THE FRANK TENSOR AS A BOUNDARY CONDITION IN INTRINSIC LINEARIZED ELASTICITY

The Frank tensor plays a crucial role in linear elasticity, and in particular in the presence of dislocation lines, since its curl is exactly the elastic strain incompatibility. Further, the Frank tensor also appears in Cesaro decomposition, and in Volterra theory of dislocations and disclinations, since its jump is the Frank vector around the defect line. The purpose of this paper is to show to which functional space the compatible strain e belongs in order to imply a homogeneous boundary conditions for the induced displacement field on a portion Gamma(0) of the boundary. This will allow one to define the homogeneous, or even the mixed problem of linearized elasticity in a variational setting involving the strain e in place of displacement u. With other purposes, this problem was originaly treated by Ph. Ciarlet and C. Mardare, and termed the intrinsic formulation. In this paper we propose alternative conditions on e expressed in terms of e and the Frank tensor Curl(t) e only, yielding a clear physical understanding and showing as equivalent to Ciarlet-Mardare boundary condition.