In English

Thorax soft tissue response for validation of human body models and injury prediction

Jan-Frederik Rater
Göteborg : Chalmers tekniska högskola, 2013. Diploma work - Department of Applied Mechanics, Chalmers University of Technology, Göteborg, Sweden, ISSN 1652-8557; 2013:07, 2013.
[Examensarbete på avancerad nivå]

Thoracic injuries like rib fractures and lung injuries are the most frequently occurring injuries in Road Traffic Collisions (RTCs). These injuries are severe and can be lifethreatening. 81 % of all car occupants in fatal car accidents have thoracic injuries with an Abbreviated Injury Scale (AIS) score of 3+. Seatbelt use and air bags reduce the fatality risk by 61 % compared to unbelted car occupants of vehicles without air bags. Nevertheless according to the National Highway Traffic Safety Administration (NHTSA) more than 30 000 people die each year due to RTCs in the USA. For the validation of new restraint systems and for injury prediction Anthropomorphic Test Devices (ATDs) were traditionally used. ATDs are only gross mechanical representations of the human body and thus the information to predict injuries accurately is limited. A second tool for the investigation of restraint systems and injury prediction are Finite Element Human Body Models (FE-HBMs). They offer a more detailed description of the anatomy of the human body, e.g. viscera are represented. The quality of Human Body Models (HBMs) is limited by the amount of details and the validation level of particular parts. Lungs are, besides ribs, the most frequently and severely injured part of the body in RTCs. Despite this no investigations to validate human lung models under frontal car crash like conditions have been carried out and experimental data for the dynamic behaviour and injury mechanism are an exception. In this study, the state of the art of HBMs, models of the thorax and currently used material models for simulating thoracic viscera were identified. To rate and validate these material models for lungs, impact experiments on swine lungs were simulated with LS-DYNA. The time and force response of the models were compared to the experimental results at an impact speed of 5.4 ms . Coefficient studies with the parameter of different material models were accomplished to enhance the model response. For the best material model, low density foam, a new stress versus strain curve was also implemented, because the model tuning due to parameter optimization was limited. The deformation behaviour of the final model was close to the experimental results. Only the force response for the first part of deformation was higher than compared to the experiments. For rating the model quality the deformation and force response were compared to the experimental data based on the Mean Square Error (MSE). Finally, the MSE of the optimized material model was only half of the MSE of the best model from literature. The final material model was implemented as material properties in the thoracic viscera of the Total HUman Model for Safety version 3.0 Modified (THUMS v3-M). The influence of the modified material model to the thoracic response and the biofidelity were proved against table top tests. The tuned material did not influence the thoracic response within the first 20 mm of chest deflection. Afterwards higher reaction forces occurred as thoracic response with the tuned model, but the forces stayed clearly inside the experimental corridor.

Nyckelord: Frontal crash, thoracic injury criteria, lung injury, Human Body Model, Finite Element, model validation, THUMS, lungs modelling

Publikationen registrerades 2013-04-12. Den ändrades senast 2013-04-12

CPL ID: 175674

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