Crash Tube Analysis using contact interface Type-7 and Type-11 and different kinematic condition using Hypermesh and Radioss
Objective - In this challenge we will be comparing the base setup simulation results that are Type-7 and Type-7 along with Type-11 on a crash tube and different kinematic condition simulation results.
Questions -
- Create the mesh for bumper assembly, mesh size should be 6mm.
- Run the crash tube model as it is.
- Change the Inacti=6 and run.
- Create the type 11 contact and run.
- Remove both notches and remove boundary conditions on the rigid body node then run.
- Create a new notch in the middle, select the whole section and run.
- Create a new notch with nodes only from opposing 2 faces and run.
Procedure -
Create the mesh for bumper assembly, mesh size should be 6mm.
- Open Hypermesh and load the .hm file.
- By using the automesh option in 2D panel with target element size of 6mm and using quads only element, creates 2D mesh on the component.
- After creating a mesh check for the quality in the tool panel > check elems.
- Check quality criteria for max element size, min element size, warpage and other value to make it error free.
- Then by using the connectors option in the 1D panel, creates the 1D connector like spot weld, seam weld and connects the parts of the bumper.
CRASH TUBE
Case - 1 Crash_tube - Run the crash tube model as it is.
- Open Hypermesh and load the .rad file for the crash tube.
- Then go to the application tab and click on the Hypercrash and open it.
- Here also load the .rad file for the crash tube.
- Then check for the contact interface.
- There are two contact interfaces. First is Type-2.
- And Type-7.
- In Hypercrash create a /TH/PART card in the data history tab and assign it to all parts of the crash tube.
- After that, export the .rad file from Hypercrash and save it as “Crash_tube_0000.rad” file.
- Import the “Crash_tube_0000.rad” file in Hypermesh.
- Then, run the RADIOSS analysis in Hypermesh and check for the results.
- After that check for the .out file for energy error and mass error.
Results obtained by the HyperGraph.
- Energy
- Rigid wall
Results obtained by the HyperView.
- Von Mises
Observations -
- Internal energy increases gradually with time and kinetic energy starts decreasing with time.
- The Contact energy was very high during the collision between the crash tube and the wall where in the total energy observed is directly opposite to contact energy.
- Hourglass energy remains constant.
- Resultant Tangent force was increasing and decreasing quite steadily wherein Resultant Normal force increased rapidly and it reached its maximum value and after the impact its falls gradually.
Case - 2 Crash_tube_type7 - Change the Inacti=6 and run.
- In Hypercrash, after exporting the file. Change the values of Inacti in Type-7.
- Enter the recommended Type-7 values in the Type-7 card in contact interface.
- After that, export the .rad file from Hypercrash and save it as “Crash_tube_type7_0000.rad” file.
- Import the “Crash_tube_type7_0000.rad” file in Hypermesh.
- Then, run the RADIOSS analysis in Hypermesh and check for the results.
- After that check for the .out file for energy error and mass error.
Results obtained by the HyperGraph.
- Energy
- Rigid wall
Results obtained by the HyperView.
- Von Mises
Observations -
- Internal energy increases gradually with time and kinetic energy starts decreasing with time.
- The Contact energy was very high during the collision between the crash tube and the wall where in the total energy observed is directly opposite to contact energy.
- Hourglass energy remains constant.
- Resultant Tangent force was increasing and decreasing quite steadily wherein Resultant Normal force increased rapidly and it reached its maximum value and after the impact its falls gradually.
Case - 3 Crash_tube_type11 - Create the type 11 contact and run.
- In Hypercrash, after exporting the file. Create a new card named as Type-11 in contact interface along with Type-7 interface card.
- Type-11 interface (edge to edge) card enters the recommended value and assigns it to the crash tube component part.
- After that, export the .rad file from Hypercrash and save it as “Crash_tube_type11_0000.rad” file.
- Import the “Crash_tube_type11_0000.rad” file in Hypermesh.
- Then, run the RADIOSS analysis in Hypermesh and check for the results.
- After that check for the .out file for energy error and mass error.
Results obtained by the HyperGraph.
- Energy
- Rigid wall
Results obtained by the HyperView.
- Von Mises
Observations -
- Internal energy increases gradually with time and kinetic energy starts decreasing with time.
- The Contact energy was very high during the collision between the crash tube and the wall where in the total energy observed is directly opposite to contact energy.
- Hourglass energy remains constant.
- Resultant Tangent force was increasing and decreasing quite steadily wherein Resultant Normal force increased rapidly and it reached its maximum value and after the impact its falls gradually.
Compare the results of Case - 1, Case - 2 and Case - 3.
Von mises
Contact Energy
In case 1 Inacti is 0 which means that there is no action taken for removing initial penetration and in case 2 and case 3 Inacti is defined as 6 in which means it removes the initial penetration where possible. There is no initial penetration. So, there is no major change in case 2 and case 3 and they follow the almost same curve.
Graph follows the same behavior in all cases. As in case 1, it is less than case 2 & 3. Due to Igap= 3, more elements come under the minimum gap for impact activation.
Internal Energy
As the crash tube impacts the ground the internal energy rises. Similarly here the same behaviour is observed in a simulation. In case 2 & 3 it rebounds early from case 1 that why in case 1, it stores more energy w.r.t time and in case 2 & 3 releases its internal energy while rebound.
Rigid Wall
Rigid wall forces are the forces which act on the rigid wall while the crash tube is crushed. As the crash tube crushes and makes a curve in the surface at that moment there is change observed in rigid wall forces.
We observe from all three simulations that in case 2 and case 3, crash tubes rebound one frame earlier than the case 1. From this we can say that the rigid wall force is more in case 2 & case 3 which we can see in the above graph.
Case - 4 Crash_tube_no_notch - Remove both notches and remove boundary conditions on the rigid body node then run.
- In this case after exporting the .rad file, delete or remove the Boundary conditions on the rigid body.
- After that, export the .rad file from Hypercrash and save it as “Crash_tube_no_notch_0000.rad” file.
- Import the “Crash_tube_no_notch_0000.rad” file in Hypermesh.
- Remove both the notches in Hypermesh.
- Then, run the RADIOSS analysis in Hypermesh and check for the results.
- After that check for the .out file for energy error and mass error.
Results obtained by the HyperGraph.
- Energy
- Rigid wall
Results obtained by the HyperView.
- Von Mises
Observations -
- Internal energy increases gradually with time and kinetic energy starts decreasing with time.
- The Contact energy was very high during the collision between the crash tube and the wall where in the total energy observed is directly opposite to contact energy.
- Hourglass energy remains constant.
- Resultant Tangent force was increasing and decreasing quite steadily wherein Resultant Normal force increased rapidly and it reached its maximum value and after the impact its falls gradually.
Case - 5 Crash_tube_middle_notch - Create a new notch in the middle, select the whole section and run.
- Now in this case, create a notch in the middle of the crash tube.
- Then, run the RADIOSS analysis and name it as “Crash_tube_middle_notch_0000.rad” in Hypermesh and check for the results.
- After that check for the .out file for energy error and mass error.
Results obtained by the HyperGraph.
- Energy
- Rigid wall
Results obtained by the HyperView.
- Von Mises
Observations -
- Internal energy increases gradually with time and kinetic energy starts decreasing with time.
- The Contact energy was very high during the collision between the crash tube and the wall where in the total energy observed is directly opposite to contact energy.
- Hourglass energy remains constant.
- Resultant Tangent force was increasing and decreasing quite steadily wherein Resultant Normal force increased rapidly and it reached its maximum value and after the impact its falls gradually.
Case - 6 Crash_tube_side_notch - Create a new notch with nodes only from opposing 2 faces and run.
- Now in this case, create a notch only from opposing 2 faces of the crash tube.
- Then, run the RADIOSS analysis and name it as “Crash_tube_side_notch_0000.rad” in Hypermesh and check for the results.
- After that check for the .out file for energy error and mass error.
Results obtained by the HyperGraph.
- Energy
- Rigid wall
Results obtained by the HyperView.
- Von Mises
Observations -
- Internal energy increases gradually with time and kinetic energy starts decreasing with time.
- The Contact energy was very high during the collision between the crash tube and the wall where in the total energy observed is directly opposite to contact energy.
- Hourglass energy remains constant.
- Resultant Tangent force was increasing and decreasing quite steadily wherein Resultant Normal force increased rapidly and it reached its maximum value and after the impact its falls gradually.
Compare the results of Case - 4, Case - 5 and Case - 6.
Von mises
Contact Energy
Here we can see that in case 6 (Opposite side notches) has higher contact energy. Case 4 (crash tube with no notches) has less than case 5 and case 6 both. This is due to less elements coming under the minimum gap compared to case 5 and case 6.
Internal Energy
As the crash tube starts crashing into the rigid wall the internal energy is more in case 4 as compared to case 5 and case 6. That means a crash tube without notches absorbs more energy at a faster rate. At the end when the whole crash tube crashes, the internal energy gets constant.
Rigid Wall
For all three cases, Rigid wall forces fluctuate in the beginning. As the crash tube crashes, rigid wall force increases. Rigid wall force increases drastically and then comes to zero which we can see in the above graph.
Conclusion -
- Performed meshing on the bumper and then checked for the quality also by using 1D connectors, connecting the bumper component.
- Performed crash analysis on the crash tube and compared the simulation results of Type-7 contact interface with and without recommended interface properties and Type-11 along with Type-7 with recommended properties.
- Compared simulation without a notch, all side middle notches, and opposite side notch in the last three cases.
- For all cases internal energy, contact energy, rigid wall and von mises graphs obtained.
Google Drive Link - It contains all case file - that are .rad, .out, hyperview file and plots, hypergraph file and graphs, .hm and .tpl files and bumper meshing file.
https://drive.google.com/file/d/1B0Iy7bOHt-ixWYik5mipUVtZgnY1hYDv/view?usp=sharing