On a model of nonlocal continuum mechanics part II: Structure, asymptotics, and computations

We consider the asymptotic behavior and local structure of solutions to the nonlocal variational problem developed in the companion article to this work, On a Model of Nonlocal Continuum Mechanics Part I: Existence and Regularity. After a brief review of the basic setup and results of Part I, we conduct a thorough analysis of the phase plane related to an integro-differential Euler-Lagrange equation and classify all admissible structures that arise as energy minimizing strain states. We find that for highly elastic materials with relatively weak particle-particle interactions, the maximum number of internal phase boundaries is two. Moreover, we also develop an explicit upper bound on the number of internal phase boundaries supported by any material and show that this bound is essentially proportional to the particle size. To understand the question of asymptotics, we utilize the Young measure and show that in the sense of energetics and measure, minimizers of the full nonlocal problem converge to minimizers of two limiting problems corresponding to both the large and small particle limits. In fact, in the small particle limit, we find that the minimizing fields converge, up to a subsequence in strong-L-p, for 1 less than or equal to p < infinity, to fields that support either a single internal phase boundary, or two internal phase boundaries that are distributed symmetrically about the body midpoint. We close this work with some computations that illustrate these asymptotic limits and provide insight into the notion of nonlocal metastability.