The National Crash Analysis Center The George Washington University Un-Constrained Models Comparison For Elastic Roof – Production Roof – Strong Pillars

The National Crash The National Crash Analysis CenterAnalysis CenterThe George Washington The George Washington UniversityUniversity

Prepared by: Fadi [email protected]

(703) 726-8327

Slide 2

Study OverviewStudy Overview

FE Model Model Validation to Static Tests (NHTSA test number

C0139 & C0140) Un-Constrained Model Set up Different Roof Property Simulations Different Roadbed Weight Simulation

Deformable Roof Elastic Roof

Different Roadbed Speed Simulation 145° Initial Roll Angle 180° Initial Roll Angle

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Slide 304/18/23

FEA ModelFEA Model

The Finite Element model of a 2003 Ford Explorer was used

The suspensions, drivetrain and engine were removed to reduce the model (shown in yellow)

The weight and inertia of these parts were replaced by adding concentrated mass and inertia elements at six points on the ladder frame (shown in red)

Full Model Reduced Model

Slide 4

Model Validation Model Validation - - Based on FMVSS 216 TestsBased on FMVSS 216 Tests

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Validation to NHTSA test number C0139 Validation to NHTSA test number C01405° Pitch; 25° Roll 10° Pitch; 45° Roll

Slide 504/18/23

Roof Material Properties Effect On

Un-Constrained Model

(Elastic Roof – Production Roof – Strong Pillars Properties)

Slide 6

3 Different Roof Models – 3 Different Roof Models – Material ChangeMaterial Change

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Elastic Roof Model; SWR is measured to be 3.9Components shown in blue have pure elastic properties (Properties shown in next slide)

Production Roof Model; (No material change) SWR =

Strong Pillars & Production Roof Rails Model; SWR =Components shown in green are made from DF140T (Properties shown in next slide)

E= 200GPaWith No Yielding

Strong Roof & Production Roof Rails MaterialsE= 200GPa; Yield at ~775 MPa

Slide 7

Material CharacteristicsMaterial Characteristics

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Yield (True) Stress: ~ 775 MpaMaximum Plastic Strain: ~ 13.3%

E= 200GPa

Yield (True) Stress: N/APlastic Strain: N/A

E= 200GPa

Based on Arcelor-Mittal Steels

What SWR?

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U-C Model – SetupU-C Model – Setup

Front View

Side View

ISO View

Initial Conditions Value Rotational Speed 190 °/sec

Vertical Drop Distance 10 cm Roadbed Speed 24.2 km/h

Roll Angle at Impact 145°Pitch Angle 5°Yaw Angle 10°Coefficient of Friction 0.2

Slide 9

Model Setup - Roadbed DimensionModel Setup - Roadbed Dimension

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4550 mm (~ 180 in – 15 ft)

2800 mm (~

110 in – 9 ft)

The roadbed weight is 3183 kg (7000 lbs)

Vehicle weight is 2255 kg ( 4971 lbs)

The roadbed surface is made of wood of 25.4 mm (1 in) thick

Slide 10

U-C – Roadbed Normal Force Vs Roll AngleU-C – Roadbed Normal Force Vs Roll Angle

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Roof Material VariationProductionElastic Strong

Slide 11

U-C – Roll Rate Vs Roll AngleU-C – Roll Rate Vs Roll Angle

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Filtered Curves (SAE 060)Roof Material VariationProductionElastic Strong

Slide 12

U-C – Passenger & Driver Intrusion CharacteristicsU-C – Passenger & Driver Intrusion Characteristics

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0.271 m

0.223 m


Slide 13


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Slide 14

U-C Animation –U-C Animation – Elastic Roof Vs. Strong Pillars Elastic Roof Vs. Strong Pillars

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Slide 15

U-C – Elastic Roof Vs. Strong Pillars OverlayU-C – Elastic Roof Vs. Strong Pillars Overlay

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Elastic Roof Model&

Strong Pillars Model

Overlaid on top of each other (t = 0 s)

Roof Crush at ~ 195° Roll Angle (t = 0.2 s) Roof Crush at ~ 215° Roll Angle (t = 0.3 s)

Slide 16

Conclusion For Different Roof PropertiesConclusion For Different Roof Properties

It is assumed that using an elastic roof model can be used for

simplification for the rollover parametric study since:

The roadbed normal force for the strong pillars model follows

similar pattern as the elastic model

The roof crush mode is attributed to the location of the buckling at

the structure or excessive elasticity for elastic model

The driver side intrusion for the strong pillar model is only 21%

more than the elastic model

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Slide 1704/18/23

Roadbed Weight Effect On


(4 Different Weights)

Slide 1804/18/23

U-C Model – SetupU-C Model – Setup

Front View

Side View

ISO View




Slide 19

Model Setup - Roadbed DimensionModel Setup - Roadbed Dimension

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4550 mm (~ 180 in – 15 ft)

2800 mm (~

110 in – 9 ft)

Four different roadbed weights were investigated:

• 2255 kg (4971 lbs) Similar weight of the vehicle with initial roadbed speed of 6.7 m/s

• 3183 kg (7000 lbs) Baseline analysis with initial roadbed speed of 6.7 m/s

• 4183 kg (9222 lbs) 1 ton more than the baseline model with initial roadbed speed of 6.7 m/s

• 3183 kg (7000 lbs) with constant roadbed speed (assumption made to cover heavy roadbed weight)

Slide 20

Roadbed Force, Roll Angle & Intrusion Characteristics Roadbed Force, Roll Angle & Intrusion Characteristics

ComparisonsComparisons

Deformable Deformable Roof Roof

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Slide 21


04/18/23 Deformable Roof

Variations in Roadbed Weight2255 kg 3183 kg 4183 kg 3183 kg

Slide 22


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Filtered Curves (SAE 060)

Deformable Roof


Slide 23



Passenger Driver

Passenger Driver


Slide 24

U-C – Roadbed Speed (Deformable Roof)U-C – Roadbed Speed (Deformable Roof)


at 350 ms

Slide 25

Roadbed Force, Roll Angle & Intrusion Characteristics Roadbed Force, Roll Angle & Intrusion Characteristics

ComparisonsComparisons

ElasticElastic Roof Roof

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Slide 26

Strong Roof Assumption - Strong Roof Assumption - Elastic ModelElastic Model

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Representative of future vehicles that are going to meet the new FMVSS 216 requirements

All roof components were switched to linear elastic

The Strength to Weight Ratio (SWR) is measured to be 3.9

Elastic Roof

Slide 27


04/18/23 Elastic Roof


Slide 28


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Elastic Roof


Slide 29



Passenger Driver

Passenger Driver


Slide 30

U-C – Roadbed Speed (Elastic Roof)U-C – Roadbed Speed (Elastic Roof)

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at 350 ms

Elastic Roof

Slide 31

Conclusion For Different Roadbed WeightsConclusion For Different Roadbed Weights


•The normal roadbed force, the roll rate and the intrusion characteristics were

similar for both the Deformable and Elastic roof models.

•When the roadbed weight increased, the difference between the initial and

final roadbed speeds decreased. The percentage decrease for the Deformable

model was greater than for the Elastic model.

Roadbed WeightFinal Roadbed Speed (m/s)

Percentage Decrease

Final Roadbed Speed (m/s)

Percentage Decrease

2255 kg 5.423 19.06% 5.777 13.78%3183 kg 5.919 11.66% 6.061 9.54%4183 kg 6.104 8.90% 6.213 7.27%

Deformable Roof Elastic Roof

Initial Roadbed Speed is 6.7 m/s; Final Roadbed Speed is at 350 ms

* The heavy roadbed weight is assumed by applying a constant speed

Slide 32

Conclusions Roadbed Weight

What difference does it make on the test?

What weight to I need?

Slide 3304/18/23

Roadbed Speed Effect On


(6 Different Speeds)

Slide 34

Strong Roof Assumption - Strong Roof Assumption - Elastic ModelElastic Model

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Representative of future vehicles that are going to meet the new FMVSS 216 requirementsAll roof components were switched to linear elasticThe Strength to Weight Ratio (SWR) is measured to be 3.9

Elastic Roof

Slide 3504/18/23

Baseline Model – SetupBaseline Model – Setup

ISO View

Side View

Front View




Slide 36

Different Roadbed SpeedsDifferent Roadbed Speeds

Roadbed Force, Roll Angle & Intrusion CharacteristicsRoadbed Force, Roll Angle & Intrusion Characteristics

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Roadbed Speed Roll Rate Drop Height Initial Roll Anglekm/h degree/sec cm degree

09

1824

3036

190 10 145

Slide 37

Baseline Simulation – Elastic ModelBaseline Simulation – Elastic Model

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Simulation tracked at the C.G.

Slide 38

Roadbed Normal Force Vs Roll AngleRoadbed Normal Force Vs Roll Angle

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Variations in Roadbed Speed0 kph09 kph18 kph24 kph30 kph36 kph

Slide 39

Roll Rate Vs Roll AngleRoll Rate Vs Roll Angle

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Variations in Roadbed Speed0 kph09 kph18 kph24 kph30 kph36 kph

Slide 40

Passenger & Driver Intrusion CharacteristicsPassenger & Driver Intrusion Characteristics

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Roadbed Speed

Roll RateDrop

HeightInitial Roll

Angle

km/h degree/sec cm degree

9 84.3 1.27 104.2 1.1518 61.1 1.47 221.3 2.3624 56.9 1.60 260.4 3.3030 58.1 1.66 248.1 3.6136 58.5 1.68 229.8 4.20

190 10 145

Passenger (near) Side Driver (far) Side

Roll Rate

km/h degree/sec cm degreeDynamic Intrusion

mm

Intrusion Ratem/s

9 84.3 1.27 104.2 1.1518 61.1 1.47 221.3 2.3624 56.9 1.60 260.4 3.3030 58.1 1.66 248.1 3.6136 58.5 1.68 229.8 4.20

Maximum Passenger A-Pillar

Roll Rate

km/h degree/sec cm degreeIntrusion

Ratem/s

Dynamic Intrusion

mm

Intrusion Ratem/s

9 84.3 1.27 104.2 1.1518 61.1 1.47 221.3 2.3624 56.9 1.60 260.4 3.3030 58.1 1.66 248.1 3.6136 58.5 1.68 229.8 4.20

Maximum Passenger A-Pillar

Maximum Driver A-Pillar

Slide 41

Different Roadbed SpeedsDifferent Roadbed Speeds

Roadbed Force, Roll Angle & Intrusion CharacteristicsRoadbed Force, Roll Angle & Intrusion Characteristics

04/18/23

Roadbed Speed

Roll RateDrop

HeightInitial Roll

Angle

km/h degree/sec cm degree

9 91.4 1.5618 125.7 1.8824 141.5 1.8630 163.5 2.5036 192.5 3.40

190 10 180

Slide 42

Model Setup & Initial ConditionsModel Setup & Initial Conditions

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Initial condition ValueRotational Speed 190 0/s

Vertical Drop Distance 10 cmRoadbed Speed 24.2 km/h

Roll Angle at Impact 1800

Pitch Angle 50

Yaw Angle 100

Front View Side View

Same set up as previous model with initial roll angle of 180°

Roadbed

Slide 43

Baseline Simulation – Elastic ModelBaseline Simulation – Elastic Model

04/18/23Simulation tracked at the C.G.

Slide 44

Roadbed Normal Force Vs Roll AngleRoadbed Normal Force Vs Roll Angle

04/18/23

Variations in Roadbed Speed180o Roll Angle09 kph18 kph24 kph30 kph36 kph

Slide 45

Roll Rate Vs Roll AngleRoll Rate Vs Roll Angle

04/18/23


Variations in Roadbed Speed180o Roll Angle09 kph18 kph24 kph30 kph36 kph

Slide 46

Driver Intrusion CharacteristicsDriver Intrusion Characteristics

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Roadbed Speed

Roll RateDrop

HeightInitial Roll

Angle

km/h degree/sec cm degreeDynamic Intrusion

mm

Intrusion Ratem/s

9 91.4 1.5618 125.7 1.8824 141.5 1.8630 163.5 2.5036 192.5 3.40

190 10 180

Maximum Driver A-Pillar

Slide 47

Intrusion Characteristics Comparison (180° & 145°)Intrusion Characteristics Comparison (180° & 145°)

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Dynamic Intrusion Intrusion Rate

Driver (far) Side

Slide 48

Conclusion For Different Roadbed SpeedsConclusion For Different Roadbed Speeds

The minimum roadbed speeds necessary to obtain 3 quarter turns rollover is of 24 km/h (14.9 mph) (Have you tried 20 and 22?)

The roadbed normal forces follow the same pattern for roadbed speeds between 24 and 36 km/h (14.9 - 22.4 mph) for initial roll angle of 145°

When the roadbed speed increases, the roll rate after initial contact increases for speeds above 18 km/h (11.2 mph)

For different roadbed speeds and the baseline initial conditions, the dynamic intrusion and the intrusion rate for initial roll angle of 145° are higher than for 180° initial roll angle

04/18/23

Slide 4904/18/23

QUESTIONS?QUESTIONS?

Documents

The National Crash Analysis Center The George Washington University Un-Constrained Models Comparison For Elastic Roof – Production Roof – Strong Pillars