Frontal Crash Simulation of Dodge Neon BIW using Radioss
OBJECTIVE :
To Conduct a Simulation of a Frontal Crash for the provided Dodge Neon BIW based on the guidelines listed below :
- Check unit system and either follow[Mg mm s] or [Kg mm ms].
- Create appropriate interface ,friction 0.2 and recommended parameters.
- Make sure of no penetrations and intersection.
- Correct rigid bodies if any issues.
- Create rigid wall with friction 0.1.
- Compare the model weight with the full scale 300k nodes model and use added masses to reach target weight 700kg while getting CG about the required range.
- Initial velocity 35 mph.
- Use model checker to ensure good quality.
- Time-step :0.5 to 0.1 microseconds.
- Run 80 ms.
Output requests:
i) The following sectional Forces
- Sectional force in the rails at location of indicated node : (Node ID : 174247 for LH)
- Shotgun cross sectional forces
- A-pillar cross sectional force
- A-pillar B-O cross sectional force
- Headlight Bracket Crossectional Forces.
ii) Axial force received on the rails from bumper.
iii) Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
iv) Intrusions on the dash wall 66695,66244.
STUDY OF PROVIDED FILE :
File 1 : Full Car Model
From the above file, we only require the value of total Mass of the vehicle and the location of the center of gravity :
Using the Mass Balancing Toolbar in Hypercrash UI, Both of the required values are checked as shown below :
Mass of the Vehicle : 1216.55 kg
Center of Gravity (C.O.G) of the Vehicle :
The C.O.G was found to be near the transmission tunnel region as shown below :
File 2 : Partial BIW
- On first look, it is noted that The provided model contains 74 Components each described by an unique property but is defined using only 68 material cards.
- Additionally, there are 390 Rigid bodies defined across the components, with most Rigid bodies being defined for very few nodes. This can be attributed to the need for replicating the actual way in which the nodes should behave.
- Also, there are 6 contact interfaces, which on closer look can be deleted as it is not required for our current simulation.
- It is also noted that, within the 89 additional masses defined, some of the additional masses are defined with 0.001 kg which have no effect on the simulation and hence can be deleted.
- On closer look, the difference in number of material cards and number of components is due to the presence of 5 Joints which are defined in the system using Spring Property cards.
- Addionally, another observation that was made was that, one component had been defined with a Solid property Card and a Drucker-Prager (Type 21) Rock and Concrete material card and that the component defined with these cards overlapped with the bumper shell component.
SIMULATION :
- As per the provided guidelines, the system used for this simulation is [kg], [mm], [ms] unit system.
- As discussed above, once importing the system into the Hypercrash UI, the unnecessary datas are deleted.
Pre-Processing :
i) Setting up of Interfaces :
- Based on the provided guidelines, it is clear that only 2 interfaces need to be set up.
* For Self Contact between the Parts : A self impact Type 7 Contact with all Parts selected.
* For getting the contact forces recieved by the rails from the bumper : A Type 7 Contact with Bumper as master and Rails as Slave
ii) Setting up a Rigid Wall :
- A Rigid wall was setup Perpendicular to Global X-axis and infront of the BIW by a small gap.
- This gap was created for visualization purposes only, so that we can see the movement of the BIW system towards the wall without crashing during the animation.
- As per the provided guidelines, the infinite plane Rigid wall was created with a friction value of 0.1.
iii) Defining Additional masses to meet Target weight and C.O.G Requirements :
As per the guidelines provided, it is required for the setup to weight around 700g with the C.O.G at optimum location as mentioned.
- The current weight of the provided model is checked using the Mass Balancing option in Hypercrash
- The mass is found to be 188 grams with C.O.G near the transmission tunnel area.
- Hence, additional mass of 512 grams should be added to the BIW using the added mass tool.
- The location of C.O.G and Weight of the C.O.G after mass addition is shown below :
iv) Defining an Initial Velocity to the Nodes :
As per the guidelines provided, an initial velocity of 35mph should be provided to all the nodes in the positive x-direction.
Since the current units is mm/ms, the mph needs to be converted before entering in UI.
35mph = 15.646 mm/ms
v) Check for Penetrations :
Using the Check penetration tool available in Contact Interfaces tab in Hypercrash UI, the system is checked for any initial penetrations.
vi) Defining Accelerometers to measure node accelerations :
As per the guidelines, two accelerometers are setup, one at the base of each B-Pillar as shown :
vii) Defining Sections to measure required sectional Forces :
The following sections are required as per the guidelines
- Sectional force in the rails at location of indicated node : (Node ID : 174247 for LH)
- Shotgun cross sectional forces
- A-pillar cross sectional force
- A-pillar B-O cross sectional force
- Headlight Bracket Crossectional Forces
viii) Control card Definitions :
Currently, 17 Control cards are defined. They are :
- As per the guidelines the Run time and Time frequency to write data on history plot file T-file are checked in the RUN card and TFILE Card. The required values of 80ms run time and 0.5ms T_freq are present already, hence it is not changed.
- Additionally another control card is defined /ANIM/VECT to animate the Displacement, stresses etc while Post-Processing. The following outputs are requested.
ix) Time/Data History Definitions :
Currently 4 Time history requests are created :
Additionally, TH of Rigid Wall and Sections are requested as shown below :
x) Setting up for Intrusion measurement :
To measure the intrusions of the nodes where the acceleration and brake pedals would conventionally be present, we set up a seperate Time history Reques (/TH/NODE) with respect to an user defined frame of reference, in this case on the cross bar.
xi) Model Checker :
Model checker available under Quality tab in Hypercrash UI is used to check the model as shown below
- According to the model checker, 2 errors and 8 warnings are present in the current system.
- On closer look, The warnings are not severe and can be ignored.
- The errors arise due to poorly defined skew frames and spring elements which are unnecessary for the current study and can be resolved. The final Model Checker screen is shown below :
*Once the Pre-processing is done in Hypercrash, The system is exported to be solved in RADIOSS.
Post-Processing :
The Engine output file is opened using Notepad to check if the Energy and Mass Errors in solution is Acceptable.
- From the output file, we can see that the maximum Energy is -2.0% on the system (Acceptable is around -5%), hence it is acceptable
- The mass error of the system is 0.0249 which is also acceptable.
Hence it is clear that the above system can be post-processed further.
i) Animation of The Crash :
Displacement Plot -
Stress Plot -
ii) System Plots
Rigid Wall Force vs Time -
Energy Plots vs Time -
iii) Axial Force from Bumper to Rails :
iv) Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
v) Intrusions on the Dashwall
vi) Sectional Forces :
a) Rail Sectional Forces -
b) A-Pillar Sectional Forces -
c) Fender Sectional Forces -
d) A-Pillar BO Sectional Forces -
e) Headlamp Bracket Sectional Forces -
REPORT :
The Datas were compiled onto a presentation and is attached at the end. Screenshots of the same are shown below :
CONCLUSION :
- Thus the Frontal Crash Analysis for the provided Dodge Neon BIW was conducted as per provided guidelines.
All relevant datas are attached in the link shared below :
https://drive.google.com/file/d/1C250TR_vt-CKETPZKegmOkFrRqa90Nlw/view?usp=sharing