Applying the Dynamic Relaxation Step to Determine Influence on Global Model Response from Shock Tube Loading for Mounted Hybrid III Head Neck Assembly

Blast-induced traumatic brain injury (bTBI) is a critical issue for warfighter protection. Since bTBI has many features in common with injuries due to impact loading, the Hybrid III crash test dummy can be used to study many aspects of this injury, and the head-neck assembly of the Hybrid III dummy can provide a relevant initial bench test for computational studies of traumatic brain injury. LS-DYNA® has provided finite element models (FEM) of various Anthropomorphic Test Dummies (ATDs), and in this study the head-neck subassembly from the LSTC- NCAC 50th% Full FE H-III Dummy was used. To study the effects of blast on the head a shock tube experiment was simulated and the relevant loading conditions were applied to the head-neck assembly of the Hybrid III dummy FEM. The results were then compared to similar experimental test data. Since the initial tension in the neck cable of the Hybrid-III head-neck assembly is a key factor in the experimental response, simulating the initial tension in the neck cable is required in order to maintain a consistent boundary condition for the model. The neck cable definition in the Hybrid-III FEM was modified to include an initial stress, which was implemented using a dynamic relaxation step applied to initialize the model. The dynamic relaxation step is applied using explicit techniques and a sensitivity study is explored to understand impact of the initialization on the global response. The relative influence on the resulting global behavior response depends on the loading conditions.