A simple yet effective ALE-FE method for the nonlinear planar dynamics of variable-length flexible rods

TL;DR

This paper introduces an ALE-FE method for simulating the nonlinear planar dynamics of variable-length flexible rods, offering simplicity, efficiency, and open-source tools for complex structural analysis.

Contribution

The paper presents a novel ALE-FE approach for modeling variable-length flexible rods, simplifying implementation and improving computational efficiency over existing methods.

Findings

The ALE-FE method accurately predicts rod dynamics under various boundary conditions.

The approach demonstrates fast convergence and robustness in case studies.

Open source code facilitates further research and applications.

Abstract

With recent advances in variable-length structures for use in soft actuation, energy harvesting, energy dissipation and metamaterials, the mathematical modelling and numerical simulation of physical systems with time-varying domains is becoming increasingly important. The planar nonlinear dynamics of one-dimensional elastic structures with variable domain is formulated from a Lagrangian approach by using a non-material reference frame. An Arbitrary Lagrangian-Eulerian (ALE) scheme is proposed where the domain is reparametrized based on a priori unknown configuration parameters. Based on this formulation, a Finite Element (FE) method is developed for theoretically predicting the evolution of a rod constrained at its ends by one or two sliding-sleeves, whose position and inclination can be varied in time, and under external loadings. Finally, case studies and instability problems are investigated to assess the reliability of the proposed formulation against others available and to demonstrate its effectiveness. With respect to previously developed methods for this type of structural problems, the present ALE-FE approach shows a strong theoretical and implementation simplicity, maintaining an efficient and fast convergence according to the cases analyzed. An open source code realized for the present ALE-FE model is made available for solving the nonlinear dynamics of planar systems constrained by one or two independent sliding sleeves. The present research paves the way for further extensions to easily implement solvers for the three-dimensional dynamics of flexible one- and two-dimensional structural systems with moving boundary conditions.