Coupling of strasbourg university head model to thums human body FE model: validation and application to automotive safety

Human body segments and whole body models are more and more used in automotive safety research. Detailed in deep validated segmental models exist and are used for the definition of improved injury criteria, transforming the models into injury prediction tools. The present collaborative work’s objective is to couple and to validate the Strasbourg University Head FE Model (SUFEHM) with the THUMS human body model under Ls-Dyna code before applying the new tool under accidental environment. In a first effort, Strasbourg University Head Model and related injury criteria developed in earlier studies under RADIOSS code had to be transferred under Ls-Dyna code, both at constitutive laws and injury criteria definition level. For this, a validation of the SUFEHM against Nahum and Yoganandan’s experiments in order to validate brain and skull behavior respectively under LsDyna has been done. After these validations the reconstruction of 59 real world head trauma has been conducted in order to propose head tolerance limits to specific injuries under Ls-Dyna code. After this, the SUFEHM was coupled to the THUMS neck in order to create a hybrid “THUMS-Strasbourg head” model. At geometrical level the coupling was performed by creating interfaces at bone contact level and connecting ligaments and soft tissue elements to the head model. At mechanical level the coupled FEMs was validated under front, lateral and oblique impact regarding head-neck kinematics superimposed to experimental data. This coupled model constitutes an original research tool for further investigation on the importance of human head boundary condition in case of head impact, whatever the accident condition are, car occupant, pedestrian or even motorcyclists. INTRODUCTION Since several years human body models became a useful tool for the simulation of the human body under impact conditions. Human body models are directly modelled like the human body. In comparison the common dummy simulation models are modelled like the anthropomorphic test device which they are representing. Generally the results which can be obtained by a simulation model of the dummy are limited to the measurements which are delivered by the anthropomorphic test device. The results which human body simulations deliver have of course also limitations. But compared to an anthropomorphic test device human body models are able to represent the kinematics of the human body in a more realistic way. A human body model can be loaded from different directions. For instance the same model is able to simulate the frontal and the side impact loading of an occupant. In fact the same model should be able to simulate a pedestrian accident situation if positioned in a standing posture. All over the world several human body models are available. Additionally detailed models of body regions are also available. Body region models can be used for special impacts like a leg model impacting a front end model of a car. Regarding the body regions under the aspects of crash and impact the head is one of the most vulnerable body regions despite of having a strong bone structure. Therefore models of the head have been developed to simulate the impact and the possible injury caused by these impacts. A typical human body model for the whole human body is the THUMS model used with LsDyna code [Iwamoto2002, Oshita 2002]. Due to the fact, that the basic version of the THUMS model has a rigid skull modelling, the head impact of this whole body human model cannot be evaluated for possible head or brain injuries.