Prescribed displacement definition

@PRESCRIBED_DISPLACEMENT_DEFINITION {
@PRESCRIBED_DISPLACEMENT_NAME {PrdName} {
@EDGE_NAME {EdgeName}
@DEGREE_OF_FREEDOM {di}
@FUNCTION_1D_NAME {Fun1DName}
@COMMENTS {CommentText}
}
}

Introduction

The prescribed displacement element is used to prescribed a time dependent motion of a point of the system. If the displacement component of a specific point of the system is to be prescribed to a constant zero value, it is more convenient to apply a boundary condition at that point. The prescribed displacement element is associated with an edge, EdgeName. Vertices Vertex0Name and Vertex1Name are associated with this edge. Find more information about: the representation of multibody systems and the formulation of constraints in multibody systems.

NOTES

  1. The degree of freedom di of vertex Vertex0Name will be prescribed. It is also possible to use the prescribed displacement element to prescribe the relative motion between two bodies connected by a joint.
    • To prescribe the relative displacement between two bodies, the relative displacement element is first used to define the relative displacement, then, the prescribed displacement element is used to prescribe this relative displacement. Figure 1 illustrates the combination of elements: a prismatic joint associated with edge EdgePrj, the corresponding relative displacement element with associated edge EdgePru, and finally the prescribed displacement element with associated edge EdgePrd. The labels v0 and v1 indicate the Vertex0 and Vertex1, respectively, of each edge. Use di = 1 for relative displacements, which can be defined for cylindrical joints, planar joints, or prismatic joints.
    • Figure 1. Prescribing relative displacements and rotations.
    • To prescribe the relative rotation between two bodies, the relative rotation element is first used to define the relative rotation, then, the prescribed displacement element is used to prescribe this relative rotation. Figure 1 illustrates the combination of elements: a revolute joint associated with edge EdgeRvj, the corresponding relative rotation element with associated edge EdgeRvr, and finally the prescribed displacement element with associated edge EdgePrd. The labels v0 and v1 indicate the Vertex0 and Vertex1, respectively, of each edge. Use di = 4 for relative rotations, which can be defined for cylindrical joints, planar joints, revolute joints, or universal joints.
  2. The time history of the degree of freedom will be prescribed by a 1D function, TimFunName.
  3. It is possible to attach comments to the definition of the object; these comments have no effect on its definition.

Sensors

  1. Sensors can be defined to extract information about prescribed displacements. The following SensorType and associated FrameName specifications are allowed for prescribed displacements: DRIVING_FORCE, DRIVING_MOMENT. (Default option: DRIVING_FORCE if 1 ≤ di ≤ 3; DRIVING_MOMENT if 4 ≤ di ≤ 6).
  2. No u value or v value are accepted for prescribed displacements.