Week 5

AIM : To check for geometrical errors an fix them and execution of solid mesh using ansa software.

PROCEDURE : we use tetra mesh(tria). the surface mesh is transformed into a volume mesh.

Mid surface is not generated here as the model dont consists of a uniform thickness. only by a thickness value, its possible for us to generate a mid surface. solid mesh is used as its a 3 dimensional model as well as the cross sectional thickness cant be measured properly.when we use boolean operations like not and Inot and hide any surface , we could see an incomplete volume between the surfaces. A volume is generated and meshing is obtained by the use of following operations.

firstly the rear view mirror model is imported.

Topology is swtiched and topo is obtained.

Geometry check is done.

By selection mesh-perimeter-length, the optimum average nodal length is fixed.

shell mesh :

After doing the above processes , meshing is carried out in mesh mode.

Quality criterias , min and max lengths are specified as 0.5 and 2 respectively .

Average length is fixed as 1 and type of tria is mentioned as ortho tria.

Since the body is unstructured , it is difficult to generate a proper mesh flow by selecting it all and executing best mesh. so instead , we use spot mesh where individual macro areas are selected and meshing is done to obtain a good mesh flow.

For the fillet ares we use ortho trias and for non fillet areas we use tria to obtain a proper mesh.

It is important to use reconstruction to get good mesh flow and while doing it it is necessary to chech whether the corresponding mesh type is used like when we use ortho trias in spot meshing we need to use ortho trias for reconstruction .

After completing the mesh , it is necassary to check for external projections or quality criteria failures.

fixing quality criteria and extended surfaces :

Quality failures can be fixed by using reconstruction and by moving macros. we need to make sure that there is'nt any extended surfaces generated.

To fix it we can use same options mentioned above. checking for all the areas is mandotary.

volume generation :

Next , V MESH mode is used for volume generation. quality criteria need to be fixed in solids like min and max lengths and tetcollapse. Define volume is first done. volumes-define-manual is used. next box selection is done and body is selected. in the list box we can see the body selected and it has defiend it as unmeshed. to execute meshing , unstructure-tetra rapid or tetra fem can be used by selecting remesh option or it can be done sepearately by selecting the necassary method.

We can check whether the volume have been generated or not by using bounds option that is present near wire mode. this has to be done for different properties separately. after finishing the process , while using not entity and hiding the areas , we could see the volume generated between the surfaces. Any collapsed surfaces have to be fixed and since its a solid mesh , there can be failures due to to min and max length criteria which can be avoided.

learning outcome : the difference between shell mesh and solid mesh was learnt. usage of volume mesh was new to learn.

before topo

after topo

quality criteria

v mesh

Conclusion : Geometrical errors were cleared and solid mesh was carried out with the given criteria.