THE ENERGY OF A GROWING ELASTIC SURFACE

The potential energy of the elastic surface of an elastic body which i s growing by the coherent addition of material is derived. Several equ ivalent expressions are presented for the energy required to add a sin gle atom, also known as the chemical potential. The simplest involves the Eshelby stress tensors for the bulk medium and for the surface. Du al Lagrangian/Eulerian expressions are obtained which are formally sim ilar to each other. The analysis employs two distinct types of variati ons to derive the governing bulk and surface equations for an accretin g elastic solid. The total energy of the system is assumed to comprise bulk and surface energies, while the presence of an external medium c an be taken into account through an applied surface forcing. A detaile d account is given of the various formulations possible in material an d current coordinates, using four types of bulk and surface stresses: the Piola-Kirchhoff stress, the Cauchy stress, the Eshelby stress and a fourth, called the nominal energy-momentum stress. It is shown that inhomogeneity surface forces arise naturally if the surface energy den sity is allowed to be position dependent. (C) 1998 Elsevier Science Lt d. All rights reserved.