Vibrações ressonantes não-lineares em estruturas tipo viga sob excitação paramétrica e combinada / Nonlinear resonance vibrations in beam type structures under parametric and combined excitations

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

This document presents results of theoretical and experimental investigations on the non-linear vibration characteristics of an important class of flexible structures. The motivation for such a study arises mainly from the increasing need for lightweight structural members. The weight reduction associated to the use of novel materials contribute to the increase of flexibility what can cause the appearance of nonlinear effects not previously observed. These nonlinear phenomena associated to the fact that, in field conditions the structure is frequently subjected to complex dynamic loads of different nature, results in a complex dynamic environment when estimation of the structure s dynamic response is concerned. Moreover, these nonlinear effects potentially may cause undesired vibration level, in some cases causing bad function and failure of the entire structure. The research is focused on studying the effects of medium viscosity as well as combined excitations on parametrically resonant vibrating structures. It is speciffically aimed characterize the phenomenons either analytically and experimentally by constructing laboratory test specimens that resemble aircraft structures. For that purpose a vertical fin is built in order to conduct experiments on the principal parametric resonance phenomenon. An analytical single degree of freedom model of this structure including nonlinear terms is derived and the results of numerically simulated results through perturbation technique are compared to experimental results obtained in the laboratory. A second structure is built that resembles a typical wing-pylon-engine substructure and it is used to study autoparametric resonance vibrations. In this case the structure is considered with multiple degrees of freedom and the results of a finite element model is correlated with experimentally obtained results. Theoretical and experimental results show that the environment viscosity affects in a significant manner the dynamic response of the structures under test, decreasing the maximum vibration levels in steady-state regime, simplifying the dynamics in transient responses and facilitating the relationship between instability/stability. At the end, it is shown experimental results demonstrating that vibratory energy from the wing substructure can be transferred by an autoparametric resonance to the substructure pylon-engine. All the experimental results do not found linear theory counterparts.

ASSUNTO(S)

autoparametric excitation parametric excitation nonlinear vibrations combined excitation excitação combinada vibrações não-lineares excitação paramétrica excitação autoparamétrica

ACESSO AO ARTIGO

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