ProductsAbaqus/Standard ConventionsCoordinate 1 is r, coordinate 2 is z. Referring to the figures shown in Choosing the element's dimensionality, the r-direction corresponds to the global X-direction in the plane and the negative global Z-direction in the plane, and the z-direction corresponds to the global Y-direction. Coordinate 1 must be greater than or equal to zero. Degree of freedom 1 is , degree of freedom 2 is . The degree of freedom is an internal variable: you cannot control it. Element typesStress/displacement elements
Active degrees of freedom1, 2 Additional solution variablesThe bilinear elements have 4N and the biquadratic elements 8N additional variables relating to . Element types CAXA4HN and CAXA4RHN have additional variables relating to the pressure stress. Element types CAXA8HN and CAXA8RHN have additional variables relating to the pressure stress. Pore pressure elements
Active degrees of freedom1, 2, 8 at corner nodes 1, 2 at midside nodes Additional solution variables8N additional variables relating to . Nodal coordinates requiredr, z Element property definitionInput File Usage SOLID SECTION Element-based loadingEven though the symmetry in the r–z plane at 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 CAXA element with 4 modes, the nodal forces are 1/8, 1/4, 1/4, 1/4, and 1/8 at , , , , and , respectively. Distributed loadsDistributed loads are specified as described in Distributed loads. *dload
FoundationsFoundations are specified as described in Element foundations. *foundation
Distributed flowsDistributed flows are available for elements with pore pressure degrees of freedom. They are specified as described in Coupled pore fluid diffusion and stress analysis. *flow/ *dflow
Element outputThe numerical integration with respect to employs the trapezoidal rule. There are equally spaced integration planes in the element, including the and planes, with N being the number of Fourier modes. Consequently, the radial nodal forces corresponding to pressure loads applied in the circumferential direction are distributed in this direction in the ratio of in the 1 Fourier mode element, in the 2 Fourier mode element, and in the 4 Fourier mode element. The sum of these consistent nodal forces is equal to the integral of the applied pressure over . Output is as defined below unless a local coordinate system in the r–z plane is assigned to the element through the section definition (Orientations) in which case the components are in the local directions. These local directions rotate with the motion in large-displacement analysis. See State storage for details. Stress, strain, and other tensor componentsStress and other tensors (including strain tensors) are available for elements with displacement degrees of freedom. All tensors have the same components. For example, the stress components are as follows:
Node ordering and face numbering on elementsThe node ordering in the first r–z
plane of each element, at ,
is shown below. Each element must have N more planes
of nodes defined, where N is the number of Fourier
modes. The node ordering is the same in each plane. You can specify the nodes
in each plane. Alternatively, you can specify the node ordering in the first
r–z plane of an element, and
Abaqus/Standard
will generate all other nodes for the element by adding successively a constant
offset to each node for each of the N planes of the
element. By default,
Abaqus/Standard
uses an offset of 100000 (see
Element definition).
Numbering of integration points for outputThe integration points in the first
r–z plane of integration, at
,
are shown below. The integration points follow in sequence at the
r–z integration planes in ascending
order of
location.
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