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New Method to Characterize Airbag Inflators On the Way to OoP Simulation

An accurate Out-of-Position (OoP) simulation will be a mile stone for the development of restraint systems, as this would save hundreds of expensive hardware tests. OoP load cases are currently required by the US legislation and as in-house specification by many car manufactures for other markets. But simulating OoP is a difficult issue, as several challenges have to be addressed, for example: An improved dummy model validated against new component tests and an accurate modeling of the folding/unfolding of an airbag including an appropriate gas model. One of the missing pieces for this simulation is the accurate representation of the inflator mass flow. The current method to characterize gas inflators is the tank test. This method has big advantages, being cheap, reproducible and independent of the inflator geometry. The tank test shows, however, some important drawbacks: The lack of similarity of the bag inflation regarding volumetric work of the gases and initial conditions, a uniform and immediate pressure distribution must be assumed, the measurement –tank pressure– must be derived to obtain the inflator gas mass flow resulting in a higher measurement error and heat losses are high and not uniform during the process.

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