Simulation of Frontal Crash Analysis of Neon BIW
SIMULATION OF FRONTAL CRASH ANALYSIS OF NEON BIW
OBJECTIVE:
To simulate the frontal crash analysis of neon BIW is by creating a rigid wall infront of the bumper to impact. The distributed mass of 700Kgs is created to move the COG of model at the middle and near to driver's area. Finally the simulation is Pre-Processed using HYPERMESH, Then RUN using RADIOSS as solver. Various output results like Axial force received on bumper, forces received on cross sectional areas are studied using HYPERVIEW and HYPERGRAPH.
DESCRIPTION:
Model Setup:
The model is imported using Hypermesh, Then run model analysis to check for errors and warnings.
- There is an free nodes, free masses and unwanted Springs attached in the model. Those are deleted.
- There are no penetrations and intersection in this model.
- Some contact interfaces are already defined for individual parts. But i would like to make this model with proper self-contact, so those defined contacts were also deleted.
- Now, the meshed model of neon BIW is ready for pre-processing. The unit system followed is KG KN mm ms.
CONTACT INTERFACE:
The TYPE 7 contact interface is used to define "self-contact" for the whole model. The nodes are assigned as slaves and the elements are assigned as master. The recommended parameters are
RIGID WALL:
An Infinite plane rigid wall is created infront of the front bumper for crash scenerio. The parameters like friction 0.1 and dsearch 1000mm is defined.
PROPERTY CARD:
The shell property is edited according to the recomended parameters like ISHELL = 24 (QEPH SHELL FORMULATION) and ISOLID = 24 (HEPH with physical stabilisation) are assigned to reduce the hourglass effects on shells and solids.
ADDED MASS:
The distributed mass of 700Kgs is added to floors and B-Pillar.These distributed mass are added using admas card in 1D panel. The added mass are assigned to move the COG of model to the middle and right next to the driver. Because the COG is a main thing to define Rolling behaviour of model when the event of crash.
INITIAL VELOCITY:
The Initial velocity of the model is 35MPh which is 15.65mm/ms. Because the whole model is in KG KN mm ms. The initial velocity is given for entire model in positive X-axis direction.
TIME STEP:
The Constant Nodal Time Step DT/NODA/CST of 0.0005ms and a Run time of about 80ms is set. The animation frequency is 5ms, so every 5ms it produces animation file as output. The nodal time step cost high run time but the result will be more accurate.
CROSS-SECTION AND ACCELEROMETER:
The cross-section is created on some parts to analyse the forces received on that section. The section is created on Rails, shotgun, A-Pillar is created and sections have been created on both RH and LH sides. These sections are created using local co-ordinates using frame system. The normal is set as local Z-Axis to process the flow of forces.
An Accelerometer is created on the rocker at the base of B-Pillar. The accelerometer is used to analyse the rate of change of velocity on the rocker during crash.
TIME HISTORY:
The TH card is created in such a way that we can request output in HYPERGRAPH. The output requests are like contact interface forces, sectional forces, axial force received on bumper are defined.
POST-PROCESSING:
Sectional forces on Rails:
The resultant forces are plotted using hypergraph. The RH of rail section(SECT_RAIL_R) experiences 32.4KN and LH of rail section(SECT_RAIL_L) experiences 21.8KN at 15ms approximately. The RH of Rail experiences more forces than LH of Rails.
There is an mounting hole above the RH of rail which tends to bends at first and after that it shears inwards which causes the RH of model bends smoothly along the wall. Due to which more stiffness of part it experiences more force for bending on RH rail.
Sectional forces on shotgun:
The LH of Shotgun(SECT_SHOTGUN_L) experiences 12.9KN and RH of shotgun(SECT_SHOTGUN_R) experiences 9.7KN at 20-40ms approximately. The LH of shotgun experiences more force than RH of shotgun. when the RH of shotgun shears inward which transmit less forces on section and LH side of shotgun bends like a cut which transmits more forces on LH of shotgun.
Sectional forces on A-Pillar:
The RH of A-Pillar section(SECT_A-PILLAR_R) experiences 3.7KN and LH of A-Pillar section(SECT_A-PILLAR_L) experiences 3.5KN at 20-40ms approximately. The both A-Pillar experience nearly same amount of force but the LH of A-Pillar tends to bending but RH of A-Pillar have high stiffness acting on it because of which it transmits high forces in section.
Accelerations on Rocker:
The rate of change of velocity with respect to time on LH of rocker(ACCEL_L_RAIL) experiences 0.8 `(mm)/(ms^2)` and RH of rocker(ACCEL_R_RAIL) experiences 0.4 `(mm)/(ms^2)`at 40ms approximately. The LH front end of model moves upwards so it experiences more accelerations because of more spaces at the base to stop rocker and RH of front end moves downwards thus it experiences less accelerations on Rocker.
Axial forces transferred from bumper-rail:
from bumper to rails.
There are edges in between the bumper and rails so in association with TYPE7 and TYPE 11 contact between them it can capture accurate results. The maximum contact force experience on the LH of rail is -30KN at 10ms along x-axis approximately, The negative sign indicates axial force of comression because when impact ocurs normally components gets compressed. In the graph there is no axial force captured along x-axis received on component from 20-40ms thats why it shows plane line, this is due to bending of component.
Intrusions on Dash-Wall:
The measure option is used in hyperview to post process the intrusion by nodes and create plot is used to plot intrusion by graph. The dashwall intrusion is measured at the node 66695 with respect to 121739. The global intrusion is 151.73mm. The individual intrusion along the respected axis are X = 252.28 mm, Y = 18.349mm, Z = 288.694mm .
Intrusions on the foot pedal:
The foot pedal intrusion have been measure at the node 66244 with respect to 122048. The global intrusion is 159.685mm. The individual intrusion along the respected axis are X = 267.902mm, Y = 19.862mm, Z = 300.659mm.
ENERGY GRAPH:
The impact energy absorbed is the increase in the internal energy of the system. From the graph it can be seen that the maximum increase in the internal energy is 39078.84 Joules. Initially the system is in equilibrium and the internal energy is zero. The kinetic energy of the car is 85899.13 Joules, after the crash it reduces to 43830.96 Joules. therefore 39078.84 Joules is the maximum energy absorbed at 80ms. There is no hour glass energy generation because of QEPH stiffness method used in this model and there is a slight increase in contact energy.
Energy error = -1.9%
mass error = 0.001%
Time Taken = 8007.42s
No. of cycles = 160057
There is an energy error of -1.9% which is due to energy dissipation, there is an slight increase in contact force which may be the reason for it. The mass error of 0.001% is due to nodal time step for mass addition in the system. The both energy and mass error are in acceptable limit.
RESULT:
- Internal Energy = 39078.84 Joules
- Energy Error = -1.9%
- Mass Error = 0.001%
- Sectional force on Rails = 32.4KN(RH), 21.8(LH)
- Sectional force on Shotgun = 9.7KN(RH), 12.9(LH)
- Sectional force on A-Pillar = 3.7(RH), 3.5(LH)
- Acceleration on Rocker = 0.4`(mm)/(ms^2)` (RH), 0.8`(mm)/(ms^2)`(LH)
- Axial forces transferred from bumper-rail = -30KN(Compression)
- Dash wall intrusion = 151.73mm
- Foot pedal intrusion = 159.69mm