Assignment 2 3D Meshing and Engine File Editing

Objective:

In this Report, I will answer some theoretical questions and conduct 3D meshing for some models.

Answers:

1. To calculate the speed of sound traveled in steel rail, we should first have the steel Young\'s Modulus and density:

`E=210000 MPa`

`ρ=0.0078 g⁄〖mm〗^3`

Therefore, speed of sound in steel rail is:

`c=√(E/ρ)=√(210000/0.0078)=5188.75 mm⁄ms`

2. The length of the rail is 1000 mm, the time it takes a shock wave to travel from one end of the rail to the other end is calculated by:

`∆t=l/c=1000/5188.75=0.19 ms`

3. The time for sound to travel by the length of the rail is the same as the time for a shock wave to travel that same amount of length `∆t=l/c=1000/5188.75=0.19 ms`

4. To monitor the stress wave moving along the length of the rail, we can set the termination time equal to the time it takes the stress wave to move by this length of the rail (0.19 ms).

5. To have 20 animation steps (frames), we can set the frequency of animation output to 0.19/20 = 0.0095 ms.

6. The printout frequency is set to -10.

The change of engine file is as follows:

7. 3D Meshing: Tetra Mesh and Hexa Mesh

a. Tetra Mesh for Housing

- Method 1: Create surrounding faces with Tria mesh (Element type: first order Tria3, mesh size = 5 mm) and then 3D mesh by Tetra mesh (Element type: Tetra4, Min = 3 mm, Tet collapse = 0.15).

Some comments: Assign a material with density `ρ=7.89e-3 g⁄〖mm〗^3` to this component and check element quality:

• Tet collapse criteria = 0.15 --> No failed elements.
• Timestep criteria = 5e-4 ms, min timestep of component = 6.66e-5 ms < 5e-4 ms --> some elements failed --> we have to remesh the model with coarser mesh to increase the minimum timestep (by increasing minimum element length).

- Method 2: Create Tetra mesh using Volume Tetra: Element type: first order Tetra4, size = 5 mm.

Some comments: Assign a material with density `ρ=7.89e-3 g⁄〖mm〗^3` to this component and check element quality:

• Tet collapse criteria = 0.15 --> No failed elements.
• Timestep criteria = 5e-4 ms, min timestep of component = 5.73e-5 ms < 5e-4 ms --> some elements failed --> we have to remesh the model with coarser mesh to increase the minimum timestep (by increasing minimum element length).

- Method 3: Quick Tetra Mesh.

Some comments: assign a material with density `ρ=7.89e-3 g⁄〖mm〗^3` to this component and check element quality:

• Tet collapse criteria = 0.15 --> No failed elements.
• Timestep criteria = 5e-4 ms, min timestep of component = 2.88e-5 ms < 5e-4 ms --> some elements failed --> we have to remesh the model with coarser mesh to increase the minimum timestep (by increasing minimum element length).

b. Hexa Mesh for Arm Bracket

- Step 1: Create Hexa mesh for Base using Element offset - Solid layers (Original element size to offset = 10 mm, Element type = Quad4 number of layers = 5):

- Step 2: Create Hexa mesh for Arm curve using Spin (angle = 90, on spin = 25):

- Step 3: Create Hexa mesh for Arm straight using Linear solid (density = 12):

- Step 4: Create Hexa mesh for Boss using Solid map (general method):

--> Final Mesh of the whole model is as follows: