Application of the finite element method to predict the crashworthy response of a metallic helicopter underfloor structure onto a hard surface

摘要

This paper assesses the performance of a finite element model developed using the commercial non-linear finite element code, LS-DYNA3D, in predicting the response of a generic metallic helicopter underfloor structure impacting a hard surface at 8ms~(-1). The application of LS-DYNA3D has demonstrated that the code is extremely capable in predicting structural collapse, as good agreement was obtained for the locations of frame collapse and force-time histories. This paper discusses modelling guidelines indicating where improvements can be gained through prudent choice of element formulation, material type, integration rule sensitivity and contact algorithm. The existing structure is capable of absorbing the impact energy, but achieves energy absorption in an inefficient manner due to the limited use of the available stroke. Characterising the failure modes, together with assessing the performance of the intersection joints has revealed two limitations with the existing design. The first is that consideration should be given to frame construction to ensure progressive collapse through careful selection of geometry, material type and inclusion of a trigger. The second is through redesign of the joints. Progressive joint failure is critical to allow increased and controlled frame collapse, which requires that both issues will have to be addressed in order to improve the crashworthiness of future metallic designs.