Frontal Crash Simulation

 AIM:

        i) To perform frontal crash for neon car BIW model by initially setting up with the following parameters:

• Check unit system and either follow[Mg mm s] or [Kg mm ms].
• Create appropriate interface ,friction 0.2 and recommended parameters.
• Make sure of no penetrations and intersection.
• Correct rigid bodies if any issues.
• Create rigid wall with friction 0.1.
• Compare the model weight with the full scale 300k nodes model and use added masses to reach target weight 700kg while getting CG about the required range.
• Initial velocity 35 mph.
• Use model checker to ensure good quality.
• Time-step :0.5 to 0.1 microseconds.
• Run 80 ms.

        ii) After running the simulation we have to lookup for the following output requests:

• Sectional force in the rails at location of indicated node 174247.
• Axial force received on the rails from bumper.
• Shotgun cross sectional forces.
• A pillar cross section.
• Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
• Intrusions on the dash wall 66695,66244.

DESCRIPTION:

THEORY:

        Cars are tested against a rigid barrier with full overlap at a test speed of 50 km/h. A small female frontal impact dummy is seated in the front driver's seat and in the rear passenger side seat. This test places high demands on the restraint systems in front and rear seating positions.

BIW:

       Body-in-white (BIW) is the name given to a car body's sheet when all its components barring moving parts (e.g; hoods, fenders, etc.), trims (e.g., glass, seats, etc.), or chassis subassemblies have been welded together. Also, it should be easy to weld and form, as well as be highly paintable and easy to design. It refers to the welded sheet metal components which form the vehicles structure to which the other components will be married, i.e., engine, chassis, exterior and interior trim. Services: Designing of prototype and series production welding fixtures.

PROCEDURE:

BIW model is given below & it is one which considered for further analysis of the frontal crash.

MODEL SET-UP:

Check the unit system for the model by oening the o.rad file in notepad as shown in the image given below. The unit system is in [Kg mm ms] 

Then create a type-7 contact interface by selecting the master, slave nodes are not selected since it's a self impact. The value of friction i.e; 0.2 is given as input paramaters & other recommended parameters are modified as shown in the image.

Then we have to check penetrations & intersections in the model. We run the penetration checker for both group contacts & components. So collision is found when penetration takes place.

Then check all the rigid bodies & find is there's any issue in it. COG is found by using mass balancing in Hypercrash. We are using ADDMASS to add weight & finally bring the weight of the body to 700Kg & COG moves backward to the location, where driver's seat is located. Create rigid wall by applying sliding friction as 0.1 is given in the input parameters. So car can hit the wall by giving the initial velocity.

Then the initial velocity is given by creating a card which is called INVEL input the initial velocity as 35 mph/ 15.6464 mm/ms in the positive x direction where the rigid wall is located.

Then we create sections in the model as mentioned above, we have to create moving frames & has to create section by mentioning their values of N1, N2, N3 by selecting the nodes, seelct the frame which has been created, as well as elements needed to be part section. Create history files for them so the output results could be obtained & can be plotted using Hypergraph 2D

Once sections are created, we should create accelerometer on B pillar rocker, so that we can measure the acceleration that is received on B pillar.

 Then we run the simulation to find wheather any errors or warning occurs in the model, so that we can clear it before running the simulation. 7 errors has been identified all errors & warnings are rectified & eliminated.

Then go to Analysis module & go to Radioss, save the starter file & run the simulation.

Once simulation get's done, we are looking for mass & energy error in the form of .0001 out file.

Energy error - -1.4% 

Mass error - 0.1102 kg

Total no of cycles - 80001

Then go to Hyperview & import the h3d file to check contour plot on von misses with simple average method & displacement in the form of animations. 

 Displacement:

Von Mises:

 Then plot the graphs in Hypergraph-2D for internal, kinetic, contact, hourglass & total energy.

From this plot internal energy increases & kinetic energy decreases at the end of simulation. Hour glass & contact energy slightly increases. By the end of whole simulation, there's no energy loss occurs.

RESULTS:

•  We have set-up the model for frontal crash according to the given parameters.
•  Then we have checked penetrations & intersections.
•  Before simulating the model, we are identifying if any errors & warnings are occured. If any, it's been reectified & simulation is                   done.
•  Once the simulation is done, we are looking for energy & mass error wheather both are under the limits.
•  Then animations are displayed for displacement & von misses in simple average method.
•  We are plotting the graphs for internal, contact, kinetic, hourglass & total energy by using Hypergraph-2D