Simulation of Side Crash Pole Impact Analysis of Neon BIW
SIMULATION OF SIDE CRASH POLE IMPACT ANALYSIS OF NEON BIW
OBJECTIVE:
To simulate the side crash analysis of neon BIW is by creating a cylindrical rigid wall on the side of B-Pillar. 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 forces received on cross sectional areas, Peak Velocity of node and intrusions 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 are free nodes 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 cylindrical rigid wall i.e pole is created right next to the B-Pillar. The parameters like Radius 150mm, 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 over the rockers, rails 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.
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 Y-axis direction for side impact.
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:
A Local frame of reference is created in the cross members and after that a Section is created on both sides of the cross members of the model.
TIME HISTORY:
A Time history TH card is created and the sectional force, peak velocity of the node is assigned for to view the results in HyperGraph.
POST PROCESSING:
Sectional force on cross members:
The maximum resultant sectional force acting on the cross beam member 1 is 13.2 KN at 55ms approximately and on the cross beam member 2 is 3.6KN at 25ms approximately.
Since the pole is situated at the infront of the B-Pillar and the cross member 1 and the cross member 2 having some distance form the pole. so the cross member 1 section experiences very high amount of force than cross member 2. if we move the pole inbetween the two cross members we might get the sectional force result equally distributed to that members.
Intrusion on B-Pillar:
The measure option is used in hyperview to post process the intrusion by nodes i.e., distance between two nodes and create plot option is used to plot intrusion by graph. The B-Pillar intrusion is measured at the node 123140 with respect to 124134 is 735.112 mm. The Individual intrusions are X= 3.877mm, Y = 735.717mm, Z=29.31mm.
Intrusion on Hinge pillar:
The Hinge pillar intrusion have been measured at node 123322 with respect to 124182. The measure option used in hyperview to post process the result by graph. The global intrusion observed is 448.368mm. The Individual intrusion are X = 268.79mm, Y = 484.532mm, Z = 99.645mm.
Intrusion on fuel tank region:
The Fuel tank intrusion have been measured at the node 123362 with respect to 124355. The nodes are taken from the rails then the measure option is used to post process the results. The global intrusion observed is 974.471mm. The individual intrusion are X = 139.131mm, Y = 1017.864mm, Z = 61.486mm.
Nodal Velocity:
The node 337772 is requested in the time history card TH/NODE and the Resultant Nodal velocity of node 337772 is plotted using hypergraph. Since the initial velocity of the node is 15.65mm/ms, then after hitting the pole the nodal velocity increases due to moment is 16.26mm/ms and after that impact it keeps decreasing because of the kinetic energy is reducing so the velocity of the node is reduced continuosly.
Method to reduce fuel tank intrusion:
- The underbody is the best way to reduce fuel tank intrusion. By adding another cross member it increases a weight of 5-10 kgs but it adds up some resistance during side crash.
- By replace the material of B-Pillar as Hot formed Ultra high strength steel can reduce the kinetic energy with great efforts.
Door plays a predominent role during side impact so if we use DSI - dynamic side impact beams we can decrease intrusions during crash. when we use aluminum alloy of composite beams we can reduce weight of beams as well as decrease the intrusion into the fuel tank region.
or also by adding composite beam on the side door can also reduce the intrusion during crash.
When we implement internal baffles and rigid foam filled tubular members to strengthen and stiifen the vehicle structure and strengthen doors with full perimeter overlap. It adds up some cost but at the end of the safety is an important issue so it will be worth.
ENERGY GRAPH:
Energy error = -2.9%
mass error = 0.4E^-4
Time Taken = 7881.06s
No. of cycles = 160009
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 31221.85 Joules. Initially the system is in equilibrium and the internal energy is zero. The kinetic energy of the car is 85779.58 Joules, after the crash it reduces to 51628.74 Joules. therefore 31221.85 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 and negative external energy is created.The Work done by an external force on a system is always a transfer of energy i.e by friction and to some other form of energy and this negative work represents the transfer of energy during the simulation and this is fine. The energy error is negative its because of some amount of energy like contact energy is dissipated during crash.
RESULT:
- Internal Energy = 31221.85 Joules
- Energy Error = -2.9%
- Mass Error = 0.00004%
- cross member 1 sectional force = 13.2KN
- cross member 2 sectional force = 3.6KN
- Intrusion on B-PIllar = 735.112mm
- Intrusion on Hinge pillar = 448.368mm
- Intrusion on Fuel tank region = 974.471mm
- Peak velocity of node 337772 = 16.26mm/ms
Link to view:
https://drive.google.com/file/d/1x6NO0-B9XraBpvNCUg60xgYbx_nCxss8/view?usp=sharing