António P.V. Urgueira

Evaluation of the Performance of Three Different Methods Used in the Identification of Rigid Body Properties

The identification of the rigid body properties of a structure is an important matter in various structural dynamic applications, namely in structural modification (coupling/uncoupling), optimization and vibration control. In most situations, the experimental route is the only via to obtain the desired dynamic properties. This goal is achieved by an inverse process which starts from the measurement of Frequency Response Functions (FRFs) and ends on matrices describing the mass distribution of a rigid body.

The use of transmissibility properties to estimate FRFs on modified structures

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.

An Overview of the Transmissibility Concept and Its Application to Structural Damage Detection

The notion of transmissibility, in what mechanical vibrations are concerned, may lead to various potential applications. Depending on the related quantities, responses or forces, it is possible to use different formulations and to deduce important properties. All these aspects are overviewed in the present article, where transmissibility can be oriented to the evaluation of unmeasured frequency response functions, to the estimation of reaction forces and, with special focus here, to the detection of damage in a structure. This important application of the transmissibility concept leads to the damage detection phase. To accomplish such a goal, the authors present some indicators and numerical simulations are given to illustrate the theoretical developments.