Biomechanical differences between contact and non-contact head impacts in vehicle crash tests

Zhang, Jiangyue; Yoganandan, Narayan; Pintar, Frank A.; Guan, Yabo; Gennarelli, Thomas A.

The purpose of this research is to study brain biomechanics between contact and non-contact head impact during vehicle crash tests in head kinematics, global brain injury metrics, and region brain strain. Nine array accelerometer package data from dummy head were extracted from 13 lateral and 14 rigid pole crash tests conducted by the National Highway Traffic Safety Administration (NHTSA). Head accelerations, HIC values and their duration were computed. Cumulative strain damage measure 15% (CSDM), dilatational damage measure (DDM), and relative motion damage measure (RMDM) were studied using SIMon finite element head model (FEHM). Averaged regional brain strains were conducted by grouping brain element in SIMon FEHM into frontal, parietal, occipital, cerebellum, fronix and brain stem region. Head contact occurred in two lateral and six rigid pole tests. Head contact durations were less than one millisecond in rigid pole tests and ranged from 3-7 ms in lateral impact tests. The ratio of biomechanical measurements between contact and non-contact cases in lateral tests were: translational acceleration 4x, rotational acceleration 3.5x, HIC 12x, and CSDM 5x, regional brain 1.5x. The ratios were higher for rigid pole tests: translational acceleration 14x, rotational acceleration 25.7x, HIC 29.5x, CSDM 12x, regional brain strain 1.5-3x. Head accelerations, HIC values, DDM and RMDM increased with increasing rotational accelerations. They were the lowest in non-head contact rigid pole tests, followed by non-contact lateral impact tests, contact lateral impact tests, and the highest in head contact rigid pole tests. However, CSDM values were higher in lateral tests than rigid pole tests for head contact cases, indicating a higher chance of diffused axonal injury in head contact lateral impact tests. On the other hand, averaged brain strain in cerebellum increased 3x for contact cases, indicating high probability of injury to this region during this model of impact.

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