Application of ALE to airbag deployment simulation

Abstract

For the past 15 years, automotive safety engineers have mainly relied on the Control Volume (CV) approach to simulate airbag deployment. The CV approach assumes that the gas is uniformly distributed in an inflated bag and therefore the airbag fabric is subject to uniform pressure. This assumption makes the CV approach inappropriate for Out-of-Position-Safety (OOPS) analysis in which the airbag-occupant interaction occurs before the bag is fully inflated. This paper details the theory and application of a new airbag simulation tool, an Arbitrary-Lagrange-Eulerian (ALE)-based solution. This tool is aimed at using ALE as a Computational Fluid Dynamics (CFD) tool to simulate the gas flow inside a deploying airbag. This paper starts with the introduction to ALE. Then, the ALE-based CFD approach is described. To evaluate the feasibility and robustness of this new tool, the ALE code in LSDYNA-970 is applied to a series of tests. The tests used for evaluation include two inflator tank pressure tests, a series of nine pendulum tests and one OOPS test. Following the description of the tests will be the correlation results and the discussion of the results. The correlation shows that ALE can trace the gas flow inside a deploying airbag and therefore can be an efficient and accurate tool for OOPS simulation.