Stilt WErks
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The explanation of this extraordinary behavior lies in the choice of Urethane, a high Poisson-ratio polymer, for the in0fill. Classical engineering analysis shows that the stiffness and strength of these components

           Figure 4. Variation in ultimate tip force, Pult, with  Poisson ratio Vu, for l = 11.5 inches.

Increases dramatically as the Poisson ratio approaches (1/2). Nevertheless, the observed behavior was stiffer and stronger than predicted by classical analysis.

            The components as currently designed are much stronger than a human leg. The leg would break before the stilt. Since the leg braces exhibited linear elastic behavior without any noticeable permanent deflection or damage, the amount of urethane could potentially be reduced and should be validated by further finite element analysis and testing.

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