Assignment 5

                                 

                                                                                                                                         ASSIGNMENT-5

OBJECTIVES:

• Carry out simulations of Crash tube model by varying the different parameters such as initial penetrations, contact type, number of notches on a case basis and understand the influence of these parameters on the simulation.
• Mesh the bumper assembly with target element size of 6mm.

PROCEDURE:

Case-1

1. Download the crash tube rad file given and open it on Hypermesh.
2. Create TH Part in output requests for all the components of the model.
3. Save and export the radios file.
4. Solve on Radioss.
5. Observe the simulation on Hyperview and plot the graphs for Internal energy, Contact energy, parts internal energy and rigid wall forces on hypergraph.                                                           

           Fig: TH PART Output request

Case-2

1. Open the crash tube model on Hypercrash.
2. Go into model browser and select contact (type-7) and edit its parameters.
3. Change the Inacti=6 and hit save.
4. Export the radios file and solve on radios.
5. Observe the simulation on Hyperview and plot the graphs for Internal energy, Contact energy, parts internal energy and rigid wall forces on hypergraph.                                                        

           Fig: Inacti=6

Case-3

1. Open the crash tube model on Hypercrash.
2. Go into model browser and hit on contact, create a new contact.
3. Select contact type as type-11 and change the parameters to recommended settings.
4. Save the changes and export the radios file, solve on radios.
5. Observe the simulation on Hyperview and plot the graphs for Internal energy, Contact energy, parts internal energy and rigid wall forces on hypergraph.                                                         

          Fig: type11 contact

Case-4

1. Open the crush tube model on hypercrash, go into model browser and hit on boundary conditions.
2. Remove the boundary conditions on translations and rotations and save the changes.Export the rad file.
3. Change the version on exported rad file to 120 from 2018.
4. Open the rad file in hypermesh.
5. In the panel, go to tools and click translate.
6. Use translate to remove the notches and align the nodes.
7. Save the changes to the model and export the radios file.
8. Solve it on radioss and observe the simulation on hyperview.
9. Plot the graphs for Internal energy, Contact energy, parts internal energy and rigid wall forces on hypergraph.

Case-5

1. Open the model in hypermesh.
2. Go to tools and use translate to create notch at middle and align the nodes.
3. Save the model and export the rad file.
4. Solve on radios and observe the simulation on hyperview.
5. Plot the graphs for Internal energy, Contact energy, parts internal energy and rigid wall forces on hypergraph.                                                                                                                                      

 Bumper system meshing

1. Open bumper_system.hm file and clean up the geometry by toggling edges wherever necessary.
2. Mesh the components with 6mm target element size.
3. Create a rigid (RBE2) 1D element at the face of the crash box, thus connecting the upper and lower crash box.
4. Use seam connectors (with rigid type) to connect the edge of the flaps of crash box to the bumper rear. Pitch used is 3mm with a tolerance of 5mm.
5. Save the model

.

           Fig: Bumper assembly

RESULTS AND OBSERVATIONS:

The internal energy trend for all cases were observed to be the same, as deformation occurred the lower parts (pshell_2mm ) underwent initially with the upper parts getting deformed after some time and thus the internal energy of the lower and upper parts get superimposed. This can be viewed in the internal energy plots of the various individual parts.

                    Fig: Internal energy total and Internal energy of individual parts (Case-1)

As can be observed, at approximately 7ms , the upper parts start deforming and the superimposed internal energy can be viewed in the form of an increase in slope at around 7 ms.

A similar trend is observed for all other cases.

It was observed that rigid wall forces intially increased to a maximum and then dropped suddenly after the crash tube was fully deformed. However, it was observed that on reduction or absence of  of notches it was easier to deform the crash tube as could be interpreted from the peak rigid wall forces which were lower in these cases.

Fig: Rigid wall forces plot ( for case-1,2,3)

Fig: Rigid wall forces (case-4 without notch)

Fig: Rigid wall forces ( case-5 with single notch in the middle)

Fig: Rigid wall forces ( case-6 with notches on opposite faces)

It can be seen that maximum Rigid wall force for Case-1,2,3 >Case-6>Case-5>Case-4.Thus, in the absence of notches rigid wall forces are lowest, while notches on opposite faces experience higher rigid wall forces compared to component with a single notch on all sides.

Contact energy variation had a similar trend across cases. The contact energy is observed to increase once the deformation reaches the notch and owing to the geometry of the notch and the component greater self contact within the component is observed. The self-contact increases upto a maximum until the entire component can no more be deformed. This is followed by  little drop in contact energy as some spring back is observed.The presence of notches showed a greater contact energy than case without notch.

                   Fig: Contact energy (Case-1,2,3)                            Fig: Contact energy (Case-4 no notch)

           Fig: Contact energy (Case-5 single notch)                       Fig: Contact energy (Case-6 opposite faces)

 Maximum contact energy Case-1,2,3>Case-5>Case-6>Case-4.Thus, the presence of notches indicates greater contact energy in the simulation.

CONCLUSION:

Thus, through the assignment different types of contact modelling and their parameters were understood. The effects of the notches on the results were studied and the outcome was that the presence of notches in the geometry leads to higher rigid wall forces and greater contact energy generation during the course of simulation. Also, 2D meshing of bumper assembly was carried out and learnt how to apply 1D connectors such as seam and RBE2 elements to an assembly along with its various parameters.