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