Predicting Head Injury Criterion in Real-World Frontal Impacts

Research on modeling head injury metrics and head acceleration waveforms from real-world collisions has been limited compared to vehicle crash pulses. Prior studies have used rectangular, triangular, polynomial, half-sine, and haversine pulse functions to model vehicle crash pulses and have employed more complex approximations for head injury metrics. This study aimed to develop a method to predict 15 ms Head Injury Criterion (HIC₁₅) in frontal passenger vehicle impacts using these simple pulse functions, where only occupant peak head acceleration and head impact duration are known. Vehicle crash tests from the New Car Assessment Program (NCAP) were selected for frontal impacts that included driver occupants. Head acceleration and shoulder belt load channels of Hybrid III 50th percentile male anthropomorphic test devices were collected and separated for training a set of ratios and testing their performance. Rectangular, triangular, quadratic, half-sine, and haversine pulse functions were modeled using peak head acceleration and the duration of significant head acceleration from each ‘training’ NCAP crash test. Duration ratios were values calculated to scale each pulse function to predict the same HIC₁₅ as the driver’s experimental acceleration-time curve. Duration ratios were evaluated on each ‘testing’ NCAP crash test by comparing the HIC₁₅ predicted by each scaled pulse function against the driver’s HIC₁₅. All five pulse functions generated from the model ‘training’ NCAP tests had significantly different duration ratios. There were no significant differences in predicted HIC₁₅ to the driver’s HIC₁₅ from the model ‘testing’ NCAP tests for all pulse functions. Findings indicate that applying the presented duration ratios to the five pulse functions can effectively predict HIC₁₅ in frontal crashes similar to NCAP tests, making them useful tools when only peak head acceleration and head impact duration are known. This work will help biomechanical safety experts evaluate head injury risk when real-time occupant kinematics are not available.