Layout, Validation and Benchmark of an all new Frontal Offset Barrier FEM Model

For the customer, passive safety is one of the driving reasons for the decision when buying a new car. To ensure high safety standards, passive safety is demonstrated in vehicle crash tests. Instead of vehicle to vehicle crash tests, one vehicle is replaced by an aluminium honeycomb based crash barrier. This barrier represents the front of a vehicle by the shape, the deformation behaviour and the energy absorption. Using Finite Element Method (FEM) it is possible to show and predict the behaviour of the vehicle’s structure during a previous mentioned crash test. To ensure good simulation results compared to reality it is not only necessary to correctly build up the FE model of the vehicle, but to simulate the real behaviour of the crash barrier too. Experience shows that the deformation behaviour of the FEM crash barrier seriously influences the quality of the full vehicle simulation. The barrier models that are currently in use, show insufficient reliable results. The modelling techniques are not able to show the principle deformation and failure behaviour of aluminium honeycomb. Moreover huge barrier deformation is able to cause serious instability problems of the models. That leads to an inaccuracy in predicting the vehicle safety during a virtually based development process. It has to be considered that CAE driven design processes are only feasible when the simulation delivers results with reliable prognosis quality. During the last years a new modelling method for aluminium honeycomb structures especially based on the IIHS side impact barrier was developed. In the meanwhile the method proved to work also with the high relative deformations that have to be faced in a frontal offset crash test. A very specific sequence of tests was carried out to determine the structural properties of the aluminium honeycomb, the cladding and the whole barrier itself as well. The tests were planned to show the reproducibility of the results but also for example the dependence on the test velocity at the same energy levels. The output of this process is a stable barrier model capable to show localized deformations. This prevents overestimation of energy absorption by distributing the deformation on the whole barrier. The developed method to simulate crash barriers contributes to the improvement of full vehicle crash simulations. Reliable calculation results based on more accurate barrier models will help to reduce the risk of changes in already released toolings after analysing first real crash results.

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