What do single-headed and double-headed arrows represent?

In many cases Abaqus/CAE uses arrows to represent prescribed conditions in the viewport. These arrows represent each component of the prescribed condition (except for fluid boundary conditions, in which case the arrows represent the resultant direction). For example, the arrows that appear in Figure 1 represent the three components of a concentrated force that is applied to two vertices.

See Also
Understanding symbols that represent prescribed conditions
Controlling the display of attributes
Figure 1. A concentrated force with three components.

An arrow with a single arrowhead represents a component of a prescribed condition that is applied to a translational degree of freedom. For example, the three components of the concentrated force in Figure 1 are applied to degrees of freedom 1 through 3; therefore, each arrow in the figure has a single arrowhead.

When a component of a prescribed condition is applied to a rotational degree of freedom, that component appears as a double-headed arrow. The arrows in Figure 2 indicate that a Velocity/Angular Velocity boundary condition is applied to degrees of freedom 4 and 6 of the vertices.

Figure 2. A boundary condition applied to rotational degrees of freedom.

A magnified view of the double-headed arrows appears in Figure 3.

Figure 3. Magnified double-headed arrows.

If you apply a prescribed condition to both translational and rotational degrees of freedom, both the single-headed and the double-headed arrows appear. For example, a Velocity/Angular Velocity boundary condition is applied to degrees of freedom 1, 3, 4, and 6 of the vertex in Figure 4.

Figure 4. Magnified view of a boundary condition applied to translational and rotational degrees of freedom.

In this figure the single-headed arrows are sandy brown and indicate that degrees of freedom 1 and 3 of the vertex are fixed.The double-headed arrows are magenta and appear directly behind the single-headed arrows; the double-headed arrows indicate that degrees of freedom 4 and 6 of the vertex are fixed.

For information on arrow color, see Understanding prescribed condition symbol type, color, and size. For information on when to expect arrows to point toward or away from a region, see Understanding symbol location and direction.