Sensitivity Analysis of the Response of a 6-Year-Old Child in Automotive Crashes

Prior studies have shown that child anthropometric test devices (ATDs) could benefit from improved biofidelity. Defining child ATD biofidelity based on traditional biomechanical testing methods can be ethically and technically (e.g., scaling) difficult. Therefore, this project explored a modeling approach for defining biofidelity test conditions/responses that could be applied towards new frontal child ATD development. This project used new knowledge from child-focused biomechanical and anthropometry studies as input in efforts to update, parameterize, and optimize a Hybrid III 6-year-old-based numerical model that was then applied in defining new biofidelity targets for a 6-year-old frontal ATD. The first phase of the study involved parameterizing and updating a Hybrid III-based 6-year-old model to include improved pelvis, abdomen, and shoulder anthropometry and an additional joint in the thoracic spine.The updated and parameterized 6-year-old model was then used to complete a parameter sensitivity analysis. Twelve setups were implemented, all representing biomechanical test conditions. These conditions included four belt load tests on the abdomen and thorax, pendulum and cardiopulmonary resuscitation tests on the thorax, neck flexion/extension and tension tests, and three whole-body conditions. Almost all stiffness and damping parameters were found to be sensitive. The model was then optimized for various responses (e.g., force-displacement, head excursion) and various criteria (e.g., peak value, curve fit). The same 12 setups from the parameter sensitivity analysis were used together with a few additional conditions. In general, the optimization process improved the response of the model. However, the final optimized model did not achieve biofidelic head excursions in whole body sled conditions. This may be attributed to parameter limits implemented in the spine (tensile and flexion properties). Shoulder flexibility may also have contributed. While the shoulder was updated, shoulder flexibility was not parameterized. The final task involved using the updated and optimized model to develop biofidelity targets for a frontal 6-year-old ATD. The conditions largely represented those from existing standards or from biomechanical studies used in the sensitivity and optimization tasks. Proposed conditions and biofidelity targets are presented.