USING 3D MESHING FOR THE HOUSING & ARM BRACKET | HYPERMESH

OBJECTIVE:

1. To check the material property of the rail component and calculate the speed of sound in steel rail.
2. 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.
3. Time for sound to travel length of rail.
4. To edit the engine file so that the stress wave can be monitored moving from one end of the rail to the other.
5. To set the frequency of animation output to a time that will give 20 animation steps(/ANIM/DT).
6. 3d meshing tetra mesh and hex mesh.

RESULTS:

For given steel

E = 205000 `N // mm^2`

`rho` = 0.0078 `g // mm^3`

L = 1000 mm

1. Speed of sound (c) = `sqrt (E // rho)` = `205000 / 0.0078` = 5126 m/s

2. Elemental time step = L/c = 1000/5126 = 0.195083 s

3. Time for sound to travel length of rail = 0.195083 s

4. On editing the engine file:

Fig 1 - editing the file

5. For 20 animation dividing the elemental time by 20 = 0.195083/20 = 0.0097541

MESHING THE MODEL:

To mesh the housing using the tetra mesh:

Fig 2 - Shows the hub & cover

• We first create a 2D mesh and the mesh type is tria with element size 5mm.
• Tis 2D mesh is then converted to 3D mesh by using the tetramesh option, the tetramesh parameters the minimum tetra size is maintained at 3 mm & tet collapse value is set to be 0.15.
• All the elements are chosen and then meshed by using tetramesh.

Fig 3 - Tetramesh on the hub

• There are zero elements that have tet collapse less than 0.15.

Fig 4 - Tetramesh on the cover

Tet collapse: Tet collapse of a tet element is minimum of (h)/(1.24 `sqrt`A). Where h is the perpendicular distance from a node to the opposite face of the TET & A is the area of the opposite face.

Meshing the arm bracket with mesh type hex and with element size 10 mm:

• For the base 2D mesh is first created on the surface and the mesh type has been chosen to quads only.
• After creating the shell mesh element offset has been to create a solid mesh.
• Since the arm curve is a curved geometry the spin feature was used to create the mesh.
• For the arm straight it is a tapered geometry. The mesh is generated using the linear solid. The source elements were chosen and then the destination elements were first created using 2D automesh then selected. After that the nodes were selected on the source face and then the nodes on the of the elements of the destination face.
• The solid map operation was used to create hex8 elements on the boss.

Fig 5 - Arm bracket

Conclusion:

• Tetramesh of size 5 mm created on the hub model.
• Hex8 of size 10 mm created on the arm bracket.