Concepçâo e avaliação numérica e experimental de um absorvedor dinâmico de vibrações termicamente sintonizável

Abstract

The present work is devoted to the study of a dynamic vibration absorber (DVA) that can be tuned by the voluntary introduction of stress induced by temperature distributions in plate-like structures, based on the effect known as stress-stiffening. After summarizing the underlying theory of dynamic vibration absorbers and modeling the dynamic behavior of thin plates in the presence of thermally-induced stresses, numerical simulations based on finite element discretization have been made to characterize the dynamic behavior of rectangular plates under different thermal loads and mechanical boundary conditions. For this purpose, a general multiphysic modeling procedure based on a finite element commercial code has been developed, enabling to considerer all the possible forms of thermal load and thermal and mechanical boundary conditions. The results of these simulations have shown that significant variations of the natural frequencies can result from the induction of thermal stresses. Based on these results, a DVA has been designed, consisting of a thin circular metallic plate constrained at its outer border by thick metallic rings, in such a way that the natural frequency associated to the first axissymmetric bending mode can be adjusted according to the difference between the temperatures of the plate and the rings. A number of numerical simulations based on finite elements have been made aiming at optimizing the geometry and predicting the performance of the DVA. A prototype of the absorber has been built, having foil resistive heaters for the controlled application of heat to the plate and the rings. Dynamic tests have been carried-out on the prototype for the characterization of its dynamic behavior with and without thermal effects. The experimental results confirmed the significant influence of the thermal stresses on the natural frequencies of the DVA and the possibility of achieving frequency tuning.