Numerical simulation of a riveted helicopter panel during a ditching maneuver

The following study aims to present an impact analysis in water of a simplified geometry of a riveted helicopter panel. The analyses were conducted using Ls-Dyna solver, applying the FEM methodology to simulate the impacting body and the water, which was modelled using the SPH (Smoothed-Particle Hydrodynamics) method. The study focuses specifically on a geometry representing an aluminium box of dimensions compatible with those found in the underfloor areas of helicopters. In the first part of the paper, different types of rivet models will be investigated considering a single riveted lap joint under tension, highlighting the best choice especially when elastic-plastic behaviour should be considered. The focus will be, in the second part, on the forces that develop on the bottom plate and the rivets connecting the plate to the two reinforcement elements, namely the stringers and frames, during a ditching maneuver. A comparison will be conducted between the measured pressures and those projected by analytical theories. Additionally, the influence of air-cushioning will be investigated, discussing the benefits and the conditions under which it can be neglected.