NEON ROOF CRASH ANALYSIS USING HYPERMESH AND RADIOSS

OBJECTIVE:

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

GIVEN MODELS FOR ROOF CRUSH - BIW:

• Car

• Impactor

PROCEDURE:

Import

• Car
• Impactor

Transforms

• This will require (in order)
• A 180° rotation about the global z-axis
• A 5° rotation about the axis through axis AB
• A 25° rotation about the axis through axis AC
• A translation to put point A at global ( -2145.26, 584.822, 1343.06)

Reference image ( Full Vehicle Model )

Interfaces

• Create a Type 7 contact interface between the impactor and the car
• choose an appropriate stiffness definition
• choose an appropriate minimum gap
• change the coefficient of friction to 0.2
• choose the appropriate friction penalty formulation
• Save the data from the interface to the time history file.

Gravity and boundary condition

Apply gravity to the whole model but keep the suspension shock tower nodes
locked in Z.

Impactor Boundary Conditions

• The impactor assembly contains a spring attached for stability. Create a BCS
collector to fix the free end of the spring.
• Create a moving SKEW to define the direction normal to the impactor’s
face.
• Create a BCS collector to guide the master node of the impactor rigid body
so that it is free to translate normal to the face of the impactor, but is fixed
in all other DOFs.

Imposed Displacement

• Impose the velocity of the impactor starting from 0 mm/s at t = 0. The
displacement of the impactor should be 200 mm @ 200 ms.
• Avoid abrupt changes in the acceleration of the impactor.

Control Cards

• /ANALY card
• /DEF_SHELL card,
• /DEF_SOLID card, and
• /IOFLAG card
• /SPMD card
• /TITLE card

Engine File

• Use a constant nodal time step
• Print time history every 0.0001 seconds
• Solve for 200 ms
• Create an animation file every 0.005 seconds

Include selected output in animation files:

• Elemental Energy
• Elemental equivalent plastic strain
• Elemental hourglass energy
• Elemental von Mises stress
• Nodal added mass
• Turn on parallel arithmetic

Solution and Results Post Processing

• Run the model
• Plot force vs. displacement. Check that the FMVSS 216 target load of
47,000 N (= 3 * GVW) has been met.
• Plot the energy vs. time curves

MODEL:

CREATING CONTACT INTERFACE:

DEFINING IMPOSED DISPLACEMENT FOR THE IMPACTOR:

CURVE USED TO DEFINE IMPOSED DISPLACEMENT:

APPLIED BOUNDARY CONDITIONS:

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:

MASS ERROR, ENERGY ERROR:

INTERNAL AND KINETIC ENERGY:

TOTAL ENERGY AND CONTACT ENERGY:

CONTACT FORCE AT INTERFACE:

CHECK FOR FMVSS 2016 TARGET LOAD:

As per the Standard of FMVSS 216 (Roof crush resistance, Passenger vehicle), the reaction forces higher than 42.6 KN said to be a good car body.

According to standard, the vehicle should have at least a 2.5 strength-to-weight ratio.

As per FMVSS 216 target load,

Required force=47KN

47,000 N (= 3 * GVW) , which 3*model mass*9.81

i.e, 3*1400*9.81=41.2KN

The obtained for is below the required force. FMVSS 2016 target load criteria were not met.

CONCLUSIONS:

As per the Standard of FMVSS 216 (Roof crush resistance, Passenger vehicle), the reaction forces higher than 42.6 KN said to be a good car body.

According to standard, the vehicle should have at least a 2.5 strength-to-weight ratio.

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 results are less accurate.

Passenger Car Roof Crush Strength Requirements:

• better integrity for the side windows;
• increasing A and B pillar strength;
• providing more energy-absorbing padding in the head-strike areas
• modification of the framing in the door/roof region to reduce the risk of the head locking into this angle
• improvements in seat belt design to reduce occupant movement in rollovers;
• improvements in door integrity and side padding.