Frontal Crash Analysis of  Dodge  Neon BIW - Using Hypermesh RADIOSS

Objective: To Perform Frontal Crash Analysis On Dodge Neon BIW Using Test Protocols of FMVSS 208 Standards

Introduction:

The Full Frontal Fixed Barrier Crash test (or Rigid Barrier test) represents a vehicle-to wall full-frontal engagement crash with the vehicle moving at the same impact velocity. The test is intended to represent the most real-world crashes vehicle-to-fixed object) with significant frontal engagement in a perpendicular impact direction. This systems test which evaluates the energy-absorbing vehicle structure.

FMVSS 208 Standards which regulates that the vehicle should impact longitudinally to a fixed rigid barrier at 48.3 km/h (30 mph). The barrier is perpendicular to the line of travel of the vehicle and at any angle up to 30 degrees in either direction from the perpendicular to the line of travel of the vehicle

Full Car Model

Reduced Model

Unit System used throughout the simulation is Length (mm), Time(ms),Mass(Kg),Force(KN), Pressure(Gpa),Velocity(mm/ms) Density(M Kg/L) Energy(J)

Contact Interface

The Self Contact is created for the car model using Type 7

Igap(Determines how the size of the gap is calculated): 3 Variable gap + gap scale correction of the computed gap + size of the mesh is taken into account to avoid initial penetrations during self-contact.

Fscale_gap(Gap scale factor) : 0.8

Gapmin(Minimum gap for activation of the interface ): 0.5

Inacti(Action to take if initial penetrations exist): 6 Gap is variable with time but initial penetration is computed

Istf(Affects how the stiffness of the interface is calculated): 4 Kmin=(Km, Ks)

Iform(Friction formulation): 2 Stiffness

Stmin(Minimum stiffness to use in the interface): 1

Idel(What to do with slave nodes and master segments if an element fails (deleted) that they are attached to): 2 when a element is deleted, the corresponding segment is removed from the master side of the interface

Fric(coefficient of friction ): 0.2

Penetration Check

Once the contact is defined we have to make sure there is no initial penetration and Intersection.

Connectivity Check

We have to make sure all parts are connected and there is no free-floating part, if so that part alone will move separately in their own degree of freedom during the simulation

Floating part are connected using spring 2N element and P13_SPR _BEAM Properties is created for the spring element

Rigid Wall Creation

The rigid wall is the body is having high stiffness and we made the model to collide with the rigid wall. We here use an infinite plane rigid wall. For defining the rigid wall, first, select the tail coordinate as a node in the bumper and copy those coordinates to head. Then we can tweak with the value of the coordinates in the normal direction of the plane to get the Rigid wall at a distance from the model. Here we shouldn't move the Rigid wall very far away from the model. This is because if we do that the time taken for the car to run and reach the rigid wall is actually a wastage of CPU time, We don't want any results from that motion.So rigid wall should be only a little apart from the model Bumper. Here we need a friction with rigid wall with sliding friction of 0.1 Then the search distance for the slave nodes should be given. it should search the nodes till A-pillar, because up to that region the nodes may get interacted with the wall.

Mass Distribution

Then the centre of gravity of the model should be inline with the C.G of the full car , because in order to compare with the full model we should have the C.G in the same place. The location of the C.G is at the position when the line from the bottom of the driver seat meets with the central line. So in order to get the C.G at that place,

The total mass of the Full car model is 700kg, So we need to match these mass in our model and attain the C.G at Correct place by Distributing those mass in front and rear

The current model as the total mass of 187kg still 513kg has to be added to the model We can add the remaining mass on the floor panel

350kg is added to the rear part of the floor and 163kg is added to the front part of the floor so that C.G lies inline from the bottom of the driver seat meets with the central line.

Load Collector

Initial Velocity

• 35mph is 15.6mm/ms. So, a Load collector of initial velocity is created along the Global X-axis with friction of 0.1
• All the nodes of the car body are selected

Cross Section

Cross Section was created on the following component to get the Sectional force of that component and Load distribution

• A-Pillar Right
• A-Pillar Left
• Rail Right
• Rail Left
• Shotgun Right
• Shotgun Left
• Bumper right
• Bumper Left

Time History output

Time History Output of the 66695 nodes is required to measure Intrusion on the dash wall.

Also, the accelerations of the node below the B pillar rocker is also needed. So in order to get this, an accelerometer is placed at one of the node in B pillar rocker on both the sides. And put the accelerometer into time history.

Model Check

• A constant nodal time step
• T_scal:0.67
• Time step:0.5
• Termination Time: 80ms.

Before running the simulation is better to do the model checker and make sure there is no error in the simulation

.Out File

Number of Cycle	ELAPSED TIME	Energy Error	Mass Error
80001	3225.42 s	-1.4%	0.3015E-01

The energy error is -1.4% which is acceptable and mass error gradually increases but didn't exceed more than 5%, So the Result is acceptable for this Simulation.

Results

Displacement

Max Displacement: 1190mm

Von Mises Stress

Max Stress: 0.41GPa

Plastic Strain

Max Plastic Strain: 1.387

Specific Energy

Max Specific Energy: 6685 J

Graphs

Energy Graph

Section Force

Bumper Section Force

• The Energy absorption starts right from the beginning of the Simulation that is because the Bumper is the first contact with the wall. As the Bumper gets deformed completely or reaching its fracture zone the Rail and ShotGun starts absorbing the energy and reaches it maximum capacity at 10-15ms an then deforms gradually.
• The unevenness in both sides of the bracket is that the deformation at the left end is different from the right.
• Maximum energy absorbed by right bracket is 16KN
• Maximum energy absorbed by left bracket is 8.2KN

Rail Section Force

• The front region of the front rail plays an important role and absorbs a significant amount of energy during collisions
• Front rail absorbs around 45% of the total energy during frontal impact as compared to the subassemblies
• Since the Rail I behind the Bumper once the bumper is fully deformed the remaining force from the rigid wall is transfer to the Rail Component.
• That's why The section Force of both rail is higher than the other components
• The force doesn't start at T=0 because the bumper is doing it job by then only after the bumper is totally deformed
• The force from the bumper transfer to the Rail and from Rail it distributed to the Shotgun and A-pillar
• Section Force at Right Rail = 25KN
• Section Force at Left Rail = 32.5KN

ShotGun Force

Sectional Force on RightShotGun is 17kN.

Sectional Force on Left Shotgun is 11KN

The force begins to rise just after some time after T =0. This indicates that the bumper has done its job properly and it Force Start as soon as the bumper is a full collision,so that the transmission of energy is lower than the impact energy.

Generally, Short gun is made of advanced high strength materials which are having high strength as well as high toughness, So that the shotgun absorbs all of the Force and deforms and buckles so that the energy transmission to the occupant area will be less

A-Pillar Section Force

Sectional Force on Right A-Pillar is 3.25KN

Sectional Force on Left A-Pillar is 2.7kN.

A-pillar Receives the only 20% of the total force transfer Reamaning is transferred to the floor panel of the car

Thats why the Section force of both A-pillar are less Compare to the other components

Intrusions on the Dash wall

The displacement of the Dash Wall is 200mm which is pretty high But This is due to the absence of Components in the Engine compartment

The components in the engine compartment will absorb energy before transferring to dash wall Since these components aren't there the force is directly transferred to the dash wall

By increasing the material Grade and Thickness of the Dash wall components That will Increase stiffness and reduce the intrusion

Accelerometer

Right B-Pillar

Left B-Pillar

The acceleration values at the B pillar rocker are obtained. These values depict the value of acceleration sustained by the occupant when the collision happens.

The maximum value of the acceleration is at the Right B pillar rocker is 4.25mm/ms^2

and that at left B pillar rocker is 0.65mm/ms^2.

Conclusion

The Frontal crash analysis is done on the surrogate model of neon Dodge due to limitations with the student version of the Hyperworks. The improper meshing leads to some errors which are in an acceptable range

we obtained the values of the sectional forces at the A-pillar, Shotgun and front Rails. We obtained the intrusion and accelerations as well

The Components in Crumble Zone absorbs more energy while deforming.

The bumper rail and shotgun which are the components in the crumble zone they absorb more energy and transfer less energy to the passenger section that why a section of A-pillar has less force.

Improving the Components in the Crumble Zone will help in protecting the occupants.

File: https://drive.google.com/file/d/1QmBtlKeN_E5W-6h0CmPoP9kMXmpVkU1g/view?usp=sharing