MODIFYING STARTER FILE BASED ON COMPONENT PROPERTIES AND CREATING 3D TETRA AND HEXA MESH FOR SOLID COMPONENTS
OBJESCTIVE
To create tetra mesh and hex mesh for given solids with given specifications in Hypermesh.
Modify the engine file and edit the properties of Steel rail component by using Radioss
PROCEDURE
1. The Radioss starter file is imported in the Hypermesh window and the component is displayed
2. The Radioss starter file is opened and the material property of the rail component is found as Steel.
By navigating to the card under Solver>MAT>LAW_2PLAS_JOHNS>STEEL.
3. Properties of the steel used in the component are present in the property ID
Modulus of Elasticity E = 2100000.0 Gpa and
Density ρ = 0.0078 g/mm3
Speed of the sound in Steel rail = √ (E/ρ) = √ (2100000.0/0.0078) = 5188.7452 mm/s
4. Time for the Shock wave to travel a distance of 1000mm in the steel rail component
Time = distance / speed
= length of component / speed of sound in the component
= 1000 / 5188.7452
= 0.1927 ms
5. Editing the engine file so that impact of shock wave can be monitored and changing the frequency of the animation to animation steps
Here the timestpe value is entered for the component as 0.1927ms
To calculate the frequecy the timestep value is divided by number of steps
frequency = timestep/no. of steps
= 0.1927/20
= 0.009635
Once the file has been modified, the engine file is alone exported.
The exported engine file is opened in notepad to view the changes.
Thus the Radioss is file is edited to have desired input parameters based on the component properties.
7. 3D meshing - Tetra mesh and Hex mesh
A) Creating a Tetra mesh with tet size of 5mm and checking tet collapse for a value of 0.15
The Solid housing component is imported and viewed in solid form.
First for the hub, 2D mesh is created with Trias only of element size 5mm.
By masking few elements, the 2D surface mesh is clearly seen.
Then under 3D tab, by using the Tetramesh option the 2D tira elements are made into 3D tetramesh elements and the Tet collapse valus is set to 0.15.
Under the TOOL tab, check elements option is chosen to test the quality of mesh. For Tet collapse value of 0.15 no elements fail.
Lastly for the cover component Volume tetra option is chosen by navigating to Tetramesh under 3D mesh. The element size is given as 5mm and tet collapse value is 0.15
Then the elements are checked for tet collapse and zero of them fail.
Thus 3D tetra mesh for a given component is created and checked for Tet collapse.
7) B) Creating a 3D Hex mesh fot the arm bracket component.
The model is imported in hypermesh and viewed in solid view.
(1) Base
The base part is first the top surface alone is meshed by using 2D surface mesh with Quads only option with an elemet size of 10mm.
Then Element Offset option is chosen Under 3D tab for creating 3D mesh.
Total thickness value of 25 mm is given for 5 layers of elements along the two normal surfaces. These normal surfaces act as direction in which element offset takes places.
(2) Arm Curve aprt
Using F5 key, the hex elements are masked. The remaining 2D mesh elements are alone visible
The wire frame view of arm part is switched on and the Spin option is chosen under 3D Tab.
For the base point, by selecting three points of the arc and creating the base point node on circle centre.
The elements needed for the spin option are selected. Angle = 90 degree.
In the end the 2D mesh elements of the base component are deleted.
(3) Arm Straight
The arm straight part is meshed using Linear solid option.
To use Linear solid option the start and end face elements of the part is required.
For that the by using faces tab the find faces option is used to create end face elements of the arm_curve part.
Then the end face of arm_straight part is 2D meshed with quads only and it is made sure that both the faces contain same number of elements in all rows and columns.
After this the alignment points are selected in both the face elements. It is to be noted the alignment points must have same direction of rotation in both faces.
Then the element density is given as 12 and mesh is created. The faces created is deleted after this step.
(4) Boss
The top surface of the Boss is 2D meshed and the mesh is altered such that the elements in the outser surface match with the elements on the arm_straight part\'s end face
For propragating this 2D mesh along the length of the boss Solid mapping is used.
Source geometry is selected as none and for destination geometry bottom surface is selected. The elements are selected to drag and direction is defined by creating a node path along the length of the cylinder.
After creating 3D mesh, it is moved to BOSS elemet and the 2D mesh is deleted.
The final mesh for the entire arm bracket component is displayed below.
CONCLUSION
- The RADIOSS FILE IS EDITED BASED ON COMPONENT PROPERTY
- TIMESTEP VALUE IS CALCULATED
- 3D TETRA MESH IS CREATED AND CHECKED FOR TET COLLAPSE
- 3D HEX MESH IS CREATED FOR THE ARM BRACKED COMPONENT
Google drive link for the files used in this project
https://drive.google.com/open?id=1F8p997zW-xN0Dwb8_Rb1UMjOEcqsiSBb