This feature assumes a finite deformation domain length in the z direction, as opposed to the infinite value assumed for standard plane strain. It provides a more efficient way to simulate certain 3D deformations using 2D options.

The deformation domain or structure is formed by extruding a plane area along a curve with a constant curvature, as shown below.

The extruding begins at the starting (or reference) plane and stops at the ending plane. The curve direction along the extrusion path is called the fiber direction. The starting and ending planes must be perpendicular to this fiber direction at the beginning and ending intersections. If the boundary conditions and loads in the fiber direction do not change over the course of the curve, and if the starting plane and ending plane remain perpendicular to the fiber direction during deformation, then the amount of deformation of all cross sections will be identical throughout the curve, and will not vary at any curve position in the fiber direction. Therefore, any deformation can be represented by the deformation on the starting plane, and the 3D deformation can be simulated by solving the deformation problem on the starting plane. The Plane Strain and Axisymmetric options are particular cases of the Generalized Plane Strain option.

All inputs and outputs are in the global Cartesian coordinate system. The starting plane must be the x-y plane, and must be meshed. The applied nodal force on the starting plane is the total force along the fiber length. The geometry in the fiber direction is specified by the rotation about the x-axis and y-axis of the ending plane, and the fiber length passing through a user-specified point on the starting plane called the starting or reference point. The starting point creates an ending point on the ending plane through the extrusion process. The boundary conditions and loads in the fiber direction are specified by applying displacements or forces at the ending point.

The fiber length change is positive when the fiber length increases. The sign of the rotation angle or angle change is determined by how the fiber length changes when the coordinates of the ending point change. If the fiber length decreases when the x coordinate of the ending point increases, the rotation angle about y is positive. If the fiber length increases when the y coordinate of the ending point increases, the rotation angle about x is positive.

For Eigenvalue Buckling and Modal analyses, the Generalized Plane Strain option usually reports fewer Eigenvalues and Eigenvectors than you would obtain in a 3D analysis. Because it reports only homogeneous deformation in the fiber direction, generalized plane strain employs only three DOFs to account for these deformations. The same 3D analysis would incorporate many more DOFs in the fiber direction.

Because the mass matrix terms relating to DOFs in the fiber direction are approximated for Modal and Transient analyses, you cannot use the lumped mass matrix for these types of simulations, and the solution may be slightly different from regular 3D simulations when any of the three designated DOFs is not restrained.