The stress tensor describes the traction across oriented surfaces in a continuum. In the convention used here, a unit normal 
gives traction 
. For linear isotropic elasticity with displacement 
, its constitutive relation is
 |
where 
is the infinitesimal strain tensor and 
are the Lamé coefficients. In the absence of
a body force, static equilibrium requires 
. Boundary displacement-to-traction
data define the Dirichlet-to-Neumann
operator of this system.
