Three-Dimensional Equilibria and Stability of Nonlinear Curved Beams Using Intrinsic Equations and Shooting

Abstract

This article describes a shooting method that provides numerical solutions to static equilibrium equations for intrinsically curved beams in three-dimensions. Notably, the method avoids iteration for cantilever beams subjected to distributed or point follower loads. This is due to the governing equations being given in first-order form such that the specification of a single boundary condition on the forced end results in automatic satisfaction of the fixed boundary condition. Also documented is a general procedure for finding all solutions to static beam problems with conservative loading. This is particularly useful in beam buckling problems where multiple stable and unstable solutions exist. The procedure for finding all solutions is built around the Picard-Lindelöf theorem on the uniqueness and existence of solutions to initial value problems. Using the presented approach, three-dimensional equilibrium solutions are generated for many loading cases and boundary conditions, including a three-dimensional helical beam, and are compared to similar solutions available in the literature. The stability of the generated solutions is assessed using a dynamic finite element code based on the same intrinsic beam equations. Due to the absent need for iteration, the presented approach may find application in model-based control for practical problems such as the control of equipment utilized in endoscopic surgeries and the control of spacecraft with robotic arms and long cables.