Abstract
The material frames associated with an edge of a discretized curve is discussed in this chapter. For the discrete curve, a pair of material vectors play the role of directors in Kirchhoff’s rod theory. The motion of these vectors is calibrated using either a Bishop frame or a reference frame that is continually being updated. The pair of parallel transport operators defined in the previous chapter combined with a rotation about the tangent vector to an edge are used to define the motions the material vectors. Of particular interest is the difference in an angle of twist between two adjacent edges. This angle will be identified with the torsion of the rod-like body that the discrete elastic rod is modeling. In this chapter the bending strains will also be defined. The developments in this chapter and, in particular, the twist of the reference frame are illustrated using the example of a rod uncoiling under its own weight.
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Notes
- 1.
In some works, the material vectors are identified as the discrete directors: \(\mathbf {m}^k_1 = \mathbf {d}^k_1\) and \(\mathbf {m}^k_2 = \mathbf {d}^k_2\).
- 2.
In the code, \(\varDelta m^{k+1}_{\mathrm{ref}}\) is known by the variable name signang.
- 3.
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Jawed, M.K., Novelia, A., O’Reilly, O.M. (2018). Material Frames and Measures of Twists. In: A Primer on the Kinematics of Discrete Elastic Rods. SpringerBriefs in Applied Sciences and Technology(). Springer, Cham. https://doi.org/10.1007/978-3-319-76965-3_5
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