Eshelbian mechanics of novel materials: Quasicrystals

In this work, the so-called Eshelbian or configurational mechanics of quasicrystals is presented. Quasicrystals are considered as a prototype of novel materials. Material balance laws for quasicrystalline materials with dislocations are derived in the framework of generalized incompatible elasticity theory of quasicrystals. Translations, scaling transformations as well as rotations are examined; the latter presents particular interest due to the quasicrystalline structure. This derivation provides important quantities of the Eshelbian mechanics, as the Eshelby stress tensor, the scaling flux vector, the angular momentum tensor, the configurational forces (Peach–Koehler force, Cherepanov force, inhomogeneity force or Eshelby force), the configurational work, and the configurational vector moments for dislocations in quasicrystals. The corresponding [Formula: see text]-, [Formula: see text]-, and [Formula: see text]-integrals for dislocation loops and straight dislocations in quasicrystals are derived and discussed. Moreover, the explicit formulas of the [Formula: see text]-, [Formula: see text]-, and [Formula: see text]-integrals for parallel screw dislocations in one-dimensional hexagonal quasicrystals are obtained. Through this derivation, the physical interpretation of the [Formula: see text]-, [Formula: see text]-, and [Formula: see text]-integrals for dislocations in quasicrystals is revealed and their connection to the Peach–Koehler force, the interaction energy and the rotational vector moment (torque) of dislocations in quasicrystals is established.

A Reciprocity Relation Couples Newtonian and Eshelbian Mechanics

By considering a stressed elastic body subjected sequentially to a material displacement of a defect and the application of a physical force, the authors have succeeded in arriving at a novel type of coupling of Newtonian and Eshelbian mechanics by means of a reciprocity theorem analogous to that of Maxwell. This reciprocity relation is more involved than those in strictly physical or strictly material space. An order of magnitude analysis was required to obtain consistent relations. Several illustrative examples are worked out, and suggestions for some experiments, which in their evaluations would make use of the new expressions, are offered.

Material Forces: Concepts and Applications

The unifying notion of material force which gathers under one vision all types of driving “forces” on defects and smooth or abrupt inhomogeneities in fracture, defect mechanics, elastodynamics (localized solutions) and allied theories such as in electroelasticity, magnetoelasticity, and the propagation of phase transition fronts, is reviewed together with its many faceted applications. The presentation clearly distinguishes between the role played by local physical balance laws in the solution of boundary-value problems and that played by global material balance laws in obtaining the expression of relevant material forces and devising criteria of progress for defects, in a general way. The advances made along this line, which may be referred to as Eshelbian mechanics, are assessed and perpectives are drawn.