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AutoFEM Analysis Requirements for 3D Model |  |
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AutoFEM Analysis Requirements for 3D Model | |
The quality and possibility of constructing a finite element mesh is strongly dependent on the quality of volume models, so when building 3D models imposed more stringent requirements than conventional modelling in AutoCAD. You should consider the following requirements to create three-dimensional models of your products in terms of the finite element analysis.
•Mutual or self-intersection bodies are not allowed. It is impossible to construct a finite element mesh for intersecting bodies. Before you create a study you always should test your model on the intersections by special AutoCAD command INTERFERE. This command shows intersections between bodies if they are. One advice is how intersections may be removed from the assembly if intersecting bodies consist of the same material. You can use the command of AutoCAD: UNION and unite intersecting bodies in a whole body.
Original 3D model of a pump in AutoCAD. |
Using the AutoCAD's command INTERFERE for checking the model. There are lots of intersections. Creating a finite element study impossible. |
Correct 3D model has no intersections between its parts. The finite element mesh may be constructed.
•Between the bodies must be no gap, except when there are no actual gaps between the bodies. All bodies, which are included in a study, must have a contact by a face, or edge, or vertex, with any other body of the study. So in the study, a totally unengaged body should not exist as it is like freely “hovering” in space.
Model with gap between its parts. Mesh may be constructed in some cases, but calculation can be incorrect or impossible.
•3D body should be closed volume. Finite element mesh can be constructed only for a limited volume.
•In AutoCAD one can create a solid 3D model which consists of multiple separate volumes. For instance if you have extruded multiple profile (see at the picture). Meshing of the such 3D body is impossible. So the 3D solid which consists of multiple separate volumes is not allowed in the FEA study. If you have such 3D solid you need use the AutoCAD's command SOLIDEDIT|SEPARATE before creating the FEA study to separate the single solid on multiple independent volumes.
The 3D solid consists of multiple volumes. That solid after using SOLIDEDIT|SEPARATE command.
•It is recommended to avoid to do rounding, chamfering, holes and decorative elements, which are not important for the strength of design. They can complicate the construction of the finite element grid and increase the dimension of the problem (time to find a solution). But items which are bearing influence on strength of design, e.g., fillets, ribs, etc., must be present in the model.
•The bodies, united in a block are treated as one solid body which is obtained using a Boolean union of all bodies in the block. The bodies in the block may intersect with each other. No gap should exist between the bodies as this will generate an error of grid generation.
