FEM best practices and examples: Difference between revisions
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===FEM-solver=== | |||
The FEM-solver is written completely in C# with. It is geometrically linear. So second order effects are not taken into account. | |||
===Mesh element/theory=== | |||
The mesh element used with in plates in [[XFEM4U]] is a modified [https://en.wikipedia.org/wiki/Bending_of_plates Kirchhoff] element. It is extended in 2021 by [https://nl.wikipedia.org/wiki/Johan_Blaauwendraad | Professor Blaauwendraad]. Usually Kirchhoff is less precise regarding shear force distribution. In the modified element this is solved. Therefore it is a extremely robust element with very reliable shear force distribution. | |||
===Mesher=== | |||
The mesher is using 4-nodes quadrangle elements because they are more accurate than 3-nodes triangle elements. On a edge | |||
===Mesh Size=== | ===Mesh Size=== | ||
Below we describe a method how to find the right mesh size for your structure. If you make the mesh too dense, internal forces will be higher then reality. First some basics. | Below we describe a method how to find the right mesh size for your structure. If you make the mesh too dense, internal forces will be higher then reality. First some basics. | ||
* Element size should never be smaller then the plate thickness. Otherwise the theory of Kirchhoff is not correct anymore. | * Element size should never be smaller then the plate thickness. Otherwise the theory of Kirchhoff is not correct anymore. | ||
* Element size also at least the smallest spansize in the structure to expect a correct result. | * Element size also at least the smallest spansize in the structure to expect a correct result. | ||
* Steel plate structures: If you make you mesh 50% smaller the stress should not | * Steel plate structures: If you make you mesh 50% smaller the stress should not increase more then 10-12%. | ||
Workflow to find the right meshsize within a steel structure. | Workflow to find the right meshsize within a steel structure. | ||
Revision as of 07:21, 28 August 2022
FEM-solver
The FEM-solver is written completely in C# with. It is geometrically linear. So second order effects are not taken into account.
Mesh element/theory
The mesh element used with in plates in XFEM4U is a modified Kirchhoff element. It is extended in 2021 by | Professor Blaauwendraad. Usually Kirchhoff is less precise regarding shear force distribution. In the modified element this is solved. Therefore it is a extremely robust element with very reliable shear force distribution.
Mesher
The mesher is using 4-nodes quadrangle elements because they are more accurate than 3-nodes triangle elements. On a edge
Mesh Size
Below we describe a method how to find the right mesh size for your structure. If you make the mesh too dense, internal forces will be higher then reality. First some basics.
- Element size should never be smaller then the plate thickness. Otherwise the theory of Kirchhoff is not correct anymore.
- Element size also at least the smallest spansize in the structure to expect a correct result.
- Steel plate structures: If you make you mesh 50% smaller the stress should not increase more then 10-12%.
Workflow to find the right meshsize within a steel structure.