NEON SIDE CRASH ANALYSIS USING HYPERMESH AND RADIOSS

OBJECTIVE:

To perform a side crash test using the given model of car and to determine the forces acting on different cross-sections of the car during the impact.

Neon side crash -BIW

• Check unit system and either follow [Mg mm s] or [Kg mm ms].
• Create an appropriate interface, friction 0.2 and recommended parameters.
• Make sure of no penetration and intersections.
• Create a rigid wall with friction 0.1 as per the reference model.
• Compare the model weight with the reference model and use added masses to reach the target weight of 700kg while getting CG about the required range.
• Initial velocity is set as shown in the picture.
• Use the model checker to ensure good quality.
• Timestep :0.5 to 0.1 microseconds.
• Run 80ms.

Output requests:

• Sectional force in the cross member.
• The intrusion at B pillar, hinge pillar and fuel tank region. Provide recommendations on what can help to reduce Fuel tank intrusion.
• Peak velocity of an inner node of the door.

MODEL OF THE CAR:

GIVEN MODEL OF SIDE CRASH-BIW:

PROCEDURE:

The main stages of this crash impact analysis are :

1. CHECKING THE UNIT SYSTEM:

The unit system is set to [Kg mm ms]

2. CREATING CONTACT INTERFACES:

A type 7 contact interface is created with the recommended properties.

• [Istf] Stiffness definition=4: K=min(Km,Ks)
• [Igap] Gap/element option=2: Variable gap + scale correction
• [Gapmin] Min. gap for impact activ =.5.
• [Inacti] Stiffness deactiv. (init. penetration)=6: Gap is variable with time (init. penetration is computed)
• [Fric] Coulomb friction=0.2.
• [Iform] Friction penalty formulation=2: Stiffness.

3. CENTER OF GRAVITY AND MASS ADDITION:

The given model has a mass of 188kg and the target mass is 700kg.

Masses were added at certain cross-sections to reach the target mass and to maintain the position of COG as per the requirements.

4. CREATING SECTIONS AT DIFFERENT LOCATIONS:

5. CREATING TIME HISTORY FOR NODE INTRUSIONS:

6. CREATING TIME HISTORY FOR RESULTANT VELOCITY AT NODE 337773 :

7. CREATING RIGID WALL:

8. SETTING UP INITIAL VELOCITY:

Velocity = 35mph =15.6464mm/ms

9. SETTING UP TIME HISTORY:

10. CHECK FOR PENETRATIONS AND INTERSECTIONS:

The penetrations and intersections check was done in hypercrash and in hypermesh, all the intersections and penetrations were removed before starting the simulation.

RESULTS:

DISPLACEMENT:

VON MISES:

NODE INTRUSIONS:

The displacement of the nodes under the hinge pillar, B-pillar and near the fuel tank during the crash impact are shown below.

The resultant displacement of the node near the hinge pillar is higher as expected followed by the node near the fuel tank. The node under the b-pillar has the lowest displacement since the impact is concentrated in this region.

The node near the hinge pillar has the highest displacement as it is a little away from the direct impact region.

RESULTANT VELOCITY AT NODE-337773:

TOTAL RESULTANT FORCE IN VARIOUS SECTIONS:

INTERNAL AND KINETIC ENERGY:

The kinetic energy decreased from 87000j to 58000j whereas the internal energy increased from 0 to 28000j.

TOTAL ENERGY AND CONTACT ENERGY:

The maximum contact energy is around 1600 J and the total energy is 86170 J.

CONCLUSIONS:

A good rating requires a strength-to-weight ratio of at least 4. In other words, the roof must withstand a force of at least 4 times the vehicle's weight before the plate crushes the roof by 5 inches. For an acceptable rating, the minimum required strength-to-weight ratio is 3.25. For a marginal rating, it is 2.5. Anything lower than that is poor.

The model used for this analysis has only the biw body and therefore the impact is higher. Another reason is that the diameter of the rigid cylindrical wall is only 200mm. Since the initial velocity of the car is also higher, the impact has also increased.

The overall strength of the A-pillar, B pillar, hinge pillar needs to be increased in order to resist the impact.

The results are a little inaccurate since the given model is only a biw model of the car which has only the required parts.

The Center of gravity also plays an important role in the crash analysis. It is an important concept in determining the stability of a structure.

The kinetic energy is reducing because it is converted into internal energy and total energy. The energy error, mass error and hourglass energy are under the acceptable values.

Increased side door strength, internal padding and better seats can improve protection in side-impact crashes. Most new cars have side intrusion beams or other protection within the door structure. Some cars also have padding on the inside door panels.