Mechanical Interactions - Preventive Biomechanics - page 275

chosen tissue material point at skin level at the gluteal region (situated approx. at
mid length of path 2 in Fig. 6.31 b). In Fig. 6.34 a and b, a distinct decrease of
contact stress S 33 and material point displacement can be observed, respectively.
Both phenomena have not reached steady state after 30 9 10 3 s (approx. 8.3 h). In
this process, the increased displacement of the chosen tissue material point can be
most adequately compared to the stress decrease and most likely will consume
more time before reaching steady state.
6.3 Car- and Airplane Seats
6.3.1 Introduction
In Sect. 6.2 , the numerical mechanical interaction between various bedding
systems and B OSS -Models was analyzed, whereby particular emphasis was put
upon internal tissue stress and strain evaluation in the gluteal region. Critical sites
of increased stress and strain were found to be situated adjacent to the bone
structure of the os sacrum (see Fig. 6.12 ). The same approach can be applied to
body-seat interaction involving automotive and airplane seating systems, where
tissue stress and strain is evaluated in the gluteal and upper leg region.
6.3.2 Usual Seating Systems
Figure 6.35 depicts the seat systems (automotive seat systems: car seat A,
Fig. 6.35 a and car seat B, Fig. 6.35 b and airplane seat A, Fig. 6.35 c and airplane
seat B, Fig. 6.35 d) analyzed in Sect. 6.3.4 . One car seat system is used in the E-
Class car of DAIMLER automotive and both airplane seats are manufactured by
RECARO Aircraft Seating. The mechanical characterization of the materials
employed in both seat systems are described in detail in Sect. 4.2.2 .
6.3.3 Critical Body Sites
Similar to bedding systems, critical body sites prone to mechanical tissue stress
and strain can be identified. In the seated position such regions are located in the
tissue covering the ischial tuberosity, cf. positions 3 and 3a in Fig. 6.12 in
Sect. 6.2.4 .