ROOF CRUSH- BIW (Quasi -static case study)

OBJECTIVE:

The main objective of this challange is to set all the pre processing parameters for the simulation in the given model. then run it into the RADIOSS solver and get all the desired output request.

These are the recommended checks performed in the model:-

1)Set the impactor above the car.

2)Set Boundary conditions.

3)Set Imposed displacement for the impactor.

4)Set all recommended parameters as asked in the assingment to run in Radioss.

5)Plot Displacement vs force and Energy vs Time graphs.

FULL MODEL OF CAR:

FRONT VIEW

SIDE VIEW

TOP VIEW

BOTTOM VIEW

ISOMETRIC VIEW

PROCEDURE NEEDS TO BE FOLLOWED TO PERFORM SIMULATION ON THE GIVEN MODELAS PER THE RECOMMENDETATION:

Import

• Car
• Impactor

Transforms

• This will require (in order)
• A 180° rotation about the global z-axis
• A 5° rotation about the axis through axis AB
• A 25° rotation about the axis through axis AC
• A translation to put point A at global ( -3500.00, 584.822, 1343.06)

Reference image ( Full Vehicle Model )

• Create a Type 7 contact interface between the impactor and the car
• choose an appropriate stiffness definition
• choose an appropriate minimum gap
• change the coefficient of friction to 0.2
• choose the appropriate friction penalty formulation
• Save the data from the interface to the time history file.

Boundary condition

keep the suspension shock tower nodes locked in Z.

Impactor Boundary Conditions

• The impactor assembly contains a spring attached for stability. Create a BCS
collector to fix the free end of the spring.
• Create a moving SKEW to define the direction normal to the impactor’s
face.
• Create a BCS collector to guide the master node of the impactor rigid body
so that it is free to translate normal to the face of the impactor, but is fixed
in all other DOFs.

Imposed Displacement

• Impose the velocity of the impactor starting from 0 mm/s at t = 0. The
displacement of the impactor should be 200 mm @ 200 ms.
• Avoid abrupt changes in the acceleration of the impactor.

Control Cards

• /ANALY card
• /DEF_SHELL card,
• /DEF_SOLID card, and
• /IOFLAG card
• /SPMD card
• /TITLE card

Engine File

• Use a constant nodal time step
• Print time history every 0.0001 seconds
• Solve for 200 ms
• Create an animation file every 0.005 seconds

Include selected output in animation files:

• Elemental Energy
• Elemental equivalent plastic strain
• Elemental hourglass energy
• Elemental von Mises stress
• Nodal added mass
• Turn on parallel arithmetic

Solution and Results Post Processing

• Run the model
• Plot force vs. displacement. Check that the FMVSS 216 target load of
47,000 N (= 3 * GVW) has been met.
• Plot the energy vs. time curves

Locating the Impactor above the car on the recommended co-ordinates:

A 180° rotation about the global z-axis
A 5° rotation about the axis through axis AB
A 25° rotation about the axis through axis AC
A translation to put point A at global .

CREATION OF CONTACT INTERFACES:

• Self Contact with recommended parameters

All the nodes of the car is selected as master and slave.

• Contact interface for impactor

All the nodes of the impactor is selected as Master and all the nodes of car is selected as slave.

BOUNDARY CONDITIONS:

• Boundary condition collector to fix the free end of the spring.

• Boundary condition collector to guide the master node of the impactor rigid body
  so that it is free to translate normal to the face of the impactor, but is fixed
  in all other DOFs.

• The suspension shock tower nodes locked in Z.

IMPOSED DISPLACEMENT:

Impose the velocity of the impactor starting from 0 mm/s at t = 0. The displacement of the impactor should be 200 mm @ 200 ms.

ENGINE FILE SETTING:

• Print time history every 0.0001 seconds

• Animation file every 0.005 seconds.

• Run time

SIMULATION Results (RADIOSS):-

Energy error= -13.4%

Mass error=0.4651E-1

Animation Of the crash model:-

OUTPUT REQUEST:

i) Energy vs Time graph

Internal Energy:- Initially internal energy till 40 ms is zero, then it starts increasing and at time= 200 ms it reaches its maximum value i.e 412.883 mj

Kinetic Energy:-Similar to Internal energy, till 40 ms value of kinetic energy is almost zero then its starts gradually increasing and at time=199.7 ms it attains its maximum value 80.8409 mj.

Contact Energy:- Maximum contact energy is seen at time=197.7 ms and its value at this point is 75.4379 mj.

Total Energy:- Total energy is the sum of internal energy, kinetic energy, contact energy, hourglass energy..etc in the model. And its maximum value is 493.083mj at time =199.8 ms

ii)Displacement vs Time graph

When selected a perticular node just below the impactor and on the car's model to measure the total displacement after the impact. It is observed that the node is displced after impact of impactor from its original position to 152.468 mm in Z- direction.

iii)Force Vs Time graph

As from the graph it is seen that at initially till 40 ms the impact is not happening so the force value is zero and once the impactor came into contact with the car body than the deformation starts due to force on the car body. Maximum force acted on the car body at time =181.3 ms and its magnitde is 6.3333KN. Due to quasi static condition the jump in the focre is seen in the graph.

iv) Force vs Displacement graph

• Checking that the FMVSS 216 target load of 47,000 N (= 3 * GVW) has been met or not:

As per the Standard of FMVSS 216 (Roof crush resistance, Passenger vehicle) , the reaction forces higher than 42.6 KN said to be a good car body.

But in our case the maximum Resultant focre obtained in the graph is 6.3333 KN. Which is facr from the recommended.

A/p,

47kN=(NOT)=3*174.8487*9.8

=5140.55178N= 5.140KN

SO, Due to less Gross vehicle weight, the checking condition is failing for this simulation as the reaction force is very less as compare to required.

RESULTS AND DISCUSSION:

i)Accepable energy error is upto 15% and the occuring energy error after simulation is -13.4%, thus it is within the acceptable range.

ii) Mass error is also within the acceptable range i.e 0.4651E-1.

iii) Plot for energy is also looks fine, as normal flow and tranformation of energy can be seen in the graph.

iv)Due to less Gross vehicle weight, the checking condition i.e Standard of FMVSS 216 , is failing for this simulation as the reaction force is very less as compare to required.

v)After impact of impactor on the car, Total displacement on car's node 152.468mm is seen.

CONCLUSION:

By setting all the recommended parameters , and running it into the radioss solver all the required output results are obtained and explined. By adding proper weight to the passanger car's body ,the standard passanger car crash testing experiment can be performed successfully. Thus all the objectives are achived successfully.