Biomedical Engineering Reference
In-Depth Information
Fig. 7.19 Tissue normal
stress S 33 along node path 3
(see Fig. 7.18 ): a all
investigated bedding systems
and b systems with lowest
tissue stress
7.1.6 Result Transfer for Prototype Generation
7.1.6.1 Soft Foam Material
The factorized soft foam material F0.5 has therefore been shown to be the ideal
material to minimize internal tissue normal and shear stress. This material does not
physically exist. A comparison with physically existing foam materials shows that
the theoretical material characteristic is in good agreement with soft foam material
S AF
6060,
a
trademark
of
F OAM P ARTNER
F RITZ
N AUER
AG,
Switzerland,
cf. Fig. 7.21 : curves in black and brown.
In spite of deviations of both stress-strain characteristics of mattress foam
materials F0.5 and S AF 6060, resulting effects on the tissue in terms of normal and
shear stress along node path 1 are identical, cf. Fig. 7.21 b. This leads to
replacement of the theoretical foam model F0.5 used in simulations with the
physically existing S AF 6060 material for a prototype. However, since S AF 6060
material exhibits strong viscoelastic features, two similar, with respect to static
equilibrium characteristics, but more highly resilient foam materials were
considered: E VO P ORE HRC 150 P and HME 7, both trademarks of F OAM P ARTNER
F RITZ N AUER AG, Switzerland. The force-displacement characteristics of the latter
foams are located in the region of larger displacement (approx [7.5 mm) between
the reference foam F1 and the factorized material F0.75, cf. Fig. 7.22 .
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