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

. OBJECTIVE:- To mesh the given bumper model with mesh size of 6mm.

TO run the crash tube simulation with given 6 cases and plot the graph for energies.

. Procedure to mesh the bumper.

Import the .hm go to file>import>model. click on select file icon. select the .hm file and on import.

switch to by topo geomectric color mode. few free edges are found these are easily fixed by using surface edit tool and edge edit tool availabe under geom page.

go to perferences>criteria file setting> target element size. enter target element size = 6. now press F12 to go to automesh panel. enter element size = 6 and mesh typs to 6.

perform the meshing manually surafce by surface.

now connect the crush boxes with the bumper using spot weld. go to 1D> connector > spot > spot. in the loaction select the nodes of the crush box. in connect what selector 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 types as weld with diameter = 2 and click on create. the connecetros will be create as seen elow.

similary connect the crash boxes.

Thus, meshing is done on the bumper and the crash boxes are connected to the bumper using 1D connectros . Now we can proceed to run the simulation for the given crash tube.

case 1:

we have to run the simulation as it is with no change open hypermesh with user profile as radioss to import the 0000.rad file, click on file > import > solver deck and import the file.

after importing the file, we can check the define interface in the model. type 7 interface is used it is a general purpose interface which can simulation all types of import between a set of nodes and a master

surface major advantage of types 7 interfce is that it is non oriented and slave nodes can belong to the master surafce enabling self impact. following are the define parameters in the model-

1. Istiff = 4 (affects how the stiffness is calculation)

2. Igap = 0 (determine how the sizee of the gap is calculated)

3. Gapmin = 1 (min. gap for activation of interface)

4. Ifrom = 2 (stiffness based formulation of sliding force)

5. Iacti = 0 (action to take if initial penetration exists)

6. Stmin = 1 (min thickness in the contact to aviod too soft contact)

Istiff = 4 set the stiffness of interface based on the softer of master and slave.

Igap = 0 will take the size of gap define by gapmin

Iacti = 0 will take no action againest initial penetrations, if any.

to run the simulation, go to analysis, go to analysis radioss. using the save as option given the destination to where the file is to be saved. toggle the export option to all and run option to analysis.

Click on radioss the simulation will start runing.

as seen below, having a notch in the crush tube affect the way the model deforms. after hitting the rigid wall, the crush tube deforms in the area of notch first and then deforms further.

As seen in the graph, the kinetic energy is maximum at the beinning which atarts decreaseing once the crush tube impacts the rigid wall. this energy is convert into strain energy as the crush tube deforms.

as observed by the increase in internal energy of the system. energy arror 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

Raduces contact energy increase. contact energy = contact force*distace moved to aviod penetration. the contact force is basically the energy spent by enabling a contact force to aviod penetraction. this

Should be miniumum as seen above the contact energy is very less for must of the time and there is slight increase in the contact energy at the and of simulation.

for rigid wall, there is sudden rise i the peak value of rigid wall force after T = 25. by this time the crush tube is completly crush and therefore the deformed model having no further scope for deformation get pushed against the wall with some velocity to which the rigid wall reacts

CASE 2:-

In this case we have to change the inact = 0 to Inacti = 6 will remove any initial penetraction present. elsewhere, it will reduce the define gap to less than 30% of the define value and adjust the gap. to change the Inacti to 6, click on solver browser>interface>typs7 >Inacti. set it to 6

After this run the simulatiuon the procedure is same as discussed earlier.

The natural of deformation and the energy graph are similar in nature compared to case 1. energy error is -3.8% which is acceptable.

CASE 3.

In this case we have to create types 11 contact and run the simulation to create the contact we will use hypermesh, which is a specialized preprocessor for radioss. after importing the file,

go to loadcase > contactct interface. click on create icon and select edge to edge type 11 interface is define by identifying master and slave lines this contact, when added with

Types 7 can help to capture the physical correctly. this is very helpfull is case of edges crossing where the node of the element are far away and the element is in close proximity of another

surface

types 7 uses penatly method in interface which treat the behaviour between slave nodes and master segment as spring that generates resistive force as a function of penetration. typs 11

work in similar mannare as type 7 in terms of penatly formulation, gap definition and search ,ethod.

After setting all the recommended values (same as typs 7) we can export the file and open it in hypermesh and run the simulation.

Here too, the nature of deformation and energy graph nature are similar as previous case. the notches portion is first to defrom energy error is about -3.8% which is acceptable.

CASE 4.

Here we have to remove both the notchs and the boundary condition on the rigid body and run the simulation. to remove the notches we can use allign option from the node edit option available under

Geom page . go to geom >node edit > align. in the 1st and 2nd and selector selet 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 condition on the rigid body, go to solver BCS>BCS>rbody_12456. uncheck DOF1, DOF2, DOF3, DOF4, DOF5, DOF6 which will alow traction in X,Y, Z and rotation in X,Y,Z.

Now run the simulation.

As seen here, there no notches on the crush tube, during impact, there is no localized deformation as there are no notches presnt and the deformation progresses as expected. the nature of energy graph

is also similar to previous case. energy error is about -2.4% which is acceptable.

CASE 5:-

in this case, we have to create a new notch in the centre and run the simulation. we can create notch by using traslate option available under tool page. to properly create the notch, use the N1,N@,N3

option to define the plane of traslation. translate the nodes by 4mm and create the notch.

The nature of deformation and the energy graph are similar in nature com[pared to previous cases. energy error is about -2.3% which acceptable.

CASE 6:--

Create notches on two opposing surface and run the simulation the procedure to create is the same as discusses eariler using translate tool.

now run the simulation.

Deformation is first observation in the notches region and the energy graph is similar in nature compared to previous cases. energy error about -3.5% which is acceptale.

CONCULSION:-

It is observed that in case 4 where the notch is remove the stree induced in the crush tube is the least compared to other case the crush tube undergo stress concentration and these

Areas are the first to undergo deformation. the deformation are predictable in case of notches component. no initial penetration is observed in case 1 where inacti = 0 if initial penetration existed,

It could have been indicated by the graph of contact energy which could have piked up at the start itself before anty impact. energy error for all case is between -3.8% to -2.3% which is acceptable.