Universal Theorems for Total Energy of the Dynamics of Linearly Elastic Heterogeneous Solids

TL;DR

This paper establishes universal bounds for the total energy in the dynamics of heterogeneous elastic solids, providing fundamental limits that are independent of microstructure details, applicable to general composites under harmonic motion.

Contribution

It introduces universal theorems for dynamic energy bounds in heterogeneous elastic solids, extending static case results to harmonic elastodynamics without assuming homogeneity or isotropy.

Findings

Uniform-stress boundary data minimize total elastic plus kinetic energy.

Uniform velocity boundary data minimize total complementary elastic plus kinetic energy.

The theorems are applicable to arbitrary microstructures and can inform bounds on dynamic properties.

Abstract

In this paper we consider a sample of a linearly elastic heterogeneous composite in elastodynamic equilibrium and present universal theorems which provide lower bounds for the total elastic strain energy plus the kinetic energy, and the total complementary elastic energy plus the kinetic energy. For a general heterogeneous sample which undergoes harmonic motion at a single frequency, we show that, among all consistent boundary data which produce the same average strain, the uniform-stress boundary data render the total elastic strain energy plus the kinetic energy an absolute minimum. We also show that, among all consistent boundary data which produce the same average momentum in the sample, the uniform velocity boundary data render the total complementary elastic energy plus the kinetic energy an absolute minimum. We do not assume statistical homogeneity or material isotropy in our treatment, although they are not excluded. These universal theorems are the dynamic equivalent of the universal theorems already known for the static case (Nemat-Nasser and Hori 1995). It is envisaged that the bounds on the total energy presented in this paper will be used to formulate computable bounds on the overall dynamic properties of linearly elastic heterogeneous composites with arbitrary microstructures.