General formulations of the Toupin-Mindlin strain gradient theory in orthogonal curvilinear coordinate systems are derived and then described for the situations of cylindrical and spherical coordinates. In both coordinate systems, expressions for the relevant equilibrium equations, boundary conditions, and physical components for strains and strain gradients are supplied.
Ravichandran Shanmugam Can you share the link with me? I am seeking stress-strain relations in the non-orthogonal system in terms of covariant and contravariant components of the metric tensor.