Acetabulum Injury Investigation of Proposed US-NCAP in OI Mode

In December 2015, the National Highway Traffic Safety Administration (NHTSA) published a Request for Comments on proposed changes to the New Car Assessment Program (NCAP). One potential change is the addition of a frontal oblique impact (OI) crash test using the Test Device for Human Occupant Restraint (THOR). The resultant acetabulum force, which is a unique and specifically defined in the THOR dummy, will be considered as a new injury metric.

In this study, the results of ten OI tests conducted by NHTSA on current production mid-sized vehicles were investigated. Specifically, the test data was used to study the lower extremity kinematics for the driver and front passenger THOR dummies. It was found that the acetabulum force patterns varied between the driver and passenger and between the left leg and the right leg of the occupants. The maximum acetabulum force can occur either on the left side or right side of a driver or a front passenger in an OI event. Femur and pelvis free body diagrams were established to identify the key factors contributing to the acetabulum force. The femur load and lap belt force acting on the THOR dummy were two main factors contributing to the force acting on the acetabulum. Their contributions were quantified by two finite element subsystem analyses. According to the simulation results, 60%~80% of femur force and 30%~50% of lap belt force can be attributed to the acetabulum force on the dummy. From the finite element analyses a mathematical equation was developed to determine the acetabulum force in OI crash mode. This equation was verified by NHTSA OI tests.