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forced-oscillations
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Nonlinear behaviour of the regenerative chatter in turning process with a worn tool: Forced oscillation and stability analysis
, Article Mechanism and Machine Theory ; Volume 45, Issue 8 , 2010 , Pages 1050-1066 ; 0094114X (ISSN) ; Bakhtiari Nejad, F ; Movahhedy, M. R ; Ahmadian, M. T ; Sharif University of Technology
2010
Abstract
Self-excited and forced vibrations are important topics in machining processes because their occurrence results in poor surface finish, increase in tool wear and reduction of material removal rate. In this paper, turning process is modeled as a single degree of freedom (SDOF) dynamic system including quadratic and cubic structural nonlinearities. The effect of tool flank wear, as a contact force between the workpiece and tool, is addressed vigorously. Multiple scale method is used to find the solution of the nonlinear delay-differential equation including regenerative chatter, forced excitation and tool wear. During the stability analysis, it is shown that width of cut can be considered as...
Investigation of planing vessels motion using nonlinear strip theory–an experimental and numerical study
, Article Ships and Offshore Structures ; Volume 14, Issue 7 , 2019 , Pages 684-697 ; 17445302 (ISSN) ; Khorasanchi, M ; Seif, M. S ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
This study is aimed to improve Zarnick’s (1978, A nonlinear mathematical model of motions of a planing boat in regular waves. David W. Taylor Naval Ship Research and Development Center, Bethesda, MD, USA) analytical model for motions of planing vessels. A nonlinear time domain mathematical model was developed for dynamic behaviour of longitudinal motion of high-speed planing crafts in regular waves. This model was based on two-dimensional strip theory method using expanding wedge theory and momentum. Due to the nonlinearity and complex dynamic behaviour of these vessels, the time-domain simulation was adopted. Total resistance, heave and pitch motions as well as acceleration were found very...
Investigation of planing vessels motion using nonlinear strip theory–an experimental and numerical study
, Article Ships and Offshore Structures ; Volume 14, Issue 7 , 2019 , Pages 684-697 ; 17445302 (ISSN) ; Khorasanchi, M ; Seif, M. S ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
This study is aimed to improve Zarnick’s (1978, A nonlinear mathematical model of motions of a planing boat in regular waves. David W. Taylor Naval Ship Research and Development Center, Bethesda, MD, USA) analytical model for motions of planing vessels. A nonlinear time domain mathematical model was developed for dynamic behaviour of longitudinal motion of high-speed planing crafts in regular waves. This model was based on two-dimensional strip theory method using expanding wedge theory and momentum. Due to the nonlinearity and complex dynamic behaviour of these vessels, the time-domain simulation was adopted. Total resistance, heave and pitch motions as well as acceleration were found very...
Dynamic Modeling and Analysis of Delaminated Isotropic and Multi- Layered Composite Beam under the Action of Moving Force/Oscillatory Mass
, Ph.D. Dissertation Sharif University of Technology ; Kargarnovin, Mohammad Hossein (Supervisor) ; Ahmadian, Mohammad Taghi (Co-Advisor)
Abstract
In this thesis, a laminated composite beam with single delamination under the action of moving force/oscillatory mass has been modeled and analyzed. The beam has been divided into four sub-beams and based on Bernoulli-Euler and also shear deformation theories and by applying the Hamilton’s principle, equations of motion along with boundary conditions and continuity and compatibility conditions are obtained. Primarily, based on the constrained mode model the delaminated layers have been analyzed then by implementing the Lagrange multipliers method, the nature of dynamic contact is incorporated. In the analysis of delaminated beam based on the constrained mode, by applying the mode summation...
Semi-active control of forced oscillations in power transmission lines via optimum tuneable vibration absorbers: With review on linear dynamic aspects
, Article International Journal of Mechanical Sciences ; Vol. 87, issue , 2014 , p. 163-178 ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Abstract
Due to flexibility, relatively small weight and low energy-dissipative characteristics of cables, they are vulnerable to external excitations such as wind, wind-rain, earthquake and traffic loadings. Among them, galloping phenomenon is one of the most important sources of electrical/mechanical failures in power transmission lines. In this paper, tuneable vibration absorbers (TVAs) are used to suppress galloping forced vibrations (as a semi-active control approach). Using mode summation technique, mathematical model of the hybrid problem including the transmission line and an arbitrary number of absorbers is presented. Developing a sophisticated multi-loops optimization algorithm, best values...
Crack Localisation In Homogeneous Plates by Analyzing the Dynamic Responses of the Plate Excited by the Moving Load
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor) ; Nikkhoo, Ali (Co-Supervisor)
Abstract
The purpose of the study: The purpose of this study is to identify the crack position in homogeneous plates through health monitoring methods based on vibration. Identifying structural damage is one of the issues that attention can prevent the sudden collapse of structures and causing heavy loss of life and property. For this reason, extensive studies have been conducted in this field in recent decades. In this study, plates are examined as one of the most used structural members, and their damage is identified through a proposed method based on wavelet transform. Research method: In this study, through the wavelet transform method, the dynamic responses of a homogeneous plate excited by a...
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
On the relationship between unsteady forces and shock angles on a pitching airplane model
, Article Scientia Iranica ; Volume 17, Issue 2 B , 2010 , Pages 102-107 ; 10263098 (ISSN) ; Soltani, M. R ; Sharif University of Technology
2010
Abstract
A series of supersonic visualization tests were performed on an airplane model in both static and dynamic pitching cases. After image processing, the wave angles originating from different parts of the model were carefully measured and averaged over several oscillation cycles. These findings were then compared with the corresponding normal force under similar conditions. The results reveal a hysteresis loop in variations of the model shock angles with instantaneous angles of attack during upstroke and down-stroke motions. In comparison with the normal force hysteresis loop, it has been found that there is an interesting relationship between the shape of the hysteresis loop of the shock angle...