Creating 1-D Spring, Mass, Bar, Beam and Rod elements by forming RBE2 and RBE3 links on a set of brackets using Hypermesh and Hyperbeam.
Objective:
The objective of the project is to understand and create 1D Bar, Beam and Rod elements by creating RBE2 and RBE3 links on set of brackets and use Hyperbeam to effectively set the dimension and cross sections of the elements.
Procedure:
1. Import the file by going to File -> Import geometry and choosing the IGES file required
2.Create a Midsurface for the geometry by going to Geom -> Midsurface. Select the top bracket and click on extract to create the Midsurface for the same.
3. Now, rename the Midsurface component in the component tree as Bracket 1 and change the colour of the Midsurface if required.
4. Perform the same operation for the bottom bracket as well.
5. Create a new component and rename it as Bracket_2 such that both the midsurfaces created are not considered as one single component.
6. Delete the solid brackets by going to Delete -> solids and choosing the two brackets.
7. Delete the components which are not required in the Model tree such that only the Midsurface is visible.
8. Go to Tools -> Organize and Move the new Midsurface to component – “Bracket_2” and delete the Midsurface.
9. Next, we need to represent this 2D component as 3D. Hence, we need to assign a thickness by creating material and creating property.
To do this go to:
a)Create -> Material
b)Create -> Property.
Set the material as steel by applying the Young’s Modulus and Poisson’s ratio values and set two different properties (since there are two brackets). Select card ID as PSHELL for the Optistruct profile. Assign the material in the property section as steel which we created earlier.
10. Update the property for the components Bracket_1 and Bracket_2 in the property section.
11. We now create Washer Splits for the holes. To do this, go to Geom->Quick Edit->Washer Split. Set any offset value that is desired. (eg: 5)
12. Next, we are required to create the mesh
a)Go to 2D-> Automesh and set the required parameters and select the entire model that needs to be meshed.
b)Set element size as any desired value.(eg:8)
c)Adjust the number of nodes around the washer split such that we get equal number of nodes and the mesh is better.
13. Let us create Rigids and rbe3 elements.
a) Rigids are also known as rbe2 elements and have infinite stiffness.
b)Reb3 elements can be moved in different directions based on the loading conditions.
For the challenge we are required to create rbe2 links on the upper left hole on the top and bottom brackets.
To create rigids, go to 1D->Rigids and create links by selecting multiple nodes around the hole. Also select the calculate node option, otherwise the links will not be created properly.
Perform this on both the left side holes of the upper and lower brackets.
Set the dof as required. The challenge requires us to set only translational degrees of freedom.
14. An rbe3 link should be created on the middle hole, rbe3 on the right hole, and rbe2 on the bottom holes of the top and bottom bracket. Follow the same procedure used for reb2 link creation and create the rbe3 links with the required number of DOFs.
15. After this, join the two brackets using a spring element on both sides. Go to 1D -> Springs.
CELAS1 represents the spring element.
16. Next, the links that were created need to be connected using beams, bars and rods.
Go to 1D -> Hyperbeam -> Standard section and set the three cross sections that need to be created.
The required cross sections are:
ROD : BOX- Dimension a= 12 mm
Dimension b=10 mm
Thickness t= 0.75 mm
b. Beam : I Section- Dimension a= 8 mm
Dimension b= 10 mm
Dimension c= 8.5 mm
Thickness t1= 0.75 mm
Thickness t2= .6 mm
Thickness t3= .6 mm
c. Bar :CROSS section- Dimension DIM1= 5 mm
Thickness DIM2= 1.2 mm
Dimension DIM3= 10 mm
Thickness DIM4= 1.2mm
17. Create the Box with the required dimensions:
18. Create the I section with the required dimensions:
19. Create the Cross with required dimensions:
20. Create the Rod elements on the left holes by going to 1D -> Rods.
Select the middle node of the links of the top and bottom bracket. Set the element type as CROD.
21. Similarly create the BEAM element by going to 1D -> BAR, choose the element type as CBEAM and choose starting and ending nodes along with orientation as shown below:
22. Create the beam:
23. Similarly create the bar:
24. Create properties for Rod, Beam and Bar by going to Create -> Property. And set the properties accordingly.
25. Update the assigned properties to Rod, Beam and Bar by going to 1D -> Rod or Beam.
26. Update the local axis, Property and elem type and update these for all the three 1D elements.
27. Now change the view to 1D detailed element representation to view the applied cross section of the elements.
28. The 1D elements have been created.
29. Let us now add masses on the two outer holes on the top bracket. Go to 1D -> Masses. Add the required mass (eg: 10). Set element type as CMASS1.
Result:
The required 1D Spring, Mass, Rod, Beam and Bar elements were created using Hyberbeam and were fixed on the set brackets. A better understanding of the usage of rods, beams and bars for different loading conditions was achieved. The image of the final result can be seen below.