RESUMEN
OBJECTIVE: A novel anthropomorphic test device (ATD) representative of the 50th percentile male soldier is being developed to predict injuries to a vehicle occupant during an underbody blast (UBB). The main objective of this study was to develop and validate a finite element (FE) model of the ATD lower limb outfitted with a military combat boot and to insert the validated lower limb into a model of the full ATD and simulate vertical loading experiments. METHODS: A Belleville desert combat boot model was assigned contacts and material properties based on previous experiments. The boot model was fit to a previously developed model of the barefoot ATD. Validation was performed through 6 matched pair component tests conducted on the Vertically Accelerated Loads Transfer System (VALTS). The load transfer capabilities of the FE model were assessed along with the force-mitigating properties of the boot. The booted lower limb subassembly was then incorporated into a whole-body model of the ATD. Two whole-body VALTS experiments were simulated to evaluate lower limb performance in the whole body. RESULTS: The lower limb model accurately predicted axial loads measured at heel, tibia, and knee load cells during matched pair component tests. Forces in booted simulations were compared to unbooted simulations and an amount of mitigation similar to that of experiments was observed. In a whole-body loading environment, the model kinematics match those recorded in experiments. The shape and magnitude of experimental force-time curves were accurately predicted by the model. Correlation between the experiments and simulations was backed up by high objective rating scores for all experiments. CONCLUSION: The booted lower limb model is accurate in its ability to articulate and transfer loads similar to the physical dummy in simulated underbody loading experiments. The performance of the model leads to the recommendation to use it appropriately as an alternative to costly ATD experiments.
Asunto(s)
Traumatismos por Explosión/fisiopatología , Explosiones , Extremidad Inferior/fisiología , Modelos Biológicos , Ropa de Protección , Zapatos , Antropometría , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Humanos , Personal Militar , Estrés Mecánico , Tibia/fisiologíaRESUMEN
Soft materials (e.g. polymers) are widely used in biomechanical devices to represent the nonlinear viscoelastic properties inherent in biological soft tissues. Knowledge of their mechanical properties is used to inform design choices and develop accurate finite element (FE) models of human surrogates. The goal of this study was to characterize the behavior of eight polymeric materials used in the design of a novel anthropomorphic test device (ATD) and implement these materials in an FE model of the ATD. Tensile and compressive tests at strain rates ranging from 0.01s-1 to 1000s-1 were conducted on specimens from each material. Stress-strain relationships at discrete strain rates were used to define strain rate-dependent hyper-elastic material models in a commercial finite element solver. Then, the material models were implemented into an FE model of the ATD. The performance of the material models in the FE model was evaluated by simulating experiments that were conducted on the ATD lower limb. The material characterization tests revealed viscoelastic strain rate-dependent properties in the flesh and compliant elements of the ATD. Higher modulus polymers exhibited rate-dependent, strain-hardening properties. A strong agreement was seen between the material model simulations and corresponding experiments. In component simulations, the materials performed well and the model reasonably predicted the forces observed in experiments.