Since force entities do not add or remove Degrees of Freedom (DOFs) from a model, they do not prohibit or prescribe motion. They may be used to resist motion, such as in a spring-damper system, or induce motion such as with gravity. Force entities can therefore be classified as connecting forces or actuating forces as follows.
Connecting forces on pair bodies
These forces are always applied between two bodies and you need compliance characteristics to calculate them.
Figure 6.1: List of connecting forces
| Type | Description |
| Spring | Use to represent a single-component relative force acting between two bodies over a distance and in a particular direction. |
| Rotational Spring | Use to represent a single-component relative torque acting between two bodies in a specified direction. |
| Bushing | Use to represent a six-component relative force vector acting between two bodies. A diagonal stiffness matrix is required to calculate the force. |
| Matrix | Use to a represent six-component relative force vector acting between two bodies. A 6-by-6 stiffness matrix is required to calculate the force. |
| Tire | Use to represent a six-component force vector acting between two bodies. RDF and TPF are required to calculate the force. |
| Motor EM Force | Use to represent a five-component relative force vector acting between two bodies. |
Actuating forces on pair bodies or single body
These forces are applied between bodies or on single body without a reaction force. The force is defined by a Function Expression or User Subroutine.
Figure 6.2: List of actuating forces
| Type | Description |
| Translational Scalar | Use to represent a single-component force acting between two bodies or action bodies in a particular direction. |
| Rotational Scalar | Use to represent a single-component torque acting between two bodies or action bodies in a specified direction. |
| Vector | Use to represent a six-component force vector acting between two bodies. |
| Concentrated Load | Use to represent a six-component force vector acting on nodes. |
| Pressure Load | Use to represent a single-component pressure acting on surfaces. |
Body forces
These forces are always applied on single body without a reaction force.
Figure 6.3: List of body forces
| Type | Description |
| Gravity | Use to represent the three-component acceleration of gravity. |