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Seat structural design choices and the effect on occupant injury potential in rear end collisions

University of British Columbia

The seat is the most important safety device available to vehicle occupants during rear end collisions, and thus proper design and structural integrity of the seat under expected impact loading is essential. The objective of the current research work is to increase the understanding of design requirements for seat performance in relation to injury producing collisions, and to examine how various seat design parameters affect both structural integrity and occupant protection. A numerical model-based finite element parametric sensitivity study (conducted in LS-Dyna) was employed with the goal of assessing the effect of seat structural properties on occupant kinematics and injury response. A 2002 Pontiac Grand Am seat was utilized to create the base geometry for the finite element seat model used in the study. The parametric study utilized a 50th percentile male dummy, applied the CMVSS 202 standard crash pulse to selected structural variations of this seat, and then utilized the neck injury criterion (NIC), neck displacement criterion (NDC) and relative neck accelerations to assess the likelihood of injury. Seatback and recliner angle, and the degree of seatback twist are utilized to indicate seat performance. Based upon this work, there are significant structural components of the seat that contribute to injury mitigation. The recliner rotational stiffness and the head restraint stiffness are the most significant seat structural design choices, which can mitigate injury potential. Recliner stiffness results indicate that stiff recliners offer injury risk reduction. A stiff head restraint that absorbs little energy mitigates injury. The seatback frame can mitigate injury by absorbing energy through plastic deformation. The risk of occupant ejection is reduced through the use of seatmounted seatbelt retractors, although dual retractor systems mounted to the vehicle's b-pillar and seat base provide comparable ramping reduction. Energy correlations have been derived that offer a first step toward relating seat design to injury.

Text

2009-12-11

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http://hdl.handle.net/2429/16463

Mechanical Engineering

University of British Columbia

UBCV

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