<
From version < 135.1 >
edited by Fredrik Lagerström
on 2020/03/27 06:58
To version < 136.1 >
edited by Fredrik Lagerström
on 2020/03/27 07:14
>
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96 96  
97 97  FEM-Design offers a fully automatic finite element mesh generation by using optimized (factory default) or custom mesh settings. Of course, the generated mesh can be modified with special easy-to-use **edit and modify function//s//**.
98 98  
99 -Fully automatism means that the program generates the mesh with elements having average element size optimized for the structure and its environment (supports and loads). The process can contain automatic element refinement and **peak smoothing** algorithm according to the settings.
99 +Fully automatism means that the program generates the mesh with elements having average element size optimized for the structure and its environment (supports and loads). The process can contain automatic element refinement and [[**peak smoothing**>>||anchor="#HEditingpeaksmoothingregions"]] algorithm according to the settings.
100 100  
101 101  Automatic mesh generation can be done according to the **mesh settings**:
102 102  
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127 127  [[image:1585286149995-843.png]]
128 128  
129 129  * **Merge objects**
130 -The program merges **fixed points**, **fixed lines**, **supports**, **beams**, **columns** and **walls** (only in the //Plate// module) to **plate** and/or **wall** regions (the border of the regions). It is decided randomly which objects will be let in their place or removed. The objects shorter than a merging //distance// will be deleted. The objects being at the same place (covering) and having same properties will be deleted except one.
130 +The program merges **fixed points**, **fixed lines**, **supports**, [[**beams**>>doc:Manuals.User Manual.Structure definition.Beam (Geometry).WebHome]], [[**columns**>>doc:Manuals.User Manual.Structure definition.Column (Geometry).WebHome]] and [[**walls**>>doc:Manuals.User Manual.Structure definition.Wall (Geometry).WebHome]] (only in the //Plate// module) to [[**plate**>>doc:Manuals.User Manual.Structure definition.Plate (Geometry).WebHome]] and/or [[**wall**>>doc:Manuals.User Manual.Structure definition.Wall (Geometry).WebHome]] regions (the border of the regions). It is decided randomly which objects will be let in their place or removed. The objects shorter than a merging //distance// will be deleted. The objects being at the same place (covering) and having same properties will be deleted except one.
131 131  \\The program also merges columns and/or beams together. It is decided randomly which line elements will be let in their place or removed. The bars shorter than the merging distance will be deleted. After that, the supports fit to the bars. The objects being at the same place (covering) and having same properties will be deleted except one.
132 132  \\The program merges the loads to the geometry created in the first step. Those loads that have not been merged by the previous way will be merged together. It is decided randomly which ones will be let in their place or removed. Line loads shorter than the merging distance will be deleted. If the //Avoid load multiplication// option (see later) is active, the loads having the same position and same properties will be deleted except one.(((
133 133  |(% style="width:114px" %)[[image:warning.png]]|(% style="width:1336px" %)(((
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150 150  \\[[image:1585286293852-739.png]]
151 151  Figure: Load handling in mesh generation
152 152  * **Auto peak smoothing region around...**
153 -To solve the result **singularity problems** above supports and other critical points, the program may run **peak smoothing algorithm** around the listed elements. Activating an element in the list, the program automatically creates **peak smoothing region** around it.
153 +To solve the result **singularity problems** above supports and other critical points, the program may run [[**peak smoothing algorith**>>||anchor="#HEditingpeaksmoothingregions"]] around the listed elements. Activating an element in the list, the program automatically creates [[**peak smoothing region**>>||anchor="#HEditingpeaksmoothingregions"]] around it.
154 154  
155 155  === **“Elements” settings** ===
156 156  
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175 175  \\[[image:1585286450585-494.png]]
176 176  Figure: The average element size will be four times bigger than the optimal size
177 177  \\The //Correct according to the minimum division numbers// option modifies the average element size of the 2D elements, if the minimum division number (**automatic** or **custom**) of the boundary lines and edges requires that. This option is recommended for generating uniform finite element meshes. Skipping this option causes dense mesh near edges where the minimum division numbers are predefined.
178 -\\Using the //According to the peak smoothing regions// option considers the **peak smoothing** settings of model elements in the calculation of the average element size.
179 -
178 +\\Using the //According to the peak smoothing regions// option considers the [[**peak smoothing**>>||anchor="#HEditingpeaksmoothingregions"]] settings of model elements in the calculation of the average element size.
180 180  )))
181 181  * **Line element parameters**
182 182  The default minimum number of the line elements can be set here for the bar elements. The meaning of the default division number depends on the applied element type: **standard or accurate**. For example n=2 value sets (minimum) 2 finite elements for a whole bar (if neighboring elements connect to it only in its endpoints) or a continuous part of it (in case of joined or intersected neighbors) in case //standard// element type and 4 elements at //accurate// element type.
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183 183  \\[[image:1585286487913-568.png]]
184 184  Figure: Meaning of Division number in case of Standard and Accurate element types
185 185  \\At curved beams, alpha parameter sets the minimum division number: minimum division number = central angle of the curved beam / alpha .(((
186 -|(% style="width:114px" %)[[image:warning.png]]|(% style="width:1336px" %)Division number can be set manually for all bar elements or by line elements with the **Division number// //**command.
185 +|(% style="width:114px" %)[[image:warning.png]]|(% style="width:1336px" %)Division number can be set manually for all bar elements or by line elements with the [[**Division number**>>||anchor="HDivisionnumber"]]**// //**command.
187 187  
188 188  |(% style="width:114px" %)[[image:light.png]]|(% style="width:1336px" %)For imperfection (of steel bars), stability and dynamic calculations, it is suggested to set the default //n// value to more than 1; 4-5 division number is the recommended minimum for //n//.
189 189  )))
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198 198  The automatic refinement may cause too dense mesh at special geometries (e.g. at highly depressed regions), so in that case, it would be more practical to reduce the average element size with the //Reduce average element size if necessary// option.
199 199  
200 200  * **Smooth surface mesh**
201 -Smooth procedure calculates the optimal coordinates of the corner nodes of elements. It is recommended after splitting or merging elements. The best mesh can be achieved with the iterative use of the **Rebuild** and the **Smooth// //**commands. Smoothing of a mesh is executed with iteration technique: the procedure places the nodes of the triangle elements in such a way, that the area of the triangles will be balanced. The number of the smoothing steps can be set in the //Steps// field.
202 -
200 +Smooth procedure calculates the optimal coordinates of the corner nodes of elements. It is recommended after splitting or merging elements. The best mesh can be achieved with the iterative use of the [[**Rebuild**>>||anchor="HRebuild"]] and the [[**Smooth**>>||anchor="HSmooth"]]**// //**commands. Smoothing of a mesh is executed with iteration technique: the procedure places the nodes of the triangle elements in such a way, that the area of the triangles will be balanced. The number of the smoothing steps can be set in the //Steps// field.
203 203  * **Check surface mesh**
204 204  The //Check surface mesh //option lets the program to check the geometry of the mesh after automatic mesh generation. The mesh can be controlled with respect to unsuitable geometry, overlaps and topology. This means that mesh errors, produced by an automatic or manual mesh generation can be easily found. If the program finds defective geometric elements in the model, it sends a warning message (error list) and displays the position of the mesh errors.
205 205  \\The //Geometry// tool checks the geometry of finite elements, such as the angles of the elements and the ratio of the largest and smallest sides (//Max. side ratio//).
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207 207  \\The //Topology & gap// tool checks the topology of the finite elements and finds possible gaps. A typical topological error, when for example a corner node of an element lies on a side edge of another element. This problem can easily arise manually by using the **Split** command incorrectly.
208 208  \\[[image:1585286665130-634.png]]
209 209  Figure: Topologic errors (unconnected nodes)(((
210 -|(% style="width:114px" %)[[image:light.png]]|(% style="width:1336px" %)Topological errors can be easily solved by the **Rebuild** and **Smooth** commands and quick algorithms.
208 +|(% style="width:114px" %)[[image:light.png]]|(% style="width:1336px" %)Topological errors can be easily solved by the [[**Rebuild**>>||anchor="HRebuild"]] and [[**Smooth**>>||anchor="HSmooth"]] commands and quick algorithms.
211 211  )))
212 212  
213 213  === **“Prepare” settings** ===
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255 255  
256 256  Peak smoothing regions can be generated automatically by the mesh generator or calculation processes. Automatic generation always results circular peak smoothing regions with centre points placed in the location of the singularity. The radius of a circular smoothing region depends on the geometry of singularity locations.
257 257  
258 -|(% style="width:114px" %)[[image:light.png]]|(% style="width:1336px" %)Peak smoothing regions with any arbitrary shape can be defined manually with the **Peak smoothing region** command. That command is able to edit predefined (automatically or manually) peak smoothing regions.
256 +|(% style="width:114px" %)[[image:light.png]]|(% style="width:1336px" %)Peak smoothing regions with any arbitrary shape can be defined manually with the [[**Peak smoothing region**>>||anchor="#HEditingpeaksmoothingregions"]] command. That command is able to edit predefined (automatically or manually) peak smoothing regions.
259 259  
260 260  Automatic generation of peak smoothing regions can be set and controlled at the **General** settings of mesh generation (//Settings> All…> FEM> Mesh> General//). At //Peak smoothing region around...// option you can set the places (depending on the current module) where you want the program to create circular peak smoothing regions. The radius of the circular regions is calculated from the following formula:
261 261  
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306 306  
307 307  
308 308  Figure: Peak smoothing algorithm (modified inner force diagram)
309 - [[image:1585287023608-906.png]]
307 +[[image:1585287023608-906.png]]
310 310  
311 311  Figure: Internal force “graph” and “section” diagrams after using peak smoothing algorithm
312 312  )))
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364 364  
365 365  With [[image:1585287954466-742.png]] //Fixed line//, lines (straight and curved) can be fixed in a mesh to generate nodes on it.
366 366  
367 -Click [[image:1585287959782-521.png]] //Prepare //to update the mesh according to the new nodes. The program defines nodes in the line endpoints and some points on the lines. Depending on **mesh settings**, the program automatically does refine, smooth and check processes to create an optimal mesh, if it is possible. Further node distribution of the fixed line element can be influenced by the **Division number** command.
365 +Click [[image:1585287959782-521.png]] //Prepare //to update the mesh according to the new nodes. The program defines nodes in the line endpoints and some points on the lines. Depending on **mesh settings**, the program automatically does refine, smooth and check processes to create an optimal mesh, if it is possible. Further node distribution of the fixed line element can be influenced by the [[**Division number**>>||anchor="HDivisionnumber"]] command.
368 368  
369 369  [[image:1585287965400-637.png]]
370 370  
371 371  Figure: Adding lines to a mesh
372 372  
373 -Fixed points defined in the model can be displayed with the //Geometrical system// object layer. In brackets, the number of line elements can be seen defined by the **Division number** command. If “-“ is displayed, there is no restriction on the element number.
371 +Fixed points defined in the model can be displayed with the //Geometrical system// object layer. In brackets, the number of line elements can be seen defined by the [[**Division number**>>||anchor="HDivisionnumber"]] command. If “-“ is displayed, there is no restriction on the element number.
374 374  
375 375  |(% style="width:107px" %)[[image:light.png]]|(% style="width:1383px" %)(((
376 376  //Fixed lines// display the intersection lines of structural regions (e.g. intersections of slabs and walls) too. This is very useful for defining holes/openings that connect accurately to finite element meshes (see the next figure).
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508 508  1. The program builds a mesh from triangular elements using the principles of Delaunay triangular technique.
509 509  1. It converts these triangles to quadrates corresponding to the global optimum of the mesh.
510 510  
511 -If the [[image:1585288608220-164.png]] //Rebuild// command results drastic changes in the mesh, **smoothing** algorithm is also recommended. The best, the most optimal finite element meshes can be achieved with the iterative usage of the two commands.
509 +If the [[image:1585288608220-164.png]] //Rebuild// command results drastic changes in the mesh, **[[smoothing>>||anchor="HSmooth"]]** algorithm is also recommended. The best, the most optimal finite element meshes can be achieved with the iterative usage of the two commands.
512 512  
513 513  == **Smooth** ==
514 514  
515 -Smooth process calculates the optimal coordinates of the corner element nodes. Smoothing the mesh is highly recommended after **splitting** or **merging** elements. If the mesh is modified drastically after **rebuild**, use smoothing for the model. The best, the most optimal finite element meshes can be achieved with the iterative use of the **//rebuild//** and the smoothing.
513 +Smooth process calculates the optimal coordinates of the corner element nodes. Smoothing the mesh is highly recommended after **[[splitting>>||anchor="HSplittingelements"]]** or **merging** elements. If the mesh is modified drastically after [[**rebuild**>>||anchor="HRebuild"]], use smoothing for the model. The best, the most optimal finite element meshes can be achieved with the iterative use of the //[[**rebuild**>>||anchor="HRebuild"]]// and the smoothing.
516 516  
517 517  Just apply the [[image:1585288624531-314.png]] //Smooth// command for selected mesh regions. Mesh smoothing is executed with iteration technique: the procedure places the nodes of the triangular elements in such a way, that the area of the triangles will be balanced. The number of the smoothing iteration steps can be set at **“Functions > Smooth surface mesh” settings**.
518 518  
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530 530  
531 531  == **Generate (vs. Prepare)** ==
532 532  
533 -Automatic mesh generation can be done by planar object region with the [[image:1585288673372-600.png]] //Generate// command. (**Prepare** runs automatic mesh generation for the entire structural model.) //Generate //takes into consideration the manual editing functions (such as **Fixed point**, **Fixed line**, **Peak smoothing**, **Division number** and **Average element size**) and the **Mesh settings** excluding the **Check**, the **Smooth** and the **Prepare** settings. //Generate// is also recommended to find defective geometric finite elements by checking (generating mesh) regions by regions.
531 +Automatic mesh generation can be done by planar object region with the [[image:1585288673372-600.png]] //Generate// command. (**Prepare** runs automatic mesh generation for the entire structural model.) //Generate //takes into consideration the manual editing functions (such as **Fixed point**, **Fixed line**, [[**Peak smoothing**>>||anchor="#HEditingpeaksmoothingregions"]], [[**Division number**>>||anchor="HDivisionnumber"]] and **Average element size**) and the **Mesh settings** excluding the **Check**, the [[**Smooth**>>||anchor="HSmooth"]] and the **Prepare** settings. //Generate// is also recommended to find defective geometric finite elements by checking (generating mesh) regions by regions.
534 534  
535 535  (% style="text-align:center" %)
536 536  [[image:1585288680554-394.png]]
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