Modeling Wires and Cables
Wires are thin one-dimensional structures with no bending stiffness. Ideal wires can only sustain tensile axial forces. Typically, wires act in a prestressed state. It is however also possible to model for example wires that are sagging under self-weight.
The wire elements have displacements as degrees of freedom and live on boundaries in 2D and edges in 3D. Typical uses of the wire elements are:
•
Prestressed cables.
•
Drive belts.
•
Cables that hang free, subjected to for example gravity.
The Wire interface supports the same study types as the Solid Mechanics interface.
Dependent Variables
The degrees of freedom (dependent variables) are the global displacements
u
,
v
, and
w
(3D only) in the global
x
,
y
, and
z
directions, respectively.
Modeling Wires and Cables
You use the Wire interface for modeling wires and cables, possibly sagging under gravity or other external loads. Below are some suggestions for how to model such structures efficiently:
•
Most cable problems are geometrically nonlinear. The Wire interface will force any study to be geometrically nonlinear. A wire which is not in tension is not numerically stable. Physically, it wrinkles in an unpredictable manner. In order to start the analysis, you either have to add an initial stress or some weak springs.
•
If there are no line or volume loads, the wire is straight. In this case, only one element is needed for the whole wire, since the force is constant.
•
In some problems, there are large deformations, but low tensile stresses. This would for example be the case if you model a wire hanging free under self-weight (‘the catenary problem’). Such problems are numerically ill-conditioned. They can be solved, but you may have to use tight tolerances for the nonlinear solver and allow many iterations.