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Remote Displacement

The Remote displacement boundary condition is used to guide the displacement of a face or edge of a structure from a remote point. This provides several advantages compared to the classical displacement boundary condition such as:

  • A deformation behavior can be added to the assigned entity.
  • A rotation condition can be applied to an edge or a face of a structure.

There are also some limitations. The fact that this is a linear boundary condition, it is valid only if small displacements and rotations occur in the area of the applied entity and the remote point itself.

The settings for Remote displacement boundary condition, in the Workbench, are described below:

remote displacement boundary condition panel
Figure 1: Remote displacement boundary condition parameters panel in the SimScale Workbench

Displacement

For each of the translational directions, the user defines if the displacement should either be unconstrained or predefined. Each predefined value can either be defined, in meters or inches, by a scalar value, a function, or a table. For function or table data the value may depend on time (or frequency in case of harmonic analysis) or the spatial coordinates.

Rotation

For each rotational direction, the rotation can either be predefined or unconstrained. In the case of a predefined rotation, the value is given in radians or degrees. The input methods and possible dependencies are same as for displacement.

External Point

Here the user defines the coordinates of the external point on which the displacement is applied. The coordinates are given in the global coordinate system of the domain.

The following figure illustrates a structural model with a remote displacement condition at the bottom face, and the associated displacement and rotation degrees of freedom of the remote point, located at the centroid of the face.

Degrees of freedom for the point at the centroid of the bottom face
Figure 2: Illustration of translation and rotation degrees of freedom on the remote point

Deformation Behavior

This property defines if the assigned entities (edges or faces) may deform or if they are assumed to be rigid.

When set to Deformable, no additional stiffness is generated on the applied entities. The remote point is connected to the entities by an RBE3-constraint.

When set to Undeformable, the entity behaves like a rigid part. The connection of the point and the entities is a multi-point constraint which blocks all relative displacements between the affected nodes.

remote displacement boundary condition deformable versus undeformable behavior
Figure 3: Comparison of undeformable (left) vs. deformable (right) behavior. Deformation can be observed through skewed lines.

Hint

If the deformable option is used and the number of nodes on the assigned entities is large (>1000), it is advised to use either the MUMPS or PETSC solver instead of Multfront since the performance of Multfront is not optimal for this kind of equations.

Example

As an example, let’s compare the resulting deformation and stress on a strip under bending condition. Fixed value (Figures 4 and 5) and remote displacement (Figures 6 and 7) boundary conditions are applied on a square of 0.1 \(m\) width at the center of the strip (overall dimensions are 1 \(m\) * 0.1 \(m\) * 0.01\(m\)):

Contours for fixed value von Mises stress
Figure 4: Von Mises stress contour plot on the deformed shape with a fixed value displacement boundary condition of 0.05m.
Contours for fixed value displacement
Figure 5: Total displacement contour plot on the deformed shape with a fixed value displacement boundary condition of 0.05m.
Contours for Remote displacement von Mises stress
Figure 6: Von Mises stress contour plot on the deformed shape with a remote displacement boundary condition of 0.05 m.
Contours for remote displacement total displacement
Figure 7: Total displacement contour plot on the deformed shape with a remote displacement boundary condition of 0.05 m.

Last updated: October 12th, 2020


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