Neon Frontal Crash Analysis using Hypermesh and Radioss

Objective - To perform the frontal crash analysis of BIW car model.

The preprocessing is done by the Hypermesh (Hypercrash) and the analysis is done by the RADIOSS solver and the results are interpreted using the Hyperview and Hypergraph.

Frontal crash-BIW

• Check the unit system and either follow [Mg mm s] or [Kg mm ms].
• Create appropriate interface ,friction 0.2 and recommended parameters.
• Make sure of no penetrations and intersections.
• Correct rigid bodies if any issues.
• Create a rigid wall with friction 0.1.
• Compare the model weight with the full scale 300k nodes model and use added masses to reach target weight 700kg while getting CG about the required range.
• Initial velocity 35 mph.
• Use a model checker to ensure good quality.
• Timestep :0.5 to 0.1 microseconds.
• Run 80ms.

Output requests:

• Sectional force in the rails at location of indicated node 174247.
• Axial force received on the rails from the bumper.
• Shotgun cross sectional forces.
• A pillar cross section.
• Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
• Intrusions on the dash wall 66695,66244.

Procedure -

• First import the model in Hypermesh and Hypercrash.
• Importing files in Hypercrash ensured that the unit system followed as Kg mm ms.
• Full car model.

• Frontal crash analysis model.

• In contact interface first create a TYPE7 interface as it is mostly recommended for crash analysis and self contact is given for the model, nodes are assigned as slave and elements as master.
• Recommended properties of TYPE7 interface are as follows -
• Inacti = 6
• Istf = 4
• Igap = 3 and Fscalegap = 0.8
• Idel = 2
• Gapmin = 0.5
• Stmin = 1
• Fric = 0.2
• Iform = 2

• Penetrations and intersection of the model are checked and solved.

• Then a rigid wall is created in the front normal to the x-axis with friction value of 0.1 and D_search of 1000.

• By using the added mass option, the target weight of 700kg is added in the floor panel of the car and mass is added accordingly to move the cog to the middle of the frame in the line of driver side, the cog is centred to avoid the rollover of the car towards the rigid wall during the impact

• Then the initial velocity card is created with 15.6464 mm/ms (35mph) in the positive x-direction.

• Timestep of 0.5 microseconds and run for 80ms and frequency of animation file are set to 5. So, by this we get 16 animation files for the run time of 80ms. So that the result is more accurate.
• The cross sections are created on some parts of the car body to analyze the forces experienced in the particular part or area. Parts where the section created are A-pillar left right, Shotgun left right, Rail left right, Hinge pillar left right, Bumper rail left right. All the cross sections created by using the frame i.e local coordinate.

• The accelerometer is created at the rocker and base of the B-pillar, to measure the velocity at the B-pillar at the time of crash and also a sensor for the same accelerometers.
• The Output Blocks (Hypermesh) or Data History (Hypercrash) for all the cross sections, contact interfaces, accelerometer and also for the node 66695 and 66244. For creating Output Blocks for the node, create a frame of reference too.

Results -

• Energy error is -2.0% and mass error is 0.1322E-02 both are acceptable.

Results obtained by the HyperView

Von Mises

Displacement

Results obtained by the HyperGraph.

Energy

• The above graph shows that the kinetic energy is high at the starting and goes on decreasing when the frontal body crashes onto the rigid wall.
• The kinetic energy decreases with an increase in the internal energy. Kinetic energy is transformed into internal energy during the crash.
• The total energy is nearly constant, so there will be an energy balance on both sides of the equation.
• The hourglass and the contact energy is not physical energy and it needs to be reduced.

Acceleration Curve

The acceleration experienced by the B-pillar at the base is measured by the accelerometer mount on the B-pillar. It is an important criteria evaluated during the frontal crash. The acceleration experienced at the base of B-pillar during the impact is 11.76mm/ms^2 on left and 1.02mm/ms^2 on right

Force received from bumper to rail

The frontal rails are the main component to observe the maximum force during the collision or crash and it also absorbs the more energy during collision. The maximum force received from the bumper to the rail is 15.4KN.

Cross-sectional Force in A-pillar

The maximum force acting on the left A-pillar cross-section is 5.7KN and the maximum force acting on the right A-pillar cross-section is 1.7KN.

The left A-pillar cross-section is getting more force then the right A-pillar.

The force is dropping in the left A-pillar at 55ms this may be due to the material behaviour during the deformation by the crash.

At the time of 80 ms, both the force acting on the cross-sections is reduced.

Cross-sectional Force in Rail

The maximum force acting on the left Rail cross-section is 2.4KN and the maximum force acting on the right Rail cross-section is 6.2KN.

Right rail cross-section more force is experienced.

Right rail cross-section is stiffer compared to the left rail cross-section.

Cross-sectional Force in Shotgun

The maximum force acting on the left Shotgun cross-section is 4.1KN and the maximum force acting on the right Shotgun cross-section is 6.1KN.

The right shotgun cross-section is experiencing more force compared to the left shotgun.

Right shotgun cross-section is stiffer compared to the left shotgun cross-section.

Cross-sectional Force in Hinge pillar

The maximum force acting on the left Hinge cross-section is 3.3KN and the maximum force acting on the right Hinge cross-section is 5.7KN.

Right hinge cross-section is stiffer compared to the left hinge cross-section.

Cross-sectional Force in Surface behind the bumper

The maximum force acting on the left Surface behind the bumper cross-section is 12.5KN and the maximum force acting on the right Surface behind the bumpern cross-section is 11.5KN.

At the time of 80 ms, both the force acting on the cross-sections is reduced.

Intrusions

Dash wall intrusion describes a situation in which frontal components of BIW and an automobile engine penetrate the space normally allocated for the feet of the front seat occupants. It is used to prevent injuries in the driver and passenger lower leg and feet.

Distance between the node 66695 to 121739 and 66244 to 122048 before crash

Distance between the node 66695 to 121739 and 66244 to 122048 after crash

Distance shown by the graph between 66695 to 121739 and 66244 to 122048

Intrusion at node 66695 to 121739 is 156mm and

Intrusion at node 66244 to 122048 is 140mm.

Conclusion -

• The simulation of the neon frontal crash is run and impact or crash is analyzed at the various cross sections force and also the intrusion measured.
• Type7 interface is created with recommended values.
• Initial velocity applied in positive x-direction.
• Rigid wall created with friction of 0.1 and D_search of 1000.
• Mass distributions were done by taking a 300k model as reference to match its center of gravity so there might be change that mass distribution on the left and right side is uneven due to which uneven sectional forces are observed on both sides.
• Center of gravity also plays an important role in the crash analysis. It is an important concept in determining the stability of a structure. Position of the COG plays a vital role in having proper distribution of mass on model which leads to proper distribution of force on model.
• The kinetic energy is reduced because it is converted into internal energy. The energy error, mass error and hourglass energy are under the acceptable values.
• Energy error is is -2.0% and mass error is 0.1322E-02
• Cross section force at left A-pillar is 5.7KN and on the right A-pillar is 1.7KN.
• Cross section force at left Rail is 2.4KN and on the right Rail is 6.2KN.
• Cross section force at left Shotgun is 4.1KN and on the right Shotgun is 6.1KN.
• Cross section force at left Hinge pillar is 3.3KN and on the right Hinge pillar is 5.7KN.
• Cross section force at left Surface behind the bumper is 12.5KN and on the right Surface behind the bumper is 11.5KN.
• The maximum force received from the bumper to the rail is 15.4KN.
• Acceleration experience by B-pillar is 11.776mm/ms^2.
• The daswall intrusion at node 66695 is 156mm and at node 66244 is 140mm.

Google drive link - It contains .rad, .out, hyperview file(.h3d) and hypergraph file(T01) with plots and graphs.

https://drive.google.com/file/d/1QkDfqXw3FlV72f8o593u01is-u9Iujj6/view?usp=sharing