element technique with consideration drillstring weight, centrifugal force due to rotation of drillstring, axial force resulting from bit with the formation contact and torsional torque caused by the stick-slip phenomenon. To calculate the vibrational response of drillstring, a computational finite element scheme was developed. For a typical case of oil well drillstring, the...
On the free vibration response of rectangular plates, partially supported on elastic foundation
, Article Applied Mathematical Modelling ; Volume 36, Issue 9 , September , 2012 , Pages 4473-4482 ; 0307904X (ISSN) ; Mofid, M ; Akin, J. E ; Sharif University of Technology
2012
Abstract
Rectangular plates on distributed elastic foundations are widely employed in footings and raft foundations of variety of structures. In particular, mounted columns and single footings may partially occupy the rectangular plate of any kind. This study deals with free vibration problem of thin rectangular plates on Winkler and Pasternak elastic foundation model which is distributed over a particular arbitrary area of the plate. Closed form solutions are developed through solving the governing differential equations of plates. Moreover, a novel mathematical approach is proposed to find the exact analytical solution of free vibration of plates with mixed or fully-clamped boundary conditions....
Discrete wavelet transform-neural network crack-like damage identification of welds on chassis cross members
, Article Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering ; Volume 226, Issue 9 , 2012 , Pages 1202-1210 ; 09544070 (ISSN) ; Sharifi K, A ; Azadi, S ; Kazemi, R ; Sharif University of Technology
Abstract
This paper incorporates a discrete wavelet transform and a radial basis function neural network to implement a vibration-based crack-like damage identification approach to the simulated welds of chassis cross members. After finite element method modelling of a vehicle, eight acceleration sensors are placed on the chassis, and their responses are measured to the upward displacement on the excitation of two tyres while the other two tyres are fixed. Then, a discrete wavelet transform with a Daubechies 3 mother wavelet is applied to the responses of the sensors. All detail coefficients and approximation coefficients of the nine levels of the discrete wavelet transform are introduced into the...
Analysis of nonlinear oscillations in spur gear pairs with approximated modelling of backlash nonlinearity
, Article Mechanism and Machine Theory ; Volume 51 , 2012 , Pages 14-31 ; 0094114X (ISSN) ; Salarieh, H ; Sharif University of Technology
2012
Abstract
Due to international competition and strict limitations of standards regarding the noise level, investigation of gear vibration is of great importance. In this paper, nonlinear oscillations of spur gear pairs including the backlash nonlinearity is studied. Dynamic system is described through the classical single degree of freedom (SDOF) model in terms of dynamic transmission error (DTE). Using multiple scale method, forced vibration responses of the gear system including primary, super-harmonic and sub-harmonic resonances are investigated. In each case, the jump phenomenon and stability analysis are studied. In addition, the effect of dynamic and manufacturing parameters of the gear system...
A new model for estimating vibrations generated in the defective rolling element bearings
, Article Journal of Vibration and Acoustics, Transactions of the ASME ; Volume 133, Issue 4 , April , 2011 ; 10489002 (ISSN) ; Bastami, A. R ; Mba, D ; Sharif University of Technology
2011
Abstract
Prediction of the vibration response due to defects on rolling element bearings requires having an accurate representative vibration model. In this paper, a new model for vibration generation in the rolling element bearings has been introduced. The proposed model assumes a stochastic source of vibration excitation, which is produced as a result of metallic contact between bearing elements during rolling. This model explains high frequency vibration in the acceleration spectrum clearly. When a defect grows in the bearing, the roughness of the contacting surfaces increases locally and stochastic excitation becomes stronger in the defective area. The increased vibration level at the defective...
Nonlinear forced oscillations and stability analysis of the automotive gearbox system
, Article Proceedings of the ASME Design Engineering Technical Conference, 15 August 2010 through 18 August 2010 ; Volume 5 , 2010 , Pages 1013-1020 ; 9780791844137 (ISBN) ; Salarieh, H ; Sharif University of Technology
Abstract
In this paper, nonlinear oscillation of the automobile gear system is studied. The backlash dynamic parameter is included in the nonlinear mathematical modeling of the problem. Using multiple scale method, forced vibration responses of the gear system including Primary, Subharmonic and Super-harmonic resonances are investigated. In each case, the jump phenomenon and stability analysis are studied. In addition, the effect of dynamic and manufacturing parameters of the gear system on the time responses are analyzed. Simulation and nonlinear analysis of the problem are developed in MAPLE and MATLAB environments
Effects of structural configuration on vibration control of smart laminated beams under random excitations
, Article Journal of Mechanical Science and Technology ; Volume 24, Issue 5 , 2010 , Pages 1119-1125 ; 1738494X (ISSN) ; Sharif University of Technology
Abstract
The influence of structural configuration on vibration responses of smart laminated beams under random loading is studied. The effect of laminate configurations and locations of sensors/actuators in the smart system is also investigated. The layer-wise approximation for displacement and electric potential is utilized to construct the finite element model. The closed-loop control response is determined through an optimal control algorithm based on the Linear Quadratic Regulator (LQR). The correlation coefficient between the input random force and the applied actuating voltage for various configurations is also computed. It is revealed that for softer configurations, the correlation...
Vibration suppression of offshore wind turbine foundations using tuned liquid column dampers and tuned mass dampers
, Article Ocean Engineering ; Volume 172 , 2019 , Pages 286-295 ; 00298018 (ISSN) ; Oterkus, E ; Khorasanchi, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Highly dynamic nature of the applied loads on flexible and lightly damped offshore wind turbine (OWT) foundations affects the lifetime and serviceability of the system. In this study, the excessive vibration responses of OWTs are minimized using tuned mass dampers (TMD) and tuned liquid column dampers (TLCD). Due to high efficiency of TLCDs and TMDs for certain loading conditions, a combined TLCD-TMD is also utilized to improve the overall performance in a wide range of loading conditions. First, a parametric study was performed that highlights the sensitivity of these structural control devices. The effect of two devices on fixed offshore wind turbine foundations for the benchmark 5 MW NREL...
Free vibration of joined cylindrical–hemispherical FGM shells
, Article Archive of Applied Mechanics ; Volume 90, Issue 10 , 2020 , Pages 2185-2199 ; Kiani, Y ; Bagheri, N ; Eslami, M. R ; Sharif University of Technology
Springer
2020
Abstract
Free vibration response of a joined shell system including cylindrical and spherical shells is analyzed in this research. It is assumed that the system of joined shell is made from a functionally graded material (FGM). Properties of the shells are assumed to be graded through the thickness. Both shells are unified in thickness. To capture the effects of through-the-thickness shear deformations and rotary inertias, first-order shear deformation theory of shells is used. The Donnell type of kinematic assumptions is adopted to establish the general equations of motion and the associated boundary and continuity conditions with the aid of Hamilton’s principle. The resulting system of equations is...
Semi active vibration control of a passenger car using magnetorheological shock absorber
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, Istanbul, 12 July 2010 through 14 July 2010 ; Volume 3 , 2010 , Pages 21-27 ; 9780791849170 (ISBN) ; Zabihollah, A ; Sharif University of Technology
2010
Abstract
A novel semi-active control system for suspension systems of passenger car using Magnetorheological (MR) damper is introduced. The suspension system is considered as a mass-spring model with an eight-degrees-of-freedom, a passive damper and an active damper. The semi-active vibration control is designed to reduce the amplitude of automotive vibration caused by the alteration of road profile. The control mechanism is designed based on the optimal control algorithm, Linear Quadratic Regulator (LQR). In this system, the damping coefficient of the shock absorber changes actively trough inducing magnetic field. It is observed that utilizing the present control algorithm may significantly reduce...