2D and 3D Tetra and Hexa Meshing in HyperMesh

2D and 3D Tetra and Hexa Meshing in HyperMesh

Objective:

• Create error free 2D meshing of the given models in hypermesh by using advanced pre-processing tools
• Generate 3D tera and hex volume meshing of the models in hypermesh

Description:

The following are the models on which 2D meshing is generated and generating 3d Tetra meshing with these 2D mesh:

Hexa8 meshing model:

Methodology:

• 2d mesh and Mesh quality
• Generating 3d tetra volume mesh
• Generating 3d hex volume mesh

2d mesh and mesh quality:

• Open the model, it consists of hub and cover
• 2D meshing for hub and cover has been created by:

1. 1. To open the AutoMesh panel, click Mesh > Create > 2D AutoMesh from the menu bar, or press F12.
   2. Set the entity selector to surfs.
   3. In the element size= field, type 5.0
   4. From the mesh type list, select tria.
   5. Select the model
   6. Click mesh.

• After meshing press F10 and set mesh parameters specified.
  • Min length-3.5mm, max length-7mm, aspect ratio-5, skewness- 60, jacobian-0.5, warpage-10, tria angles- [20-120], quad angles- [40-140]
  • check in quality index under 2D mesh for errors.
  • Rectify errors by remeshing the localised areas.
  • In quality index tab there are clean-up tools by using those tools we can rectify the errors.
  • Mesh flow is very important, to ensure streamline mesh flow use smooth mesh, translate, change node, combine &create elements, split elems, place node and use washer split at holes.

Generating 3d tetra volume mesh:

1. 1. Open the Tetramesh panel by clicking Mesh > Create > Tetra Mesh from the menu bar.
   2. Go to the Volume tetra
   3. Set the Enclosed volume selector to
   4. Select one of the surfaces in the model.
   5. Verify that the 2D type is set to trias and the 3D type is set to tetras. These options control the type of elements that HyperMesh creates for the surface mesh and solid mesh of the part.
   6. Verify that the toggle is set to Elems to Currrent Comp.
   7. Verify that the Use curvature and Use proximity checkboxes are clear.
   8. In the Element size field, type 5.
   9. Click mesh.

• Tet collapse:
  • The tet collapse criteria is a normalized volume check for tetrahedral elements. A value of 1 indicates a perfectly formed element with maximum possible volume. A value of 0 indicates a completely collapsed element with no volume.
  • Open the Check Elements panel. Go to the 3-d subpanel. Set tet collapse -0.15
  • Identify elements that have a tet collapse smaller than 0.15. The status bar indicates that three elements have a tetra collapse smaller than 0.15.
  • Isolate the elements and remesh those tetra elements.
• Find out if the tetra collapse has improved for the displayed elements by clicking Tet collapse

Generating 3d hex volume mesh:

• Open the model it consists of base, arm curve, arm straight, boss

Select base and make current the component:

• Create 2d mesh on base with element size-10mm
• Then create 3D mesh by:

1. 1. Open the Elem Offset panel by clicking Mesh > Create > 3D Elements Element Offset from the menu bar.
   2. Go to the solid layers subpanel.
   3. Click elems to offset: elems >> displayed. HyperMesh selects the elements on the base.
   4. In the number of layers= field, type 5.
   5. In the total thickness= field, type 25.
   6. Click offset+.

• • • The hexa mesh is created.

Select arm curve and make current the component:

• Mask hexa8 elements of the base and create a centre circle node for the curve of the arm cure component.

1. 1. Open the Spin panel by clicking Mesh > Create > 3D Elements > Spin from the menu bar.
   2. Go to the spin elems subpanel.
   3. Click 2d elems: elems >> by window.
   4. Select the plate elements within the L-shaped cross section of the arm Click select entities.
   5. In the angle= field, type 90
   6. Set the orientation vector to x-axis (Y-Z plane).
   7. Select the center node you created for the base node (B).
   8. In the on spin= field, type 25.
   9. click spin-.

• • • The hexa mesh is created.

Select arm straight and make current the component:

• Create edges on the arm curve component for the reference to 3D mesh of arm straight component by Opening the Faces panel, click comps >> arm curve, click find faces.
• Now create 2D mesh on the L-shaped surface of the arm straight component
• Then create 3D mesh for arm straight using linear solid option in 3D.

1. 1. Open the Linear Solid panel by clicking Mesh > Create > 3D Elements > Linear 3D from the menu bar.
   2. Activate the from: elems selector.
   3. Quickly select all of the necessary elements by selecting one of the elements and then clicking from: elems >> by face.
   4. Activate the to: elems selector.
   5. Select the shell elements between the arm and boss that you created using the Automesh
   6. Activate the from: alignment: N1 selector.
   7. Select three nodes on one of the \"from elements\"
   8. Activate the to: alignment: N1 selector.
   9. Select three nodes on the \"to element\" that corresponds to the \"from element\" with the three \"from nodes\"
   10. In the density= field, type 12.
   11. Click solids.

• • • The mesh is created.

Select boss and make current the component:

• Create 2D mesh on one face of the boss
• Create 3D mesh on the boss using solid map from 3D.

1. 1. Open the Solid Map panel
   2. Go to the general subpanel.
   3. click the source geom switch and select none.
   4. Activate the dest geom: surf selector.
   5. Select the top surface of the boss
   6. Click the along geom switch and select mixed.
   7. Activate the along geom: mixed lines selector.
   8. Select the middle line of the cylinder of boss.
   9. Activate the along geom: mixed node path selector.
   10. Select the 13 nodes to define the exact location of the solid element layers.
   11. Click elems to drag: elems >> by collector >> boss.
   12. Click select.
   13. Click mesh.

• • • HyperMesh creates the elements and completes the mesh on this part.
• After creating 3D mesh, delete the 2D mesh of the boss.

Questions and Answers:

1. Check the material properties of the rail component and calculate the speed of sound in steel rail=______

sol:

speed of the sound in steel can be calculated by formula:-`c=sqrt(E/rho)`

From the given First_run.oooo.rad file you can get the above data:

Now `c=sqrt(210000/0.0078) (mm)/(ms)`

c=5188.75 m/s.

2,3. The length of the rail is about 1000 mm.calculate the time takes for a shock wave to travel from one end of the rail to the other.

sol:

Time for travelling shockwave from one end to other end is given by `t=(l/c)`

where

• • l=length
  • c= speed of sound in steel

`therefore t=1000/5188.75 (ms)`

t=0.162ms

4.Edit the engine file so that the stress wave can be monitored, moving from one end of the rail to the other during impact -this will require a termination time equal to the time it takes for the sound to travel the length of the rail(set on/RUN card)

5.Set the frequency of animation output to a time that will give 20 animation steps(/ANIM/DT)

6.Change /print -10.

sol:

4,5and 6 are changes in engine files we can edit in notepad or in hypermesh after importing these rad files.

The no of animation steps depends upon frequency and run time

`animation steps=(runtime)/(Frequency)`

i.e., ANIM/DT=Tstop/Tfreq

• Runtime is 0.192 ms (4 ans)
  • based on that corresponding frequency is 0.0096 to get 20 animation steps(5 ans)
• print change is shown in below image.

• To change values in hypermesh go to view>browsers>hypermesh>click\'solver\'.
• In solver tab you can find the below shown files to edit \'double click\' and change.

Conclusion:

• Created error free 2D mesh of the given models in hypermesh by using advanced pre-processing tools.
• Generated 3D tera and hex volume meshing of the models in hypermesh.

drive link:

https://drive.google.com/open?id=1YSdYs41i1zGoevLZ_bWgU4M8qpzYd2Uk