The proposed method presented in this thesis is especially applicable
for SHM where sensors cannot be widely or randomly distributed. Thus a
strategic organization and localization of the sensors is achieved by
implementing the geometric configuration of Theodorous Spiral Sensor
Cluster (TSSC). The performance of TSSC in characterizing the impactor
types are compared with other conventional sensor clusters (e.g. square,
circular, random etc.) and it is shown that the TSSC is advantageous
over conventional localized sensor clusters. It was found that the TSSC
provides unbiased sensor voting that boosts sensitivity towards
classification of impact events. To prove the concept, a coupled field
(multiphysics) finite element model (CFFEM) is developed and a series of
experiments were performed. The dominant frequency band (DBF) along
with a Lag Index (LI) feature extraction technique was found to be
suitable for classifying the impactors. Results show that TSSC with DBF
features increase the sensitivity of impactor's elastic modulus, if the
covariance of the AUS from the TSSC and other conventional sensor
clusters are compared. It is observe that for the impact velocity,
geometric and mechanical properties studied herein, longitudinal and
flexural waves are excited, and there are quantifiable differences in
the Lamb wave signatures excited for different impactor materials. It is
found that such differences are distinguishable only by the proposed
TSSC, but not by other state-of-the-art sensor configurations used in
SHM. This study will be useful for modeling an inverse problem needed
for classifying impactor materials and the subsequent reconstruction of
force histories via neural network or artificial intelligence.
Finally an alternative novel approach is proposed to describe the
Probability Map of Impact (PMOI) over the entire structure. PMOI could
serve as a read-out tool for simultaneously identifying the impact
location and the type of the impactor that has impacted the structure.
PMOI is intended to provide high risk areas of the space structures
where the incipient damage could exist (e.g. area with PMOI > 95%)
after an impact.