# Axisymmetric shell elements with nonlinear, asymmetric deformation

 This section provides a reference to the axisymmetric shell elements with nonlinear, asymmetric deformation available in Abaqus/Standard. For an axisymmetric reference geometry where axisymmetric deformation is expected, use regular axisymmetric elements (see Axisymmetric shell element library). For an axisymmetric reference geometry where nonaxisymmetric deformation is expected and the thickness to characteristic radius is high or through the thickness detail is required, use CAXA-type elements (see Axisymmetric solid elements with nonlinear, asymmetric deformation).
 Related Topics About shell elements Choosing a shell element In Other Guides *NODAL THICKNESS *SHELL GENERAL SECTION *SHELL SECTION

ProductsAbaqus/Standard

## Conventions

Coordinate 1 is r, coordinate 2 is z. The r-direction corresponds to the global X-direction in the $θ=0∘$ plane and the global Y-direction in the $θ=90∘$ plane, and the z-direction corresponds to the global Z-direction. Coordinate 1 should be greater than or equal to zero.

Degree of freedom 1 is $ur$, degree of freedom 2 is $uz$, degree of freedom 6 is rotation in the rz plane.

Even though the symmetry in the rz plane at $θ=0,π$ allows the modeling of half of the initially axisymmetric structure, the loading must be specified as the total load on the full axisymmetric body. Consider, for example, a cylindrical shell loaded by a unit uniform axial force. To produce a unit load on a SAXA element with four modes, the nodal forces are 1/8, 1/4, 1/4, 1/4, and 1/8 at $θ=0$, $π/4$, $π/2$, $3⁢π/4$, and $π$, respectively.

The meridional direction is the direction tangent to the element in the rz plane; that is, the meridional direction is along the line that is rotated about the axis of symmetry to generate the full three-dimensional body.

The circumferential or hoop direction is the direction normal to the rz plane.