assignment 5 - Lu s Figueiredo
Assignment 5
Case specification for the assignment:
Case 1: Model as it is.
Case 2: Inacti value set to 6
Case 3: Type 11 interface created.
Case 4: Model with Type 11 interface, without the boundary condition in the master node of the rigid body and without notches
Case 5: Model with Type 11 interface, without the boundary condition in the master node of the rigid body and with only one notch around the entire section.
Case 6: Model with Type 11 interface, without the boundary condition in the master node of the rigid body and with only one notch in two of the sides of the tube.
1. Model set up
Case 2. In this case, the field corresponding to Inacti (action to take if initial penetrations exist) is switched to 6, as the following image suggests.
Case 3. In this case, a Type 11 self contact was created, in addition to the Type 7 contact that was already in the model. The parameters in the Type 11 were defined in a similar way to the ones on the Type 7 contact, as shown in the image below.
Since Type 11 in an edge-to-edge type of contact, in order to create the self contact, all the edges of the model were put into two identical sets. Then, those sets were chosen to be the master and slave contact entities.
In order to obtain the plots for the force on the Type 11 interface, an output block was created for this contact.
Case 4. For this case, the contacts were left in the same condition as case 3 but all the notches of the part were removed, with the help of the \"node align\" command. Apart from that, the boundary condition that was constraining the movement of the rigid body was removed. The next image shows the total model without the notches.
Case 5. The contacts in this model remain the same but a notch was created. This notch involves the entire cross-section, as seen in the image below. This notch was created using the \"node align\" and \"repalce node\" commands as well as other mesh editing functions.
Case 6. Similarly to the case above, a notch was also created. But, in this case, the notch only involves nodes from two opposite faced of the tube, as described in the following image.
2. Results
The results will be shown for 4 instants of the simulation: t = (7, 15, 22, 30) ms
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
3. Rigid wall forces comparison
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
4. Contact forces comparison
4.1. Type 7 interface
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
4.2. Type 11 interface
Case 3
Case 4
Case 5
Case 6
5. Internal energy comparison
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
6. Bumper meshing
The bumper was meshed using a 20 mm element side, which seemed appropriate for this situation. No triangular elements were used. The geometry was mirrored using the \"reflect\" function.
7. Conclusions
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Overall, the force registred in the Type 11 is close to zero. This is due to the fact the mesh of the components is very regular (the edges of the square elements are, most of the times, aligned with the coordinated axes), this means that, in a compression process as this one, the nodes of the elements end up impacting on each other, requesting the Type 7 contact to be activated, since this contact is being used as a general node-to-node contact. If the mesh was more irregular, there would be more edges of elements impacting on each other, leading to an increase of the forces registred in the Type 11 interface.
- The internal energy always reaches its maximum value around t = 22 ms, when the tube is completely buckled and is mostly subjected to plastic deformation, therefore, absorbing more energy.
- The force on the rigid wall reaches the maximum value also around = 22 ms, when there\'s no more room for the compression of the tube, so the model behaves in a stiffer way, allowing a greater part of the force applied on the tip to be passed to the rigid wall, which increased this value dramatically around the end of the simulation.
- From the animation of the simulation, I can conclude that notches can affect the way that the part deforms but only if they are applied to two opposite facees (as it was done for case 6). There wasn\'t much difference in the deformation shape between models with one notch around the entire section and models without notches. Adding a notch that involves two opposite faces can force that particular cross section of the model to shrink in the direction perpendicular to the faces where the notch is applied and to extend in the other direction. This is a way to make the deformed shape of the tube more predictable.