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ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

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Indenter Stroke [mm]<br />

Muscle Force [N]<br />

2<br />

1.5<br />

1<br />

0.5<br />

0<br />

0 0.05 0.1 0.15 0.2<br />

12<br />

11<br />

10<br />

9<br />

65 g<br />

115 g<br />

165 g<br />

215 g<br />

265 g<br />

0 g<br />

65 g<br />

115 g<br />

165 g<br />

215 g<br />

265 g<br />

Simulation<br />

8<br />

0 0.05 0.1 0.15 0.2<br />

Time [s]<br />

Fig. 6: Comparison of simulation and measurement for indenter stroke and muscle force<br />

Although the simulation shows deviations in both results, the developed modeling<br />

approach will be used for CASIMIR. The reason therefor is that materials of the current<br />

isolated muscle model are based on general tissue data, i.e. the specific properties of the<br />

investigated M.gastrocnemius are not considered so far, leading to small deviations per<br />

se.<br />

5. IMPLEMENTATION IN CASIMIR<br />

0<br />

0 0.05 0.1 0.15 0.2<br />

For a first qualitative test the validated modeling method is mapped from the isolated<br />

muscle state to a detailed model of the human thigh. The simulation represents a real<br />

scenario, with a test person sitting on a rigid plate and activating the muscle group for<br />

knee flexion. The simulation procedure is similar to the isolated muscle, i.e. first the<br />

model is loaded by gravity and then the muscles are contracting. In figure 7 the vertical<br />

displacement is presented for each computation step.<br />

(a) (b) (c)<br />

Fig.7: Vertical displacement: Initial state (a), loaded by gravity (b) and contracted (c)<br />

Comparing the results two effects can be observed: Firstly, that due to the gravity load a<br />

reliable seating behavior for the thigh (b) can be determined. Secondly, that the<br />

influence of the muscle activation is apparent as the vertical displacement due to the<br />

gravity load decreases (c compared to b), which is caused by the stiffening of the<br />

muscle tissue.<br />

The final evaluation is carried out by the seat pressure distribution. In figure 8 the<br />

simulation results are presented for one thigh after loading with gravity and after<br />

contraction. A qualitative comparison between results and real measurements of a test<br />

person sitting on rigid plate is made.<br />

2<br />

1.5<br />

1<br />

0.5<br />

12<br />

11<br />

10<br />

9<br />

Experiment<br />

8<br />

0 0.05 0.1 0.15 0.2<br />

Time [s]

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