3D Deformation and Dynamics of the Human Cadaver Abdomen under Seatbelt Loading

Abstract

According to accident analysis, submarining is responsible for most of the frontal car crash AIS 3+ abdominal injuries sustained by restrained occupants. Submarining is characterized by an initial position of the lap belt on the iliac spine. During the crash, the pelvis slips under the lap belt which loads the abdomen. The order of magnitude of the abdominal deflection rate was reported by Uriot to be approximately 4 m/s. In addition, the use of active restraint devices such as pretensioners in recent cars lead to the need for the investigation of Out-Of-Position injuries. OOP is defined by an initial position of the lap belt on the abdomen instead of the pelvis resulting in a direct loading of the abdomen during pretensioning and the crash. In that case, the penetration speed of the belt into the abdomen was reported by Trosseille to be approximately 8 to 12 m/s. The aim of this study was to characterize the response of the human abdomen in submarining and OOP. A total of 8 PMHS abdomens were loaded using a lap belt. In order to investigate the injury mechanisms, the abdominal deflection rate and the compression were imposed such that they were not correlated. The specimens were seated upright in a fixed back configuration. The lap belt was placed at the level of the mid-umbilicus, between the iliac crest and the 12th rib. The belt was pulled horizontally along the sides of the specimens causing a symmetrical loading of the abdomen. In addition to the local parameters such as the belt and back forces or the belt displacements, the 3D external deformation of the abdomen was recorded. The forces measured between the back of the cadaver and the seat showed that a mass effect should be taken into account in the abdominal behaviour in addition to viscosity. The back force was greater than the belt force in low speed (submarining like) tests while it was lower for high-speed (OOP like) tests. A lumped parameter model was developed to confirm the experimental results and to be able to compare the load penetration characteristics to the results reported in the literature. The injury outcomes are provided and compared to all the published data. The PMHS sustained MAIS2-3 abdominal injuries in the low speed tests and MAIS2-4 injuries in the high speed tests. Finally, the dynamic 3D deformation of the abdominal wall was reconstructed and is provided for further validation of finite element models of the human abdomen.