Optimization Potential of the Method - Preventive Biomechanics - page 335

Table 7.10 Maximum stress values S 11 ,S 33 and S 12 prior to and after shape optimization (in the
sagittal plane)

Mises
(MPa)

S 11 (MPa) S 33 (MPa) S 13 (MPa)

Max Tension Compression Tension Compression Max Min

Prior to
optimization

0.0100 0.0028 -0.0142 0.0021 -0.0140 0.0021 -0.0140

After
optimization

0.0023 0.0015 -0.0087 0.0011 -0.0085 0.0011 -0.0008

Fig. 7.60 a graphic representation of stress from Table 7.9 (transversal plane) and b from
Table 7.1 0(sagittal plane)

topology optimization procedure shown in Sect. 7.2.3 led to the optimized seat
contour depicted in Fig. 7.58 a and the tissue stress distribution depicted in
Fig. 7.58 b, due to mechanical interaction with the male Boss-Model. As a result of
surface topology optimization in the sagittal plane, and similar to tissue stress
reduction from optimization in the transversal plane, direct compressive tissue
stress S 22 (absolute values) was reduced by 40 % (from -0.0139 to -

0.0083 MPa).
In Table 7.9 and Fig. 7.60 b the direct stress components S 11 and S 33 , as well as
shear stress S 12 , at the ischial tuberosity prior to and after seat surface optimization
in conjunction with the male human model are depicted. In Fig. 7.59 direct stress
components S 11 ,S 33 and S 12 , as well as VON M ISES equivalent stress, is shown in
the transversal plane. The seat surface optimization led to a distinct reduction of
compressive,

tensile and shear stress (absolute values in Table 7.10 and

Fig. 7.60 b) after surface shape optimization.

7.3.1.3 Generation of the Optimized Seat Surface in Three Dimensions

Based on the separate procedures, i.e. seat surface optimization in the transversal
and sagittal planes and employing plane-strain models, an optimized seat shape
was generated in 3D. This was accomplished by extrusion of either the optimized