Axisymmetric modeling greatly reduces modeling and analysis time when compared to equivalent 3D modeling. In some cases, however, certain components of the model may be nonaxisymmetric, or the geometry may be axisymmetric but loading is nonaxisymmetric.
General axisymmetric elements offer much more utility than standard harmonic axisymmetric elements. For example, the elements:
Introduce the Fourier series into interpolation functions to describe the change of displacements in the circumferential (θ) direction. (The elements can therefore apply to any analysis type, including geometric nonlinear analyses, and can support any load and deformation mode.)
Can have any axis as the axisymmetric axis.
Do not require the input of peak loads and multiple load steps for each Fourier term. (Loads can therefore be applied anywhere in 3D space and only one solve operation is required to obtain the solution.)
With general axisymmetric elements, it is necessary only to define base elements (quadrilaterals or triangles) on a master plane. (See General Axisymmetric Element Terminology.) The program generates a 3D mesh (based on a 2D mesh) on the master plane, after which boundary conditions and loading can be applied at nodes in 3D space.
For more information, see the following resources: