Biomedical Engineering Reference
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Fig. 7.74 Shear stress S 12 distribution resulting from mechanical interaction with female model
E-BCSS 4 a prior to and b after cushion shape optimization
7.3.2 Optimization of Car Seat 'B' Under Female
Boss-Model Loading
Since car seat optimization involving a female human model, a female Boss-
Model in this case, is identical to the approach described previously, only the
essential results are shown.
7.3.2.1 Generation of the Optimized Seat Surface in Three Dimensions
Surface Seat Cushion Contour in the Transversal Plane: Fig. 7.71 a depicts the
initial unloaded non-optimized seat surface contour in the transversal plane of car
seat 'B' introduced in Fig. 6.30 b. Figure 7.71 b and c show the deformed tissue and
seat materials under gravitational body weight loading, as a result of the
mechanical interaction of 'E-BCSS-4' in terms of S 22 and S 12 stress contour plots.
In Figs. 7.71 d-f the optimized seat surface contour (at the unloaded and loaded
state, corresponding to Figs. 7.71 a-c) is depicted.
The (negative) shear tissue stress beneath the ischial tuberosity of the female
model
is
significantly
reduced,
employing
the
optimized
cushion
shape
(cf. Figs. 7.71 c, f).
Figure 7.72 a depicts the direct stress components S ii (i = 1, 2, 3) as well as
shear stress S 12 and the VON M ISES equivalent stress at the ischial tuberosity prior to
and after seat surface optimization. As with the male human model, the stress
components are shown as a bar graph. After optimizing the cushion, all three
compressive stresses S ii (i = 1, 2, 3) were reduced by nearly 50 %. The (positive)
shear stress S 12 as well as the tensile stress S 22 , however, increased.
Surface Seat Cushion Contour in the Sagittal Plane: Fig. 7.73 a and b depict
the initial non-optimized seat cushion shape in the sagittal plane and under gravi-
tational body weight loading as a result of the mechanical interaction of 'E-BCSS-
4', in terms of a S 22 stress contour plot. Figure 7.73 c and d show the corresponding
images resulting from mechanical interaction with the optimized seat cushion.
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