FRED II Quasistatic Seat Testing Rearward: An Improved Method Based on the SAE H-point Manikin 2019-01-1032
Objective: Various methods have been used to load a seat in a rear direction, including FMVSS 207, body block and QST (quasistatic seat test). A simple method was developed using a variation of the SAE H-point manikin, so that the weight of the occupant is on the seat, the height of loading reflects the center of pressure from a seat occupant and the energy transfer to the seat is measured along with the moment strength at peak force.
Methods: A metal-cast H-point manikin, called FRED II, was modified to support a loading bar, so it is pulled rearward into the seatback by a hydraulic cam. The force and displacement of the loading is measured and the inboard and outboard seatback angle was measured in the test. The seat was mounted on steel stantions in the design position. Six videos record the response of the seat. The moment at peak force was determined by aligning the center of the recliner in side views of the seat position initially and at peak load. The height of the cable above the center of the recliner was determined giving the moment arm at peak load. The force was integrated with displacement to determine energy transfer to the seat.
Results: Twelve tests were performed with FRED II and twelve additional tests were performed with the same seat using the CRA body block. Ten test involved matched seats. With FRED II, the average peak moment was 21,197 ± 3,865 inlb and the energy transfer was 1,503 ± 379 ftlb. With the body block, the average peak moment was 22,422 ± 2,624 inlb using the same method to determine the moment at peak force and the energy transfer was 1,266 ± 282 ftlb. Additional FRED II tests were run with ABTS and other strong seats resulting in over 50,000 inlb moment and 2,600 ftlb energy transfer.
Conclusion: A new method is presented to determine the strength of seats in rear impacts. FRED II is based on the SAE H-point manikin and loads the seatback as the Hybrid III dummy does in sled tests. It provides the energy transfer capability of the seat in a manner that is similar to occupant loading in a rear impact. FRED II is an improved quasistatic method for seat testing. FRED II also provides the H-point location and can be used to measure head restraint position.
David C. Viano, Roger Burnett, Samuel White
ProBiomechanics LLC, Ford Motor Company, Collision Research & Analysis Inc