2D meshing and element quality check.

Objective:- To clean up the given geometry and then mesh them with shell elements.

Quality Parameters(Given):-

Sr.no	Parameter	Value
1.	Minimum Element Size	3.5mm
2.	Target Element Size	5.0mm
3.	Maximum Element Size	7.0mm

Solution:-

Step 1- Importing file:- Select user profile as optistruct and Import Part 1 in workspace by File>Import>Model.

Step 2- Geometry Cleanup:-

Why is geometry cleanup required?

Sometimes while importing files from cad software the geometry may get distorted and may lead to difficulty in pre-processing & non-uniform mesh. So before preprocessing the geometry must be cleaned up.

Once the model is imported in the workspace change the view mode to By Topo mode. Red lines indicate free edge and yellow lines indicate that the edge is shared by 3 or more surfaces.

Here in part 1, we can see that there are few free edges we need to fix them. The edges are fixed by toggling the edges (geometry).

We also have an extended surface, this is fixed by (geometry).Select the surface to be trimmed and the cutting surface perpendicular to it.

All the holes below 6mm can be ignored (geometry).

Once all the edges are green except the boundary edges, the mid surface can be extracted.

Unnecessary lines in the fillet region can also be toggled for preventing element failure.

Step 3- Extract Midsurface:- Once the geometry is cleaned mid surface is extracted by (geometry)

What is the mid surface?

The mid surface is generally extracted for ease in meshing for shell elements.Mid surface is a surface same as the parent geometry created at half of its thickness.

Once the mid surface is extracted we can cleanup it accordingly by toggling unnecessary lines, filling the holes less than 6mm, etc

Step 4- Discretization/Meshing :-

What is meshing and why is it important?

Discretization or meshing is dividing complex geometry into simple elements that can be used as approximations of the larger domain. Meshing helps the finite element problem to be solved by dividing the domain into pieces each piece represents the element. Meshing has an influence on the accuracy of the solution, computational time ( Mesh size is inversely proportional to computational time), and convergence. Meshing can be done for 1D,2D & 3D elements namely shell meshing, tetra mesh, Hexa mesh, etc.

For these parts, meshing is done with shell elements, since their thickness is less than 6mm.

For meshing,[2D<Automesh<surface(select surface)].Once the surface is meshed nodes on each edge can be adjusted by left click(increase) or right-click(decrease) for better mesh flow. After meshing we can also replace points(2D<replace<node-node) for better mesh.

Incase of symmetry we can mirror the mesh by reflecting command. For using reflect command we need to create a plane as shown in the figure by creating nodes exactly at the center (F4).Once the nodes are created we can reflect the mesh by (Tool<Reflect). Select the elements that are needed to reflect and duplicate them, select the center nodes created, and select proper alignment.

Note:- While meshing, try to avoid triangular elements because they add stiffness, Quad elements are preferred.

1. After meshing some trials can be eliminated by combining[2D]two trias to one quad.

2. If there are two opposite trias then they can be fixed by remeshing those elements and their neighboring elements.

Step 5- Element Quality Check:- Element Quality is the most important parameter in pre-processing. Element Quality is directly proportional to accuracy and computational time. In these parts minimum edge size(3.5mm), maximum edge size(7mm) was the quality parameters that have been checked. Element quality can be checked by F10 on the keyboard.

Once the element quality is checked, the mid surface mesh can be transferred to the part [Tool<Organize<Elems(displayed)].

Property can be assigned to the part by right-clicking on the model in the browser and selecting property and apply the desired thickness.

Note:- Few elements failed especially near the fillets because their actual surface size was less than the min edge size.

Meshed Parts

Conclusion:- The given parts are meshed successfully using shell elements and abiding all the quality parameters(min edge size & max edge size) mentioned.