Abstract
Frictionless specimen/platen contact in unconfined compression tests
has traditionally been assumed in determining material properties
of soft tissues via an analytical solution. In the present study,
the suitability of this assumption was examined using a finite element
method. The effect of the specimen/platen friction on the mechanical
characteristics of soft tissues in unconfined compression was analyzed
based on the published experimental data of three different materials
(pigskin, pig brain, and human calcaneal fat). The soft tissues were
considered to be nonlinear and viscoelastic; the friction coefficient
at the contact interface between the specimens and platens was assumed
to vary from 0.0 to 0.5. Our numerical simulations show that the
tissue specimens are, due to the specimen/platen friction, not compressed
in a uniform stress/strain state, as has been traditionally assumed
in analytical analysis. The stress of the specimens obtained with
the specimen/platen friction can be greater than those with the frictionless
specimen/platen contact by more than 50%, even in well-controlled
test conditions.
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