Session: SYMP 2-1: Magneto-Responsive Materials Modeling, Optimization, and Performance

Paper Number: 140391

140391 - Comparison of Coupled and Nonlinear Magnetoactive Elastomer Topology Optimization Formulations 

Magnetoactive elastomer (MAE) devices are magnetic particle-filled polymer matrices that can be programmed for specific actuations and controlled remotely by an external magnetic field. They garner considerable research interest as an emerging technology for actuators in soft robots or in applications restricting direct physical contact. Topology optimization can help to generate MAE devices with superior performance or cost for a given set of objectives and constraints than conventional design. This work presents a 2D multimaterial topology optimization scheme for soft magnetoactive devices using a density approach in COMSOL Multiphysics that demonstrates the benefit of coupling the magnetic and mechanical physics in magnetoactive elastomer design and shows performance increases when considering nonlinear deformations during optimization. Some past works have only considered one set of physics during topology optimization, and some use a linearized approach to deformation when large deformations are expected. The purpose of this paper is to quantify the importance of using both a coupled physics formulation and nonlinear deformation in the design domain during topology optimization through a simple case study of a magnetoactive elastomer extender device under a uniform magnetic field. The performance benefits are shown in this simulated case study where results for uncoupled and coupled, and coupled with and without geometric nonlinearity are compared. Uncoupled simulations only consider the magnetic physics, while coupled simulations include magnetic and solid mechanical physics, where material with high Young’s modulus also has a high relative permeability, and vice versa. The nonlinear formulation distinguishes the spatial (x) and material (X) coordinates by the displacement vector u, such that u=X+x, as well as using a Green-Lagrange strain formulation. No distinction is made between spatial and material coordinates when geometric nonlinearities are not considered. The resulting geometries from the topology optimization were compared in identical static simulations to measure their performance, with both coupled results performing better than the uncoupled result with significantly less material cost. In addition, considering nonlinear deformations in the coupled topology optimization increased performance by 36.1% over the linear formulation. The material cost of the nonlinear formulation was 14.8% of the original design domain compared to the linear with 13.8%. While both the coupled simulations produced a geometry that resembles a compliant mechanism compared to the uncoupled geometry, using a nonlinear topology optimization produced a more complex multi-hinged structure than the linear solution. More deformation was also observed for the nonlinear formulation with a similar material cost for a given magnetic field.

Presenting Author: Christian Bergen Penn State University

Presenting Author Biography: Christian is a PhD student studying at Penn State University that specializes in the modeling and optimization of magnetoactive elastomers geared towards 3D printing. He works under Dr. Zoubeida Ounaies in the Electroactive Material Characterization Lab (EMCLab), as well as his previous advisor Dr. Paris Von Lockette at the University of Maryland, Baltimore County.

Authors:

Christian Bergen
Paris Von Lockette
Zoubeida Ounaies