Setting up a Crash Simulation of a Aluminium rail against a rigid wall.

1. Setting Up a Crash
Simulation in LS-Dyna
Made By:
Akshay Mistri

2. Scenario under Consideration
• Given Aluminium rail needs to be crushed against a
rigid (non-deforming) wall.
• Velocity of rail is 15.6 mm/milli-sec.
• 500 KG mass is distributed on the non-impacting
end.

3. Material Properties
Density
[kg/𝒎𝒎 𝟑]
Youngs Modulus
[GPa]
Yield Stress
[GPa]
Tangent Modulus
(ETAN)
Poisson
Ratio
Aluminum 2.7 x 10−6
70 0.20 2.00 0.33

4. Importing the Rail into LS-Dyna
• Go to file > open > Keyword file.
• Browse your file (should be a .k file).
• You would see your rail imported into the LS-Dyna software.

5. Adding a Wall
• Go to page 5 > Wall > Create > Planar.
• Select the normal vector for the wall. (NormX here, refer picture below.)
• Click in the box under Tail, against X. (refer picture below.)
• Then click on the last corner node on the impacting end.
• As you click on the node, you would see some values entered in the Tail and Head
columns.
• Currently, the wall is coinciding with the corner node.
• Click on the first box under Tail and enter -1, hit enter key. (Click on NormY option
and again click on NormX option to refresh the position of the wall.)
• This will shift the wall behind by 1 mm.
• Click on apply and then on done.

6. Wall Normal Vector
• The normal vector of the wall should be against
(opposite) to the motion of the wall.
• To check that, go to Page 5 >Wall > Modify > Click on
the Wall name PLANAR.
• You can see the blue arrow pointing in the direction
opposite to the motion of the rail.
• This will ensure that the rail elements would see the
wall (take contact).

7. Adding Mass
• Go to page 5 > MassD > Create.
• Click on the “Top” button provided in the bottom area. (refer picture below)
• Click on the “Area” option. (refer picture below)
• Now drag and select the end nodes of the non impacting end.
• This would select all the nodes in the cross section.
• Now add mass value (per node mass, 500KG/80 = 6.25 here).
• Click on apply.

8. Describing Material
• Go to Page 3 > *MAT > Select 024 Piecewise_Linear_Plasticity.
• Click on edit.
• Click on the NewID > Enter Title.
• Enter the Material Properties.
• RO = Density
• E = Youngs Modulus
• PR = Poisson Ratio
• SIGY = Yield Strength
• ETAN = Tangent Modulus
• Click on Accept > Done

9. Describing Property
• Go to Page 3 > *Section > SHELL.
• Click on edit > NewID.
• Enter thickness in T1 and hit enter. (3 mm here)

10. Assigning Material & Property to the Rail
• Go to Page 5 > PartD > Assi (Assign).
• Select the rail (the only part we have).
• Click on SECID and choose the section we created. (refer picture below.)
• Similarly, select the MID (Material ID).
• Click on Apply.

11. Assigning Velocity
• Go to *Initial > Velocity.
• Click on edit.
• Put NSID = 0.
• This would assign velocity to all the
nodes.
• Give velocity in VX = -15.6 mm/msec.

12. Simulation Time
• We need to provide the time for which the
program will simulate the scenario.
• Go to page 3 > *Control > Edit.
• Provide 50 m-sec in ENDTIM.
• Analysis will be simulated for 50 milli-seconds.

13. Simulation Steps
• Also, we need to provide the steps in which the
calculation will be done.
• Go to page 3 > *Dbase > BINARY_D3PLOT.
• Here we provide the value of DT to be 2.5
• So, will have results for 𝐸𝑁𝐷𝑇𝐼𝑀
𝐷𝑇 = 50
2.5 = 20 steps. (
at 0, 2.5, 5, 7.5…. Milli-seconds).

14. Providing History Node
• We can define a node for which the program will make
more accurate calculation (not in steps of 2.5 milli-
seconds).
• For this, go to page 3 > *Dbase > HISTORY_NODE.
• Click on ID1 and click on Pick.
• Pick a node from the rail displayed on the non-impacting
end. Click on Insert.
• This is provided to note the displacement of the rail in x-
direction.
• Nodes on the impacting end will have erratic motion due
to crushing, so we select one from the non-impacting
end.

15. Getting the Results we desire
• Also, we need to ask the program the for any special results
we want to see. This could include Rigid Wall forces, material
summary, more accurate calculation for any special nodes.
• For this, go to page 3 > ASCII Option > Edit.
• Check mark on MATSUM which will provide the material
summary.
• Providing value DT = 0.001 will do calculations in 𝐸𝑁𝐷𝑇𝐼𝑀
𝐷𝑇 =
50
0.001 = 50000 steps. (0.001, 0.002, 0.003… milli-seconds)
• We will use this value of DT for other result options as well.

16. Results for Special Nodes
• For the history node we provided in slide 14 (node ID 3128), we
can define the more accurate calculation here in ASCII Option.
• Scroll down and check mark on NODOUT.
• Provide the value of DT to be 0.001.
• So, for the node 3128, the calculation will be done in 50000
steps.

17. Getting the Rigid Wall Forces
• We can also request the Forces generated with time on the
rigid wall we made.
• For this, check mark on RWFORC and provide the DT value.

18. Running the Simulation
• We are now ready to provide use this file for analysis.
• First, we need to save the keyword file with .k extension.
• The keyword file can be run by using LS-Dyna Manager.
• We could load the results by going to File > Open > Binary Plots.
• After the simulation is completed, we could see the results in page 1 > History.

19. Special Results
• For the special results, go to page 2 > Binout.
• Click on Load (shown below) and load the Binout file.
• Click on open files and you would get the special results requested.
• MATSUM will give material details.
• NODOUT will give results for the special node (3128).
• RWFORC will provide rigid wall forces.

20. Thank you!