2D and 3D meshing with calculations for critical length of element

## Comments by grader

Hi Sandesh, good to see your submission.

Objective: To mesh and edit given geometries and engine files as per conditions provided.

Question 1:Find the speed of sound in the steel rail component.

Answer: Speed of sound in a material in this case AISI 1018 Steel considering 1 DOF i.e. 1D element can be calculated by :

c = (E/Rho)^1/2

where, c – speed of sound in the material.

E – Modulus of Elasticity of the material.

Rho- Density of the material.

c = (205 e9 (Pa) / 7.8 e3 (N/m³) ) = 5126.60 m/s (as per the formula the unit should be Nm/kg hence the value is approximate )

t_c – target/ Critical time step is 0.5 micro seconds

hence,

t_c = l / c , here ‘l’ is the element length.

5 e-7 = l / 5126.60

l = 5e-7 * 5126.60

= 2.5633e-3 m

= 2.5633 mm.

As we know, time step t < t_c , let us consider the minimum element length to be slightly larger than the critical length such that at end of time step the shockwave won’t reach the next element and we would get more realistic results. Hence, l = 2.7mm

Question 2: Length of rail is 1000mm.Find the time required of the shock wave to travel across the rail.

Answer: Total Time required= Total No. Of elements * Time step

= (1000 / 2.7) * 5e-7

= 371 * 5e-7 = 1.85185e-4 seconds

= 0.185185 milliseconds.

Question 3: Time for sound wave to travel through rail is:

= Length / speed of sound in rail material

= 1 / 5126.60 = 1.95061e-4 seconds

= 0.195061 milliseconds.

Question 4,5 and 6:

Question 7:

No any 2D meshed component provide.

Question 8: Arm Bracket Hex Mesh:

1. First of all the upper face of the Base was meshed with Quad elements. Using the Element offset option the base component was meshed with 5 layers.
2. For the Arm component, Spin option was used. For that the 2D mesh on Base was selected as elements to spin. Using Find centre option the centre of the arc which makes the arm was found and made the Base node. The angle was given as 90 with 20 layers of elements.
3. For the Straight arm part, Linear solid option was used. First the 2D face of the arm mesh was obtained using find faces option in Tools tab. This face is used as the source mesh.Now the opposite face of the arm straight is meshed with 2D quad elements using automesh option. It is made sure that the element column and rows are exactly as the 2D face obtained previously. Now these elements are selected as target mesh. For alignment equivalent nodes on a single element were selected in the exact order for both source and target face. An element density of 10 is given and the part is meshed.
4. For the Boss component it is essential to include the mesh of the straight arm for connectivity. Here, Solid map option is used. First the face on the plane surface which makes the top/bottom of the cylinder is meshed with 2D quad elements. It is made sure that the mesh on face is matching the mesh on the side of the straight arm. Now, for the mesh to follow along a node path across the boss needs to be identified. Hence the end node of the arm mesh is copied and projected on the other face of cylindrical boss. Now, the 2D mesh on boss is selected as source mesh. The target mesh is not needed here hence is kelp on none. For the drag along option the nodes along path option is selected and the end nodes are added. A 10 layer mesh is formed on the boss in this way.
5. In the delete window, element by configuration- 2D – QUAD4 is selected to get rid if any unnecessary elements.

https://drive.google.com/open?id=14tZipcyWVFQQ2rZOtppKjrsvuJGE4cIp

Housing Cover Tetra Mesh:

1. As the cover is to be meshed with tetra elements, 3D tab- tetramesh – volume tetra. Is the process.
2. As not many element criteria were given in the problem statement, simple mesh with target size 5mm and tet collapse of 0.15 was observed here. To capture the edges and smaller geometry features, Use curvature and proximity was turned on with min. element length 1mm.
3. Finally the mesh was checked for the tet collapse condition using element check option.

https://drive.google.com/open?id=1T2BoqLcI95o5EdxZZE1gPGHm-UfGQAAg

Drive folder with the .hm files:

https://drive.google.com/open?id=1SNIr6Y52tM8KZQDmtuZ6g8ftebSI5eCU

File with suggested changes:

https://drive.google.com/open?id=18jrbuVH8_mqdL1kI21IXmYf1FzvCi5BJ