The numerical and experimental validation of multistable behavior of cantilever shells is address... more The numerical and experimental validation of multistable behavior of cantilever shells is addressed. The design of the laminated composite shells is driven by a recently proposed semi-analytical shell model, whose predictions are verified and critically examined by means of finite element simulations and stability tests on two manufactured demonstrators. In addition, the influence of the main design parameters on the shells stability scenario is discussed. Despite its simplicity, the reduced model allows to depict a fairly faithful picture of the stability scenario; therefore, it proves to be a useful tool in the early design stages of morphing shell structures.
Vibration based damage detection methods are among the most popular and promising approaches for ... more Vibration based damage detection methods are among the most popular and promising approaches for health monitoring of structures. In this work a critical review of different methods for damage detection methods of structures is presented. The theoretical bases of the most popular methods based on the changes in the modal properties of the structures are deduced. The review includes the modal displacements, the mode shape slopes, the modal curvatures and the strain energy methods. The efficiency of all these methods is compared by using a finite element analysis of intact and damaged beams. The methods are tested experimentally by using a scanning laser vibrometer to measure the modal properties of specially prepared composite beams with defects. All this methods are compared with the damage detection method based on the analysis of the Poincaré maps of the motion of the structures). Conclusions concerning the advantages and the applicability of the considered methods are deduced.
Influence of external force on the parametric and self-excited system
Journal of Technical Physics, 2001
Influence of an external harmonic force on a non-linear parametrically and self-excited system wi... more Influence of an external harmonic force on a non-linear parametrically and self-excited system with two degrees of freedom has been investigated in this paper. Vibration analysis has been carried out for coupled Rayleigh-Mathieu-Duffing oscillators. By means of the multiple scales' method, the existence and stability of periodic and quasi-periodic solutions close to the main parametric resonances have been considered. Influence of a small external force on vibrations in the synchronization, chaotic and hyperchaotic region has been analyzed. Transition from regular vibrations to chaotic and hyperchaotic motion has been presented as well.
On Numerical Simulations of a Nonlinear Self-Excited System With Two Non-Ideal Sources
Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - DETC2005, 2005
Universidade Regional Integrada do Alto Uruguai e das Missoes Departamento de Ciencias Exatas e d... more Universidade Regional Integrada do Alto Uruguai e das Missoes Departamento de Ciencias Exatas e da Terra, CEP 98802-470, Santo Angelo, RS
Large amplitude vibrations of heated Timoshenko beams with delamination
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2015
In this work, the large amplitude vibration of a heated Timoshenko composite beam having delamina... more In this work, the large amplitude vibration of a heated Timoshenko composite beam having delamination is studied. The model of delamination considers the contact interaction between sublaminates including normal forces, shear forces, and additional damping due to the interaction of sublaminates. This work is an extension of the previous analysis based on a model of the dynamic behavior of a beam with delamination considering additionally the nonlinearities due to large displacements and temperature changes. Numerical calculations are performed in order to estimate the influence of the delamination, the geometrically nonlinear terms, and elevated temperature on the response of the beam.
Vibration Supression of Composite Plate Wit MFC Active Elements
Dynamics of a Timoshenko beam under an influence of mechanical and thermal loadings is analysed i... more Dynamics of a Timoshenko beam under an influence of mechanical and thermal loadings is analysed in this paper. Nonlinear geometrical terms and a nonuniform heat distribution are taken into account in the considered model. The mathematical model is represented by a set of partial differential equations (PDEs) which takes into account thermal and mechanical loadings. The problem is simplified to two PDEs and then reduced to ordinary differential equations (ODEs) by means of the Galerkin method taking into account three modes of a linear Timoshenko beam. Correctness of the analytical model is verified by a finite element method. Then, the nonlinear model is studied numerically by a continuation method or by a direct numerical integration of ODEs. An effect of the temperature distribution on the resonance near the first natural frequency and on stability of the solutions is presented. The increase of mechanical loading results in hardening of the resonance curve. Thermal loading may stabilise the beam dynamics when the temperature is decreased. The elevated temperature may transit dynamics from regular to chaotic oscillations. Keywords Timoshenko beam • Thermal loading • Nonlinear vibrations • Nonlinear resonances • Chaos 1 Introduction The beams are fundamental structural elements commonly used in many branches of engineering. They are often applied in order to model rotating blades, for example, blades of a helicopter rotor [1,2] or blades of turbines. Recently, these structures are often made of modern materials e.g. composites which, in spite of the Communicated by Francesco dell'Isola and Giuseppe Piccardo.
Temperature Influence on Nonlinear Responses of Timoshenko Beam
Volume 7B: 9th International Conference on Multibody Systems, Nonlinear Dynamics, and Control, 2013
Delamination Detections of Laminated, Nonlinear Vibrating and Thermally Loaded Beams
Springer Proceedings in Physics, 2011
Abstract In this work, the geometrically nonlinear vibrations of fully clamped composite beams su... more Abstract In this work, the geometrically nonlinear vibrations of fully clamped composite beams subjected to thermal changes are used to study the sensitivity of selected vibration response parameters to the presence of delamination (damage) and elevated temperature. The damage detection criterion formulated earlier for non-heated plates, based on analyzing the points in the Poincare sections of the damaged and healthy plate, is modified and tested for the case of beams additionally subjected to elevated temperatures. The importance of ...
Dynamics of a composite Timoshenko beam with delamination
Mechanics Research Communications, 2012
Abstract In this work dynamic behaviour of a composite beam having delamination is presented. The... more Abstract In this work dynamic behaviour of a composite beam having delamination is presented. The model of delamination takes into account a contact interaction between sublaminates including normal forces, shear forces and additional damping. Numerical calculations are performed in order to estimate the influence of the new terms included into the model.
Parametric Study for Lock-In Detection in Vortex-Induced Vibration of Flexible Risers
IUTAM Symposium on Nonlinear Dynamics for Advanced Technologies and Engineering Design, 2012
An observation that a parameter plot of a harmonically forced wake oscillator, which shows three ... more An observation that a parameter plot of a harmonically forced wake oscillator, which shows three distinct regions, in qualitative sense corresponds well with results of numerical and experimental investigations has prompted further investigations into dynamical behaviour of a flexible cylinder experiencing vortex-induced vibration. For this purpose, a reduced-order model representing a vertical pipe excited by surrounding fluid flow was built and certain aspects of its dynamics were studied. When resonance curves of a numerical and an analytical solution obtained with the method of multiple scales were compared, it became apparent that the former gives a much wider resonance region as the latter. This difference expectedly narrowed for lower values of the coupling strength parameter, indicating not only that the initial value might have been very large as defined in the method used, but also that because of this the overall dynamics were dominated by the linear part, the structure.
State control with LQR algorithms applied in vibration damping of cantilever beam
2012 15th International Power Electronics and Motion Control Conference (EPE/PEMC), 2012
ABSTRACT Composite structures with embedded active MFC (Macro Fiber Composite) actuators give new... more ABSTRACT Composite structures with embedded active MFC (Macro Fiber Composite) actuators give new possibilities in regulation of responsible systems. Application of these structures allow to form and change mechanical characteristics. One of the main applications is vibration damping. For such application, the MFC actuators are powered by transistor converters which are controlled by DSP microcontrollers. Presented paper describes results obtained for a cantilever beam with an embedded piezoelectric MFC actuator. Operational characteristics of this composite structure are formed in closed loop control systems, because of the beam and actuator nonlinearities, linear and resonant controllers don’t give satisfactory solutions [5]. Therefore a LQR controller is applied, for which mutual test allows to estimate the influence of feedback signal delay time on damping properties and MFC supply voltage characteristics
Vibrations of an autoparametric system, composed of a nonlinear mechanical oscillator with an att... more Vibrations of an autoparametric system, composed of a nonlinear mechanical oscillator with an attached damped pendulum, around the principal parametric resonance region, are investigated in this paper. The aim of the work is to show the chaotic motion in instability region. Two kinds of chaotic motion are detected: chaotic swings and chaotic motion composed of swings and rotation of pendulum. The results are confirmed experimentally on especially designed laboratory model. Additionally, the latest methods of chaos identification are applied to confirm chaotic dynamics experimentally.
The influence of self-excited and parametric vibrations on system vibrations has been examined in... more The influence of self-excited and parametric vibrations on system vibrations has been examined in this paper. External harmonic excitation in the main area of the parametrical resonance was taken into account as well. The influence of the parameter values, including the system external excitation, on its behavior in the synchronization area was calculated analytically. The vibration amplitudes, the width of the synchronization areas and the characteristic system features were calculated as well. The solution stability analysis was verified by numerical and analog simulation.
Optimal control methods for vertical and horizontal beam dynamics
Journal of Physics: Conference Series, 2012
ABSTRACT An application of the Macro Fiber Composite (MFC) actuators for damping of a composite b... more ABSTRACT An application of the Macro Fiber Composite (MFC) actuators for damping of a composite beam is presented in this paper. The effectiveness of vibration reduction by a selected control method is tested for vertical and horizontal position of the beam. The original model has been studied numerically by using Galerkin's discretisation method. The numerical results for the vertical and horizontal beams are compared.
Nonlinear phenomena in mechanical system dynamics
Journal of Physics: Conference Series, 2012
ABSTRACT The goal of the paper is to present selected, untypical, and intuitively unexpected phen... more ABSTRACT The goal of the paper is to present selected, untypical, and intuitively unexpected phenomena from nonlinear mechanics. Particular attention is paid to the dynamics of self-, parametric and external excited systems. Interactions between these various vibration types lead mainly to quasi-periodic responses. However, in the selected domains of system parameters, the effect of frequency locking is observed. Furthermore, external harmonic force imposed on such a system produces a specific internal loop inside a resonance zone. As an example of nonlinear autoparametric systems, a structure (oscillator) with an attached pendulum is presented. The nonlinear terms introduced by pendulum motion cause instabilities in the resonance region. This instability transits the pendulum to rotation or chaotic motion. An application of nonlinear couplings for the reduction of unwanted vibrations is also studied. In order to reduce vibrations, the main structure is coupled to an electrical oscillator by a quadratic term. It has been shown that such a coupling leads to the amplitude saturation phenomenon which can then be used to design a nonlinear control strategy.
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Papers by J. Warminski