The consistent coupling boundary condition for the classical micromorphic model: existence, uniqueness and interpretation of parameters

TL;DR

This paper introduces a weaker boundary condition for the classical micromorphic model, ensuring existence and uniqueness of solutions while clarifying the interpretation of parameters.

Contribution

It proposes a new consistent coupling boundary condition that reduces boundary influence and derives conditions for existence and uniqueness in the micromorphic model.

Findings

Existence and uniqueness of solutions under the new boundary condition.

Derived new coercive inequalities for tensor fields.

Modified interpretation of constitutive parameters.

Abstract

We consider the classical Mindlin-Eringen linear micromorphic model with a new strictly weaker set of displacement boundary conditions. The new consistent coupling condition aims at minimizing spurious influences from arbitrary boundary prescription for the additional microdistortion field P. In effect, P is now only required to match the tangential derivative of the classical displacement u which is known at the Dirichlet-part of the boundary. We derive the full boundary condition, in adding the missing Neumann condition on the Dirichlet-part. We show existence and uniqueness of the static problem for this weaker boundary condition. These results are based on new coercive inequalities for incompatible tensor fields with prescribed tangential part. Finally, we show that compared to classical Dirichlet conditions on u and P, the new boundary condition modifies the interpretation of the constitutive parameters.