MODELLING OF INTAKE MANIFOLD USING 3D ELEMENTS USING ANSA V19.1.5

OBJECTIVE:

To mesh the given component using tetra elements as per the quality criteria given in the data.

Quality criteria

S.No	Quality Criteria	Value
1	Target/Average length	3
2	Minimum Length	1
3	Maximum Length	5
4	Tetcolapse	0.2

Geometry cleanup and Mid-surface extraction.

• A new .ansa file is opened and the .igs file of the given model is then imported on to the workpage.
• The model is then viewed in ENT( entity mode) from drawing style to check for any orientiation issues (Top portion should be gray and bottom to be yellow in colour) and if there is any issues its then corrected using Faces>Orient(tool)>visible.
• Turn on the Cross-hatches form Face draw so that surfaces can be selected easily.
• To join the near by parts a Topo is done from Topology module>Face>topo.
• The pixel correction can be done using, Mesh module>Lenght (Perimeter=1, Macro=1). Its can be also done from Topo module using Auxillaries>fine.
• The model is then subjected to geometry check up to find out any missing surfaces, free edges, duplicates etc. Tools tab>Checks>geometry>Execute.
• When check up was carried out, Ansa throwed out error messages, in which some of them can be fixed automatically and others were done manually using other tools.
• The surfaces are then splitted and defeatured with respect to the quality criteria using cut, join, datch etc, so that there won't be any failure of elements while meshing.
• Any component whose cross sectional thickness is more than 5mm, solid modelling methodology is generally followed as per the CAE standared.

Meshing.

• Before doing tetra mesh, The surface of the solid model is meshed with shell elements and then its been converted to volume mesh.
• Shell Meshing is done in mesh module and its turned on.

• The mesh parameter from untility is opened to enter the target element size, element type etc.

• Similarly the quality criteria option is also selected from the same toolbar and the values given as per the given data is then entered accordingly. From presentation parameter sub-option, check wheather the percentage element box is ticked also from detailed from demand effect drag the cursor towards all details.
• Now each splitted surfaces are meshed seperately using Mesh generation>Batch or Best or Spot.
• Normal trias and ortho tias are the element type used while meshing the surfaces.
• For the regions such as fillets, curved areas etc, ortho trias are prefferable and for plannar surfaces normal trias can be used. Even though ortho tria caputure the surfaces well as compared to normal trias, but takes more time for computation.
• For better mesh flow the region can be again remeshed using Shell mesh> Reconstruct.
• Paste, swap,split etc can aslo be further used to correct the mesh.
• The elements can be arranged uniformly using smooth tool from shell mesh option and while using this tool some of the elements gets displaced from the splitted lines and these can projected on to those line using Grids>origin.
• Quality criteria applied can be viewed using Hidden view> Drawing styles, Where the elements gets highlated in different colours indicating the failures to respective criteria and correction has to be made further.
• After the shell mesh and checking the quality criteria and ensuring the parts are fully closed, its been now taken for doing tetra mesh.

• Tetra Meshing is done in volume mesh module and its turned on.

• Now we need to define the model as volumes for generating the volume mesh. For the current model four seperate volumes were defined by using Volume mesh module>define>manual>New>P-Solid.
• List option from volume will shows all the defined volumes and the tetra mesh is now performed on each defined volume by right clicking each volume>Remesh>Tetra Rapid or Tetra FEM.

Tetra Rapid

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

  The parameters used during the automatic generation of volume elements are defined in the Options window:

  - The Maximum growth rate, which is the approximate growth factor of volume element size from layer to layer while the generation moves towards the interior of the Volume.

  - Maximum Element Length. Specify the maximum allowable length of the tetra elements to be generated. Useful when specifying a growth rate factor while keep the length of the elements below a certain value.

  - Quality Criterion and Threshold Value. The user can select the quality criterion definition with respect to which the generated tetra elements will be optimized, and specify a threshold value to guide the optimization process. Furthermore, this function gives the option of identifying possible problematic regions of already defined volumes, prior to volume meshing.

Tetra 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.

  The parameters used during the automatic generation of volume elements are defined in the Options window:

  - The Maximum growth rate, which is the approximate growth factor of volume element size from layer to layer while the generation moves towards the interior of the Volume.

  - Maximum Element Length. Specify the maximum allowable length of the Tetra elements to be generated. Useful when specifying a growth rate factor while keep the length of the elements below a certain value.

  - Quality Criterion and Threshold Value. The user can select the quality criterion definition with respect to which the generated Tetra elements will be optimized, and specify a threshold value to guide the optimization process. Furthermore, this function gives the option of identifying possible problematic regions of already defined volumes, prior to volume meshing.

  - Create pyramids flag. The user can enable or disable the creation of pyramids.

• Once its completed the volume mesh can be viewed using the boolean operators or putting it in bounce mode. Also turn on the volume icon from the visibility tool bar.

• Here the quality check is done only fo the tet collapse.

Tet collapse

• Defect generated when the height of tetrahedron 3D element is less than the target element length. Tet collapse defects were cleared by re meshing the failed elements and changing the height of tetra element by translating nodes. Fix quality from volume mesh module and MV free tools from mesh module can be further used for this correction.
• Its should noted that, the final mesh should be free from peaks (element projecting outward) and kinks (element projecting inward).
• Save the file.

RESULT:

Volume mesh has been performed for the given model using tetra mesh following the quality criteria given in the data.

LEARNING OUTCOMES:

Concepts of modelling solid components

Volume meshing.

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File: https://drive.google.com/drive/folders/1Mu_hmpnb9Fubuq__oj_32yJD7Cptw6Zb?usp=sharing