Plane Stress
For two-dimensional problems, there are tree possible approximations:
Plane Strain
,
Generalized Plane Strain
, and
plane stress
. The selection is made in the settings for the Solid Mechanics node.
In the plane stress formulation in COMSOL Multiphysics, the plane stress conditions
(3-12)
are not enforced through a modified constitutive relation, as is common in many textbooks. Instead, an extra set of degrees of freedom for the out-of-plane strains are introduced, and
Equation 3-12
is enforced by solving for the strains.
For a general anisotropic linear elastic material in case of plane stress, COMSOL Multiphysics solves three equations. For isotropy and orthotropy, only one extra degree of freedom is needed since the out-of-plane shear components of the stress tensor are zero.
•
For isotropic and orthotropic materials, the extra degree of freedom is named
wZ
, and represents
∂
w
/∂
Z
.
•
For anisotropic materials in 3D or 2D, two more degrees of freedom area added,
uZ
and
vZ
. They represent
∂
u
/∂
Z
and
∂
v
/∂
Z
.
