CABLE280 Element Description

CABLE280 is suitable for analyzing moderate to extremely slender cable structures (such as undersea cables). The element is a quadratic three-node line element in 3D space. Each node has three degrees of freedom: translations in the nodal x, y, and z directions.

Elasticity, isotropic hardening plasticity, kinematic hardening plasticity, Hill anisotropic plasticity, Chaboche nonlinear hardening plasticity, and creep are supported. Added mass, damping, compressive stiffness scaling, viscous regularization, and initial state are available.

For more information about this element, see CABLE280 - 3D 3-Node Cable in the Theory Reference.

Figure 280.1: CABLE280 Geometry

CABLE280 Input Data

The geometry, node locations, and coordinate system for this element are shown in Figure 280.1: CABLE280 Geometry. The element is defined by nodes I, J, and K in the global coordinate system.

Section orientation (the y-z local coordinate plane) is required only for defining distributed loads. Node L is the preferred way to define the section orientation of the element. Defining cable elements with orientation nodes is the same as for beam elements. For information about generating node L automatically, see LMESH and LATT.

The element can also be defined without the orientation node L. In this case, the element x axis is oriented from node I (end 1) toward node J (end 2). Without node L, the default orientation of the element y axis is parallel to the global X-Y plane.

If the element is parallel to the global Z axis (or within a 0.01 percent slope of it), the element y axis is oriented parallel to the global Y axis (as shown). To control the element orientation about the element x axis, use node L. If both are defined, node L takes precedence. If used, node L defines a plane (with I and J) containing the element x and z axes (as shown).

If using this element in a large-deflection analysis, the location of node L serves only to orient the element initially.

By default, the element allows the cross-sectional area to change as a function of axial elongation; therefore, the volume of the element is preserved even after deformation. The default behavior is suitable for elastoplastic applications. (You can also maintain a constant or rigid cross-section via KEYOPT(2) = 1.)

CABLE280 is a 1D line element in space. It can be associated with a link section. The cross-section details are defined separately (SECTYPE and SECDATA). A section is associated with the cable element via the section ID number (SECNUM).

Element loads are described in Element Loading. Temperatures can be input as element body loads at the nodes. The node I temperature T(I) defaults to TUNIF. The node J temperature T(J) defaults to T(I).

The element ignores real constant data.

Damping

The damping portion of the element contributes only damping coefficients to the structural damping matrix. The damping force  is given by:

where is the damping coefficient given by , where is the velocity calculated in the previous substep.

The second damping coefficient is available to produce a nonlinear damping effect characteristic of some fluid environments. The damping coefficient units are Force * Time / Length.

Input damping coefficients via SECCONTROL,,,CV1,CV2.

Viscous Regularization

The element uses viscous regularization to overcome convergence difficulties which may arise when a cable switches from tension to compression (or vice versa). Viscous regularization of stiffness is given by:

where is the stiffness before viscous regularization, is the stiffness after viscous regularization, and is the viscous regularization factor (SECCONTROL,,,,,,CV4). The default viscous regularization factor is 0.05.

CABLE280 Output Data

The solution output associated with the element is in two forms:

A general description of solution output is given in Solution Output. Element results can be viewed in POST1 via PRESOL,ELEM.

The Element Output Definitions table uses the following notation:

A colon (:) in the Name column indicates that the item can be accessed by the Component Name method (ETABLE, ESOL). The O column indicates the availability of the items in the file jobname.out. The R column indicates the availability of the items in the results file.

In either the O or R columns, Y indicates that the item is always available, a number refers to a table footnote that describes when the item is conditionally available, and - indicates that the item is not available.

Table 280.2: CABLE280 Item and Sequence Numbers lists output available through ETABLE using the Sequence Number method. See The General Postprocessor (POST1) and The Item and Sequence Number Table in this reference for more information. The following notation is used in Table 280.2: CABLE280 Item and Sequence Numbers:

CABLE280 Assumptions and Restrictions

CABLE280 Product Restrictions

When used in the product(s) listed below, the stated product-specific restrictions apply to this element in addition to the general assumptions and restrictions given in the previous section.

Ansys Mechanical Pro  —  

Ansys Mechanical Premium  —