For challenging cases such as airbag deployment in out of position scenarios, airbag simulation technology is being continuously enhanced. The airbag internal pressure can be calculated in different ways. The traditional scheme uses the assumption that the airbag internal pressure is uniform at any given time. This so-called Uniform Pressure (UP) method is efficient and accurate for In-Position frontal impact scenarios, when the occupant-airbag interaction takes place after the airbag is almost fully deployed, and over a relatively long time-span. However, in Out-of-Position scenarios, there is strong interaction between occupant and airbag during the airbag deployment phase and during deployment, the airbag pressure is strongly non-uniform. Complex gas flow (GF) models such as Coupled Lagrangean-Eulerian (CLE) methods and Mesh Free (MF) methods enable a physical description of the gas flow. This paper presents verification of the MADYMO gasflow method using relatively simple analytical references as well as realistic folded and unfolded airbag load cases. For predictive airbag simulations accurate input data is needed including inflator properties, folding pattern, permeability, fabric and environment parameters. An adapted gasflow formulation is supplied, which eliminates through flow while gasflow cells may cross fabric layers. This formulation improves physical accuracy while limiting CPU demands. Fundamental tests like the 1D shock tube and the Emery test show good correlation. This proves the ability of MADYMO gasflow to predict shock waves. The application range of the "multichamber" option for gasflow has been extended by an improved formulation of the flow between chambers for high gas flow velocities. In tank test validation good correlation is obtained using gasflow. On airbag pendulum tests with folded and unfolded airbags, gasflow provides an improved prediction in particular for the initial inflation phase. Gasflow simulation results can be obtained from an overnight run.@en

One of the current activities of EEVC Working Group 13 (WG-13) "Side Impact Test Procedures" is to develop a test procedure for Free Motion Head impact tests supplementary to the full-scale mobile deformable barrier (MDB) test specified in ECE Regulation 95. Amongst the factors needed for development of the test procedure, is the determination of "worst case" test conditions for specifying contact point and approach angle. The goal of this research project was to give an objective prediction of head impact location, related head impact angle and impact speed for small, average and large sized belted front occupants in realistic seating positions in a wide range of side impact crash scenarios. Head contact at A-pillar, B-pillar and Roof-rail in two vehicle types (light / heavy) and for different interior dimensions were studied. The prediction of head impact location, velocity and angle was realized by means of virtual testing using MADYMO. Simple but efficient multi-body vehicle models were used in combination with human body models. In this study head impact horizontal and vertical angles were found between 50 deg and 115 deg and between -35 deg and -5 deg respectively. The corresponding head impact velocities were between 3 and 9 m/s, with an average value of 6.7 m/s.

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This study investigates the relevance of certain parameters for virtual testing of the driver's side OOP problem and attempts to answer the following questions: Which level of detail is needed in the airbag models to assess occupants' injury values for OOP scenarios? What is the influence of the airbag cover on the occupant response for OOP situations and how to accurately model the airbag cover? Are current dummy models suitable to assess the localized human injuries and/or is it beneficial to include human models for injury assessment? The combined multibody-FE code MADYMO was used. A virtual set-up of a folded driver airbag including cover, steering wheel and a simple seat forms the base model. Occupants were positioned according to the two OOP driver positions defined in FMVSS 208, i.e. chin on module to maximize neck injury risk and chest on module to maximize chest injury risk. The 5^th percentile Hybrid III. dummy model as well as the 5^th percentile human model were used and different airbag inflation and cover modeling techniques were investigated. Attention was focussed on analyses of the injury values obtained from the simulations of the different situations (with / without cover, use of gasflow, human / dummy model). From this study, it is concluded that it is important to take into account the geometrical effects of the airbag cover on airbag deployment and hence injury generation in OOP simulations. Adding a gasflow description to the airbag deployment simulation resulted in differences in the early deployment phase. If the dummy's injuries are determined in this phase (dependent of scenario), gasflow contributes to improved airbag modeling at the cost of higher CPU times. From the human model simulations, it is concluded that for this specific scenario, using dummy models could lead to underestimation of human injuries in the chest region, in contrast to overestimation of the head acceleration and the neck loads in the rebound phase. Therefore, human models could provide additional value compared to dummy models.

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