Side crash analysis Using Pole
AIM:
To perform Side Crash Analysis on the BIW model and Observe Changes in The model with respect to the Different Boundary Conditions in the Simulation and Graph.
INTRODUCTION:
Crash analysis is an integral part of safety analysis and is often completed at intersections and corridors. The crash analysis can help assess concerns and help determine potential improvement options. A Crash test is a form of destructive testing usually performed in order to ensure safe design standards.
New Car Assessment Program (NCAP):
It 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
FMVSS ( Federal Motor Vehicle safety standards)
Federal Motor Vehicle Safety Standards (FMVSS) are US federal Vehicle Regulations specifying design, construction, performance, and durability requirements for motor vehicles and regulated Automobile safety-related components, systems, and design features. They are the U.S. counterpart to the UN Regulations developed by the World Forum For Harmonization of Vehicle Regulations and recognized to a varying degree by most countries except the United States.
BIW (BODY IN WHITE)
Body in white (BIW) is the stage in Automobile Manufacturing in which a car body's frame has been joined together, that is before painting and before the motor, chassis sub-assemblies, or trim (glass, door locks/handles, seats, upholstery, electronics, etc.) have been integrated into the structure. Assembly involves different techniques such as Welding (spot, MIG/MAG), Riveting, clinching, bonding, and laser Brazing.
SIDE CRASH:
PROCEDURE:
Case setup & Execution:
1. Import the given model "neon_side_reduced_0000" into Hypermesh.
2. Open the same model "neon_side_reduced_0000" in Hypercrash as well with the unit system "Kg mm ms".
3.Delete the unsupported cards found in the Browser menu.
3. Perform model check and penetration check in the Quality menu in Hyper crash before applying the conditions.
4.Note the errors and Warnings showed and keep them as a reference for later use.
STEP-1: BALANCING COG.
1. Before performing analysis the center of gravity of the vehicle should be balanced exactly at a point.
2. The BIW model doesn't consist of the exact weight of the vehicle in, completed condition, so Additional mass should be added to the BIW model considering the weight of the Body after manufactures ie. with the weight of the seats, the weight of the persons in average and all other weights in realistic condition.
3. For adding mass, three major types are used here,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 the part group)
4. The target weight given is 700kg where the actual mass before adding is 180kg
5. To Add the mass, Click on added mass, and to create a new object Select Type 1 - Mass is distributed to each node of the node group, and click save
6. Check COG, Simultaneously after giving the mass in the balancing menu.
7. Add mass according to the needs till the point reaches the center and till the mass attains the target value.
The yellow color indicates the node group where mass added.
The red point in the middle indicates the mass is perfectly balanced in the center.
STEP-2 CREATING RIGID WALL:
1. A rigid wall is created after balancing the mass.
2. In load case, select Rigidwalls > new object > Cylinder
3. Friction is defined for the rigid wall with a coefficient of 0.1 and in the Slide option, sliding with friction is selected
4. Approximately a center node in the b pillar is selected and the normal is specified and the diameter of the pole is given as 254mm ( default value followed by FMVSS)
5. Click save to see the Rigid wall created
6. The parameters are given as required.
7. 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 1400
8. The transparent volume in the image represents D_search distance.
STEP-3:Creating the Initial velocity (INVEL)
1. As for performing the Simulation in a realistic case, the Velocity must be defined for the Body.
2. The velocity here makes the car move and crashes the pole.
3. The initial velocity is 20mph as per FMVSS and it changed to 8.9mm/ms as per solver requirements.
4. The velocity is defined in the Y-axis where the body should move in that direction.
5. In the load case, select Initial velocity > new object creation and enter the parameters.
6. The Arrow indicates the direction of the velocity Applied.
STEP-4: CREATING CONTACT INTERFACE:
1. A contact interface should be defined to view the contact energy.
2. Here the type-7 Contact is used (Node to Surface), because of its high accuracy and correct physical representation.
3. The self impact is defined in the Contact interface as the body acts as both master and Slave.
All the parameter values are set to be recommended values for the crash application.
Self impact-full body:
The red color in the image Indicates the nodes with both master and slave, whereas the master is defined as blue and the red as Slave.
After all these Steps The model is Exported as Radioss, and opened in Hypermesh.
STEP-5: CREATING CROSS SECTION.
1. The cross-section is created to observe the forces Distributed in various components such as Rails, Shotguns, and A-pillars.
2. The cross-section must be Created in such a way that the Normal force observed in the component should be opposite to the velocity Applied.
3. For creating a cross-section a new set is defined as Cross beam-1 and cross beam-2.
4. Give the card image as Grshell and Select a set of elements in the entity id where the cross-section might be placed and click proceed.
5. Follow the same procedure for Crossbeam-2
6. In The solver, area Create a new section by right-clicking > create > SECT.
7. Create a Frame for each section created.
8. Frame is created by right-clicking > create > FRAME > MOV
9. Assign the frame system to the respective Cross-section and give the value of the nodes in the frame.
10. Assign the set created in the model area in grshel_id
Repeat the same for another crossbeam
11. As we can see all the normal forces are acting in the opposite direction to the velocity applied.
STEP-6: OUTPUT REQUEST:
1. Give the required time step for running the simulation in the Control card.
2. Specify the time step = 0.0005 and time-frequency = 1.6 and runtime = 80ms.
3. Create intrusion at B pillar, hinge pillar, and fuel tank region.
4. In this model Springs are used as Intrusions to measure the Displacement.
5. create a Node at the Door to measure its peak velocity at the time of impact.
1. Time history should be created individually for requesting outputs for the cross-sections, Rigid wall, intrusions, Accelerometer, and interfaces.
2. Create TH for Rigid wall created.
3. Create TH for the node at the door created for finding the peak velocity
4. Create TH for Contact interface created.
5. Create TH for all the sections created.
6. Create TH for the Springs Created.
RUN THE SIMULATION:
1. Since the simulation cannot be performed in Hypercrash the model is exported as a RADIOSS file, which is then imported into Hypermesh to Run the simulation.
2. Click on the analysis panel in the Hypermesh.
3. Save the model in the local directory.
4. For Running The analysis: Analysis > Radioss is selected from the panel
5. The analysis runs and shows the result.
6. The energy error And mass errors are checked.
CYCLE TIME TIME-STEP ELEMENT ERROR I-ENERGY K-ENERGY T K-ENERGY R EXT-WORK MAS.ERR
159500 79.75 0.5000E-03 NODE 121247 -2.3% 0.1326E+05 0.1317E+05 3.996 -673.2 0.4492E-04
159600 79.80 0.5000E-03 NODE 121247 -2.3% 0.1327E+05 0.1316E+05 3.967 -673.9 0.4492E-04
159700 79.85 0.5000E-03 NODE 121247 -2.3% 0.1327E+05 0.1316E+05 3.966 -674.6 0.4493E-04
159800 79.90 0.5000E-03 NODE 121247 -2.3% 0.1328E+05 0.1315E+05 4.019 -675.3 0.4493E-04
159900 79.95 0.5000E-03 NODE 121247 -2.3% 0.1328E+05 0.1314E+05 4.042 -675.9 0.4493E-04
ELAPSED TIME = 8275.04 s
2:17:55
NORMAL TERMINATION
TOTAL NUMBER OF CYCLES: 160001
** COMPUTE RUNTIME INFORMATION SUMMARY **
STARTER RUNTIME = 5.64s (00:00:05)
# 001 ENGINE RUNTIME = 8275.04s (02:17:55)
------------------------------
STARTER+ENGINE RUNTIME = 8280.68s (02:18:00)
7. The energy error is -2.3 and the Mass error is 0.4493-04 which lies within the Acceptable Conditions.
8. Click results for viewing the Analysis in an Animated and Graphical Format.
DISPLACEMENT OBSERVATION:
Maximum displacement:8.235E+02 is at node 124803
Minimum displacement: 0.000E+00 is at node 346252
VON MISES OBSERVATION:
Maximum displacement: 3.968E-01 is at node 121240
Minimum displacement: 0.000E+00 is at node 346252
GRAPHICAL REPRESENTATION:
Graph 1: Time versus Internal energy, Kinetic energy, Hourglass energy, and Total energy:
1. The kinetic energy is constantly decreasing due to the deformation while the strain energy or internal energy is increasing during the impact.
2. The total energy of the system remained balanced also a negligible spike in contact energy can be noted towards the end of the cycle.
3. There is no hourglass energy is formed due to the QEPH element formulation.
Graph-2: Contact Energy.
It is the energy developed between the MAster and slave in the interface while deformation.
The contact energy seems to be rising gradually throughout the system.
Graph-3: Time vs Interface (For observing the axial force)
1. In self impact, both master and slave experience the force while acting on the rigid wall
2. 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
3. this indicates that the forces are directly distributed to the components of the car.
Graph-4: Rigid wall Forces:
1.The Rigid wall force is constant till 9ms
2. The Resultant force is 62kN peak value around 56ms just after collision with the wall
3. Variation in forces on the rigid wall due to impact of different components on that come into contact based on D_Search value and material property
Graph-5: Sectional Forces:
1. The Cross-sectional force on member -1 is greater than the other.
2. it attains the peak value of around 21kn at 79ms
3. The force on the member-2 is less because it's located far from the pole impact.
Graph-6: Spring Displacement Forces:
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 the max value of 31KN,12KN,2.8KN at 70ms,60ms, and 79ms.
Graph-7:Node Velocity:
1. As the body is moving with some initial velocity the node is in Kinetic condition.
2. when the body impacts on the pole the velocity reduces and the node velocity starts decreasing around 15ms.
3.The velocity drops irregularly throughout the System.
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.