Development and Calibration of the Large Omnidirectional Child ATD Head and Neck Complex Finite Element Model

The National Highway Traffic Safety Administration (NHTSA) has developed the Large Omnidirectional Child (LODC) Anthropomorphic Test Device (ATD) to improve the biofidelity of the currently available Hybrid III 10-year-old (HIII-10C) ATD. The improvements of the LODC over the HIII-10C include changes in sub-assemblies such as the head and neck, where the LODC head is a redesigned HIII-10C head with pediatric mass properties and the neck has a modified atlanto-occipital joint to replicate observations made from human specimens. The current study focuses on developing a dynamic, nonlinear finite element (FE) model of the LODC ATD head and neck complex. The FE mesh is generated using HyperMesh based on the three-dimensional CAD model. The material data, contact definitions and initial conditions are defined in LS-PrePost and converted to LS-Dyna solver input format. The initial and boundary conditions are defined to replicate the neck flexion experimental tests. Next, an inverse method is used to identify the in-situ material parameters primarily for the highly compliant viscoelastic components and the lumped torque-moment characteristics of the occipital condyle (OC) joint. Material parameters of the viscoelastic components and the coefficients of joint stiffness models are identified by minimizing objective functions based upon the difference between experimental test and the simulation results. The approach is applied to the LODC ATD head-neck complex to improve the predictive capability of the finite element model.