The Straight Edge Constraint controls the addition of an additional constraint, forcing the edge to be straight. The default is to add this constraint to all edges unless linear shape functions have been chosen in the
Discretization section of the interface. Using this additional constraint removes the need to use a mesh with only one element per edge. Internal nodes make the model singular because the truss element only has stiffness in the axial direction in a geometrically linear analysis. The same problem appears when using higher-order shape functions, even if there is only one element along an edge since there are internal nodes.
The additional constraints increase the solution time, especially for large 3D and transient problems. The default mesh, when using Physics-controlled mesh in the
Mesh node, is to use one element per edge only, so that the extra constraints are not needed unless the shape functions are of higher order.
Select a Automatic,
On, or
Off. The
Automatic option adds the straight edge constraints on the selected edges except when linear shape functions are applied to a single mesh element per edge. This is the default setting.
Select Off to always disable the straight edge constraints.
The Straight Edge Constraint is not applicable to edges that are embedded in a solid domain through the
Embedded Reinforcement multiphysics coupling.
