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Comparison of seat belt force-limiting methods using the MADYMO multi-body/finite element program.
E M Sieveka1, R W Kent, J R Crandall
1Automobile Safety Laboratory, University of Virginia, Charlottesville, Virginia, USA.
Summary
Force-limiting seatbelt systems, whether retractor- or webbing-based, reduce chest compression and head acceleration duration compared to standard belts. Webbing-based systems show potential but require further evaluation for pelvic excursion and femur force.
Area of Science:
- Occupant safety
- Automotive engineering
- Biomechanics
Background:
- Seatbelt systems are crucial for vehicle occupant protection.
- Force-limiting technologies aim to mitigate injury by controlling belt tension during impacts.
- Two primary force-limiting approaches exist: retractor-based and webbing-based systems.
Purpose of the Study:
- To compare the occupant injury response between standard (non-force-limiting) seatbelts and two types of force-limiting systems.
- To evaluate the effectiveness of retractor-based versus webbing-based force limitation in reducing occupant kinematics and injury metrics.
- To analyze the trade-offs associated with webbing-based force limiting.
Main Methods:
- Development of MADYMO multi-body/finite element models of a Hybrid-3 male occupant in a simulated sedan.
- Simulation of occupant loading under three seatbelt conditions: standard, retractor-based force-limiting, and webbing-based force-limiting.
- Comparison of key injury metrics including chest acceleration, head acceleration, chest compression, pelvic excursion, and femur force.
Main Results:
- Force-limiting designs (both retractor and webbing) resulted in approximately 10% lower peak chest acceleration compared to the standard belt.
- Chest compression was reduced by about 60% with both force-limiting systems versus the standard belt.
- While head acceleration magnitude was similar across all systems, force-limiting belts significantly narrowed the acceleration duration. Webbing-based systems increased pelvic excursion and femur force compared to baseline and retractor-based systems.
Conclusions:
- Webbing-based force limiting demonstrates potential for reducing head and chest responses in frontal impacts.
- The benefits of webbing-based force limiting must be weighed against increased pelvic excursion and femur force.
- Further research is needed to assess submarining potential, non-frontal impact performance, and advanced concepts like programmable force limiting.