Evaluation of Anti-Whiplash Seat Robustness for Multi-Peak Crash Pulses in Low-Speed Rear-End Crashes

The mechanism of whiplash is not well understood and thus preventing a certain motion or force in an occupant might not mitigate this injury. However, a number of injury criteria have been proposed to evaluate the neck injury risk in a rear-end crash. In the safety design of the seat and the headrest assembly, robustness or invariability of whiplash protection must be secured not only under the assessment pulses applied in sled tests but also under such pulses that show random multiple peaks in real-world car-to-car rear-end crashes.

The aim of this study is to investigate a method of evaluating the invariability of whiplash protection performance in low-speed rear-end crashes, not with multiple injury criteria but with a single newly proposed objective function. The function was determined based on the hypothesis that the ideal seat is rigid in terms of such invariability. A series of finite element simulations were performed based on the design of experiments to obtain car-to-car rear-end crash pulses (delta Vs = 16 km/h and 24 km/h). The signal-to-noise (SN) ratio of the objective function was then evaluated based on the dynamic characteristics of the Taguchi method, using both the BioRID II model and a human model under actual usage conditions (seat and headrest configurations, including reactive and proactive types of headrest) and environmental conditions (car-to-car crash pulses) at the customer level. The optimal configuration, which maximized the SN ratio, reduced all the injury criteria used in this study except Nkm for the BioRID II model. The proactive type of headrest, having a configuration similar to the optimal one, showed more invariability in reducing the injury indicator values than the reactive type did. The neck width can affect the invariability of flexion and head-forward motion. The validity of the objective function, or the robustness evaluation method, might be verified by adding the detailed geometry and material characteristics of the superficial soft tissue of the neck to the human model.