Challenge

Assignment 5-RADIOSS Interfaces & Study of Effect of Notches Challenge

Objective:-

To mesh the given bumper model with a mesh size of 6 mm.
To run the crash tube simulation with the given 6 cases and plot the graph for energies.

Procedure to mesh the bumper:-

Import the .hm file. Go to File > Import > model. Click on the Select File icon. Select the .hm file and click on
Switch to By Topo geometry color mode. Few free edges are found.
These are easily fixed using the surface edit tool and edge edit tool available under the Geom page.
Go to Preferences > Criteria File Settings > Target element size. Enter Target element size = 6. Now press F12 to go to the auto mesh
panel. Enter element size =6mm.

Now connect the crash boxes with the bumper using spot weld. Go to 1D > connectors > spot > Weld
In the location selector, select the nodes of the crash box.
In connect what selector, select the components to be connected, i.e crash box and bumper rear. enter no. of layers = 2 and search tolerance as 2.5.
Select type as weld with diameter = 2 and click on create. The connectors will be created as seen below

Case 1:

We have to run the simulation as it is with no changes. Open Hypermesh with user profile as Radios. To import the 0000.rad file,
click on File > Import > Solver deck, and import the file.

After importing the file, we can check the defined interface in the model.Type7 interface is used. It is a general-purpose interface
that can simulate all types of impact between a set of nodes and a master surface.
The major advantage of the Type7 interface is that it is non-oriented and slave nodes can belong to the master surface enabling
self-impact.
Following are the defined parameters in the model -
Istiff = 4 (affects how the stiffness is calculated)
Igap = 0 (determines how the size of the gap is calculated)
Gapmin = 1 (min. gap for activation of interface)
Iform = 2 (stiffness based formulation for sliding forces)
Inacti = 0 (action to take if initial penetration exists)
Stmin = 1 (min thickness in the contact to avoid too soft contact)
I stiff = 4 will set the stiffness of interface based on the softer of master and slave.
Igap = 0 will take the size of the gap defined by Gapmin.
Inacti = 0 will take no action against initial penetrations if any.
To run the simulation, go to Analysis > Radios. Using the save as option, give the destination to where the file is to be saved. Toggle the export options to all and run options to analysis.

Click on Radios. The simulation will start running.
As seen below, having a notch in the crush tube affects the way the model deforms.
After hitting the rigid wall, the crush tube deforms in the area of the notch first and then deforms further.

As seen in the graph, the kinetic energy is maximum at the beginning which starts decreasing once the crush tube impacts the
rigid wall.

RIGID WALL FORCE

This energy is converted into strain energy as the crush tube deforms as observed by the increase in internal energy of the system. Energy error is about -3.8% which is acceptable.
A part of total energy is used by the contact energy as seen in the graph. As total energy reduces, contact energy increases.
Contact energy = contact force * distance moved to avoid penetration.
The contact force is basically the energy spent by enabling a contact force to avoid penetration. This should be minimum.
As seen above, the contact energy is very less for most of the time and there is a slight increase in the contact energy at the end of the simulation. For rigid walls, there is a sudden rise in the peak value of rigid wall force after T=25.
By this time, the crush tube is completely crushed and therefore the deformed model has no further scope for deformation gets pushed against the wall with some velocity to which the rigid wall reacts.

Case 2:

In this case, we have to change the Inact = 0 to Inacti =6. Inacti = 6 will remove any initial penetration present. Elsewhere, it will reduce the defined gap to less than 30% of the defined value and adjust the gap.

To change the Inacti to 6, click on Solver browser > Interface> Type7 > Inacti . Set it to 6.
After this, run the simulation. The procedure is the same as discussed earlier.

The nature of deformation and the energy graph is similar in nature compared to case 1. Energy error is -3.8% which is
acceptable.

Case 3:

In this case, we have to create Type11 contact and run the simulation. To create the contact, we will use Hyperworks, which is a specialized preprocessor for Radios.

After importing the file, click on create icon and select Edge to edge (Type11). Type11 interface is defined by identifying master and slave lines.
This contact, when added with Type 7 can help to capture the physics correctly. This is very helpful in the case of edges crossing where the nodes of the element are far away and the element is in close proximity to another surface.
Type 7 uses the penalty method in Interfaces which treat the behavior between slave nodes and master segments as springs that generate resistive force as a function of penetration.
Type 11 works in a similar manner as Type 7 in terms of penalty formulation, gap definition, and search method.

Here too, the nature of deformation and energy graph nature is similiar to the previous case. The notched portion is first to deform. Energy error is about -3.9% which is acceptable.

Case 4:-

Here, we have to remove both the notches and the boundary conditions on the rigid body and run the simulation.
To remove the notches, we can use align option from the node edit option available under the Geom page.
Go to Geom > node edit > align. In the 1st and 2nd end selector, select two nodes (black) respectively, which will define
a line along which the selected nodes on the notch (white) will be placed, thus removing the notch. Click on align.

The nodes will be aligned as seen below. Repeat the same procedure for the entire notch.
To remove the boundary conditions on the rigid body.

As seen here, there are no notches on the crush tube. During impact, there is no localized deformation as there are no notches present
and the deformation progresses as expected.

The nature of the energy graph is also similiar to the previous case. Energy error is about -2.6% which is acceptable.

Case 5:-

In this case, we have to create a new notch in the center and run the simulation.
We can create a notch by using the translate option available under the Tool page. To properly create the notch, use the N1, N2, N3
option to define the plane of translation. Translate the nodes by 4.2mm and create the notch.

Also here, after impact, deformation is first observed in the middle in the portion where the notch is.

The nature of deformation and the energy graph is similar in nature compared to previous cases. Energy error is about -2.7%
which is acceptable.

Case 6:-

Create notches on two opposing surfaces and run the simulation. The procedure to create a notch is the same as discussed earlier
using the Translate tool.

Now run the simulation.
Deformation is first observed into the notched region and the energy graph is similar in nature compared to previous cases.

Conclusion:-

The Bumper model have meshed and welded with the element size of 6mm and is ready for further solving and
post-processing.
All 6 cases of the crash tube have been simulated and results are compared using various energies plots.

Ship work like this
in your own course.