Development and Validation of a Pelvis Finite Element Model for Side Panel Intrusion Threats

Loading conditions resulting from the detonation of improvised explosive devices (IEDs) have posed a serious risk to the warfighter in modern military conflicts. Vehicle bourn IEDs result in high-rate lateral loading to the vehicle structure that can cause side panel intrusion into occupant compartment, and potentially into the body of a mounted warfighter inside. These impacts can cause severe injury throughout the body, including the pelvis. Combat-related pelvis fractures are linked to increased mortality rates and amputation risk. Biomechanical research is needed to improve the design of vehicles and protective equipment to mitigate injuries to the pelvis.
Finite element (FE) models are useful tools in evaluating the biomechanics of impact and injury. FE models can provide quick analyses over a range of loading scenarios, and can be used directly in the countermeasure design process. With this in mind, an injury-predictive FE model of the human pelvis was developed using modeling methods appropriate for evaluating the high-rate injurious loading characteristics found in military combat. The response and injury predictions of this pelvis model were assessed against experimental lateral impact testing performed on human cadaveric pelvises. Signal correlation analysis was applied to objectively rate the validity the FE pelvis force responses. Injuries predicted by the pelvis model, when using maximum principal strain failure criteria, were consistent with those occurring in the experiments.
The pelvis model was then used to perform an injury threshold analysis where impactor mass and velocity was varied. This study identified the anterior pelvis as being more vulnerable to lateral impact. Recent research has highlighted a lack of consensus on a consistent injury predictive metric for the pelvis in lateral impact. Injury risk functions were constructed based on anterior and posterior pelvis force, and the posterior force of the pelvis was identified as a more consistent injury predictive metric than anterior force. This finding has potential implications for dummy design.
Finally, the model developed in this study was part of a larger development project to create a whole human body FE model for analyses of human body exposure to military-relevant impact events. The addition of the developed and validated pelvis model will aid future vehicle development for improved safety features. Side panel safety design efforts should focus on mitigating acetabular loading in the event of a lateral impact scenario, and dummy instrumentation should include load cells located in the posterior pelvis for measuring pelvis injury risk.