Project 1 - Meshing of Floor Panel

Project 1 - Meshing of Floor Panel

AIM: -

To mesh the given floor panel model for the given quality criteria’s without any failure in the elements.

Objective:

The objective of this project is to perform pre-processing i.e. geometry clean-up, mid surface extraction, and 2D shell meshing for the floor panel of a car. After meshing, component thickness needs to be assigned to the mesh. And the mesh should follow the following quality criteria.

Target Element Length = 5 Units

SR NO	QUALITY CRITERIA	VALUE
1	ASPECT RATIO	5
2	SKEWNESS	45
3	WARPING	15
4	TAPER	0.5
5	MINIMUM LENGTH	2
6	MAXIMUM LENGTH	8
7	MINIMUM ANGLE QUAD	45
8	MAXIMUM ANGLE QUAD	135
9	MINIMUM ANLGLE TRIA	20
10	MAXIMUM ANGLE TRIA	120
11	TRIA PERCENTAGE	10

Project description: -

FLOOR PANEL MODEL: -

Procedures for Meshing a 2D component: -

i) Importing the CAD model into ANSA: -

The cad model is imported into the Ansa software by clicking File ---> New command.

ii) TOPO Operation & assigning length: -

Before assigning length, we will perform TOPO operation on the model inorder to stitch all its parts together properly. For this command is FACES>TOPO in TOPO module. Then to assign the component its minimum target length of 5 mm we can use command CLASSIC MESH>PERIMETERS>LENGTH

iii)Geometry Checks: -

Then the important step is to check the geometry of the CAD model. This will help us to clear all the surface errors, unwanted cons and also any disruptions present in the model

For this command is Tools > Checks > Geometry. After geometry checks is performed some of the errors like unchecked faces, crack between faces etc is possible to be auto fixed. Some of the errors like single cons errors are need to be manually fixed. After fixing the geometrical errors below windows shows with status as ticked

once again to release all the cons use command FACES>TOPO in TOPO module

Then FACES>ORIENT command is used to check the orientation is proper in all the faces of the CAD geometry.

iv)Midsurface extraction: -

Before extracting the Mid surface of the components, it is important to measure the thickness of the component in order to determine whether the component is sheet metal component or plastic component. For measuring thickness command used is UTILITIES>Measure. And by choosing the extreme end of two hot points we can measure thickness of the geometry.

After measuring thickness of the component, it is determined that the component is sheet metal component.

In order to generate midsurface of the component we can use FACES>OFFSET command in TOPO module. We will have to capture the mid surface of the given component in two phases.

The highlighted portion or faces in the highlighted area are captured separately rest of the parts are captured in one shot. For capturing the highlighted portion’s midsurface we can offset its top face and add that into the same PID and we can connect both the midsurfaces by adding new faces in between them

Captured midsurface is as follows and a PID is provided to it along with thickness of 1mm.

v)Fixing Quality criteria and Mesh parameters: -

Once the Mid surface is generated, the CAD model is now ready for the meshing. And for that the quality criteria for the mesh is defined using the command UTILITIES>QUALITY CRITERIA ( or by clicking F11 )

Then use command UTILITIES> MESH PARAMETERS and give the target length as 5 and minimum length as 2 mm

The quality criteria dialog box will appear as follows

1. vi) Meshing: -

given component can be meshed using the command MESH GENERATION>BEST MESH.After when all the defeaturing works are done, the complex component can be subdivided into smaller portions to obtain better quality mesh and that can be achieved by introducing cuts in between the parts we can use the command MACROS>CUT command and then meshing can be applied for the individual places.

PERIMETERS> SLIDE option is used to slide the holes in the component and make the perimeters almost parallel, to get an proper mesh flow in the component.

And hence the Mesh will be generated in the component.

In the mesh, the following things should be followed:-

1) The mesh should be smooth and clean

2) Back-to-Back trias should be avoided

3) Tow opposite trias nearer to each other should be avoided

4) Tria elements in the fillets should be avoided

5) Tria elements in adjacent to outer edges should be removed

6) Tria elements attached to the hole edges should be avoided

So, after obtaining the mesh, the above things to be taken care and the tria elements can be mostly avoided by using the following commands: -

Elements ---> Split, Elements ---> Swap, Grids ---> Paste These commands are used to move the trias forward and backword and also to split them . Elements ---> Join command is also used to reshape many tria elements and by using these commands we can achieve the above conditions and the tria elements can be avoided.

Shell mesh ---> Reconstruct and Shell mesh ---> Smooth commands are also used to obtain the smooth elements in our meshed model.

And hence, when our meshes are failing to fill the quality criteria provided, they can be cleared with the help of the above steps and commands provided.

Meshed model looks as follows

After meshing we have to recheck if the thickness for the midsurface is provided or not. After that we have to draw the shells as solids for that we can use command UTILITIES>QUALITY CRITERIA>PRESENTATION PARAMETERS>DRAW SHELLS AS SOLIDS

Conclusion:

Geometry clean-up, mid surface extraction, and 2D meshing of the given floor panel model were successfully done. And all the elements pass the quality criteria. All the features in the model are captured properly with good mesh flow. Tria concentration is kept low.