A methodology to obtain kinematic corridors for pediatric occupants in frontal impacts

Abstract

Pediatric Anthropomorphic Test Devices (ATD) provide a reasonable approximation predicting maximum head excursion. However, the exact trajectory followed by the human head and the flexible human spine cannot be replicated by the stiff spine of ATD. Lack of knowledge on pediatric whole body kinematics during a frontal impact precludes the development of more biofidelic pediatric ATD. In this study, human volunteers (pediatric and adult) were subjected to a non injurious pulse simulating a low speed frontal crash (10 km/h). Three adult Post Mortem Human Subjects (PMHS) tests were performed using an equivalent test setup to that of the volunteers. Each PMHS was also subjected to a high speed test (40 km/h). This paper integrates the results from all these experiments and proposes a method to obtain kinematic corridors for pediatric occupants in frontal impacts.

Youngest volunteer subjects exhibited greater head and spine (cervical and thoracic) translation and rotation than adult subjects. In the cadaveric experiments, the spine showed a marked different behavior depending on the speed of the tests. To account for these differences between pediatric and adult subjects and low and high speed tests, an analytical model consisting on rigid links connected by rotational joints is proposed. The mass and moment of inertia of each link and joint equivalent stiffness can be obtained using optimization. The right set of generalized coordinates leads to a diagonal stiffness matrix. Thus, a scaling factor can be obtained between the effective stiffness of each joint for the different test conditions that incorporates the biomechanical response of children.