Biomedical Engineering Reference
In-Depth Information
Fig. 6.21 a Comparison of direct compressive stress S
33
progress from the skin surface through
the fat and muscle layer onto the sacral bone edge surface for the homogenous and contoured soft
foam support. b Buttock model in section cut view at position of crista sacralis mediana on
contoured S
AF
foam support: S
33
contour plot at static equilibrium
Fig. 6.22 a Comparison of direct compressive stress S
33
progress from the skin surface through
the fat and muscle layer onto the ischial tuberosity for the homogenous and contoured soft foam
support. b Buttock model in section cut view at the ischial tuberosity on contoured S
AF
foam
support: S
33
contour plot at static equilibrium
(Figs.
6.21
a,
6.22
a). Stress paths originating from the skin (point A) and ending at
the sacral bone edge and at the ischial tuberosity (point B) are depicted in
Figs.
6.21
b and
6.22
b, respectively. Stress curves along the nodal paths were
generated for contoured and homogeneous foam using S
AF
material and for con-
toured foam using the stiffer virtual material. The path distance displayed the true
distance of the deformed tissue layers at the particular sites at static equilibrium.
Fat and muscle layer thickness at the lateral sacral bone edge were 7.5 and
9.6 mm, respectively, 17.4 and 25.7 mm at the ischial tuberosity.
Based on the presented simulations, it has been shown that at all considered
sites all direct stress components S
ii
(i = 1, 2, 3) were approximately of the same
magnitude, Fig.
6.23
a, stress progress was qualitatively and quantitatively similar.
In addition, the direct stress components were almost equivalent to the principal
