Product: ABAQUS/Standard
Extending the master surface or a slide line:
can prevent nodes from “falling off” or getting trapped behind the master surface (or slide line) in finite-sliding problems;
allows the slave node to find a master surface when the slave node has no intersection with the master surface at the start of the analysis in small- and infinitesimal-sliding problems;
can avoid numerical roundoff difficulties associated with contact modeling;
should not be used in lieu of proper contact modeling techniques; and
should not be used to reduce the number of underlying elements of a contact surface.
If a slave node cannot find an intersection with the master surface at the start of the analysis, it will be free to penetrate the master surface because no local tangent plane will be formed. This type of problem, which typically occurs when the slave node is aligned with the edge of the master surface, is illustrated in Figure 21.2.6–1 and may be caused by numerical roundoff errors when a preprocessor is used to generate the nodal coordinates.
Figure 21.2.6–1 Slave node fails to find an intersection with the master surface for small-sliding contact if 
=
.
You can specify the size of the extension zone, , as a fraction of the end segment or facet edge length (see Figure 21.2.6–2). If is set to zero, ABAQUS will not extend the ends. The value given must lie between 0.0 and 0.2. The default value is 0.1.
| Input File Usage: | *CONTACT PAIR, SMALL SLIDING, EXTENSION ZONE= |
To prevent nodes from “falling off” or getting trapped behind the master surface, an open surface or slide line can be extended.
You can specify the size of the extension zone, , as a fraction of the end segment or facet edge length (see Figure 21.2.6–2). The geometry in the extension zone is extrapolated from the end segment or facet edge. If is set to zero, ABAQUS/Standard will not extend the ends. The value given must lie between 0.0 and 0.2. The default value is 0.1. Extensions should be considered only if other modeling techniques to prevent “falling off” are not feasible and when the slave node is expected to travel in the extended zone for a short period of the solution phase or during nonconverged iterations.
| Input File Usage: | Use either of the following options: |
*CONTACT PAIR, EXTENSION ZONE= |
