Week 5

                                                              PRE-PROCESSING OF A VIEW MIRROR COMPONENT BY ANSA

AIM:

The aim of this project is to do TETRA or UNSTRUCTURED meshing for a solid mirror component which should accept Quality criteria,by using ANSA.

ABSTRACT:

In this project we are going to do TETRA meshing for a solid component.Here we are going to define volumemetric surface for the entire solid component.At the same time we are not conserned about minimum and maximum errors in volumetric surface,we are conserned about TETCOLLAPSE errors.The meshing pattern we are going to follow is Tetra and ortho tetra.

METHODOLOGY:

• Import geometry.
• Check for Topological errors.
• Geometry clean up.
• mesh the component by ortho tetra meshing
• List the volumetric surface for solid model
• mesh the volumetric surface.
• check for collapse errors.

PROCEDURE:

There are certain steps to be followed to mesh the solid model.

STEP 1: Import the geometry

• After opening ANSA open the model by using file command.

                                                                             FIG: Model imported to ANSA

STEP 2:

Check for the Topological errors in the model.

• After importing do topo and check for the errors.
• If there are any errors in the model rectify them by using Automatic or manual methods.
• After rectifying make sure that the geometry does not have any errors,and it is clean.

                                    FIG: Image with errors                                                                                             FIG:Image without errors  

STEP 3:

Geometry clean up(defeaturing)

• After rectifying the Topological errors,do geometry clean up in the model.This avoids Quality issues in the meshing.
• Remove unwanted lines,hotpoints etc.

Defeaturing: This defeaturing can be done either in manual method by the user or by automatic method by ANSA.

MANUAL METHOD:Check every part of the model,and remove all unwanted hotpoints,double cons,and removes lines which are very near to each other.

AUTOMATIC METHOD:Here,defeaturing will be done by BATCH MESH in addition with meshing.

NOTE: If the mesh flow is good we can proceed with Batch mesh,or else we can ERASE the mesh.But what ever defeaturing is done we can proceed with that.

BATCH MESH:

• Open batch mesh
• Go to new-Mehing scenario
• Import the model in contents of meshing scenario.
• Give Mesh parameters and Quality.

• Run the model.In this defeaturing and meshing will be done automatically.

                                    FIG:Image showing BATCH mesh

NOTE:ERASE the meshing for the entire component and keep defeaturing.

FIG: Above image we can see that mesh is removed but defeaturing is kept which is given by BATCH MESH

STEP 4:

MESH THE COMPONENT BY ORTHO TETRA MESHING:

• Now mesh the model by ortho tetra meshing.
• Mesh each part seperately,so that good mesh flow is obtained.
• In curved surfaces mesh the surfce by tera meshing,which gives best results.
• Flat surfaces can be meshed by ortho tetra meshing.

                                                        FIG:Image with Quality issue

• There are off elements in the model so do rectify them.
• In one part some elemets fail for the given Quality ,where we are not supposed to remove those lines.So change the Quality of minimum length from 0.5 to 0.45.
• After rectifying there will not br any Quality failures in the shell model.

                                               FIG:Image without Quality issue

STEP 5:

VOLUMETRIC SURFACE FOR THE MODEL:

• Check for Geometry error.
• Go to volumetric mesh,in that define the model by manual method.
• Creat a new PID as Solid.
• Then the surfce is added in the list.

                                                                       FIG:Image showing volume for the model

STEP 6:

MESH THE VOLUME FOR THE MODEL:

• After creating the volume,Remesh the model by right clicking the mouse in list,or go to UNSTRUCTURED MESH and do tetra rapid or Tetra Fem mesh.
• This meshes the volumetric surface of the model.

TERTA FEM:

• This function automatically creates a Tetrahedral mesh inside selected Volumes, initially with pyramid elements if the starting surface mesh contains quad elements. It is to be used mainly for structural applications. Volumes to be meshed with this function must have been defined using the Define(Volumes) function.

TETRA RAPID:

• The Tetra Rapid algorithm meshes the Volume with Tetra Elements.

                                                                                 FIG: Image showing TETRA RAPID mesh

• Like wise do the meshing either by tetra rapid or tetra fem.

                                               FIG:Image showing the tetra rapid mesh for the model

• We can observe that the volumetric mesh is done for the model.
• We can observe some off elements in the model.
• If these off elements are of MInimum and maximum error,then we are not worried,if these are of the tetcollapse errors then we have to clear them.
• For our safety we can observe the model in the bounce mode.

                                                                 FIG:Image showing the model in BOUNCE mode

TETCOLLAPSE:

• These are the errors we will check for the volume meshing.
• These can be resolved by fix quality option and by Move free option.

      FIG:Image showing tetcollapse elements

                                                                      FIG:Image showing tetra mesh of the view mirror

• Above we can observe that the image showing meshing for the volume of the model.
• We can see that,there is no pattern or order for the mesh.
• All the elements are in unstructured manner,that's why we call tetra meshing as unstructured mesh.

NOTE:Make sure that the model is not having KINKS and RAISED Edges present in the model.

KINKS:If the elements on the surface of the model goes a bit down then they are called as KINKS.

RAISED EDGES:If the elements on the surface of the model goes a bit raised then they are called as PEAK or RAISED EDGE.

IMAGE OF THE MODEL BEFORE AND AFTER:

FIG:Image showing Before model                                                                                                          FIG:Image showing after model

LEARNING OUTCOMES:

• Able to do topological clean up for solid model.
• Got to know about Batch mesh.
• Able to use volumetric surface foe solid model.
• Able to do tetra meshing for solid model.
• Can fix the errors in solid model.

CONCLUSION:

• For any component,if there is more thickness then tetra meshing is same for every model.The above model is done with tetra meshing which accepts the Quality criteria.But for some part of the same surface of the model the quality fails for which we need to reduce the Quality by 0.5mm.The geometry should not be change at any cost when we are meshing.In volume surface we are consered about only tetcollapse errors,but not for minimum and maximum errors,where are in surface meshing we need to consider minimum and maximum errors.Majority of the elements should accept the Quality criteria.

LINK OF THE PROJECT:  https://drive.google.com/file/d/1R4Zj43o1NTIyCJYaosjJY-ATRbTgo1Go/view?usp=sharing