Side Impact Crash Analysis on BIW Component

Objective:

To Perform side impact crash analysis on the given BIW component of the car and observe the changes in the model.

Theory:

Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of the vehicles. Several criteria are used to assess crashworthiness prospectively, including the deformation patterns of the vehicle structure, the acceleration experienced by the vehicle during an impact, and the probability of injury predicted by human body models. A Crash test is a form of destructive testing usually performed to ensure safe design standards.

New Car Assessment Program (NCAP): is a government car safety program tasked with evaluating new automobile designs for performance against various safety threats.

Standard crash tests performed by NCAP:

1:Frontal offset testing (64 km/h proposed)

2.Side-impact testing

3.Pedestrian protection testing

4.Rear impact testing

5.Child dummy dynamic crash testing

BIW Model :

Side Impact testing:

Procedure:

Case setup & Execution:

1. Import the given model "neon_side_reduced_0000" into hypermesh.

2. Simultaneously the model "neon_side_reduced_0000" is imported into hypercrash as well with the unit system as "Kg mm ms".

unsupported card found in the model is deleted.

3. Once the model is imported into the hypercrash Model checker which is available in the Quality section is used to check for the errors that is available in the model to rectify them

It can be noted that there is no major error is Seen in the model, so the errors can be neglected.

4. Balancing the center of Gravity:

• In hypercrash under mass menu balancing option is selected.
• Here the available mass in the model can be noted.
• To bring the Center of gravity point to the center, mass needs to be added manually.
• To achieve the target mass of 700 Kgs, Added mass option in the Browser menu is used.
• In added mass, the major types used here are 0,1&3. (Type 0 = Mass is added to each node of the node group, Type 1 = Mass is distributed to each node of the node group, Type 3 = Additional mass distributed on part group)

5. Creating the Rigid Wall:

• once the mass is balanced, a pole with the friction of 0.1 needed to be created.
• In load cases, menu Rigid wall is selected and the following steps are carried out.
• Create a new object `rarr`Rigid Walls `rarr`Cylinder
• Then approximately center node in the b pillar is selected and the normal is specified.
• In Slide option sliding with friction is selected and the friction is given as 0.1

• The Important parameter which needed to be specified is "[D_search] Distance for slave search" which will consider the nodes as a slave up to a specified value
• Here D_search is given as 1000, If the D_search is given as zero no collision will take place in the model.

6. Creating the Initial velocity (Inivel):

• After creating the rigid wall, there must be a velocity in which the car moves and crashes into the rigid wall.
• This is initial velocity is taken given as 8.05 mm/ms
• The value can be applied to the model via the initial velocity option available in load cases.

7. Creating Contact Interface:

• Here the type of contact used is type 7, because of its high accuracy and correct physical representation.
• Full component is selected as self impact.
• All the parameters values are set to be recommended values for the crash application.

8. Creation of Cross section:

• cross section is needed to be created to observe the distribution of forces in horizontal structural members.
• The cross sectional normal force needed to be specified in the opposite direction of velocity.
• The following steps are carried out: Data history `rarr`Section `rarr`Section `rarr`Create a new object `rarr`Default section
• To create a section a frame needed to be created which specifies the local axis of the section. In create frame option the frame type is selected as moving frame (MOV) then three nodes N1, N2, N3 are selected.
• After this group of elements needed to create the section is selected.

9. Run the simulation:

• Since the simulation cannot be performed in hypercrash the model is exported as RADIOSS file, which is then imported into hypermesh to Run the simulation.
• In Hypermesh under Analysis panel Radioss option is selected.
• Specify the location in which the file needed to be saved, In the command options bar "-nt_4" is given, then radioss is selected to run the simulation.
• If the starter file showed any error that should be rectified then again the steps should be repeated.

Result and Analysis:

Open the file "neon_side_reduced_0001" in notepad to check Energy error, mass error and time elapsed.

** COMPUTE RUNTIME INFORMATION SUMMARY **

STARTER RUNTIME = 5.62s (00:00:05)
# 001 ENGINE RUNTIME = 7264.52s (02:01:04)
------------------------------
STARTER+ENGINE RUNTIME = 7270.14s (02:01:10)

TOTAL NUMBER OF CYCLES: 160001

since the energy error is -1.6% which is less than 15% so it is acceptable, also the mass error is found out to be 0.5438E-03

Since the energy error is acceptable, the model is moved for further observations by changing the environment to hyper view, then importing the file "neon_front.H3d"

Simulation Without any contour:

Displacement observation:

Maximum displacement: 7.186E+02 is at node 35257

Minimum displacement: 0.000E+00 is at node 9904911

Von-mises Stress Observation:

Maximum displacement: 3.297E+01 is at node 23231

Minimum displacement: 0.000E+00 is at node 346252

Graph 1: Time versus Internal energy, Kinetic energy, Contact energy, Hourglass energy and Total energy

observations:

1. Contact between the car and the rigid walls started at 13 ms
2. The kinetic energy is constantly decreasing due to the deformation while the strain energy or internal energy is increasing during the impact.
3. hence the total energy of the system remained balanced also a negligible spike in contact energy can be noted towards the end of the cycle.
4. here no hourglass energy is formed due to the QEPH element formulation.

Graph 2: Time vs Interface

Observations:

1. The axial force on the car is starting at 13.00 ms then suddenly a huge spike is noted at 21 ms of 42.47 KN on the graph
2. this indicates that the forces are directly distributed to the components of the car.
3. the maximum peak force reaches at 21 ms during which the highest force 42.47 `(KN)/(MM)^2`was distributed to the car.

Graph 3: Time vs Displacement

Observations:

1. It is noted that the displacement increases over time, which indicates that the force is directly distributed on the spring.
2. The displacement reaches its maximum value of 123.84, 81.00, 300 mm at 79 ms respectively.

Graph 4: Time vs velocity

Observations:

1. To observe the damages taken by the fuel tank we have kept a node there to understand its damages.
2. It can be noted from the graph that the fuel tank is getting damaged at a comsiderable rate.
3. The maximum velocity recorded is 7.6 mm/ms.

Graph 5: Time vs Sectional Forces

Observations:

1. The sections created on the cross beam to observe the forces acting on it.
2. From the graph, it can be noted that the force on section 1 is higher when compared to that on section 2 because section 1 is attached to the B pillar.
3. The maximum force on section 1 is 7.3 KN at 47.5 mm/s
4. The maximum force on section 2 is 3.2 KN at 36.5 mm/s
5. The Displacement increament proves that the passengers are in danger during impact.

Conclusion:

Performed side impact analysis on the given model of the car and it can be seen from the results and graph observations that the given BIW fails the side impact test.