Side crash pole impact analysis using RADIOSS. 

Problem statement:

Side crash pole impact analysis using RADIOSS.

Objectives:

Pre Processing

1. Check unit system and either follow [Mg mm s] or [Kg mm ms].
2. Create appropriate interface ,friction 0.2 and recommended parameters.
3. Make sure of no penetration and intersections.
4. Create rigid wall with friction 0.1 as per referance model.
5. Compare the model weight with the referance model and use added masses to reach target weight 700kg while getting CG about the required range.
6. Initial velocity 35mph.
7. Use model checker to ensure good quality.
8. Timestep :0.5 to 0.1 microseconds.
9. Run 80ms.

Post Processing

1. Sectional force in the cross member.
2. Intrusion at B pillar,hinge pillar and fuel tank region.
3. Peak velocity of inner node of the door.

I Pre Processing

1. Unit System:

Unit system used for analysis is "kg mm ms".

Fig 1: Unit system

2. Connectivity check:

Initially there were 3 free parts as shown in following list this parts are latter connected by rigid bodies as shown in figure 3.

Fig 2: Connectivity check.

Fig 3:Free part connection with rigid bodies.

Initially there were no error in the model.

3. Interfaces:

By creating single interface of type 7 contact is replaced with the old interfaces. The interface assigned with recommended properties for crash analysis as shown below. The friction in contact is 0.2.

Fig No. 4: Final interfaces with recommended properties.

3.1 Penetrations and Intersections:

There were no penetration and intersection in the model.

Fig No. 5: Penetration and Intersection.

4. Rigid Wall:

As the car is impacting on a pole as per guidelines the pole of 54 mm diameter is placed at the B pillar with D search value 1000mm and friction of 0.1 as shown below.

Fig No. 6: Rigid Wall.

5. Mass Distribution:

The initial mass of the structure was 166kg. In order to achieve 700kg of mass some weight are added to the structure so that it will be like actual car and the C.G. of the car will be in the line of driver. The bellow figure shows the mass distribution and location of the C.G.

Fig No. 7: Mass distribution and C.G. location.

6. Initial Velocity:

The initial velocity of the car is set 35mph which is 15.64mps in global Y direction.

7. Run time and time step:

The run time is set to 80ms. and time step is 0.5ms. as shown below.

Fig No. 8: Run time and time step.

8. Sections:

There are 2 section defined to see the effect of the forces due to impact. These section are defined at both the cross members. The below figure shows the section created with its normal direction.

Fig No. 9: Sections.

9. Intrusions:

There are 3 intrusion installed to observe deformation.All this points are in very region. To see the impact of car three springs are installed with minimum stiffness. First spring is installed at drivers area. Second is installed at B pillar region. Third is installed at fuel tank. The below figure shows intrusion.

Fig No. 10: Intrusion.

10. Peak Velocity:

The output block is introduced at a node to observe the effect of impact at the door. The local skew is introduce at the opposite side of the door for a reference frame.

11. Model Checker:

After completing Pre-processing the model is checked through model checker. Initally there was no error and 6 warnings in the model.

Fig No. 11: Error.

II. Processor (Solver):

From SID_0001.out file, The Total number of cycles was 80000. The energy error is -2.0% which is in acceptable limit. The mass error is 0.8% which also less than 5% it is accepted. There is increase in mass which is due to reduction in time step at that node, to maintain time step the mass is increased. The run was "normal terminated" which implies the was successfully completed. There was no sudden changes in energy as well as in error. As shown below.

Fig No. 12: SID_0001.out file.

Fig No. 13: Energy graphs.

Fig No. 14: Total final mass and inertia.

Fig No. 15: Total initial inertia.

From the above graph, the kinetic energy and internal energy decreases and increases respectively in a gradual manner. There are no sudden falls or rise in energy which means there is no much error in simulation. The contact energy increases gradually and hourglass energy is almost negligible. Moving to next step the mass and inertia before and after is same. Which means we can move to post processing.

III.Post-Processing:

For post processing the output requested are as follow:

1. Sectional force in the cross member.
2. Intrusion at B pillar,hinge pillar and fuel tank region.
3. Peak velocity of inner node of the door.

1. Sectional force in the cross member:

Since pole is placed near B pillar the force will be transfered through cross members to the other side. So there are 2 section at the cross members.

a. Sectional force in the front cross member:

Fig No. 16: Cross section 1 force.

The cross section 1 is near drivers area. After impact at 14ms. there is increase in force gradually at time t=42ms. the maximum force is 2.8kN. and there is decrease in force.

b. Sectional force in the second cross member:

Fig No. 17: Cross section 2 force.

The cross section 2 is near B pillar area. At time t=63ms. the maximum force is 6.15kN. and there is decrease in force. There is more jerks on the first cross members than second.

2. Intrusion:

There are 3 intrusion installed to observe deformation.All this points are in very region. To see the impact of car three springs are installed with minimum stiffness. First spring is installed at drivers area. Second is installed at B pillar region. Third is installed at fuel tank.

a. Intrusion at drivers area:

Fig No. 18: Intrusion at drivers area.

After the impact, the deformation increases gradually and at time t= 79.5ms. the maximum deformation of 541.50mm which is very high. In order to reduce the deformation stiffer material should be introduced.

b. Intrusion at B pillar:

Fig No. 19: Intrusion at B pillar.

The pole is placed near the Bpillar so there will be maximum deformation compared to other component. After the impact, the deformation increases after t=14ms and than increases gradually and at time t= 79.5ms. the maximum deformation of 893.84mm which is very high. In order to reduce the deformation stiffer material should be introduced.

c. Intrusion at Fuel tank:

Fig No. 20: Intrusion at Fuel tank.

This is most critical area since the fuel may leak or catches fire. so it must be protected from effect of impact. From the above graph the maximum deformation is observed at t=79.5ms. which is 770.75mm. Which is very high.

How to reduce intrusion near fuel tank:

In order to protect the fuel the tank material should be stiffer. There should be more component before the tank i.e. the transfers the forces to the fuel tank. So there must be more component in the door as shown below. There can be more cross rods or beam introduced in the door which absorbs the forces and there will less deformation at fuel tank.

Fig No. 21: Door.

3. Peak Velocity at door:

Fig No. 22:Resultant Peak Velocity at door.

The initial velocity of the car is 15.64m/s. As the car impacts on the pole there is sudden drop in velocity. The decrease in velocity is due to decrease in kinetic energy. Due to collision there is increase in velocity at t=8.5ms. this is the maximum velocity of 16.21m/s. and then it starts decreasing.

3.1 Velocity in global Y direction:

Fig No. 23:Velocity in global Y direction.

The initial velocity of the car is 15.64m/s. Since it moving towards positive y direction the initial velocity is negative. At t=71.5ms. the velocity is 1.88m/s is observed. The velocity is positive from t=66ms. since the node is moving in positive Y direction.

Conclusion:

1. The forces are transferred through cross members to the other side.
2. The cross section at B pillar is expressing maximum forces due to the pole is placed near the B pillar.
3. The maximum intrusion is at B pillar followed by area near fuel tank.
4. The stiffness should be increased of the component near fuel tank so there will be less intrusions.
5. The Peak velocity is maximum of magnitude 1.88m/s in Y direction.

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