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

Aim-

• Create the mesh for bumper assembly,mesh size should be 6mm. 
  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.

Objective-

• Plot RWALL forces ,contact forces,internal energy and Create TH/PART for all parts and compare results for all cases.
• Comment your thought on why there is a change in the internal energies.
• How does the notch affect the results?
• Plot energies and note any difference.

Procedure-

1. To mesh the bumper Assembly-

•  Import the .hm file. Go to File > Import > model. Click on Select File icon. Select the .hm file and click on Import.

• Switch to By Topo geometry color mode. Few free edges are found. These are easily fixed by using surface edit tool and edge edit tool available under Geom page.

     Go to Preferences > Criteria File Settings > Target element size. Enter Target element size = 6. Now press F12 to go to automesh panel. Enter element size =6 and mesh type to 6.

      Perform the meshing manually surface by surface.

      Now connect the crash boxes with the bumper using spot weld. Go to 1D > connectors > spot > spot. In the location selector, select the nodes of the crash box. In connect what selecctor, select the

      components to be connected, i.e crash box and bumper rear. enter no. of layers = 2 and search tolerance as 2.5. Select type as weld with diameter = 2 and click on create. The connectors will be created as

      seen below.

      Similarly connect the crash boxes.

• Thus, meshing is done on the bumper and the crash boxes are connected to the bumper using 1D connectors.

2.  Crash Box Simulation-

   a. Run the crash tube model as it is.

• After the Model is imported, The Simulation needs to be performed without changes in model in this case.

• In order to create the THPART we have to click on the output Blocks and create the TH PART , in entity id instead of nodes keep components and select all four components and click on ok. Then the TH part is created.

• To simulate the model, Go to the Analysis tab, Select the Radioss option > Select the location to save the file > Check include collectors box > In the options tab, type “-nt 4” > Click Radioss.

• Open hyperview to view animation and contour plots from H3d file. The simulation is shown in GIF below.

• From output file energy error is -3.8%% and mass error is 0% which is less than -15% to 2% and 1% respectively, so we can accept the results and plot the graphs by using hypergraphs.
• Open hypergraph 2d for observing the energy plot data from TA01 file.

• For this simulation, the max stress in von mises stress is 0.7356 MPa with max contact force is taken as 220N. The Time history for all the components is created in order to study the deformation and energy variation in each component with respect to time.

  The internal energy is rising which is shown in the graph with the rise in the beginning and with notch area as there will be less area at the position there will be smooth curve produced at that point.

  Kinetic energy is getting decrease as there will be contact with the rigid wall from the component and will decrease consistently as shown in the graph.

  The contact energy will be less at the beginning and there will be a peak on the energy in the graph as there will be accumulation of energy at one point.

  b. Change the Inacti=6 and run-

• In this case, we have to change the Inact = 0 to Inacti =6. Inacti = 6 will remove any initial penetration present. Elsewhere, it wiill reduce the defined gap to less than 30% of the defined value and adjust the gap.
• To change the Inacti to 6, click on model browser > groups>self contact> Type7 > Inacti. Set it to 6.

• After changing the parameters run the simulation with same steps to be carried as per previous case. The simulation is shown in GIF below. Plot the graphs of energies same as above case.

• The results of the energy error and mass error are below 10% which is acceptable. The graphs are plotted using the hypergraph.

• since all the load cases are similar, there is no change in the trend of energies and rwall forces for case 1. The maximum Rwall forces value is at 1400 N, which is the lowest compared to previous simulation values.

 c. Create the type 11 contact and run-

• For case 3, a type 11 contact is created between 2 edges. The recommended parameters for type 11 contact are set and then the analysis is run.

• After changing the parameters run the simulation with same steps to be carried as per previous case. The simulation is shown in GIF below. Plot the graphs of energies same as above case.

• The results of the energy error and mass error are below 10% which is acceptable. The graphs are plotted using the hypergraph.

• s seen in the graph, the kinetic energy is maximum at the beginning which starts decreasing once the crush tube impacts the rigid wall. This energy is converted into strain energy as the crush tube deforms.

• As observed by the increase in internal energy of the system. Energy error is about -3.8% which is acceptable. A part of total energy is used by the contact energy as seen in the graph. As total energy reduces, contact energy increases. Contact energy = contact force*distance moved to avoid penetration.

• The contact force is basically the energy spent by enabling a contact force to avoid penetration. This should be minimum. As seen above,the contact energy is very less for most of the time and there is slight increase in the contact energy at the end of simulation.

• For rigid wall, there is sudden rise in the peak value of rigid wall force after T=25. By this time, the crush tube is completly crushed and therefore the deformed model having no further scope for deformation.

   d. Remove all the notches from the model-

• Here, we have to remove both the notches and the boundary conditions on the rigid body and run the simulation. To remove the notches, we can use align option from the node edit option available under geom page. Go to Geom > node edit > align (F7). In the 1st and 2nd end selector, select two nodes (black) respectively, which will define a line along which the selected nodes on the notch (white) will be placed.

• Thus removing the notch. Click on align. The nodes will be aligned as seen below. Repeat the same procedure for the entire notch.

• To remove the boundary conditions on the rigid body, go to Solver > BCS > BCS > rbody_12456. Uncheck DOF1, DOF2, DOF3, DOF4, DOF5, DOF6 which will allow translation in X, Y, Z and rotation in X, Y, Z direction respectively.

• After changing the parameters & removing Notches run the simulation with same steps to be carried as per previous case. The simulation is shown in GIF below. Plot the graphs of energies same as above case.

• As seen here, there no notches on the crush tube. During impact, there is no localized deformation as there are no notches present and the deformation progresses as expected. The nature of energy graph is also similiar to previous case. Energy error is about -2.7% which is acceptable. 

• since all the load cases are similar, there is no change in the trend of energies and rwall forces for case 4. The maximum Rwall forces value is at 1080 N, which is the lowest compared to previous simulation values.

  e. Create a new notch in the middle ,select the whole section and run-

• In this case we have to create the notch at middle to the model. To create the notch we have to translate the elements from their original possition by using align the element option (shift+F4).

• After changing the parameters & adding Notches run the simulation with same steps to be carried as per previous case. The simulation is shown in GIF below. Plot the graphs of energies same as above case.

• As seen here, there no notches on the crush tube. During impact, there is no localized deformation as there are no notches present and the deformation progresses as expected. The nature of energy graph is also similiar to previous case. Energy error is about -2.8% which is acceptable. 

• since all the load cases are similar, there is no change in the trend of energies and rwall forces for case 4. The maximum Rwall forces value is at 1080 N, which is the lowest compared to previous simulation values.

  f. Create a new notch with nodes only from opposing 2 faces and run-

• Create notches on two opposing surfaces and run the simulation. The procedure to create notch is the same as discussed earlier using Translate tool.

• After changing the parameters & adding Notches to opposite side run the simulation with same steps to be carried as per previous case. The simulation is shown in GIF below. Plot the graphs of energies same as above case.

• As seen here, there no notches on the crush tube. During impact, there is no localized deformation as there are no notches present and the deformation progresses as expected. The nature of energy graph is also similiar to previous case. Energy error is about -2.5% which is acceptable. 

• since all the load cases are similar, there is no change in the trend of energies and rwall forces for case 4. The maximum Rwall forces value is at 1280 N, which is the lowest compared to previous simulation values.

Comparision of Result-

Comparison of different cases:

• We have separated the first 3 cases as contact type and the second 3 cases based on notches.
  In the first 3 cases, we find that no differences were noted between Cases 1 and 2 because there were no initial penetrations in the model for the Inacti to have an effect.
• The has increased no of cycles and increase other because we have defined a Type 11 edge to edge contact.
• There are no physical differences in the path of the curve of the internal energies only difference is present in the values of it which are obtained according to the case definition.
• There is no hourglass energy since there are recommended properties i.e. shell formulation inputted by default.

Conclusion-

• It is observed that in case 4 where the  notch is removed, the stress induced in the crush tube is the least compared to other cases. The crush tube with notches undergo stress concentration and these areas are the first to undergo deformation. The deformations are predictable in case of notched components. No initial penetration is observed in case 1 where Inacti = 0. If initial penetration existed.
• Due to addition of notches introduces a multiaxial state of stress in the notch throat plane. The stress at the notch root would be higher than the nominal applied stress.
• Since there is no change in graph pattern of the internal energy as per screening of all energies