Preprocessor for Structural Analysis using ANSA Tetra Meshing for RearView Mirror

Objective:

• For the given component, We need to check for the geometrical errors and mesh with the given element Quality criteria. Use tetra elements to model the component.

Using Volumetric mesh for solid element.

S.No	Quality Criteria	Value
1	Target/Average length	1
2	Minimum Length	0.5
3	Maximum Length	2
4	Tetcolapse	0.2

Software Used: ANSA Pre-processor.

Theory for Meshing.

• It is common practice to classify meshes into two main types: structured and unstructured.

Structured meshes

Structured meshes are meshes with implicit connectivity whose structure allows for easy identification of elements and nodes. Often structured meshes have orthogonal quadrilateral (2D) or hexahedral (3D) elements.

Structured meshes allow programmers to enumerate the nodes in such a way that any adjacent elements or nodes can be called upon without knowing any connectivity information. It is also possible to access coordinates easily because the size of each element does not vary element to element.

Unstructured meshes

Unstructured meshes are meshes with general connectivity (GCON) whose structure is arbitrary and therefore the connectivity of elements must be defined and stored. GCON element types are non-orthogonal, such as triangles (2D) and tetrahedra (3D).

Unstructured meshes require programmers to map more data to each node, such as adjacency lists and coordinate lists.

Structured vs GCON

OnScale primarily uses structured Cartesian meshes because they are ideal for time-domain simulations and are optimal for most applications, but there are also benefits to unstructured meshes.

When to use each mesh typeThere are a couple of questions you should ask yourself when considering what mesh type to use.

• Do you have a complex geometry in which the geometric shape is key to the design?
• Do you have localized regions of your model that require a higher resolution mesh?

If the answer to either of these questions is yes, you may want to consider using an unstructured mesh as the biggest advantage is the ability to conform to any desired geometry with localized resolutions. If you do not require any of this functionality, however, then an unstructured mesh will not be necessary and you can reduce computation time and memory requirement using a structured grid.In summary the best choice of mesh depends on many factors: ease of generation, memory requirements, computation time, numerical accuracy, and suitability for the application.

Structured mesh advantages

• Memory efficient
• Fast to Solve

Unstructured mesh advantages

• Complex geometries easier to mesh
• Arbitrary positions

Structured mesh disadvantages

• Angled and curved geometries are approximated (leads to stair stepping)

Unstructured mesh disadvantages

• Greater memory requirement
• slower to solve

Methods used to solve this problem :

1. Geomentry clean up with out error.
2. Meshing of geomentry with 2d meshing of orthotria and tria.
3. Volumentric meshing of 3d using rapidtetra.

Geomentry clean up with out error.

Model:

• Importing the Rear View Mirror stp.file to the Ansa toolbar.

Geometry Checks:

• The geometry checks are used to check the geometry setup file using checkbox by selecting the geometry option
• And it shows that various errors in the geometry on the surface.
• After that we need to surfacing cleaning is done

Surface Cleaning:

1. Surface Cleaning is the process of clean up the surface error.
2. An error such as holes, Extra surface, single cones, Crack.
3. Single cones are used to clean up using the Select the all with Topology method.
4. Some of the tools used to fix the problem are coons -surface patch, Fill holes, New for the Faces, Fixing Cracking.
5. After selecting the particular area on that surface are missing like that using the tools to patch the area with select after that clicking the middle mouse bottom.
6. Some of the Extrusion across the surface of the model is deleted according to the deleted.
7. In the surface cleaning methods, Ansa tools itself giving the Autofix for the some of the Error takes place in the model.
8. Further open edges and single cons are in the geometry are corrected using the topo options.

Before Topo:

After Topo:

Measurement:

Mesh Parameters:

Quality Criteria:

Presentation Parameters:

Meshing of geomentry with 2d meshing of orthotria and tria.

Meshing:

1. In the Meshing we are going to mesh using the orthotria and tria mesh type according to the geomentry.
2. For the smooth mesh we are going to use the spot mesh at the certain area to meash the component.
3. FE meshes are better representations of their geometric parents. Also, it is easy to maintain and update any changes in the geometry by simply reworking the updated area instead of recreating the FE from scratch.
4. Switching to the Mesh mode and we need to give the shell element size length according to the given input =1mm.
5. For getting the smooth mesh we need to segregate the surface to various cut regions.
6. Before Meshing we need to clean up the Some Geometry error also then only the flow of mesh should be smooth.
7. While Meshing we need to maintain the quality criteria then only we will get the required output.
8. We need to set up the mesh Parameters as will as presentation parameters according to given inputs.
9. In the Mesh parameters, we are giving the target length with minimum and maximum length.
10. In the presentation parameters, we need to enable Elements (%) and details on the Demand effect should be all details.
11. In the Mesh Generation, we need to give the Free or Best mesh as per the Mesh flow.

Property Id:

Property id is the process in which after the mid surface has taken we need to assign the Property to the surface with thickness.

Volumentric meshing of 3d using rapidtetra.

1. Volumentric Meshing is the method used to mesh the solid component.
2. This mesh also know as unstructured mesh.
3. First we need to define the property and assing the component.
4. And then assinged in property are listed in the tab.
5. We need to check the component.
6. In the list we need to remesh with Using Rapid Tetra method.

Cut Section to View Unstructed Volumetric mesh:

Error:

After cleaned Meshing :

• Using options such as Grids --> MV free to solve the error without distrubing the neighbour mesh and boundary.

Final FE Model:

Google drive link for RearView Mirror:

https://drive.google.com/drive/folders/1DJtzxllIiA31JooMb9JY9WlYO66bitXi?usp=sharing

Conclusion:

The giving RearView Mirror setup is pre-processed successfully, with assembled all parts with FE Mesh that satisfy all quality criteria assigned with the property of the component.