Influence of Quasi-Static and Dynamic
Loading Directions on Roof Deformation
Fadi Tahan
Prof. Kennerly Digges
Joachim Scheub
The National Crash Analysis Center
The George Washington University
1
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation, Overview
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Model Validation
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Quasi-Static Tests:
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Un-Constrained Rollover Tests
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◦ Planar Impacts
◦ FMVSS 216
◦ Normal Force for FMVSS 216 One sided Loading with Variable
Roll and Pitch Angles
◦ Roof Crush Shapes and Lateral Roof Displacements
◦ Observations
◦
◦
◦
◦
Ground Normal Force
Different Roll Angles Normal Forces
Roof Crush Shapes for Different Roll & Pitch Angles
Observations
Further Observations
2
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Finite Element Model
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The Finite Element model of a 2003 Ford Explorer was used (NCAC 2012)
The model has been validated to several tests:
NCAP Test # 03730 (35 mph)
NCAP Test # 05034 (35 mph)
CMVSS 212/301 Test # 4690 (30 mph)
SNCAP Test # 4087 (MDB 39 mph)
IIHS Test # CEF 0125 (40% Overlap, 40mph MDB)
FMVSS 216 Tests C0139 & C0140 (10 inches roof crush; See next slide)
3
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
FMVSS 216 Tests C0139 & C0140 Validation
4
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Normal Force for Different Roll & Pitch Angles
Model
Validated
Minimum
SWR = 1.75
5
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Roof Crush Section Cut Comparison (Model Overlay)
10° pitch & 25° roll (blue); 45° roll (green); 65° roll (red)
Roll Angle
5° Pitch
10° Pitch
15°
-4.1 (mm)
-3.2 (mm)
25°
8.66 (mm)
11.6 (mm)
35°
18.8 (mm)
29.0 (mm)
45°
49.5 (mm)
45.8 (mm)
55°
79.0 (mm)
82.6 (mm)
65°
123.1 (mm)
114.7 (mm)
5 in
10 in
Opposite A-Pillar Lateral
Displacement ( mm)
6
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Quasi-Static Loading Observations
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The direction of roof deformation is important
(with regard to intrusion locations) and changes
with roll angle
The lateral roof motion opposite to the loading is
not usually measured or considered
The roof strength is dependant on the roof shape
(round or square shapes)
The roof strength for 10° pitch angle is generally
lower than 5° pitch angle
7
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Un-Constrained Rollover Simulation
* Tahan, IJ-Crash Conf., Milan 2012
8
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Different Roll Angle Models Rotated Around the C.G.
Cross section plane passing through the C.G.
• The ground location is based on
the roll angle when the C.G. is
above the major radius of the roof
• Different roll angles have an
additional clearance from the
ground level as shown in the picture
and the values are shown in the
table below
Additional
Roll
RA
Drop Height
Angle from Baseline
C.G.
10 Yaw; 5 Pitch; Variable Roll; 190 Roll Rate;
15 mph; 4 in Drop Height
* Tahan, IJ-Crash Conf., Milan 2012
9
125
135
145
155
165
180
mm
86.2
27.2
BASELINE
5.9
45.3
127.4
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Typical Ground Normal Force vs. Roll Angle
* Tahan, IJ-Crash Conf., Milan 2012
10
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Ground Normal Force Comparison For Different Roll Angle
Near-side Contacts
Far-side Contacts
Hood Contacts
* Tahan, IJ-Crash Conf., Milan 2012
11
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Roof Crush: Different Roll Angle Variations
-10Y -10P 125R
190RR 15mph
4inDH
-10Y -10P 135R
190RR 15mph
4inDH
12
-10Y -10P 145R
190RR 15mph
4inDH
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Roof Crush: Different Pitch Angle Variations
-10Y -5P 125R
190RR 15mph
4inDH
-10Y -5P 135R
190RR 15mph
4inDH
13
-10Y -5P 145R
190RR 15mph
4inDH
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Dynamic Rollover Loading Observations
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Normal roof force vs. roll angle is a good indication of
the force direction and magnitude applied to the roof
Roof deformation patterns for different initial contact
conditions change dramatically with small roll and
pitch angle variations
Full-scale rollovers contribute to other vehicle parts
contacting the ground (fenders, hood, roof rear,
wheels failure, etc.) which change roll conditions
during the rollover and affects the occupants
kinematics (injuries outcome)
Dynamic loading in rollover is a lot more complicated
than the quasi-static loading used in the standard.
14
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Further Observations
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A collaboration between the Industry, the Government &
other safety laboratories is needed to achieve an
understanding of injuries associated with rollover crashes
and to properly evaluate structures and restraint systems
A collaboration in Finite Element modeling is needed for
some key components:
◦ Windows and Windshield (under different loading conditions)
◦ Roof structure model for quasi-static & dynamic loadings (under
different loading conditions)
◦ Tire and suspension model (with failure)
◦ Dummy development for rollover crashes
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Current dynamic rollover test devices (DROTS by UVA,
JRS II by UNSW, GRP by GWU, etc.) are a step forward
toward understanding the kinematics of both the
occupants and vehicle motions
15
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)
Different Roll Angle Models Rotated Around the C.G.
Cross section plane passing through the C.G.
10 Yaw; 5 Pitch;
Variable Roll;
190 Roll Rate;
15 mph; 4 in
Drop Height
• The ground location is based on
the roll angle when the C.G. is
above the major radius of the roof
• Different roll angles have an
additional clearance from the
ground level as shown in the picture
and the values are shown in the
table below
RA
C.G.
125
135
145
155
165
180
* Tahan, IJ-Crash Conf., Milan 2012
16
Additional
Drop Height
from Baseline
mm
86.2
27.2
BASELINE
5.9
45.3
127.4
Oral PAPER: Influence of Quasi-Static and Dynamic Loading
Directions on Roof Deformation (Jan.30, 2013)