An Experimental Study of the Mechanical Response of Nylon 12 Tubing: Practical Implications for Use in Concentric Tube Robots

DeMaio, Christopher

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An Experimental Study of the Mechanical Response of Nylon 12 Tubing: Practical Implications for Use in Concentric Tube Robots

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This thesis reports experimental studies on the mechanical behavior of thin Nylon 12 tubes under different loading conditions. Recent years have seen a marked interest in the use of polymers, and particularly Nylon 12, for the construction of Concentric Tube Robots (CTRs), a class of flexible surgical robotic manipulators. The kinematic accuracy of these robots, however, is fundamentally limited by the lack of models that properly account for the mechanical behavior of the material. Throughout this thesis, we report evidence that disproves one of the main modeling assumptions commonly used in the literature, namely that the constitutive equation for Nylon 12 can be assumed to be elastic. We proposed new models, based on the theory of viscoelastic solids, that more accurately capture the time-dependent relaxation and creep experimentally observed in Nylon 12 tubes.

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