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Abstract
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27th International Technical Conference on the Enhanced Safety of Vehicles (ESV): Enhanced and Equitable Vehicle Safety for All: Toward the Next 50 Years
https://www-esv.nhtsa.dot.gov/Proceedings/27/27ESV-000183.pdf
Among the studies focusing on criteria for brain injuries induced by the rotational motion of the head, one of the recent studies has compared the predictive capability of various injury criteria proposed by different studies, with the results showing that the best predictor depends upon specific impact configurations. This suggests the need for a more robust injury criterion across a variety of impact configurations with different duration of an impact event. The aim of this study is to investigate the effect of incorporating additional time constants and modifying directional interactions on the predicting accuracy of the physical model-based criterion called CIBIC (Convolution of Impulse Response for Brain Injury Criterion) proposed by the author's group. A Maxwell model was parallelly added to the simplified physical model (standard linear solid) of the CIBIC criterion to improve the time-dependent responses. One simplest candidate formulation of the cross-terms was tried to replace the originally used root sum square to combine the three components of the strain. The Global Human Body Models Consortium (GHBMC) head/brain model was used to obtain the target response of the maximum principal strain (MPS). A step function with the magnitude of 10,000 rad/s2 was used to optimize the spring and damping coefficients. The spring and damping coefficients were optimized by maximizing the CORA (CORrelation and Analysis) score. The modified CIBIC was further validated against the GHBMC model using a total of 256 time histories of the head rotational acceleration representing those of the four groups of load cases (occupants in fullfrontal, oblique-frontal and side impacts as well as pedestrian impacts). The coefficient of determination calculated from the correlation of peak MPS and the average value of the CORA score were compared between the original and the modified CIBIC. The modified CIBIC with the modified time constants was found to improve both assessment metrics for all of the four groups of the load cases, while both assessment metrics predicted by the modified CIBIC with the directional interaction was not improved. The effect of the modifications shown by the modified CIBIC suggest that further consideration of the directional interaction is needed to develop a robust criterion, requiring thorough investigations on the method to combine the responses of the three axes.
Language: en |