Week 5

REAR VIEW MIRROR CHALLANGE

AIM: This challange will be mainly focussed on tetra and tria element meshing and drawing the volume for the same which is carried out with geometric error free and meshing with tetra and tria components with minimum, maximum length error free in shell component and tet collapse error free in the volume meshed component.

GEOMETRIC CHECKS: Firstly the cad imported model should be made fine to work on it, which is shown in the below image.

The above model shown is before geometric checks that should be refined with the perimeters and macros with 1mm as it is also a target length. Then after refining the geometry the model should be checked with geometry as usual to fix the cons, unchecked faces etc., present if any in the model. The Topo clean up is used it to stitch if any non pasted cons present in the model. The below images shown is the before and after the geometry checks.

MEASUREMENTS: So the model is cleared with the geometry checks then further step taken is measuring the measurements of the model and save it in the sepetare PID that represents the model in numbers. So in this rear view mirror model the each model will be going to be meshed seperatly for our convenience so each shell thickness is given seperatly in seperate PID's. The below images shows the measurements of each part in this model for future reference.

The images shown are measurements of each shell component in the model with seperate PID and other sample measurements of parts of the model.

So as we compare to earlier models here this model contains the measurements greater than 6mm and also the surfaces have curves and comples shapes extracting of the midsurfaces were not possible, so here in this model we have to go with the tetra and tria mesh then eliminate the errors present in it and furtherly these shell component is drawn into volume and created with a solid component. Then the solid volume is meshed with a 3D or Volume mesh.

QUALITY CRITERIA: The quality for the solid mesh is given with quite changes from previous models as for the solid mesh mainly it is checked with tet collapse, sharp edges and the shell mesh is checked with minimum and maximum length criteria. The below table shows the quality criteria for this rear view mirror model.

S.no	quality criteria	values
1.	target length	1
2.	minimum length	0.5
3.	maximum length	2
4.	tet collapse	0.2

SHELL MESHING: Now it is different from the 2D mesh it has a different sequence of operation to be carried off. So after measurings were taken, the shell components were meshed with the help of spot mesh situated in the mesh generation of 2D mesh then it was changed between the tria and ortho tria option on bottom below dialogue box. The choosing of tria and ortho tria mesh should be taken care, as of now in this model the curves and fillet areas were meshed using the ortho trias and tria elements in some of the flat regions, but at finally the better mesh should be choosen out of both. The reconstructing of the mesh using the reconstruct in the 2D mesh helps to fix the maximum errors that are obtained in the mesh flow regions.

SOLID/VOLUME MESHING:

So after meshing the shell components, the shell should be defined manually with a volume that should be formed inside the shell component and create with a new PID for each volume component and then it is processed with the solid meshing using the tetra rapid or tetra FEM mesh that suits the model perfectly in the particular regions.during the volume meshing the main considerable error is tet collapse and some of those were fixed by using fix quality and others can be fixed by using grid move tool manually upto a possible extent.The sharp, raised edges and kinks like structures were also should be eliminated upto possible extent.

Now after creating the solid mesh using the tools shown above the solid components will be created with mesh and PID's were created for them.

The image for the shell mesh is shown below:

The image for solid mesh of the model is shown below:

LEARNING OUTCOMES:

*From this solid meshing learned to define and create the volume inside a shell component.

*Learnt the way to do tetra and tria meshing in required regions.

*Learned to improve rearranging construction lines for better tria and tetra mesh flow.

*Fixing quality in solid/volume meshing.

*Figured out some of the regions like where to apply tria mesh(applying in flat regions gives somewhat better mesh flow) and tetra mesh(mainly applicable in the curved, bends and fillet regions).

CONCLUSION: Though the meshing is done upto possible extent eliminating the tet collapse, there were some of the length quality errors that were to be compromised in this model and that was bit unsatisfactory as those length errors were present in the interior of the solids.

LINK FOR COMPLETE PREOCESSED MODEL:

https://drive.google.com/file/d/167uPsJQR6hYsmn26q2FYkUB8NrGGg38Y/view?usp=sharing