3-D Infinite
Boundary
INFIN47 Element Description
| Although this legacy element is available for use in your analysis, ANSYS, Inc. recommends using a current-technology element such as INFIN111. |
INFIN47 is used to model an open boundary of a 3-D unbounded field problem. The element may be a 4-node quadrilateral or a 3-node triangle with a magnetic potential or temperature degree of freedom at each node. The enveloped (or enclosed) element types may be the SOLID5, SOLID96, or SOLID98 magnetic elements or the SOLID70, SOLID90 or SOLID87 thermal solid elements. With the magnetic degree of freedom the analysis may be linear or nonlinear static. With the thermal degree of freedom steady-state or transient analyses (linear or nonlinear) may be done. See INFIN47 in the Mechanical APDL Theory Reference for more details about this element.
INFIN47 Input Data
The geometry, node locations, and the coordinate system for this element are shown in Figure 47.1: INFIN47 Geometry. The element is defined by 4 nodes, and the material properties. Nonzero material properties must be defined. A triangular element may be formed by defining duplicate K and L node numbers as described in Degenerated Shape Elements. The element x-axis is parallel to the I-J side of the element.
The coefficient matrix of this boundary element is, in general, unsymmetric. The matrix is made symmetric by averaging the off-diagonal terms to take advantage of a symmetric solution with a slight decrease in accuracy. KEYOPT(2) can be used to keep an unsymmetric matrix from being made symmetric.
A summary of the element input is given in "INFIN47 Input Summary". A general description of element input is given in Element Input.
INFIN47 Input Summary
- Nodes
I, J, K, L
- Degrees of Freedom
MAG if KEYOPT(1) = 0 TEMP if KEYOPT(1) = 1 - Real Constants
None
- Material Properties
EMUNIT command: MUZERO if KEYOPT (1) = 0 (has default value for MKS units or can be set manually), KXX if KEYOPT(1) = 1 - Surface Loads
None
- Body Loads
None
- Element Printout
None
- Special Features
None
- KEYOPT(1)
Element degree(s) of freedom:
- 0 --
Magnetic option
- 1 --
Thermal option
- KEYOPT(2)
Coefficient matrix:
- 0 --
Make the coefficient matrix symmetric
- 1 --
Coefficient matrix is used as generated (symmetric or unsymmetric, depending on the problem)
INFIN47 Output Data
The boundary element has no output of its own since it is used only to provide a semi-infinite boundary condition to a model consisting of other elements.
INFIN47 Assumptions and Restrictions
The 4 nodes defining the element should lie as close as possible to a flat plane; however, a moderate out-of-plane tolerance is permitted so that the element may have a somewhat warped shape.
An excessively warped element will produce a warning message. In the case of warping errors, triangular elements should be used (see Degenerated Shape Elements).
Shell element warping is described in detail in Warping Factor in Mechanical APDL Theory Reference.
Zero area elements are not allowed.
The semi-infinite volume is assumed to be bound on five sides (four, if triangular) by the boundary element and by four semi-infinite radial surfaces (three, if triangular) defined from the global coordinate system origin through nodes I and J, J and K, K and L, and L and I (nodes I and J, J and K, and K and I if triangular).
The boundary element should be as normal as possible to the radial surfaces.
Acute or wide intersection angles should be avoided by "filling-in" the model with the other elements so that the line of boundary elements around the model is smooth and concave when viewed from the global coordinate system origin.
The element assumes that the degree of freedom (DOF) value at infinity is always zero (0.0). That is, the DOF value at infinity is not affected by TUNIF, D, or other load commands.
The boundary element must lie "against" an enclosed element (that is, share the same nodes).
The exterior semi-infinite domain is assumed to be homogeneous, isotropic, and linear without containing any sources or sinks.
The origin of the global coordinate system must be inside the model and as centrally located as possible.
The surface of boundary elements should be located away from the region of interest of the enclosed elements for better accuracy. The surface of boundary elements need not totally surround the model.
The element may not be deactivated with the EKILL command.
When used in a model with higher order elements SOLID90, SOLID87, and SOLID98, the midside nodes of these elements must be removed at the interface with INFIN47 [EMID].
If KEYOPT(2) = 1, the matrices are presumed to be unsymmetric.