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Surviving a Crash in Rear Seats:
Addressing the Needs from a
Diverse Population
Jingwen Hu, PhD UMTRI-Biosciences
MADYMO USER MEETING 2016
Research Themes
Crash Data Analysis Statistical Morphology
Computational Modeling
Safety Design Optimization
Laboratory Testing
Injury
Biomechanics
and
Occupant
Protection
Research Motivation
Older Child
Adult Infant
Rear Seat
Environments
Background
What are the leading injuries in rear seat?
4
Data based on Kuppa et al. 2005 and Arbogast et al. 2012
Mainly by the
contact to the back
of the front seat
and B-pillar
Mainly by high
seat belt loading
We all know that wearing your seat
belt is safer than being unbelted, but
can we improve on that?
Rear-Seat Passengers
~20% of second-row passengers are ages 6-12 (smaller in body size than most adults)
Harness
restraints
???
Adult Belt
Systems
Add-On
Boosters
Rear Seat Belt Anchorage Locations
SAE J826 H-Point
Lab Conditions
Vehicle Anchorages
FMVSS 210 Zone
Data from 28 second-row outboard seats
Inboard
Outboard
• Rear seat lap-belt angles span the entire range of angles permitted by FMVSS 210
• Belt anchorage locations varied significantly among different vehicles
Rear Seat Cushion Length
Most rear seats are too long for most children ages 4-17
Huang and Reed (2006) SAE
Children = ages 4-17 years
BPL = buttock-popliteal (thigh) length
SCL = seat cushion length
Good fit: BPL > SCL
400 471
Is 4’9” (145 cm) truly
a magic number?
Study Design
Older Child
Adult Infant
Rear Seat
Environments
Optimal
Designs
Optimal
Designs
Scalable MADYMO ATD Model
Modified pelvis/abdomen to respond more realistically to belt interaction
Scaled body size, inertial properties, and stiffness, with realistic seating posture
Seat model has facet surface and two cylinders simulating anti-submarining components
6 Year Old 8 Year Old 10 Year Old 12 Year Old
Validation Example
Sled vs. Simulation
6YO
Long Seat
Rearward Anchors
6YO
Short Seat
Forward Anchors
Sled vs. Simulation
10YO
Long Seat
Rearward Anchors
10YO
Short Seat
Rear Anchors
Design Optimizations
Design Variable Range
Lap belt anchorage as measured in vehicles (spans FMVSS 210)
D-ring as measured in vehicles
Seat length 350-450 mm
Cushion stiffness 50-150% of Caravan seat
Cushion support 15mm higher/lower than that from Caravan seat
Objectives: minimize head and knee excursions
Constraint: peak torso rotation from 10 to 20 deg (forward of vertical)
Algorithm: NSGA-II (genetic algorithm), 50 generations with 50 simulations per generation, ~2500 runs
Optimization for 6, 9, and 12 YO separately
Optimal belt anchorage locations depend on body size
Side View Forward (mm)
Optimal Belt Geometry For Older Child
12YO Optimum
6YO Optimum
Adult and CRS Sled Test Matrix
450 mm 350 mm
Test ID ATD Cushion
length
Seatbelt
geometry
Cushion
stiffness
CRS/
hardware
NT1101 CRABI
12MO 450 mm Mid standard Snugride 30
NT1102 CRABI
12MO 350 mm Mid Standard Snugride 30
NT1103 CRABI
12MO 350 mm
6YO
Optimal Standard Snugride 30
NT1104 CRABI
12MO 350 mm
6YO
Optimal Stiffer Snugride 30
NT1105 CRABI
12MO 400 mm
6YO
Optimal Standard Snugride 30
NT1106 CRABI
12MO 450 mm Mid Stiffer Snugride 30
NT1108 HIII 50 350 mm Mid Standard Shin bar
NT1109 HIII 50 450 mm Mid Standard Shin bar
NT1110 HIII 50 350 mm 6YO
Optimal Standard Shin bar
NT1111 HIII 50 350 mm 6YO
Optimal Stiffer Shin bar
NT1112 HIII 50 350 mm 6YO
Optimal Standard No shin bar
NT1113 HIII 50 450 mm Mid Stiffer Shin bar Mid FMVSS213 6YO Optimal
400 mm
Model Validation Against Sled Tests
Short
Cushion
Long
Cushion
Model Validation Against Sled Tests
Side View
Top View
Design Optimizations
Design Variable Range
Lap belt anchorage as measured in vehicles (spans FMVSS 210)
D-ring as measured in vehicles
Seat length 350-500 mm
Cushion stiffness 50-150% of Caravan seat
Cushion support 15mm higher/lower than that from Caravan seat
Algorithm: NSGA-II (genetic algorithm), 50 generations with 50 simulations per generation, ~2500 runs
Adults
Objectives Minimize head and knee
excursions
Constraint Peak torso angle 10-20º
past vertical
Infants in RF-CRS
Objectives Minimize CRS angle and
3ms chest-G
Constraint HIC
Side View Forward (mm)
Optimal Belt Geometry
Adult Optimum
6YO Optimum
RF-CRS Optimum
Optimal Seat Cushion
Design Variables 6YO Children Adults Infants in RF-CRS
Cushion Length Shortest Shortest Longest
Cushion Stiffness Middle Lowest Highest
Supporting
Structure Highest High Highest
Preventing
Submarining
Balancing
Head & Knee
Excursions
Reducing CRS
Rotation &
Movement
Summaries
• From the test data: the 6YO optimal belt geometry and seat design can provide “acceptable” but not “optimal” protection to adults and infants in RF-CRS
• Tradeoff 1: More vertical lap belt that best prevents submarining for belted children is sub-optimal for adults and infants in RF-CRS
• Tradeoff 2: Short seat cushion that best prevents submarining for belted children would increase RF-CRS rotation in frontal crashes
• The design tradeoffs indicate the benefit for using adaptive/adjustable restraint systems in rear seat
Belt
Configurations
Pre-Tensioning
Load Limiting
Inflatables
Advanced Restraint Technologies
SCaRAB Bag In Roof Inflatable Belt
Suspender 4-Pt Belt ‘X’
Anchor PT Buckle PT Retractor PT
3-Pt Belt
Digressive LL Constant LL Progressive LL Switchable LL
Crash Conditions
• Rear seat compartment
– Based on a compact vehicle
• Crash pulse
– NCAP fleet severe vs. NCAP fleet soft
• Crash angle
– 0 deg vs. 15 deg to the right
• ATD Occupants
– H-III 6YO / H-III 5th / THOR 50th / H-III 95th
• Front seat position
– Mid (left) vs. more forward (right)
Sled Tests with 5th - Videos
Crash condition: 0 deg with severe pulse
Baseline 3-pt Belt with PT and LL 4-pt Belt with PT and LL
SCaRAB Bag in Roof Inflatable Belt
Crash condition: 0 deg with severe pulse
Sled Tests with 5th – Injury Measures
Model Validation
• Generally, good correlations have been achieved for
each ATD with each advanced restraint system.
3pt belt with PT+LL 4pt belt
Bag in Roof SCaRAB
Design Optimization Targets
Head Neck Chest
Excursion
(mm) HIC BrIC
Neck T
(kN)
Neck C
(kN) Nij Chest D
6 Year
Old <480 <700 <0.87 <1.49 <1.82 <1.0 <40 mm
5th <500 <700 <0.87 <2.62 <2.52 <1.0 Minimize
THOR <580 <700 <0.87 <4.17 <4.00 <1.0 Minimize
95th <600 <700 <0.87 <5.44 <5.44 <1.0 Minimize
Combined Probability of Chest Injury for 5th, THOR, & 95th Minimize
*All injury measures should be less than those in the baseline tests
3-Point Belt DoE – CLL no Airbag
• Baseline System
– Retractor Pre-tensioner
– Constant Load Limiter (CLL)
• Factors
– Additional Pre-tensioners: Anchor and/or Buckle
– Load Limiter Levels: 8 to 10.5 mm torsion bar
– Dynamic Locking Tongue (DLT)
• Observations
– Severe Pulse – None met the constraints
– Soft Pulse – 10 % (QTY 5) met the constraints
Pulse 6yo 5th THOR 95th Comb
Severe 0% 13% 0% 2% 0%
Soft 27% 75% 63% 67% 10%
Constraints Matrix
Recommendations – Soft Pulse
• Anchor PT / Buckle PT / 9mm TB / no airbag – Driver side / Passenger side
3-Point Belt with Airbag DoE
• Baseline System
– Retractor Pre-tensioner
– Constant Load Limiter
• Factors
– Advanced Feature: SCaRAB or BiR
– Additional Pre-tensioners: Anchor / Buckle
– Load Limiter Levels: 8 to 9 mm torsion bar
– Dynamic Locking Tongue (DLT)
• Observations
• 6 runs met all 4 occupants and left & right
side constraints
• 12 runs met all but one of the 4 occupants
and left & right side constraints
Constraints
Met SCaRAB BiR
6yo 94% 58%
5th 79% 98%
THOR 58% 23%
95th 88% 100%
Constraints Matrix
0 deg Severe Pulse Only
Recommendations – Severe Pulse
• Anchor PT / Buckle PT / DLT / 9mm TB / SCaRAB – Driver side
5th - 0°Severe - Videos
CONFIDENTIAL/PROPRIETARY - the information in this document is confidential/proprietary to TRW Automotive. Any disclosure of this information
without the prior written consent of TRW is strictly prohibited.
0 50 100 150 200 250 300
HIC
Ax Tens
Ax Comp
Nij
Chest Comp
BrIC
Percentage of IARV’s
Baseline Advanced-Belt Only Advanced-Belt & Bag
5th - 0°Severe - Injury Measures
Injury Risks HIC Neck T Neck C Nij Chest D BrIC
Baseline 49.3% 80.6% 0.0% 37.2% 44.1% 92.3%
Advanced-Belt Only 6.0% 5.9% 0.0% 16.5% 14.5% 22.5%
Advanced-Belt & Bag 3.0% 0.0% 0.1% 7.9% 6.2% 13.5%
System Star
Rating Pjoint Head Neck Chest Femur Sum
Baseline 95% 0.000 0.000 0.000 4.000 4.000
Adv Belt 33% 3.119 3.478 1.308 4.000 11.905
Adv Belt & Bag 16% 4.000 4.000 2.558 4.000 14.558
USNCAP EURO-NCAP
Test Summary
• Average of injury risk reduction from the baseline
restraint system
ATD Restraints HIC Neck T Neck C Chest D BrIC
HIII 6YO Belt Only -24.1% -33.3% -0.5% -20.5% -46.9%
Belt & Bag -24.1% -99.5% -0.5% -32.2% -56.1%
HIII 5th Belt Only -31.2% -67.2% -0.1% -24.5% -52.5%
Belt & Bag -34.3% -73.2% 0.0% -29.5% -62.0%
HIII 95th Belt Only -26.6% -34.5% 0.0% -40.3% -31.8%
Belt & Bag -34.4% -35.3% 0.0% -39.6% -58.8%
THOR 50th Belt Only 9.6% -25.7% 0.0% 0.8% -18.6%
Belt & Bag -18.4% -94.4% 0.0% 1.0% -46.4%
Conclusions
• Generally speaking, advanced restraints reduce the injury
risks for all the four sizes of ATDs.
• It is possible to meet the IARV’s with an advanced belt
only and an advanced belt and bag system with a ‘soft’
pulse.
• The addition of a properly optimized airbag reduced the
head and neck loads and had the potential to reduce the
chest loads.
• The reduction in chest compression from THOR 50th did
not occur on the advanced restraint system like they did
for the Hybrid III ATDs.
Thanks!
Jingwen Hu, PhD
jwhu@umich.edu
Acknowledgement: UMTRI, NHTSA, ZF TRW, ESTECO, and TASS
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