Neon Side Crash Analysis using Hypermesh and Radioss

Objective - To perform the side 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.

Neon side 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.
• Create a rigid wall with friction 0.1.
• Compare the model weight with the reference 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 cross member.
• Intrusion at B pillar, hinge pillar and fuel tank region. Provide recommendations on what can help to reduce Fuel tank intrusion.
• Peak velocity of inner node of the door 337773.

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.

• Side 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 cylindrical wall is created on the side of the BIW model with a diameter of 256mm, 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.

• Then the initial velocity card is created with 15.6464 mm/ms (35mph) in the positive y-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 cross-members. All the cross sections created by using the circle cross section option in the section card.

• For intrusion on Hinge pillar of node ID 123255, create a frame of reference at node ID 124249.
• For intrusion on B-pillar of node ID 123146, create a frame of reference at node ID 124140.
• For intrusion on the Fuel Tank of node ID 123361, create a frame of reference at node ID 124355.
• For Peak Velocity at the inner door of node ID 337773, create a skew for reference.
• The Output Blocks (Hypermesh) or Data History (Hypercrash) for both the cross sections, contact interfaces and also for the intrusion at B-pillar, Hinge pillar, Fuel tank region and peak velocity node.

Results -

• Energy error is -2.3% and mass error is 0.6826E-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 sidel body crashes onto the rigid pole.
• 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.

Cross-sectional Force in Cross-member 1

The maximum force received by the cross-member cross section 8.85KN.

Cross-sectional Force in Cross-member 2

The maximum force received by the cross-member cross section 14.31KN.

Cross-member 2 faces 14.31KN and Cross-member 1 faces 8.85kN maximum.

Cross-member 2 is receiving more force as compared to Cross-member 1.

Also due to more forces, Cross-member 2 deforms more compared to Cross-member 1.

Intrusions

Side door intrusion describes a situation in which side components of a BIW like door inner parts penetrate the space that is the driver seat. It is used to prevent injuries to the driver and passenger.

Hinge pillar, B-pillar and fuel tank intrusion before crash.

Hinge pillar, B-pillar and fuel tank intrusion after crash.

Hinge pillar intrusion

Distance between the node 123255 to 124249.

Intrusion at node 123255 to 124249 is 599mm.

B-pillar intrusion

Distance between the node 123146 to 124140.

Intrusion at node 123146 to 124140 is 928mm.

Fuel tank intrusion

Distance between the node 123361 to 124355.

Intrusion at node 123361 to 124355 is 958mm.

Recommendations or Method for Reducing The Fuel Tank Intrusions:

During side impact, the door comes first in contact with the hitting vehicle or a rigid pole or wall. Space available between the occupants sitting inside the vehicle and the inner door trims is limited and there is no space for energy absorption as compared to the front-end collisions. In the side door panel impact beam or anti-intrusion bar is placed. The design of the side impact beam inside the door should be such that it can sustain high load with smaller displacement. The role of an anti-intrusion bar is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash. Therefore increasing the side door strength by adding another anti-intrusion bar, we can reduce the amount of intrusion to the fuel tank and also by adding another cross member near the fuel tank, we can reduce the intrusions.

Peak Velocity of inner node of the door 337773.

The initial velocity of the inner node (337773) of the door is 15.6464 mm/ms after the impact the velocity increased up to 16.60 mm/ms and goes on decreasing due to the decrease in the kinetic energy of the BIW model. The peak velocity at the door is monitored because the passenger inside the car experiences more or less the same velocity.

Conclusion -

• The simulation of the neon sidel crash is run and impact or crash is analyzed at the cross-member cross sections, intrusion measured at the Hinge pillar, B-pillar and Fuel tank and also the peak velocity measured at the inner side of the door.
• Type7 interface is created with recommended values.
• Initial velocity applied in positive y-direction.
• Cylindrical Rigid wall created with diameter of 256mm, 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.
• 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 -2.3% and mass error is 0.6826E-02.
• Cross section force at cross-member 1 is 8.85KN.
• Cross section force at cross-member 2 is 14.31KN
• Hinge pillar intrusion at node 123255 to 124249 is 599mm.
• B-pillar intrusion at node 123146 to 124140 is 928mm.
• Fuel tank intrusion at node 123361 to 124355 is 958mm.
• Peak Velocity of the inner node of the door 337773 is 16.60 mm/ms.

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

https://drive.google.com/file/d/1naA8uSM-UaoyTYf8YtbuPZDOHMvMR6iO/view?usp=sharing