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Communication Dans Un Congrès Année : 2012

Numerical Assessment of Smart Spring to Attenuate Structural Vibrations

Résumé

Engineers are interested in developing new generation of small size and high power machines. The increase of machine performance using higher speeds with lighter structures enhances vibration problems. For financial reasons, down-time has to be reduced and also optimized, and above all, these machines have to operate in a safe working environment. Finally, to be environment friendly, they have to reduce energy consumption. Several solutions have been developed to attenuate the vibration level. These solutions could be passive, active or a combination of both, leading to the so-called semi-active control. New control strategies are also developed aiming at modifying the boundary conditions of the structure. In the case of rotating machinery, the technique consists in using hybrid bearings where the dynamic behavior of the system can be controlled by adding either softening or hardening effects when crossing (or in the vicinity of) critical speeds. Aiming at controlling the parameters of the machine suspension, the concept of smart spring is considered. The architecture proposed involves two springs in parallel, being one of them an active spring and the other spring is designed so that it can be activated by using a PZT actuator at the end that is responsible for the application of normal forces to the system. These forces induce friction and, consequently, introduce both hardening effect and frictional damping. This type of solution has been already visited in several applications, especially in the aerospace industry.This paper aims at exploring design strategies to improve the performance of smart springs. Three methodologies for smart springs design are proposed. The three proposed smart spring methodologies are applied to a single-degree-of-freedom vibrating system for illustration purposes. The friction model used is a macro slip model that is able to represent the friction effects for relatively small displacements.The dynamic behavior of rotating machinery with hybrid bearing can be, initially, modeled as a single-degree-of- freedom system. The numerical simulations are conducted by using this mechanical system that is submitted to a sine sweep excitation. Initial conditions of velocity and displacement are taken into account. The performance of the dynamic system is analyzed by considering the maximum amplitude of the response, the time consumed to reach the steady state position, and the RMS level of the response. The studied smart spring parameters are the additional stiffness and the friction force. Performance metrics regarding the smart spring parameters are presented.The effects of stiffness and damping parameters, introduced as a function of the normal force, are discussed. The results obtained enable an efficient and optimized design of a smart spring for a particular application and a given operating frequency range.
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Dates et versions

hal-00946666 , version 1 (13-02-2014)

Identifiants

  • HAL Id : hal-00946666 , version 1

Citer

Marcelo Braga dos Santos, Franscisco Paulo Lépore Neto, Valder Steffen Jr, Jarir Mahfoud. Numerical Assessment of Smart Spring to Attenuate Structural Vibrations. XVIII Symposium On Vibrations, Shocks And Noise VCB2012, 2012, France. pp.1-10. ⟨hal-00946666⟩
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