Kinematics
ε_xx = ∂u_x/∂x; ε_zz = ∂u_z/∂z; γ_xz = ∂u_x/∂z + ∂u_z/∂x.
Plane strain sets ε_yy = γ_xy = γ_yz = 0 for a section that is invariant and constrained in its out-of-plane direction. This does not imply σ_yy = 0; that is a different idealization, plane stress.
Constitutive response and equilibrium
σ = C(ε − ε*); ∂σ_xx/∂x + ∂τ_xz/∂z = 0; ∂τ_xz/∂x + ∂σ_zz/∂z = 0.
Transform orthotropic ply properties into the section coordinates. Thermal, moisture or cure free strain ε* enters only when the selected analysis supports that mechanism. Consistent stress continuity and interface assumptions determine how layers transfer load.
Boundaries and limitations
Prescribe displacement u or traction t = σ n on each boundary.
Restrain rigid-body motion without adding unintended constraints. Refine the section mesh and check reaction equilibrium. Elastic stress concentrations near ideal corners or point loads are mesh sensitive and are not measured failure strengths. Delamination requires an explicit interface law; ply stress alone does not supply it.
These explanations describe general mechanics and transport principles. Follow the selected Workbench model’s supported mechanisms, calibration and limitations.