1,720,976 research outputs found
An Efficient Reduced-Order Model to Investigate the Behavior of an Imperfect Microbeam Under Axial Load and Electric Excitation
No full textMultistability in an electrically actuated carbon nanotube: a dynamical integrity perspective
No full text
Dynamical integrity for interpreting experimental data and ensuring safety in electrostatic MEMS
No full textNonlinear dynamics of an imperfect microbeam under an axial load and electric excitation
No full textThis study is motivated by the growing attention, both from a practical and a theoretical point of view, toward the nonlinear behavior of microelectromechanical systems (MEMS). We analyze the nonlinear dynamics of an imperfect microbeam under an axial force and electric excitation. The imperfection of the microbeam, typically due to microfabrication processes, is simulated assuming the microbeam to be of a shallow arched initial shape. The device has a bistable static behavior. The aim is that of illustrating the nonlinear phenomena, which arise due to the coupling of mechanical and electrical nonlinearities, and discussing their usefulness for the engineering design of the microstructure. We derive a single-mode-reduced-order model by combining the classical Galerkin technique and the Padé approximation. Despite its apparent simplicity, this model is able to capture the main features of the complex dynamics of the device. Extensive numerical simulations are performed using frequency response diagrams, attractor-basins phase portraits, and frequency-dynamic voltage behavior charts. We investigate the overall scenario, up to the inevitable escape, obtaining the theoretical boundaries of appearance and disappearance of the main attractors. The main features of the nonlinear dynamics are discussed, stressing their existence and their practical relevance. We focus on the coexistence of robust attractors, which leads to a considerable versatility of behavior. This is a very attractive feature in MEMS applications. The ranges of coexistence are analyzed in detail, remarkably at high values of the dynamic excitation, where the penetration of the escape (dynamic pull-in) inside the double well may prevent the safe jump between the attractors. Copyright © 2011 by ASME
Subcombination internal resonance of the additive type in the response dynamics of micromachined resonators crossing the impacting threshold
No full textIn the present paper, a microbeam-based MEMS device is experimentally driven to experience a subcombination internal resonance (IR) of the additive type, where the second mode internally resonates with both the first and the third modes inducing a range of quasi-periodic dynamics. The main features of the experimental quasi-periodicity are analyzed, which inherently depend on the ratios established by the frequencies of the involved modes. Experimental Poincaré maps are established and tracked, exhibiting a specific underlying pattern. Numerical simulations are developed and the Fast Fourier Transform frequency trend lines are examined, showing the variations of the modes frequencies values while keeping the subcombination IR relationship. We investigate the evolution of the quasi-periodic waveform as increasing the excitation frequency. Special attention is devoted to the hardening dominance of the system, which influences the modes frequencies components. The last part of the paper is focused on the impacting regime. Since the microbeam is constituted by a dielectric layer (Silicon Nitride), impacts take place as raising the oscillation amplitudes. We analyze the experimental behavior at impacts, showing the possibility of dynamics with different characteristics, including both quasi-periodic, chaotic and periodic regions, all of them holding subcombination IR signature
Activating internal resonance in a microelectromechanical system by inducing impacts
No full textAs natural frequencies become commensurate, internal (autoparametric) resonances involving the corresponding modes may arise. This phenomenon has been recently increasingly reported in micro- and nanosystems. Due to the intrinsic nonlinearity, internal resonances may draw complex features, which can be desirable for developing novel devices with enhanced functionality based on energy transfer among the involved modes. Here, we examine the possibility of activating internal resonance by inducing impacts. Through a specially deposited dielectric layer to prevent short-circuiting, a microelectromechanical beam is deliberately operated to have impact with the substrate, which redirects the dynamics of the system. Driven by repetitive impacts, the device widens the frequency bandwidth around the first mode and activates a non-classical type of internal resonance, at a ratio of 7:2 between the first and third vibration modes. Interestingly, this internal resonance behavior is enabled in regions of the driving parameters space, where the branch would not have existed in the absence of impacts. The dynamical phenomena featured by the impacts are affected by the characteristics of the impacting surfaces, which may controllably tune the response. This study opens up research toward utilizing impacts for favoring internal resonance activations, including in cases where they are precluded in the smooth system, as well as engineering the associated modal energy exchange
Jump and pull-in dynamics of an electrically actuated bistable MEMS device
No full textThis study analyzes a theoretical bistable MEMS device, which exhibits a considerable versatility of behavior. After exploring the coexistence of attractors, we focus on each rest position, and investigate the final outcome, when the electrodynamic voltage is suddenly applied. Our aim is to describe the parameter range where each attractor may practically be observed under realistic conditions, when an electric load is suddenly applied. Since disturbances are inevitably encountered in experiments and practice, a dynamical integrity analysis is performed in order to take them into account. We build the integrity charts, which examine the practical vulnerability of each attractor. A small integrity enhances the sensitivity of the system to disturbances, leading in practice either to jump or to dynamic pull-in. Accordingly, the parameter range where the device, subjected to a suddenly applied load, can operate in safe conditions with a certain attractor is smaller, and sometimes considerably smaller, than in the theoretical predictions. While we refer to a particular case-study, the approach is very general
Theoretical and experimental investigation of the nonlinear response of an electrically actuated imperfect microbeam
No full textIn this study a theoretical and experimental investigation of the nonlinear response of an electrically actuated microbeam is performed. A mechanical model is proposed, which accounts for two common imperfections of microbeams, due to microfabrications, which are the compliant support conditions and the initially deformed profile. A computationally efficient single-mode reduced-order model is derived by combining the Ritz technique and the Padé approximation. Numerical simulations of the harmonic response of the device near primary resonance are shown illustrating nonlinear phenomena arising in the device response. Experimental investigation is conducted on a polysilicon imperfect microbeam confirming the simulation results. The concurrence between the theoretical results and the experimental data reveals that this model, while simple, is capable of properly capturing the response both at low and, especially, at higher electrodynamic voltages
- …
