Abstract
The ability of a digital image correlation technique to capture the
heterogeneous deformation fields appearing during compression of
ultra-light open-cell foams is presented in this article. Quantitative
characterization of these fields is of importance to understand the
mechanical properties of the collapse process and the energy dissipation
patterns in this type of materials. The present algorithm is formulated
in the context of multi-variable non-linear optimization where a
merit function based on a local average of the deformation mapping
is minimized implicitly. A parallel implementation utilizing message
passing interface for distributed-memory architectures is also discussed.
Estimates for optimal size of the correlation window based on measurement
accuracy and spatial resolution are provided. This technique is employed
to reveal the evolution of the deformation texture on the surface
of open-cell polyurethane foam samples of different relative densities.
Histograms of the evolution of surface deformation are extracted,
showing the transition from unimodal to bimodal and back to unimodal.
These results support the interpretation that the collapse of light
open-cell foams occurs as a phase transition phenomenon.
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