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Finite Element Analysis of Hard and Soft Tissue Contributions to Thoracic Response: Sensitivity Analysis of Fluctuations in Boundary Conditions
Technical Paper
2006-22-0008
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English
Abstract
Thoracic trauma is the principle causative factor in 30% of road
traffic deaths. Researchers have developed force-deflection
corridors of the thorax for various loading conditions in order to
elucidate injury mechanisms and to validate the mechanical response
of ATDs and numerical human models. A corridor, rather than a
single response characteristic, results from the variability
inherent in biological experimentation. This response variability
is caused by both intrinsic and extrinsic factors. The intrinsic
factors are associated with individual differences among human
subjects, e.g., the differences in material properties and in body
geometry. The extrinsic sources of variability include fluctuations
in the loading and supporting conditions in experimental tests.
Recent studies have considered the intrinsic factors, especially
the material-level response of the rib, which can be modified over
a limited range within, e.g., a finite element (FE) model in order
to fit a gross overall thoracic response corridor. Studies
typically do not, however, consider uncertainty due to extrinsic
factors.
The purpose of this work was to estimate the contribution of
selected extrinsic factors to the uncertainty in a response
corridor by using a thorax FE model. The sensitivity of twelve
response corridors to the relative positioning of the thorax, the
loader and the test fixture was analyzed. Reasonable ranges of
experimental uncertainty were established for loader angle, loader
location, and thorax orientation, and response variability was
analyzed for three tissue states (intact, denuded, and eviscerated)
with four different loaders (hub, distributed belt, single diagonal
belt, and double diagonal belts). Of the variables considered here,
the thorax orientation has the largest effect on the
force-deflection response, which increases and decreases the
effective stiffness up to 20%. The simulation work isolated the
extrinsic contribution from the corridor and indicated model
deficiencies and refinements, which have the potential to improve
model accuracy, particularly modelling the soft tissues and the
costal cartilage.