About Loads

In the context of a dynamic simulation, you can apply loads to a body using the following elements:

• Force: a translational load applied to a specific point and in a single direction across a body.
• Torque: a twisting or rotational load applied to a specific point and in a single direction across a body.

To define a force or a torque, specify an application point, a direction, and a magnitude. The application point is a marker from a body on which external forces apply.

To define the direction of the force, you can select one of the following reference systems:

• Global reference system
• Application point
• Reaction point

The global coordinate system corresponds to the system of the global frame of reference. If you use a local coordinate system, that is the reference system of the application point or reaction point, the direction of the force follows the motion of the body including the application point or reaction point.

The application point is a marker from a body on which external forces apply.

You can also define a reaction force or reaction torque, that is a marker on which supporting reaction forces or torques apply according to Newton's third law.

The reaction force or torque applies to a marker located on a different body than the one including the application point of the force or torque. As a result, you obtain a moment between the two products.

A force or torque with no reaction point corresponds to a load applied from an external source, such as the force of the air resistance on a moving object.

Based on the principle of moments (Varignon's theorem), you can use the moment of a force defined at a specific point to determine the moment of the force at another point.

For example, if point A is the application point of the $\stackrel{\rightharpoonup }{R}$ force, you can determine the moment of the $\stackrel{\rightharpoonup }{R}$ force at the B point. To do so, the following cross product is used: $\stackrel{\rightharpoonup }{m}\left(A\right)=\stackrel{\rightharpoonup }{m}\left(B\right)+\stackrel{\rightharpoonup }{AB}\times \stackrel{\rightharpoonup }{R}$ where:

• $\stackrel{\rightharpoonup }{m}\left(A\right)$ is the moment of the force at point A.
• $\stackrel{\rightharpoonup }{m}\left(B\right)$ is the moment of the force at point B.
• $\stackrel{\rightharpoonup }{AB}\times \stackrel{\rightharpoonup }{R}$ is the cross product corresponding to the $\stackrel{\rightharpoonup }{R}$ force applied on point B and according to point A.

For a torque, you can also apply a reaction torque to the element. The value of the reaction torque does not depend on the selected application point, as it opposes the applied torque.

You can define a force either by specifying constant values along the x, y, and z-axes, or by selecting time-dependent functions. Forces are defined in newton (N) and torques in newton-meters (Nm).

Following the definition of applied forces and torques, run the analysis case of the active mechanism. The app computes the dynamic simulation of the mechanism and generates the results of the applied loads in the tree.

You can display and plot the results of the computed forces and torques. For more information, see Displaying Solver Messages and Using a 2D Plot.