Abstract
When deriving an experimental model from Frequency Response Functions (FRFs), it may happen that the measurement of certain FRFs is impossible. This may be an important issue, mainly in the field of condition monitoring and damage detection, since some points of interest may become inaccessible in operational conditions. In this circumstance, it is useful to have some tools that can provide the prediction of such dynamic information. The transmissibility concept, extended to a general multiple degree-of-freedom system, can play an important role to circumvent these situations. The authors have shown in previous works that the estimation of such FRFs can be made possible by invoking important properties associated with the transmissibility function. The objective of this work is to evaluate different sets of FRFs, estimated by using the transmissibility concept and its associated properties, in an actual continuous structure to which different patterns of structural modification are applied. A supplementary study in this work shows that some of the sets for applied forces/known responses can better estimate the FRF data.
Highlights
The notion of transmissibility is presented in every classic textbook on vibrations, associated to the single degreeof-freedom system, when its base is moving harmonically: it is defined as the ratio between the modulus of the response amplitude and the modulus of the imposed motion amplitude
In order to prove that it is possible to estimate the Frequency Response Functions (FRFs) of modified systems, provided that the transmissibility matrix of the original system is known, some modifications have been made in the original structure, according to properties 1 and 2
It was observed that the predicted FRF data present a high sensitivity to any small discrepancy between the transmissibilities of the structure before and after modification, in the region of their maxima
Summary
The notion of transmissibility is presented in every classic textbook on vibrations, associated to the single degreeof-freedom system, when its base is moving harmonically: it is defined as the ratio between the modulus of the response amplitude and the modulus of the imposed motion amplitude. An application where the transmissibility seems of great interest is when, in field service, one can not measure the responses at some co-ordinates of the structure. If the transmissibility matrix of the original system can be evaluated beforehand, by measuring in service some responses, one would be able to estimate the responses at the inaccessible co-ordinates. This is possible, since there are important transmissibility properties, as it is presented by Maia et al [4] that provide us the necessary tools to estimate those responses. Almeida et al / The use of transmissibility properties to estimate FRFs on modified structures
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