Side-crash analysis of a car model using Altair HyperWorks and Radioss solver.

Objective:

Study the side-crash analysis on a model of a car and compute the following.

1. Forces acting on the cross members at the floor of the vehicle.
2. Deformation of hinge pillar, B-pillar and fuel tank in terms of displacement.
3. Peak velocity achieved by the inner door.

Setup:

Step 1: Checking the unit system being implemented to the model.

Open the starter file (_0000.rad) in to the notepad. As observed in the starter file, the unit system being implemented in this model is [kg mm ms].

Step 2: Create an appropriate interface.

A TYPE7 interface with recommended properties and 0.2 friction is created where all the nodes available in the model are slaves and all the elements of the model are masters.

Step 3: Check for penetrations and intersections.

In the tools drop-down menu, select penetration checker and select all the groups. It will automatically check for penetrations and intersections.

Step 4: Create a rigid wall.

In the solver browser, right click and then select RWALL. Assigning appropriate values and a 0.1 friction, a cylindrical rigid wall is created.

Step 5: Achieve target weight of 700kg while getting CG about the required range.

In mass details, the overall weight of the model is being evaluated at 166kg. By adding masses at appropriate locations, the target weight could be achieved along with the location of CG.

In this case, 50kg is added to each door, 100 kg is divided among the cross members on the roof, 134 kg on the B-pillar and 200 kg is divided among the cross members on the floor of the model.

Step 6: Apply initial velocity.

In the solver browser, select INIVEL in the boundary conditions. Assign 15.65 mm/ms (35 mph) in the direction of Y-axis, since the car is being crashed sideways.

Step 7: Add cross-sections.

In the model browser, right click and select cross section. Select the required component and assign the direction.

Step 8: Add intrusions.

In the solver browser, right click on the TH tab and add nodes at which the displacements and velocity needs to be recorded w.r.t a fixed skew which has been created on the opposite side of the frame, since, that section of the model will not undergo much deformation.

Step 9: Check the model.

Use model checker, to check the model for any errors or warnings. All the errors shown need to be taken care of and all the major warnings need to be eradicated too.

Simulation:

In the analysis toolbar, select Radioss solver and export the file to the desired location and let the simulation run for 80ms at an interval of 0.001ms.

At the end of the simulation, open _0001.out file and check for energy error and mass error at the last cycle (ie. 80000).

Energy error is at -4.0% and mass error is 0.85%.

Results:

1. Forces acting on the cross members at the floor of the vehicle.

The maximum recorded on the cross member during the crash was approximately 5.5kN.

2. Deformation of hinge pillar, B-pillar and fuel tank in terms of displacement.

The maximum displacement of the hinge pillar was approx. 650mm.

The maximum displacement of the B-pillar was approx. 280mm.

The maximum displacement of the fuel tank was approx. 355mm.

3. Peak velocity achieved by the inner door.

The maximum velocity achieved by the inner door was approx. 15.65 mm/ms.

Conclusion:

1. As observed from the energy graph, when the car crashes in to the rigid pole all the kinetic energy generated by the motion of the car is being converted to internal energy. Along with that, there was a loss of energy due to contact and hourglass. Hence, by the end of the simulation, there is a fractional loss of total energy.
2. Reduction of the fuel tank intrusion can be done by adding a cross member between the inner and outer panel of the door. This will increase the overall weight of the car but it will increase the overall strength of the vehicle during a side-crash. Moreover, the material used in the manufacturing of the B-pillar can be modified to increase the strength of the part.