Training nonlinear elastic functions: nonmonotonic, sequence dependent and bifurcating

TL;DR

This paper demonstrates a training approach for nonlinear elastic responses in materials, enabling functionalities like frequency conversion, logic operations, and shape change through sequence-dependent plastic deformations.

Contribution

It introduces a method to train disordered solids for complex nonlinear responses using plastic deformation sequences, expanding the functional capabilities of elastic materials.

Findings

Successful training of nonlinear responses such as frequency conversion.

Implementation of logic gates through material deformation sequences.

Controlled expansion or contraction based on transverse compression sequences.

Abstract

The elastic behavior of materials operating in the linear regime is constrained, by definition, to operations that are linear in the imposed deformation. Though the nonlinear regime holds promise for new functionality, the design in this regime is challenging. In this paper we demonstrate that a recent approach based on training [Hexner et al., PNAS 2020, 201922847] allows responses that are inherently non-linear. By applying designer strains, a disordered solids evolves through plastic deformations that alter its response. We show examples of elaborate nonlinear training paths that lead to the following functions: (1) Frequency conversion (2) Logic gate and (3) Expansion or contraction along one axis, depending on the sequence of imposed transverse compressions. We study the convergence rate and find that it depends on the trained function.