The National Highway Traffic Safety Administration (NHTSA) is considering upgrades to the FMVSS No. 213 standard seat assembly and test parameters that better represent current vehicle conditions. A preliminary prototype for the test bench was released with upgraded seat cushion stiffness, geometry, seatbelt assembly, and anchorage locations. The objective of this study was to compare the responses of the Q6 ATD (Humanetics Inc., MI) restrained in booster child seats (CRS) on the current and proposed upgrade of the FMVSS 213 test bench, and a vehicle seat in frontal impacts.
Three child seating conditions were evaluated: no-CRS, lowback booster (LBB), and a highback booster (HBB) installed on validated finite element (FE) models of the current FMVSS 213 bench, upgraded bench, and a 2012 Toyota Camry vehicle seat. Simulations (N=9) were carried out using LS-DYNA ver.971 (LSTC, CA) on a 16-node double precision cluster. Kinematics and kinetic data were extracted and processed as per SAEJ211 metrics.
Head resultant accelerations (Hr) across conditions were comparable, however, for LBB the current bench over predicted Hr by 26G (72.1G) as compared to the upgraded bench (46.1G). For HBB, there was a difference of 13.5G in Hr between the upgraded bench (60.1G) and vehicle seat (46.6G). Similarly, chest resultant accelerations (Cr) showed a difference of 23.2G (No-CRS), 14.8G (LBB), and 22.5G (HBB) between the 213 bench [no-CRS (72.9G); LBB (62.5G); HBB (56.3G)] and upgraded bench [no-CRS (49.7G); LBB (47.7G); HBB (78.8G)]. HBB showed a difference of 19.2G in Cr between the upgraded bench (78.8G) and vehicle seat (59.6G).
HIC36 values for the no-CRS and HBB conditions were lower by 53.4 and 115.4 respectively for the 213 bench [no- CRS (258.7); HBB (443.2)] compared to the upgraded bench [no-CRS (312.1); HBB (558.6)]. Similarly, these values were lower for no-CRS and HBB conditions by 74.3 and 163.6 respectively for the vehicle seat [no-CRS (237.8); HBB (395.0)] compared to the upgraded bench. Chest displacements were higher on the 213 bench [no- CRS (16.6mm); LBB (24.2mm); HBB (29.2mm)] and vehicle seat [no-CRS (18.3mm); LBB (22.6mm); HBB (25.5mm)] as compared to the upgraded bench [no-CRS (6.6mm); LBB (14.8mm); HBB (17.3mm)]. Neck Forces (Fz) were higher for the LBB on the 213 bench (2637.3N) than on the upgraded bench (1982.3N).
All injury and excursion values were within IARV limits for all simulations. However, CRSs installed on the 213 bench have larger rotations (sagittal plane) [LBB (-10.2o); HBB (-12.9o)] as compared to the upgraded bench [LBB (1.5o); HBB (-3.6o)] and the vehicle seat [LBB (4.8o); HBB (-3.6o)]. The child seats on the 213 bench, first compress the foam and then rotate over the edge of the foam [Foam thickness (Ft) = 6 inches (4+2)] due to its inherent overhang from the edge of the base structure causing higher rotations as compared to the upgraded bench (Ft= 4 inches) or the vehicle seat, which are similar in construction.
Overall, the responses of the upgraded bench matched the vehicle seat more closely than the current bench and is a step towards emulating a real vehicle seat environment.