Assignment 2 - Engine file editing and Meshing exercises
1. Speed of sound in steel rail:
The radioss starter input deck has the following units:
g mm ms
So Modulus of elasticity (E)= 2.10E5 g `(mm)^-1` `(ms)^-2`
Density (R)= 7.8E-3 g / `(mm)^-3`
Speed of sound = `sqrt(E /R)` = 5188.7452 mm/ms or m/s
The values have been taken from the input files.
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2. Time taken for a shock wave:
Speed of sound in rail = 5188.7452 mm / ms;
Length of steel rail = 1000 mm;
Time taken = Length / speed = 1000 / 5188.7452 = 0.1927 ms
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3. Time taken for sound to travel length of rail:
Speed of sound in rail = 5188.7452 mm / ms;
Length of steel rail = 1000 mm;
Time taken = Length / speed = 1000 / 5188.7452 = 0.1927 ms
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4. Editing the Engine file:
In order to monitor the stress wave which moves from one end to other of the rail, set the termination time equal to the value calculated above i.e., 0.1927 ms.
Note that in the Starter Input Deck, the system of units was already in ms. So we have to just change the value \"60.0000000000000\" to \"0.1927\" in the file ending with \"_0000.rad\".
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5. Setting the frequency of animation output:
For this, one has to change the value below /ANIM/DT.
In order to get 20 animation steps, change this value to 0.1927/20 = 0.009635 ms.
The changed lines look like below:
/ANIM/DT
0.000000000000000 0.009635000000000
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6. Charge/print -10:
The print value has been set to -10.
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Modified Engine File snapshot:
There are 20 engine animation files generated in the folder.
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7. Meshing
Component1 - Arm Bracket:
Link to the file:
https://drive.google.com/open?id=1jxqitUqSeqDS4DHHylJhSYLXSl2_0kih
Step 1: Create a 2D Quad mesh on the L shaped surface with element size = 10. After that mesh the surface which has the L Shape. It should look like the below.
Then extrude this mesh to form the hex mesh by using the \"Element Offset\" command using the Mesh > Create > 3D Elements > Element Offset.
Select the above elements, mention \"number of layers\" to be \"5\" and \"total thickness\" = \"25\". Then click \"offset+\". You should get this.
Then using the \"line drag\" command, the elements in the L-shaped surface can be revolved in the curved line to get the below mesh configuration. This can also be accomplished using \"spin\" command. But you need to have the centre of the arc which can be obtained using selecting three points in the arc.
Then mesh the L-shaped set of surfaces between the arm_straight and boss components. Then using the \"linear solid\" to build the mesh between two sets of elements to get a mesh like below.
The remaining boss will be meshed by first creating a mesh on the cricular sufrace on the bottom,
selecting a line along the height dimension of the boss (along x axis) and then use the \"solid map\" panel to get the mesh. Like below.
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Component2 - Housing:
Link to file:
https://drive.google.com/open?id=149K4wqT3cvJ7F575ihb3HkhlHgc-4x20
There are totally 3 components in this model.
The hub and the cover are surfaces. The third component called \"tetras\" which is empty at the beginning can be used to store the 3D tetra mesh generated at the later stage.
Cover:
Make the cover to be the active component.
The cover is first meshed using the tetra mesh option in 3D meshing. The tet size is kept to 5 mm and so is the tet collapse.
After the mesh is generated, check for the quality of elements to see if it has met the desired criteria.
Using the Unmask option inside the Mask Panel (F5), one can visualize like the following.
Hub surface mesh:
Note that that the \"hub\" component is just a surface mesh. Like seen below.
Hub tetra mesh(Volume):
So we have to create a volume mesh based on tets and then store it on \"tetras\" component by making it active.
Again the tetramesh option is used. The tet size is maintained to be 5 mm.
And then the element quality is checked with respect to tet collapse value.
Mesh of both hub and cover:
Both components after meshing.
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