Development of a Finite Element Model of the Flex-PLI-GTR 2012-01-0551

Evaluation of pedestrian leg protection performance using the Flex-PLI-GTR (Flexible Pedestrian Legform Impactor Global Technical Regulation) impactor is initiated in JNCAP in 2011. Therefore, a finite element (FE) model of Flex-PLI-GTR is needed for use in digital car development in order to satisfy pedestrian leg protection performance requirements. This paper describes the FE model of Flex-PLI-GTR that has been developed to meet this need.

There are three important features of this FE model for obtaining sufficient simulation accuracy. First, the shapes of all Flex-PLI-GTR structures were modeled in detail. Shape information of the inner structures was obtained by computerized tomography scanning and shape information of the inner structures of the outer skin was obtained by laser measurement. Furthermore, the shape of the wrapped skin was incorporated into the FE model based on a wrapping simulation. Second, the material and mechanical properties except the outer skin and rubber were set based on publicly released information without any tuning. The material properties of the outer skin and rubber were obtained experimentally using test pieces under different strain rates. The absence of tuning enables this FE model to be applied to different impact situations involving various velocities or impact angles. Third, pre-stressing of the outer skin and preloading of the springs in the knee structure were incorporated into the FE model by conducting preliminary simulations based on differences between before and after the skin is wrapped on the impactor. These measures have made it possible to represent faithfully the mechanical properties of the entire impactor.

A comparison of the results of pendulum impact tests and FE simulations verified that this FE model of Flex-PLI-GTR provides sufficient simulation accuracy. This FE model is now being used to evaluate pedestrian leg protection performance in the digital car development process.