Abstract
A discrete model for elastic rods undergoing planar motions based on the theory of a directed (or Cosserat) rod is presented. Edge vectors and a director are used to capture cross section deformations including stretch, stretch gradients, shear, shear gradients, and the Poisson effect. In addition, deformations such as longitudinal stretch and bending are also incorporated. The model is validated with the help of known analytical solutions to benchmark problems using Green and Naghdi’s rod theory.
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Notes
Some authors [9, 34] use the descriptor “Cosserat” to classify a theory where a rigid orthonormal triad is attached at each cross section. The authors whose work most of this article is based of [15, 16] use “Cosserat” more generally to refer to a directed rod theory, where the directors are deformable and not necessarily orthonormal.
That is, the bending moment was given by the constitutive relation \(EI \frac{\partial \theta }{\partial \xi }\) where \(\xi \) is the arc length parameter of the extensible rod in a reference configuration and \(\theta \) is the angle subtended by the tangent vector to the rod’s centerline with a fixed direction. The curvature of the rod in the present configuration is \(\kappa = \frac{\partial \theta }{\partial s} = \mu ^{-1} \frac{\partial \theta }{\partial \xi }\) where \(\mu = \frac{\partial s}{\partial \xi }\) is the stretch of the rod.
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Acknowledgements
The work of Evan Hemingway was supported by a Berkeley Fellowship from the University of California at Berkeley and a U.S. National Science Foundation Graduate Research Fellowship. The work of Oliver O’Reilly was supported by grant number W911NF-16-1-0242 from the U.S. Army Research Organization administered by Dr. Samuel C. Stanton.
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Hemingway, E.G., O’Reilly, O.M. On a planar theory of a discrete nonlinearly elastic rod. Acta Mech 231, 1217–1240 (2020). https://doi.org/10.1007/s00707-019-02581-x
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DOI: https://doi.org/10.1007/s00707-019-02581-x