Biomedical Engineering Reference
In-Depth Information
Fig. 6.47 Comparison of seat pressure distribution using vertical direct stress component S
33
of
airplane seat B in a upright and b reclined position; for coordinate system orientation see Fig.
6.46
Fig. 6.48 a Direct stress S
33
along node path 1 (see Fig.
6.45
) and b shear stress S
13
along node
path 2 (see Fig.
6.45
) for upright and reclined back rest position using system E-BASS 1
position exceeds the direct stress in upright position by one order of magnitude,
due to increased loading of the front part of the femur. Shear stress, in contrast,
is higher in the upright position. In the reclined position, a sign change of tissue
shear stress can be observed at the front seat edge.
Figure
6.47
depicts the seat pressure distribution due to gravity body loading at
static equilibrium. In the upright position maximum interface direct stress S
33
is
located at the ischium, whereas in the reclined position the interface direct stress
increase also occurs at the front seat edge.
In Fig.
6.48
, tissue direct stress S
33
along path 1 and shear stress S
13
along path
2 (see Fig.
6.45
) are compared for the upright and the reclined position. It can be
seen that tissue direct stress for both seat configurations is relatively low and
nearly constant up to a tissue depth of 60 mm and strongly increases towards the
ischial bone surface. S
33
values at the bone surface were increased by 30 % in the
upright back rest position compared to the reclined position, cf. Fig.
6.48
a. Shear
