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

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

Aim: - 

1. Mesh the bumper assembly with mesh size 6mm.

2. Run the crash tube model with different cases. 

Objectives: - 

Model 1- Create the mesh for bumper assembly, mesh size should be 6mm.

Model 2-  Run the crash tube model with the following different cases.

1. Run the crash tube model as it is.
2. Change the Inacti=6 and run.
3. Create the type 11 contact and run.
4. Remove both notches and remove boundary condition on rigid body node then run.
5. Create a new notch in the middle, select the whole section and run.
6. Create a new notch with nodes only from opposing 2 faces and run.

1. Plot RWALL forces, contact forces, internal energy and Create TH/PART for all parts and compare results for all cases.

2. Comment your thought on why there is a change in the internal energies.

3. How does the notch affect the results?

4. Plot energies and note any difference.

 

Interface / Contact Modeling

Normally the explicit analysis method solves highly complex nonlinear problems and contact definition is an important part of many nonlinear problems. In order to get the best results and real behavior of any simulations, including contacts, accurate modeling of contact interfaces between bodies is a crucial part. Based on the applications RADIOSS has a large number of contact types. Each of those interfaces was developed for a specific application field, but this field is not the only choice criteria. In RADIOSS an interface is created by defining the master segment and slave set. The master segment can be parts, elements, contact surface, node sets, and similarly for slaves the selection can be parts and node sets. Once these master-slave sets are identified the algorithm will check these locations for potential penetration of a slave node through a master segment, and this check is done in every time step.

In a simple language, Interfaces are defined to model how parts interact when they come into contact with each other.  

Types Of Interfaces Used In RADIOSS 

 

Out of the many interface types listed above, the most used ones for impact simulation are:

 

Following methods are mostly used.  

1. Interface Penalty Method.

2. TYPE7   - Variable Stiffness, Node to Surface Contact.

3. TYPE11 - Variable Stiffness, Edge to Edge Contact.

4. TYPE19 - Combination of TYPE7 and TYPE11.

5. TYPE24 - Linear Stiffness, Node to Surface, and Surface to Surface Contact.

 

1. The Penalty Method Used In Interfaces: - 

The penalty method treats the behavior between slave nodes and master segments as springs that generate resistive forces as a function of penetration Spring elements are created between the slave node and its projection.

   

The spring stiffness is automatically computed according to the material and property of both master segment and slave node

Variations Of Interfaces

Interface Type 7: Nodes to Surface Contact: - 

 1. Automatic node to surface contact interface using penalty method with variable stiffness.
 2. A gap is defined around the master segment and the slave nodes.
 3. The contact gap can be constant or variable.
 4. Resistive forces are applied to keep slave nodes out of the contact gap.
 5. The interface time step is computed to ensure stability.

Important Interface Parameters

1. Igap         - Determines how the size of the gap is calculated.
2. Gapmin    - Minimum gap for activation of the interface.
3. Inacti       - Action to take if initial penetrations exist.
4. Istf          - Affects how the stiffness of the interface is calculated.
5. Iform       - Friction formulation.
6. Stmin       - Minimum stiffness to use in the interface.
7. Idel          - What to do with slave nodes and master segments if an element fails (deleted) that they are attached to.

Interface Type 7: Recommendations For Crash Applications.

Advantages & Disadvantages

Advantages: - 

1. Physically correct representation.

2. High accuracy for describing self-contact and buckling.

3. Best used with shells to shells or solids to shells.

Disadvantages: - 

1. Requires more stringent modeling practices.

2.  Does not tolerate intersections (slave node passing master segment).

3. Time step may reduce due to increasing interface stiffness.

Limitation Of Nodes-To-Surface Interface

There are situations where the Type 7 node to surface interface will not “see” the contact due to edges crossing each other at angles.

Interface Type 11: Edge To Edge Contact

In the case of edges crossing, a Type 11 interface can be added to capture the physics correctly.

1. Type 11 is defined by identifying master and slave lines (edges).

2. Type 11 works similar to Type 7 in terms of:

• Penalty formulation.

• Gap definition.

• Search method.

 

 

Model: - 1 - Create the mesh for bumper assembly, mesh size should be 6mm. 

Procedure: - 

1. Import the model.

 

 

 

2. Now mesh the given model with element size 6.

 

 

 

 

 

3. After that, connect the two-part by using a spot weld. 

Go to the 2D>>connector>>spot

Final Model: - 

 

 

 

Model 2: - Import the given .rad file and perform all the cases one by one.

CASE 1: - Run the crash tube model as it is. 

1. Firstly, import the .rad file.

Given Model: - 

 

After that, go to analysis and select radios.

Upload .rad file and put -nt 4 in options, then press Radioss.

Wait for a minute to complete the entire procedure.

 

Now, the procedure is completed. Press Result.

After that, open the model in contour mode.

Now, open the Hypergraph 2D to view the graph and open the crush_tubeT01 file.

 

All the energies are in one graph.

 

 

CASE 2: - Change the Inacti=6 and run. 

 

After that, go to analysis and select radios.

Upload .rad file and put -nt 4 in options, then press Radioss.

Wait for a minute to complete the entire procedure.

 

 

 

Now, the procedure is completed. Press Result.

After that, open the model in contour mode.

 

Now, open the Hypergraph 2D to view the graph and open the crush_tubeT01 file.

All the energies are in one graph.

 

 

 

CASE 3: - Create the type 11 contact and run.

 

 

 

 

After that, go to analysis and select radios.

Upload .rad file and put -nt 4 in options, then press Radioss.

Wait for a minute to complete the entire procedure.

 

 

Now, the procedure is completed. Press Result.

After that, open the model in contour mode.

Now, open the Hypergraph 2D to view the graph and open the crush_tubeT01 file.

 

All the energies are in one graph.

 

CASE 4 Remove both notches and remove boundary condition on rigid body node then run. 

Remove the notches by using align node.

After that go to the solver and delete boundary conditions.

After that, go to analysis and select radios.

Upload .rad file and put -nt 4 in options, then press Radioss.

Wait for a minute to complete the entire procedure.

Now, the procedure is completed. Press Result.

After that, open the model in contour mode.

Now, open the Hypergraph 2D to view the graph and open the crush_tubeT01 file.

All the energies are in one graph.

 

CASE 5 Create a new notch in the middle, select the whole section and run.

Now, measure the distance of previous notches using nodes, so while creating notches in the middle the distance is accurate.

Create a duplicate node and measure the distance.

 

The distance is 4.236, now go to an element offset in 2D and offset the element with the of 4.236.  

Select the element for the notch.

Notches are in the middle are shown below.

After that, go to analysis and select radios.

Upload .rad file and put -nt 4 in options, then press Radioss.

 

Wait for a minute to complete the entire procedure.

 

 

 

Now, the procedure is completed. Press Result.

After that, open the model in contour mode.

 

Now, open the Hypergraph 2D to view the graph and open the crush_tubeT01 file.

All the energies are in one graph.

 

 

CASE 6: - Create a new notch with nodes only from opposing 2 faces and run. 

In this case, we have to create a notch in between the middle only, & with opposite faces, as shown below.

Use the translate command for the notch with a distance of 4.236.

Select the nodes and then translate them.

 

After that, go to analysis and select radios.

Upload .rad file and put -nt 4 in options, then press Radioss.

Wait for a minute to complete the entire procedure.

 

Now, the procedure is completed. Press Result.

After that, open the model in contour mode.

Now, open the Hypergraph 2D to view the graph and open the crush_tubeT01 file.

All the energies are in one graph.

Result Table: - 

Cases	Changes in Model	Interface Type	Cycles	Energy Error %	Internal Energy	Kinetic Energy	Max. Rigid Wall Force
1	No Change	Type 7	83500	-3.8%	0.4201E+05	592.5	1338.1
2	Change into inacti =6	Type 7	83500	-3.8%	0.8403E+05	1185	2676.1
3	Changes into recommended parameter	Type 11	83200	-3.8%	0.4203E+05	566.5	1350.83
4	Remove notches & Boundary conditions	Type 11	78000	-3.0%	0.4234E+05	557.2	1202.02
5	Create notches in the middle	Type 11	100800	-3.5%	0.4212E+05	524.4	1174.67
6	Create notches in opposite faces.	Type 11	83600	-3.1%	0.4222E+05	611.7	1282.09

 

Learning Outcomes: - 

1. We learn about different types of interfaces.

2. We learn about how the notches affect the model.

3. We learn about how the model affects due to some changes in parameters. 

4. We learn about how the internal, kinetic & total energies changes in graphs.

Conclusion: - 

 In this challenge, we mesh model 1 & connect them by using spot weld. In model 2 we run the crash file with different cases and make the result table.