Chest deflection of relaxed and braced human occupants in low severity frontal sled tests and non-censored rib fracture data in high severity PMHS frontal sled tests

Kemper, A. R.<sup>1</sup>; Beeman, S. M.<sup>1</sup>; Duma, S. M.<sup>1</sup>

This paper presents the methodologies and results of two studies involving dynamic frontal sled tests. The purpose of the first study was to investigate the effects of pre-impact bracing on the kinematics, kinetics, and chest compression of human volunteers during low-speed frontal sled tests. The purpose of second study was to obtain non-censored rib fracture data and corresponding thoracic injury timing during high severity PMHS frontal sled tests. In the first study, a total of 10 low-speed frontal sled tests (5.0g, Δv=9.7kph) were performed with 5 male human volunteers. Each volunteer was exposed to 2 impulses, one relaxed and the other braced prior to the impulse. In the second study, a total of 3 high severity frontal sled tests (28.6g, Δv=40kph) were performed on two post mortem human surrogates (PMHSs) and one 50th percentile Hybrid III anthropomorphic test device (ATD). A 59 channel chestband, aligned at the nipple line, was used to measure chest deflection for all test subjects in both studies. For PMHS tests, thoracic strain gages allowed for the precise determination of the time of each rib fracture and corresponding AIS injury severity level. In the first study, the chestband data showed that bracing prior to the initiation of the sled pulse essentially eliminated thoracic compression due to belt loading for all human volunteers except one. This study illustrates that muscle activation has a significant effect on the biomechanical response of human occupants in frontal sled tests. In the second study, the sternum compression data and maximum chest compression data, which did not occur at the sternum, illustrated that serious thoracic injury (AIS=3) occurs before peak compression and at lower chest compressions than the current ATD thoracic injury criterion. In addition, the chestband data showed that maximum chest compression had a more reasonable correlation between compression and injury timing than sternum compression. Therefore, an ATD with multiple chest deflection measurement locations would be advantageous. Overall, the two studies provide critical data that can be used in the design and validation of advanced ATDs and finite element models, as well as the establishment of improved, more stringent thoracic injury criteria.

Year

Entry

1989

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2003

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1976

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1999

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1998

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