Seatback Strength and Its Effect on In-Position and Out-of-Position ATD Loading in High-Speed Rear Impact Sled Tests 2022-01-0856

Vehicle rear structure stiffness has increased as a result of the requirements in the FMVSS 301R, which has also corresponded to an increase in front-row seat strength. This study evaluates the structural behavior and occupant response associated with production-level seats equipped with body-mounted D-rings, and very stiff all-belt-to-seat (ABTS) in a group of 12 deceleration sled tests. A double-haversine pulse with approximately 100-msec duration was used for all tests, with peak accelerations of approximately 19 g for the 40 km/h (25 mph) tests and peak accelerations of 28 g for the 56 km/h (35 mph) test. This generic pulse was designed to represent a severe rear impact crash involving vehicles with stiffer rear structures. The tests compared occupant responses and resulting structural deformation of an original equipment manufacturer (OEM) production-level driver seat from a pickup and a very stiff modified ABTS. Both seating systems were equipped with dual recliners. Various combinations of tests evaluated the effects of a rear-end impact principal direction of force (PDOF, 5:30 or 6:00), occupant pre-impact seated position (in-position or out-of-position), latch plate design (single-slotted sliding latch plate or dynamic locking latch plate), and pretensioner deployment strategies (none, anchor, and retractor for the production-level seat and buckle for the modified ABTS seat). The OEM seats showed seatback deformation patterns that were indicative of the load path from occupant engagement and were influenced by a number of test-specific factors. The very stiff ABTS seats did not demonstrate appreciable residual seatback deformation. None of the upper neck metrics exceeded the injury assessment reference values (IARVs) for ATDs in the OEM seats, regardless of the ATD pre-impact posture (IP or OOP). The out-of-position (OOP) anthropomorphic test devices (ATDs) experienced elevated upper neck tension force, extension moment, and neck injury criteria (Nij) compared to the in-position (IP) ATDs in both the production-level and the very stiff ABTS. Dynamic test data show that the yielding seat attenuated both the chest accelerations and head/neck injury metrics, whereas the non-yielding seatback in the very stiff ABTS seat enhanced upper neck injury potential by rapidly decelerating the ATD torso, particularly for the OOP ATD.