Surviving a Crash in Rear Seats: Addressing the Needs from a Diverse Population Jingwen Hu, PhD UMTRI-Biosciences MADYMO USER MEETING 2016
Research Themes Safety Design Optimization Laboratory Testing Injury Biomechanics and Occupant Protection Computational Modeling Crash Data Analysis Statistical Morphology
Research Motivation Older Child Rear Seat Environments Adult Infant
Background What are the leading injuries in rear seat? 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? Mainly by the contact to the back of the front seat and B-pillar Data based on Kuppa et al. 2005 and Arbogast et al. 2012 4
Rear-Seat Passengers ~20% of second-row passengers are ages 6-12 (smaller in body size than most adults) Harness restraints Add-On Boosters??? Adult Belt Systems
Rear Seat Belt Anchorage Locations Rear seat lap-belt angles span the entire range of angles permitted by FMVSS 210 Lab Conditions Belt anchorage locations varied significantly among different vehicles SAE J826 H-Point FMVSS 210 Zone Inboard Outboard Vehicle Anchorages Data from 28 second-row outboard seats
Rear Seat Cushion Length Most rear seats are too long for most children ages 4-17 Children = ages 4-17 years BPL = buttock-popliteal (thigh) length SCL = seat cushion length 400 471 Good fit: BPL > SCL Is 4 9 (145 cm) truly a magic number? Huang and Reed (2006) SAE
Study Design Older Child Optimal Designs Rear Seat Environments Optimal Designs Adult Infant
Scalable MADYMO ATD Model Modified pelvis/abdomen to respond more realistically to belt interaction Seat model has facet surface and two cylinders simulating anti-submarining components 6 Year Old 8 Year Old 10 Year Old 12 Year Old Scaled body size, inertial properties, and stiffness, with realistic seating posture
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 Seat length Cushion stiffness Cushion support as measured in vehicles 350-450 mm 50-150% of Caravan seat 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 Geometry For Older Child Optimal belt anchorage locations depend on body size 6YO Optimum Side View Forward (mm) 12YO Optimum
Adult and CRS Sled Test Matrix Test ID NT1101 NT1102 NT1103 NT1104 NT1105 NT1106 ATD CRABI 12MO CRABI 12MO CRABI 12MO CRABI 12MO CRABI 12MO CRABI 12MO Cushion length Seatbelt geometry Cushion stiffness CRS/ hardware 450 mm Mid standard Snugride 30 350 mm Mid Standard Snugride 30 350 mm 350 mm 400 mm 6YO Optimal 6YO Optimal 6YO Optimal Standard Snugride 30 Stiffer Snugride 30 Standard Snugride 30 450 mm Mid Stiffer Snugride 30 450 mm 400 mm 350 mm NT1108 HIII 50 350 mm Mid Standard Shin bar NT1109 HIII 50 450 mm Mid Standard Shin bar NT1110 HIII 50 NT1111 HIII 50 NT1112 HIII 50 350 mm 350 mm 350 mm 6YO Optimal 6YO Optimal 6YO Optimal Standard Stiffer Standard Shin bar Shin bar No shin bar NT1113 HIII 50 450 mm Mid Stiffer Shin bar Mid FMVSS213 6YO Optimal
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 Seat length Cushion stiffness Cushion support as measured in vehicles 350-500 mm 50-150% of Caravan seat 15mm higher/lower than that from Caravan seat Objectives Constraint Adults Minimize head and knee excursions Peak torso angle 10-20º past vertical Objectives Constraint Infants in RF-CRS Minimize CRS angle and 3ms chest-g HIC Algorithm: NSGA-II (genetic algorithm), 50 generations with 50 simulations per generation, ~2500 runs
Optimal Belt Geometry 6YO Optimum Adult Optimum Side View Forward (mm) 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
Advanced Restraint Technologies Belt Configurations 3-Pt Belt 4-Pt Belt X Suspender Pre-Tensioning Retractor PT Buckle PT Anchor PT Load Limiting Progressive LL Constant LL Digressive LL Switchable LL Inflatables Inflatable Belt Bag In Roof SCaRAB
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 5 th / THOR 50 th / H-III 95 th Front seat position Mid (left) vs. more forward (right)
Sled Tests with 5 th - Videos 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 5 th Injury Measures Crash condition: 0 deg with severe pulse
Model Validation Generally, good correlations have been achieved for each ATD with each advanced restraint system. 3pt belt with PT+LL 4pt belt SCaRAB Bag in Roof
Design Optimization Targets 6 Year Old Excursion (mm) Head Neck Chest HIC BrIC Neck T (kn) Neck C (kn) Nij Chest D <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 5 th, THOR, & 95 th 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 Constraints Matrix Pulse 6yo 5th THOR 95th Comb Severe 0% 13% 0% 2% 0% Soft 27% 75% 63% 67% 10%
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 Matrix Constraints Met SCaRAB BiR 6yo 94% 58% 5th 79% 98% THOR 58% 23% 95th 88% 100% 0 deg Severe Pulse Only
Recommendations Severe Pulse Anchor PT / Buckle PT / DLT / 9mm TB / SCaRAB Driver side
5 th - 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.
5 th - 0 Severe - Injury Measures System HIC Ax Tens Ax Comp Nij Chest Comp BrIC 0 50 100 150 200 250 300 Percentage of IARV s USNCAP Baseline Advanced-Belt Only Advanced-Belt & Bag Star Rating EURO-NCAP Pjoint Head Neck Chest Femur Sum Injury Risks HIC Neck T Neck C Nij Chest D BrIC Baseline 49.3% 80.6% 0.0% 37.2% 44.1% 92.3% Baseline 95% 0.000 0.000 0.000 4.000 4.000 Advanced-Belt Only 6.0% 5.9% 0.0% 16.5% 14.5% 22.5% Adv Belt 33% 3.119 3.478 1.308 4.000 11.905 Advanced-Belt & Bag 3.0% 0.0% 0.1% 7.9% 6.2% 13.5% Adv Belt & Bag 16% 4.000 4.000 2.558 4.000 14.558
Test Summary Average of injury risk reduction from the baseline restraint system ATD Restraints HIC Neck T Neck C Chest D BrIC HIII 6YO HIII 5th HIII 95th THOR 50th Belt Only -24.1% -33.3% -0.5% -20.5% -46.9% Belt & Bag -24.1% -99.5% -0.5% -32.2% -56.1% Belt Only -31.2% -67.2% -0.1% -24.5% -52.5% Belt & Bag -34.3% -73.2% 0.0% -29.5% -62.0% Belt Only -26.6% -34.5% 0.0% -40.3% -31.8% Belt & Bag -34.4% -35.3% 0.0% -39.6% -58.8% 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 50 th did not occur on the advanced restraint system like they did for the Hybrid III ATDs.
Acknowledgement: UMTRI, NHTSA, ZF TRW, ESTECO, and TASS Thanks! Jingwen Hu, PhD jwhu@umich.edu