An Experimental Investigation of Feature Availability in Nominally Identical Structures for Population-Based SHM

It is perhaps well known that the uncertainty in realistic structures may complicate most efforts for modelling and damage identification. In a population of structures which are considered identical, as in a wind farm for example, it is very often that the accurate modelling of one structure will be inadequate for the robust monitoring of the rest in an SHM approach. This paper presents an exploration of the common features which can be found in nominally identical structures and which can be used for damage identification with the ultimate purpose of population-based SHM. The concept of a population-based approach means that any additional new structures to the population will not need to be fully modelled in order to be monitored. Two different variants of the tail wing of a Piper PA-28 aircraft are used to create two pairs of nominally identical structures by separating the tail wings in half. The new population of four structures thus contains two pairs of them which are similar, but they have different length and different weight. A full modal test is performed in all of the structures and an exploration of possible common features is also done. The results show that common damage-sensitive features exist across the structures, a key requirement if population-based SHM is to be successfull.