In the past, several crash test dummies were developed in order to measure forces acting on the human body during different loading conditions. However, they are limited in their biofidelity and their application type (frontal, lateral etc.). Recently, several numerical human models were developed. Their main advantage in comparison with dummies is the possibility to model the human structures with its mechanical properties. The aim of this study was to redefine the material properties of the ribcage of the Finite Element mid-size male HUMOS2 model in MADYMO in order to be able to predict fractures occurring under different conditions.
The Human Model was subjected to several impact conditions, and the responses were compared with data obtained from Post Mortem Human Subject (PMHS) tests described in literature. First, three ribs separated from the model were subjected to 3-point bending tests, both quasi-static and dynamic at two different velocities. New material models, including elasto-plastic and damage behavior of the ribs were used in these simulations. Then, the model was validated by means of frontal thoracic impact and belt-restrained sled test simulations. Both types of simulations were conducted with various impact conditions according to the set-ups used in the PMHS tests.
Results obtained from all the simulations demonstrated good biofidelity of the model. About 80% of the curves obtained from the simulations fit the corridors based on the PMHS responses. Furthermore, the location of damage predicted in the ribcage correlated well with the fractures obtained from the autopsy. The computed stresses predicted multiple rib fractures. The computed Viscous Criterion correlated with a 25% chance of AIS 3+ injuries, also indicating multiple rib fractures. As a result, both global and local computed measures are able to predict rib fractures. From the results of this study it can be concluded that the HUMOS2 model can be used for the prediction of rib fractures.