Compare the base setup simulation results and different kinematic condition simulation results

Objective: Generate mesh for bumper assembly with mesh size 6mm and compare base setup simulation and different kinematic condition results for given crash tube files.

Case Set up and Execution:

Meshing:

• Open given Bumper_System.hm file in Hypermesh.
• Create mesh using automesh with size 6mm, one face at a time.
• Check element quality.

Case-1: Run as it is

• Open Crush_tube_0000.rad file in Hyperworks.
• No changes were to be made to the given file in this case, so run the file in Radioss.
• After the run, open the obtained .h3d file for animation of deformation of the crush tube in Hyperview and graphs are plotted in Hypergraph using .T01 file.

• At around 25ms, there is a increment in contact, kinetic energy, resultant velocity and decrement in resultant normal force, resultant displacment. Reason being, the deformation has travelled throughout the length of the tube and the tube has undergone a rebounce from the rigid wall causing a sudden rise in reaction force.

Case-2: Change Inacti=6

• Open Crush_tube_0000.rad file in Hypercrash.
• Change the inacti value to 6 in TYPE7 Contact in Contact interface section
• Export the file and run the file in Radioss.
• After the run, open the obtained .h3d file for animation of deformation of the crush tube in Hyperview and graphs are plotted in Hypergraph using .T01 file.

Case-3: Create TYPE11 Contact

• Open Crush_tube_0000.rad file in Hypercrash.
• In contact interface section change the TYPE7 Contact values as per recomendded values mentioned in video.
• Create a TYPE11 contact as explained in video.
• Export the file and run the file in Radioss.
• After the run, open the obtained .h3d file for animation of deformation of the crush tube in Hyperview and graphs are plotted in Hypergraph using .T01 file.

Case-4: Remove both notches and remove boundary condition on rigid body node

• Open previous case file in Hypercrash.
• Remove all the notches using Align nodes option.
• Export the file and run the file in Radioss.
• After the run, open the obtained .h3d file for animation of deformation of the crush tube in Hyperview and graphs are plotted in Hypergraph using .T01 file.

Case-5: Create a new notch in the middle

• Open previous case file in Hypercrash.
• Create a notch in the middle of the model using Align nodes option.
• Export the file and run the file in Radioss.
• After the run, open the obtained .h3d file for animation of deformation of the crush tube in Hyperview and graphs are plotted in Hypergraph using .T01 file.

Case-6: Create a new notch only on 2 opposing faces(symmetric)

• Open previous case file in Hypercrash.
• Remove the notch created for previous case.
• Create a notch symmetrical on opposite faces using Align nodes option.
• Export the file and run the file in Radioss.
• After the run, open the obtained .h3d file for animation of deformation of the crush tube in Hyperview and graphs are plotted in Hypergraph using .T01 file.

Result and Conclusion:

The results obtained are tabulated below:

Parameters		Case 1	Case 2	Case 3	Case 4	Case 5	Case 6
Energy Error		-3.80%	-3.80%	-5.10%	-5.40%	-7.30%	-4.90%
Cycles		83697	83697	84607	76679	103944	73659
Contact Forces(Kn)		93.85	93.85	410.3	334.5	685.3	404
Internal Energy(J)		42010	42010	41500	41340	39890	41490
Von-Mises stress(Mpa)		696.8	696.8	620.7	654.5	635.6	612
Contact Energy(J)		2031.58	2031.58	2671.73	2853.21	3967.32	2594.77
Rwall forces(KN)	Normal	1340.6	1340.6	1519.3	1286.22	1446.19	1479.19
	Tangent	5.298	5.298	4.651	22.63	110.45	8

• Changing the value of Inacti had no effect on results of case-2 from case-1.
• The contact force(to prevent penetration of slave nodes into master segments for TYPE7, edge slaves into edge masters in TYPE11 interfaces) and Rwall forces inceased in case-3 due to addition of TYPE11 Contact interface and TYPE7 value changes.
• In all the cases, the crush tube deformation started at the notch, except in Case-4.
• There is rotational motion on top the cube after boundary conditions on rigid body node is removed.
• There was a decrease in contact, internal energy and normal Rwall forces in case-4 when all the notches are removed along with boundary conditions because there is less inital interacting faces than the cases with initial notches.
• The 4 sided notch in case-5 at the middle of tube results in the largest contact force. Adding the notches increases contact force because of initial interactions.
• By having only 2 notches on opposite faces we can see that there is an increase in contact, internal energy and normal Rwall forces.
• The purpose of notch is to direct the deformation in a predictable manner. Without notches as a triggering mechanism, the deformation may be unpredictable which is dangerous in a crash event.