Abstract
The foam material of interest in this investigation is a rigid closed-cell
polyurethane foam PMDI with a nominal density of 20 pcf (320 kg/m3).
Three separate types of compression experiments were conducted on
foam specimens. The heterogeneous deformation of foam specimens and
strain concentration at the foam�steel interface were obtained
using the 3-dimensional digital image correlation (3D-DIC) technique.
These experiments demonstrated that the 3D-DIC technique is able
to obtain accurate and full-field large deformation of foam specimens,
including strain concentrations. The experiments also showed the
effects of loading configurations on deformation and strain concentration
in foam specimens. These DIC results provided experimental data to
validate the previously developed viscoplastic foam model (VFM).
In the first experiment, cubic foam specimens were compressed uniaxially
up to 60%. The full-field surface displacement and strain distributions
obtained using the 3D-DIC technique provided detailed information
about the inhomogeneous deformation over the area of interest during
compression. In the second experiment, compression tests were conducted
for cubic foam specimens with a steel cylinder inclusion, which imitate
the deformation of foam components in a package under crush conditions.
The strain concentration at the interface between the steel cylinder
and the foam specimen was studied in detail. In the third experiment,
the foam specimens were loaded by a steel cylinder passing through
the center of the specimens rather than from its end surface, which
created a loading condition of the foam components similar to a package
that has been dropped. To study the effects of confinement, the strain
concentration and displacement distribution over the defined sections
were compared for cases with and without a confinement fixture.
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