FRONTAL CRASH ANALYSIS OF NEON'S BIW USING HYPERCRASH AND RADIOSS.
OBJECTIVE:
The main aim of this project is to perform a frontal crash of neon's BIW model using preprocessors like Hypermesh, Hypercrash, and Radioss solver.
PROCESS:
1. The consistent unit system in this project is Kg mm ms KN.
2. Created an appropriate contact interface type-7 self impact with the recommended parameters on the model as shown below,
3. Checked for the penetrations and intersections in the model and cleared using the tools-->penetration checker option in Hypermesh as shown below,
4. Checked for the presence of flying parts in the model using quality--> check the connectivity of tree selection option in Hypercrash as shown below and deleted the parts if any.
5. Created an infinite plane rigid wall in Hypermesh using solver--> create rigid wall--> plane option as shown below,
6. Added some mass to the floor panel to reach 700kg while getting the center of gravity approximately below the driver seat, so the vehicle does not yaw or move forward when hitting the rigid wall, using options like load case-->added mass and mass--> balancing in Hypercrash.
7. Applied translational initial velocity of 35 mph(15.6464 m/s) to the whole model in the positive X direction using load case--> initial velocity in Hypermesh.
8. Created some cross-sections in the parts like Rails, A-pillars, Hinge pillars, shotguns, headlight brackets using the local coordinate systems (i,.e frames), so that the force can be calculated at the part level.
9. Created the accelerometers at the base of the B-pillar using solver--> create-->accel in Hypermesh as shown below,
10. To calculate the brake pedal and foot pedal intrusions, created two springs of mass 0.001 kg and stiffness of 0.0001 KN/mm as shown below,
11. Output requests such as time history for cross-sections, accelerometers, intrusions are created so that their results can be plotted in the Hypergraph.
12. control cards for the model.
OUTPUT:
1. sectional force in left and right rails (viewing from the front).
The maximum sectional force in the left rail is 2.85495 KN at 79.5 ms
The maximum sectional force in the right rail is 2.16397 KN at 15 ms
when comparing the two sectional forces, the force in R-rail reaches its maximum value at 15 ms but the L-rail force reaches its maximum almost at the end of the simulation, it seems that the L-rail is stiffer than the R-rail.
whenever a component deforms some energy(internal or strain energy) is absorbed in it, if the deformation is high the internal energy which is absorbed is also high.so, The internal energy stored by the L-rail is minimum that the I.E in R-rail.so, R-rail is less stiff than L-rail.
2. Axial force received on the rails from the bumper.
The maximum axial force received by the L-rail from the bumper is 2.77943 KN at 78.5 ms.
The maximum axial force received by the R-rail from the bumper is 5.88145 KN at 9 ms.
These forces are calculated by creating cross-sections at the headlight brackets because it is the component between the bumper and the rails.
when comparing these two graphs, the sectional force in R-axial force to rail reaches its maximum value at 9 ms but the L-axial force to rail reaches its maximum at 78.5 ms, it seems that the L-headlight bracket is stiffer than the R-headlight bracket.
so, the L-headlight bracket is stiffer because it absorbs less internal energy than the R-headlight bracket, so the R- rail experience less force when compared to the L-rail.
3. sectional force in left and right shotguns.
The maximum sectional force in the left shotgun is 1.26144 KN at 57.5 ms
The maximum sectional force in the right shotgun is 1.35128 KN at 77 ms
when comparing the two sectional forces, the force in L-shotgun reaches its maximum value at 57.5 ms but the force in R-shotgun reaches its maximum at 77 ms, it seems that the R-shotgun is stiffer than the L-shotgun.
The internal energy stored by the R-shotgun is minimum that the I.E in L-shotgun.so, L-shotgun is less stiff than R-shotgun. so, the deformation in L-shotgun will be more than the R-shotgun.
4. sectional force in left and right A-pillars.
The maximum sectional force in the left A-pillar is 0.660599 KN at 66.5 ms
The maximum sectional force in the right A-pillar is 0.0233472 KN at 75.5 ms
In this case, the sectional force in the L-A pillar is greater than the R-A pillar but the internal energy in the L-A pillar is less than the R-A pillar. This seems that the force transfer through the region as shown below is greater in the L-A pillar but the force transfer below the region may be low and that becomes obvious from the internal energy in the L-A pillar. so, the R-A pillar is less stiff than the L-A pillar.
5. sectional force in left and right Hinge pillars.
The maximum sectional force in the left Hinge pillar is 5.48006 KN at 79.5 ms
The maximum sectional force in the right Hinge pillar is 2.47749 KN at 11.5 ms
from the above graphs, the internal energy in the L-hinge pillar is greater than the R-hinge pillar. so, the L-hinge pillar is less stiff when compared to the R-hinge pillar.
6. Acceleration curve received on the left and right accelerometer at the base of B pillars.
the maximum acceleration received on the left accelerometer is 0.370645 mm/ms2 at 43.5 ms
the maximum acceleration received on the right accelerometer is 2.60616 mm/ms2 at 29 ms
The accelerations experienced at the base of the B-pillars are due to the sudden change in the velocity of the car from 35 mph to 0 mph.
7. Intrusions on the dash wall at foot pedal and brake pedal region.
intrusion in the brake pedal region at node 66244:
the distance of the spring between the nodes 66244 and 122048 before impact is 781.808 mm
the distance of the spring between the nodes 66244 and 122048 after impact is 641.819 mm
graph:
so, the intrusion in the brake pedal region at node 66244 is 139.989 mm.
intrusion in the foot pedal region at node 66695:
the distance of the spring between the nodes 66695 and 121739 before impact is 767.575 mm
the distance of the spring between the nodes 66695 and 121739 after impact is 658.215 mm
graph:
so, the intrusion in the foot pedal region at node 66695 is 109.36 mm
ENERGY BALANCE:
1. In the crash analysis, the ultimate target is energy absorption. when the BIW hits the rigid wall with the velocity of 35 mph, the kinetic energy starts with the maximum value and gradually decreasing as the velocity decreases. At the same time, The internal energy increases gradually as the deformation of the components increases. From the graph, it is obvious that all the kinetic energy gets transferred to internal energy.
2. The total translation energy is slightly decreasing due to loss of energy it ranges from 87662 J to 86556.7 J
3. The equation TTE=IE+KE+RKE+CE+HE, is satisfied as the calculation shown below,
energies are calculated at the end of the simulation,
TTE (TOTAL TRANSLATION ENERGY) = 86556.7 J
I.E (INTERNAL ENERGY) = 42443.2 J
K.E (KINETIC ENERGY) = 42020.8 J
R.K.E (ROTATIONAL KINETIC ENERGY) = 2.96973 J
C.E (CONTACT ENERGY) = 1695.43 J
H.E (HOURGLASS ENERGY) = 394.252 J
so, 42443.2+42020.8+2.96973+1695.43+394.252= 86556.65173 J
4. Also the condition, Hourglass energy + contact energy < 15% of total energy(IE+KE), is also satisfied as shown below,
1695.43+394.252 = 2089.682 < (15% * 42443.2+42020.8)=12669.6 J.
5. the energy error ranges from -1.4% to 0.8% is acceptable.
TIMESTEP:
Here the timestep remains constant up to the end of the simulation.
MASS BALANCE:
Here the addition of mass increases gradually due to the usage of CST, in order to maintain the timestep not decreasing less than the minimum value specified in the nodal and brick timestep formulation block.
the mass error ranges from 1.452% to 2.954%, this is at the verge of recommended value i.e, 1% to 3%.
the number of cycles is 79900.
countermeasure:
But still, the mass error can be brought within the limit by requesting the animation output to track at which node timestep decreases less than the minimum value so that remeshing can be done in that region. Also, the minimum timestep value specified in the nodal, brick timestep formulation can be reduced to minimize the mass error. mostly, defining the material card, property card, and contact interfaces with the recommended parameters help in preventing the errors.
RESULT:
Hence, the frontal crash of neon's BIW model is performed using the preprocessors such as Hypermesh, Hypercrash, and Radioss solver.
LINK TO VIEW THE MODEL: FRONTAL CRASH ANALYSIS