hybrid finite element model for side impact simulations-6june07-1

IV SEMESTER M.TECHM/C DESIGN

SEPT 2005 to Oct 2010

BANGALORE INSTITUTE OF TECHNOLOGY

UMESH G S

Hybrid Finite Element Model For Side Impact Simulations

Guide

Dr. T. JAGADEESH ,

PG Co-coordinator,

Bangalore Institute of Technology ,

Bangalore.

Project Carried out in

BANGALORE INDTITUTE OF TECHNOLOGY




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Regulatory Requirement :

It is mandatory for all passenger vehicles get Homologation (confirm officially) Certification of that country before launching any vehicles in that country.

United States : National Highway Traffic Safety Administration (NHTSA) as per FMVSS

Europe : Economic commission for Europe (ECE) India : Society of indian Automotive Manufactures (SIAMS) & Automotive research of India

Crash Tests :

Frontal Impact ( FMVSS 208 , ECE R94, Euro NCAP )

Side impact ( FMVSS214, IIHS, ECE R95, Euro NCAP )

Rear Impact ( FMVSS 301, ECE R32 )

Roll over etc..

INTRODUCTION :




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Side Impact Details :

Un struck side Struck side

Struck side :

Experiences large Elasto-plastic Deformations in Side Impact.

Unstruck side (including front and Rear_end) :

Experiences gross rigid body motion with elastic deformations.

Front End

Rear End

Dodge Neon model taken from : NHTSA (www- nrd.nhtsa.gov.com)




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Upper body beams

Under body beams

Side body

Elasto - Plastic deformation zones in side impact simulations.

LH Side_Doors with Door trims




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Why to Represent the Unstruck side in detail ?

How to Reduce the Computation time ?

How to decrease the Model Size so that Computation space can be reduced ?




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Literature Survey :

Frontal impact Reduced Order model

- Tomohiko ,Masanori et all, Kamal, etc

Side impact Struck side reduced order model

- Trella et all , Heon Young Kim, J.E Tomassoni, etc

Rear End Hybrid model :

- Lchiro Hagiwara, etc

Side impact Un-struck side representation by Hybrid element model is Not addressed in many studies.




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The project will be directed towards

• Developing a efficient strategy to build hybrid finite element vehicle model for side impact analysis by retaining the elasto-plastic deformation zones with shell elements and the elastic/ undeformed zones with one dimensiona/Reduced ordered elements.

• Reducing Model size and Computation time without sacrificing model fidelity.

Objective of the Project :




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Project Challenges

Side impact itself is a very Complex scenario

- No Crush space Availability,

- Less time for Restraint system for activation,

- Occupant is very close to the Impact Zone.

-Lateral velocity can vary along the length of the car hence mass distribution should be proper.




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Dodge Neon Baseline Simulation:

Assumptions:

1. Dodge Neon Model is Considered as a Base model and converted as a Side impact set up.

2. Unit System used in the Model.

Rigid_Barrier_Details

Mass of Rigid _Barrier 1300 kg ( 1.3 tone)

Velocity of Rigid Barrier 13.91(30 mph) 13911 mm/second

UnitsLength milimeterTime SecondMass TonneForce Newton

3 Instead of Moving Deformable Barrier (MDB) Rigid Barrier is considered for worst case scenario.




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Baseline_Side_impact Setup :




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Deformed Shape at 90 milisecond

0 milisecond

Dodge Neon Side impact Set up With Rigid Barrier.




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Base_Model_Details.

Nodes 283880

Elements 275993

No. Of Parts 342

Materials 336

Properties 336

Groups 63

No of Joint 12

Airbags 4

Rigid walls 5

Mass elements 336

Cross sections 18

Mass Details: Kg

Structural Mass 782.5

Lumped mass 534.34

Total_vehicle_mass 1316.85

Dodge_ Neon side impact base model details.

Computation Time : 64.1 Hours for 90 millisecond




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Mean_strain_rate_Distribution for Baseline Model

IP/Beam and Dash board

Bar 1

Bar 2

Bar 3

B Piller

Side structure + Dog leg

Roof_bows




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Side impact Mechanics. Collapse modes of main structure.

(Courtesy: 1999-01-3185 (SAE) Heon Young, Kangwon Nation University)




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Courtecy :CarBodydesign.com




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Matrics Parameters for Correlation :

Global Energy Plot

B-piller Intrusion Plot

Latera Y - Velocity of the Vehicle at unstruck side (Rocker)

Global Energy Plot B-piller Intrusion Plot

Y - Velocity




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ITERATION - 1: Lumped mass approach

Right Hand Side (Unstruck Side) of Full vehicle is replaced with a Lumped mass.

CG of the Mass Element is maintained same as that of the RH side CG.

Mass element is Connected with a Nodal Rigid Body to Vehicle.




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CG_NID 2907144 Mass : 471.243 kg

X Y Z

3308.58 -65.9835 523.412




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Lumped mass approach Results

Global Energy Plot

B-piller Intrusion PlotY - Velocity




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Results Comparison With Baseline:Iteration -1Baseline




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Results Discussion :

1. Results are matching till 35 milisecond as the deformation is in the struck side.

2. Due to the lack of Primary load carrying members complete geometry, Deformation stops at Struck side to mid of the vehicle.

3. Lumped mass behavior is different than the Structure deformation hence results show deviations later on.

4. Lateral Velovity Shows the difference because Absence of Structural member to transfer the Load.

5. Vehicle intrusion matches with the Baseline as the Overall Mass and Struck side structure behavious in the same manner as in baseline.




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ITERATION 2: Right hand side rigid material approach

Excluding the High deformation zone parts , Remaining parts in the Right hand side are Assumed rigid material by moving them all into one part.

Connection of this Rigid part is maintained with the body as it is.

Mass and CG of the Rigidized portion of the vehicle is maintained the same by adjusting the density of the Rigid Component.

All parts connecting to this Rigid part are taken care as a Xtra_Node option.




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Right hand side rigid material:Setup

Rigid Material

12

3B Pillar

IP/Beam and Dashboard

Roof bows

Highly deformable members are excluded from Rigid mat assignment.




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Global Energy Plot


Y - Velocity

Right hand side rigid material: Rsults




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Results Comparison With Baseline: RH Rigid materialBaselineGlobal Energy Plot


Y - Velocity




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Results Discussion :

1. Global Energy , Lateral velocity, Intrusion Plot’s matches with the base line with in the acceptable range.

2. This simulations requires extra precaution to exclude Primary load carrying members from assigning them a rigid material.

3. Finding out the Rigid material Center of gravity and tuning the mass of the rigid material as per the actual mass is one more activity needs to be performed.




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ITERATION – 3 : SUB SYSTEM LUMPED MASS

Representing the sub systems with Lumped masses with out effecting the vehicle characteristics.




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18.83 Kg

Door hinges

Door latch

SUB SYSTEM LUMPED MASS :Right hand side door replacement




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18.31 kg

Right hand side door replacement with proper connections




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Sub system lumped mass approach :Door replacement

Baseline

Right hand side door replacement Results




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11.52 Kg

SUB SYSTEM LUMPED MASS: Hood Assembly Replacement




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286.5 kg

SUB SYSTEM LUMPED MASS: Engine Assembly Replacement




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14.06 kg

9.99 kg

SUB SYSTEM LUMPED MASS: Front and Rear Wind Shield Replacement




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17.73 Kg

Battery_assembly

SUB SYSTEM LUMPED MASS: Battery Assembly Replacement




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7.60 kg

SUB SYSTEM LUMPED MASS: Radiator Assembly Replacement




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SUB SYSTEM LUMPED MASS : intermediate results




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12.29 kg

Front _ Bumper_Assembly

SUB SYSTEM LUMPED MASS : Front bumper replacement




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2.56 Kg

2.56 Kg

SUB SYSTEM LUMPED MASS : Fender replacement




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8.95 Kg

SUB SYSTEM LUMPED MASS : Lift gate(Rear hatch) replacement




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19.88 kg

SUB SYSTEM LUMPED MASS : Rear bumper replacement




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Sub systems with lumped mass final Model




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SUB SYSTEM LUMPED MASS : Results comparisonSub system lumped mass approach

Baseline




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z Case studies Assembly_NameNo of elements Nodes

Solving_time (Hours )

1 Base_line_run 275993 283862 6.41E+01

2 Case_Study-1 RH_NRB_With_Lumped_mass 141847 150284 2.89E+01

3Case_Study_

2 RH_Rigid_Mat_assigment. 132042 139780 3.60E+01

4Case_Study_

3Sub_system_with respective Lumped masses at their CG..

Doors_with_mass 250251 257467 4.44E+01

Door_and_Hood_mass 241805 248829 4.10E+01

Door_and_Hood_windshield_mass 240739 247774 3.88E+01

Door_and_Hood_windshield_powertrain 238543 245913 3.95E+01

Door_and_Hood_windshield_powertrain_battery 237784 245149 3.81E+01

Door_and_Hood_windshield_powertrain_battery_CRFM 234800 243258 3.86E+01

Door_and_Hood_windshield_powertrain_battery_CRFM_Frt_bump 226924 235719 3.63E+01

Door_and_Hood_windshield_powertrain_battery_CRFMM_Frt_bump_fender 224146 232822 3.62E+01

Door_and_Hood_windshield_powertrain_battery_CRFMM_Frt_bump_fender_lift_gate 218387 227009 3.31E+01

Door_and_Hood_windshield_power_train_battery_CRFMM_Frt_bump_fender_lift_gate_rear_bump 213534 222178 3.18E+01




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CONCLUSION :

Computation Time

Results correlation

Computation reduction

Baseline 64.1 100% 3.58 GBLumped mass 28.1 60% 1.1 GBRigid material 36 95% 1.8 GBSub system lumped mass 31.8 90% 2.2 GB

Computation Time

Results correlation


Baseline 64.1 100% 3.58 GBLumped mass 28.1 60% 1.1 GBRigid material 36 95% 1.8 GBSub system lumped mass 31.8 90% 2.2 GB

Computation Time

Results correlation


Overall Rating

Baseline 64.1 100% 4.58 GB -

Lumped mass 28.1 60% 1.1 GB PoorRigid material 36 95% 1.8 GB GoodSub system lumped mass 31.8 90% 2.2 GB Excellent




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FUTURE SCOPE OF THE PROJECT

Courtacy: Heon Young Kim, Sang Bum Kim, Kangwon Nation University

Reduced Hybrid model for side impact simulations where Struck and un struck side are represented by reduced order elements and which correlates with the experimental results.




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References :

1. T. J. Trella, R. R. Samaha, E. J. Smith, ”The use of Advanced Analytical Techniques in Side Impact Crashworthiness Research”Fifteenth International Conference on the Enhanced Safety of Vehicles, Melbourne, Australia, May 13-16, 1996. 2. T. Ariyoshi, “Development of a Beam Element Model for an Analysis of a Motor Vehicle Rear End Crash”,SAE International Congress and Exposition, Detroit, Michigan, USA, Feb26-Mar2, 1990. 3. M.Tani, R.I.Emori, “A Study no Automobile Crashworthiness”, Automotive Engineering Congress and Exposition, Detroit, Michigan, USA, Jan12-16, 1970. 4. M. M. Kamal, “Analysis and Simulation of Vehicle to Barrier Impact”, Automotive Engineering Congress and Exposition, Detroit, Michigan, USA, Feb27-Mar3, 1978. 5. H-S Kim, S-Y Kang, In-H Lee, S-H Park, D-C Han, “Vehicle Frontal Crashworthiness Analysis by Simplified Structure Modeling using Nonlinear Spring and Beam Elements”, Int. J. Crashworthiness, Vol2, No1,pp107-117,1997. 6. Heon Young Kim, Sang Bum Kim,Sang Soon Kwon,Sung Kook Oh, Chang Sup Ahn, “A Study on The Hybrid Finite Element Modeling for Side Impact Simulation” ( Copyright © 1999 Society of Automotive Engineers, Inc. ) 7. lchiro Hagiwara, Yasuo Sasakura, Tadashi Nakagawa and Yoshihiro KajioNissan Motor Co., Ltd. International Congress and ExpositionCobo Hall, Detroit, Michigan February 23-27, 1981




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hybrid finite element model for side impact simulations-6june07-1

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