Comparison of seat belt force-limiting methods using the MADYMO multi-body/finite element program

Belt force can be limited by a device in the belt retractor hardware or with force-limiting as an integral part of the webbing force/strain properties. In this research, MADYMO multi-body/finite element models of a 50th percentile Hybrid-3 male passenger in an airbag-equipped 4-door mid-size sedan were set up to compare occupant injury response under loading 1) from a baseline standard (non-force-limiting) belt system, 2) from a retractor-based force-limiting system, and 3) from a webbing-based force-limiting system. Chest acceleration was similar for the two force-limiting designs but the peak was approximately 10% greater for the standard belt. The magnitude of the head acceleration was similar for all three belts while the duration of these accelerations was much narrower for the force-limiting belts. Chest compression was similar for both force-limiting methods, and was about 60% less than the standard belt case. Compared to the baseline system and the retractor-based system, webbing-based force-limiting allowed greater pelvic excursion and a corresponding increase in femur force. It is concluded that webbing-based force limiting has some potential for reducing head and chest responses but these reductions must be evaluated with respect to other considerations such as submarining potential, non-frontal impact response, and future concepts like programmable force limiting.