Side crash analysis according to FMVSS 201 standards

Objective:

Simulate a side crash of the Neon car model to a rigid pole with appropriate interfaces. Required outputs are obtained from the side crash analysis.

Case setup:

• The side crash model with only components which are in the focus for frontal crash analysis is imported into hypermesh with radioss solver.
• Model is checked for its unit system by comparing the values of density and young’s modulus values in the material cards and [Kg mm ms] is used.
• Unsupported cards are deleted from the model.
• The multiple interfaces which are present in the given model are deleted and a single Type 7 interface is created with self impact. The type 7 interface is defined as shown below.

• Model is checked for intersections and penetrations. As no such intersections are found, no action is taken.
• A cylindrical rigid wall having a diameter of 300mm, the friction of 0.1 is created as shown below.

• The side crash model is compared with the full-scale model and the masses are added to adjust the position of Centre of Gravity accordingly. The added masses are as shown and listed below.

Component name	Mass added
Cabin rails (Left & Right)	100 Kg on each side
Seat rail 1 (Cross-member)	130 Kg
Seat rail 2 (Cross-member)	75 Kg
Floor Rails (Front)	130 Kg

• The boundary condition of the initial velocity of 35mph i.e. 15.56 m/s is applied to the model.

• Using model checker, required corrections in the model are done. Errors from the model are dealt with accordingly and corrections are done in the model.
• Since some components are missing connections with their adjacent components, they are connected with rigid bodies as shown and all these rigid bodies are organised into its respective component as shown.

• Floating elements and the free nodes are deleted from the model.

• Empty and unused categories are deleted from the model.

• Time step is monitored and appropriate time steps are used accordingly.

• Sections are created at cross members as shown with their individual frames and suitable elements are selected for each section.

• Three springs having very low stiffness is defined to record the intrusions at B-pillar, Hinge pillar and fuel tank. These springs are defined properly with its suitable material properties and are organized into a separate component.

• Time history output requests for Node: 337773(peak velocity), cross member sections and intrusion in the three springs are created.

• The model is executed under radioss with help of 4 threads.

Results and conclusions:

• Centre of gravity is adjusted to the required range of its position by adding the masses to the model at different locations and the whole mass of the model is brought from 166 Kg to 700 Kg.

• Energy and Mass errors

The simulation ran for 80 seconds run time, with normal termination. The total number of cycles is 80001 and elapsed time is 4356.54 sec. Energy error starts with 0% and ends with -2.5% while following a decreasing trend. Mass error is almost constantly increasing and is below 2% with a maximum value of 0.00927. No elements are deleted from the model.

Since the rigid pole is very near to the model, crash starts along with the simulation and time steps are maintained very constanly through out the simulation.

• Animation

From the animation, side crash of car is visually acceptable. we can say the model is deformed more into the cabin and this can be harmful to the passenger and crash energy is being absorbed in the cross members and this has to be avoided for the safety of passengers. Use of slightly stiffer components can be a better solution and this can be done by allowing the floor bed (Not included in the simulation) to distribute the crash energy.

• Intrusions

Spring 9900059: Hinge pillar Intrusion (Maximum intrusion = 564.72mm)

Spring 9900060: B-pillar base intrusion (Maximum intrusion = 883.99mm)

Spring 9900061: Fuel tank intrusion (Maximum intrusion = 848.68mm)

Maximum intrusion is observed at b-pillar and this is due to impact is happening at B-pillar.

Installing Running Boards (Footboards) as extra components can add components which will absorb crash energies and avoid more deformations into the whole model due to side crash. Using a rigid cylinder as fuel tank to deviate the incoming parts of the model, can avoid the intrusion of parts into the fuel tank.

• Sections

Resultant sectional forces in the cross-members are almost equal to the normal forces in the direction of the initial velocity (Boundary condition).

Maximum force in rail 1 is 978.56 N and in rail 2 is 1070.6 N.

• Peak velocity

Peak velocity of the inner node of the door is 16.56m/s. Initial velocity applied is 15.56m/s, but peak velocity in this particular node is more than the initial velocity even though the case is a crash scenario. This can be explained by bending moment acting on the component due to crash of model with pole and the component bends around the pole thus increasing the velocity to and then decrease in velocity is due to the accumulation of the nodes around the pole during the crash.