Boundaries (Structural)
In structural analyses, boundaries are used to represent areas where the model is supported and therefore constrained against motion in one or more directions. The words "support" and "constraint" are frequently used interchangeably.
The following three types of supports are available in Mechanical – Structural analyses. Click the links for more information on each type:
Solid elements only have translational degrees of freedom (DOF). Individual nodes along a constrained face are prevented from translating in the X, Y, or Z direction but are free to rotate. However, applying a support to a face also indirectly prevents rotation in one or more directions. The reason is that the face cannot rotate without its nodes translating in the X, Y, and/or Z direction.
General Usage Notes Common to all Boundaries
- You can include different boundary types on different faces to best represent the behavior of the structure being modeled. For example, you could have a fixed support on one face, cylindrical supports on other faces (with various radial, tangential, or axial fixity), and a frictionless support on yet another face.
- The goal is to make the model statically stable (that is, to prevent rigid body motion in all three global directions. At the same time, you have to be careful not to overconstrain the model, reducing the accuracy of the stress and deformation results. Be aware that a face with a fixed support assigned to it will not be free to expand or contract when the temperature increases or decreases. This effect causes the stress results at the face to be exaggerated.
- While you are permitted to combine two or more boundary types on the same face, there are currently no supports for which it would make sense to do so.
- Any of the available boundary types can be included in the definition of a 3D component.