Assignment 5

OBJECTIVE: To compare the effect of notches on a crash tube with the help of type 7 and type 11 contact interfaces to the results. The different cases will be compared on the basis of Internal energies, contact forces, and total resultant forces.

PROCEDURE:

CASE 1

• Go to import > import solver deck > select Crash_tube_0000.rad > import.
• Go to view > select browsers > then select hypermesh > select solvers.
• Right-click in solver tab > create > select TH > click on PART > select all the components.
• Go to analysis > Click on RADIOSS > check : include connectors > Change options to : -nt 4 > click Radioss.

CASE 2

• Go to import > import solver deck > select Crash_tube_0000.rad > import.
• Go to view > select browsers > then select hypermesh > select solvers.
• Now in solvers > select INTER > under type 7 change Inacti to 6.
• Right-click in solver tab > create > select TH > click on PART > select all the components.
• Go to analysis > Click on RADIOSS > check : include connectors > Change options to : -nt 4 > click Radioss

CASE 3

• Go to import > import solver deck > select Crash_tube_0000.rad > import.
• Go to view > select browsers > then select hypermesh > select solvers.
• Now in solvers > select INTER > under type 7 change Inacti to 6.
• In solvers > right-click > create > select INTER > Then select type 11. Set the properties of type 11 given in the picture below.
• Right-click in solver tab > create > select TH > click on PART > select all the components.
• Go to analysis > Click on RADIOSS > check : include connectors > Change options to : -nt 4 > click Radioss.

CASE 4

• Go to import > import solver deck > select Crash_tube_0000.rad > import.
• Go to view > select browsers > then select hypermesh > select solvers.
• Now in solvers > select INTER > under type 7 change Inacti to 6.
• In solvers > right-click > create > select INTER > Then select type 11. Set the properties of type 11 given in the picture above.
• Go to solvers > right-click BCS > delete.
• Right-click in solver tab > create > select TH > click on PART > select all the components.
• Go to geometry > node edit > select align nodes > remove the notch using this tool.
• Go to analysis > Click on RADIOSS > check : include connectors > Change options to : -nt 4 > click Radioss.

CASE 5

• Go to import > import solver deck > select Crash_tube_0000.rad > import.
• Go to view > select browsers > then select hypermesh > select solvers.
• Now in solvers > select INTER > under type 7 change Inacti to 6.
• In solvers > right-click > create > select INTER > Then select type 11. Set the properties of type 11 given in the picture above.
• Go to solvers > right-click BCS > delete.
• Right-click in solver tab > create > select TH > click on PART > select all the components.
• Go to geometry > node edit > select align nodes > remove the notch using this tool. And use the same tool to create the new notch in the middle.
• Go to analysis > Click on RADIOSS > check : include connectors > Change options to : -nt 4 > click Radioss.

CASE 6

• Go to import > import solver deck > select Crash_tube_0000.rad > import.
• Go to view > select browsers > then select hypermesh > select solvers.
• Now in solvers > select INTER > under type 7 change Inacti to 6.
• In solvers > right-click > create > select INTER > Then select type 11. Set the properties of type 11 given in the picture above.
• Go to solvers > right-click BCS > delete.
• Right-click in solver tab > create > select TH > click on PART > select all the components.
• Go to geometry > node edit > select align nodes > remove the notch using this tool; use the same tool to create the new notches according to the given condition.
• Go to analysis > Click on RADIOSS > check : include connectors > Change options to : -nt 4 > click Radioss.

RESULTS & Discussion

To obtain the plots we use hyper-graph. Change the application to hypergraph and then import the T01 file to obtain the results for each of the cases. The results obtained using hyper-graph are Internal energies, contact energies, total resultant forces, and part internal energies comparison between all the cases.

Along with that, we analyze animations too. This is done using Hyper-view. Change the application to hyper-view and then import the h3d file. Change the parameter to von misses/contact forces [depending on the property to be analyzed] then select all the components and use the simple method to animations for all the cases.

1. Internal energy: Internal energies in all the cases are sen to increase exponentially to a maximum value and then decreases. This maximum increase is seen between 25 - 27.5 ms. The maximum value of internal energy among all the cases is in case 1 which is to a value of 42500. Here, cases 2 and 3 have the same values of internal energies at all times. In the 4th case where there are no notches, initially the internal is seen to be maximum then its rate of increase decreases compared to cases 5 and 6. Its value between 7 to 15 ms is seen to be the same as that of cases 1,2,3&5 however the maximum value of internal energy is slightly less than cases 1,2,3. Comparing cases 5 and 6, we observe that case 6 is seen to have the maximum internal energy most of the time but its maximum value is less than case 5. Comparing cases 4, 5 & 6 we see that absence of boundary condition and increase in the notches decrease the maximum value of internal energy but these cases have greater values of internal energies at all times, but, the maximum.

2. Contact Energy: The rate of increase in the contact energy with time is exponential at the beginning, then the increase is seen to be a mix of linear and exponential for a brief period followed by a rapid exponential increment till it reaches its peak then it drops and becomes constant. The peak is seen to be different in comparison to the internal energies. Here case 6 has the maximum value of the contact energy followed by case 5, then case 4, then case 3 and 2 are seen to have the same values at all time (but the case 2 has a slighter maxima w.r.t case 3), and the least value is for case 1. The maxima are at the same instance as the internal energy maxima. This is because of the increase in notches from cases 4 to 5 and 5 to 6 the contact forces also increases and is maximum right after 25ms. This is further explained in the following topic.

3. Contact Forces: In the first three cases there are boundary conditions and an equal number of notches. With the addition of Inacti=6 that checks initial conditions, the contact forces are seen to increase. Furthermore, the contact between case 2 and 3 are the same as they have similar number of notches and BCS.

Now for cases 4,5 and 6 the notches increase as we move from 4 to 6 so the contact forces increases. This is because the increases in crevices increase the change of contact with the surfaces under it. Thus the case 6 is seen to have much more contact force compared to case 4. Also, the notches increase its susceptibility to compression of the model around that cross-section, thus increasing the contact forces.

4. Total Resultant forces / RWALL forces: The least resultant force is posed by case 6 and the maximum resultant force is posed by case 5. The curve of resultant forces is quadratic. It is also seen that cases 2 and 3 have the same change in resultant force throughout the motion. The drop in the resultant forces is sudden and becomes zero as the model gets completely compressed. But as the notches in case 6 are more, they obstruct the complete compression in the normal direction so it does not fail completely and still applies force to the rigid wall.

5. Part internal energy:

Points to remember:

• PSHELL1: GREEN part
• PSHELL2: RED part
• PSHELL_2mm: BLUE part
• PSHELL2_2mm: YELLOW part

Here we see that the green and yellow parts have similar internal energies. The same goes for the blue and yellow components. This shows the shape of the components .i.e it presence of notches affect the internal energies of the component and also that symmetrical objects have similar internal energies.

In pshell_2mm and pshell2_2mm we see that the peak value of internal energy increases as the notches increase. But its the opposite for pshell1 and pshell2 components as they don't have any notches in all the cases.

*The bumper meshing model is in the attached zip folder.