METAMATERIAL MECHANISM DESIGN BY TOPOLOGY OPTIMIZATION IN TRUSS GROUND STRUCTURE DOMAINS WITH LARGE DISPLACEMENTS

Resumo

Metamaterials are artificial structures engineered to have extremal properties that are not
found in naturally occurring materials, such as negative Poisson’s ratio (auxetic behavior). These
structures are obtained by repetitive cell patterns. Each cell of the metamaterial can be designed to
have a controlled directional movement. This allows the creation of devices with a desired mechanical
function. Compliant mechanisms perform certain functions from the elastic deformation of its body.
The topology optimization (TO) technique has been shown to be the most generic and systematic for
the design of compliant mechanisms. It consists of a method that distributes material within a domain
in order to achieve the specified objective function, satisfying the imposed constraints. In this work,
compliant mechanism is designed by using the Topology Optimization method to generate
microstructure unit cells that simulate the effect of metamaterials that have negative Poisson’s ratio
(auxetic materials). The unit cell (microstructure) of metamaterial is driven to have the same
characteristics of a compliant mechanism, that is, a monolithic body that delivers a desired motion
when is loaded in a certain way. TO is performed in domains discretized by truss elements (ground
structure), where the cross-sectional areas of the elements are the design variables. Large
displacements are considered, which establishes a nonlinear relation between deformation and
displacement and requires the use of nonlinear FEM. Computational simulations are presented to
verify the results of the metamaterial design.