7.1.2 3D Load Functions

The Modeler3D load functions are used to specify forces and moments applied to specific bodies in the mechanism model. In general, moments are specified by magnitude and direction, and forces are specified by magnitude and line of action.
By using Modeler3D axis objects to define the line of action of forces, and Modeler3D vector objects to define the direction of moments, a force can be applied to a point attached to any body in the mechanism, and the direction of a force or moment can be a global or local vector, a line from one body to another, or even the normal of a plane. The magnitude of a force or moment applied to a static model can be a constant, or it can be a function of location or velocity-dependent variables or even a function of the reaction forces at particular constraints.

3D load functions.

An option for Force and Moment.

Modeler3D load objects are typically used in a similar manner to Modeler3D constraint objects, they are defined prior to adding them to the model and then passed to SetLoads. Some examples of valid load objects follow.

This loads the Modeler3D package.

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Here is a moment of magnitude 4 and a direction vector in the global Z direction applied to the crank.

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Here is a moment applied to the crank with magnitude equal to twice the rotation angle of the crank, relative to the global reference frame, and direction vector on the local x axis.

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Here is a force applied to the crank passing through point {1, 1, 0} on the crank and pointing in the global X direction, with magnitude equal to k times the distance from the point of application to the global origin.

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The Gravity function needs to know the mass and the location of the centroid of each body to apply the gravitational force. These properties are defined with the Mass and Centroid options for the Modeler3D Body function, and added to the model with SetBodies. See Section 8.1.