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Frequently Asked Questions (FAQ)
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AnswerThe intersection point of the lines named in the warning must be created with the function "Connect Lines / Members". To do this, select the function "Connect Lines / Members" and then draw a window across the elements to be trimmed (see Figure 3).
AnswerThe main reason for this is the FE mesh size as well as the different smoothing of the results. The results should be aligned with each other with an increasingly finer FE mesh. Figure 01 shows a comparison with a relatively coarse FE mesh. The support resultant is 16.84 kN. However, the resultant of the surface results is only 14.41 kN. If the FE mesh is refined at this point (see Figure 02), the results are similar. In Figure 03, the FE mesh has been refined further. The results are now exactly equal. The deviation at the start can be explained by the singular location and by the internal force size smoothing.
AnswerUnfortunately, whether a system is sufficiently discretized can not be answered on a flat-rate basis. In general, the requirement in the calculation with finite elements is that the calculated deformations and stresses no longer deviate from the analytical solution. The goal is to find out the optimum number of FE elements where the stresses do not change anymore.The user should therefore choose the discretization as fine as necessary and as coarsely as possible. As a general rule, holes or breakthroughs in the system should always have at least 3 FE elements over the height.The treatment of singularities at re-entrant corners etc. is explained in the following FAQ .Based on the pictures in this article, it can be clearly seen from the insufficient discretization of the system that the geometric intercepts of the system are almost barely detected and the system thus approximates to a bending beam. A meaningful design is not possible.
AnswerYes, it works. To do this, in the Project Navigator - Show under "FE mesh" you have to activate the item "On surface results".
Depending on the individual dimensions of the system, the following rule is recommended:
- Generation of eight to ten elements between the boundary lines of a surface (see Figure 1), but at least four elements
The FE network settings are under "Calculation" -> See "FEM Network Settings", see Figure 2.
AnswerAdaptive Mesh Generation can only be applied to the entire model, not to individual surfaces.
AnswerPlease decrease the maximum distance between the node and the line in the FE network settings. Even with a setting of 0.001 m corresponding to the image, a smaller value can be entered. If the decimal places are adjusted via the corresponding settings, the value is also displayed completely.
In this case, the following conditions must be observed for the generation of the FE mesh:
- The two contact surfaces must be identical, that is, all nodes, lines, and integrated objects must match, even if they are not used on one of the contact surfaces.
- To be able to generate an FE mesh even taking into account the unused objects, activate the option "Integrate Unused Objects into Surfaces" within the FE mesh settings, see Figure 1.
The program interprets the entered model for the calculation in a FE mesh. This mesh depends on the shape parameters set in the "FE Mesh" dialog box.
In order to correct any inaccuracies in the model, there is the parameter ε in the FE mesh settings. In the figurative sense, it regulates the maximum distance between the FE nodes. If the distance between the elements / nodes in the model is smaller than the parameter ε, the FE nodes are merged. The result of this merging is then the described "connection" of the members in the calculation.
You can avoid this effect and simulate the members independently by setting the parameter ε smaller than the available distance.
When opening a model with results and FE mesh in a newer program version, it may happen that the FE mesh and thus the results are deleted. Therefore, it is recommended to always open models in the program version used as the last one. Updates may include customizations in the FE mesh generator, for example, which require to delete the mesh.
In Project Manager, there is an option to check the file with respect to its properties. You can also see the version number here (see Figure 01).
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