The use of adaptive FEM-SPH technique in high-velocity impact simulations

It is well known that while the meshless smoothed particles hydrodynamics (SPH) technique is often advantageous in modelling scenarios involving extreme deformations and fragmentation, the finite element method (FEM) in its Lagrangian implementation is wellsuited for tracking the materials' interfaces. To use the advantages of both techniques simultaneously, an adaptive FEM/SPH approach can be employed. In this method, the local and adaptive transformation of Lagrangian solid elements to SPH particles is triggered by erosion of the solid elements when they become highly distorted and inefficient. The SPH particles replacing the eroded solid elements inherit all the nodal and integration point quantities of the original solids and initiated being attached to the neighbouring solid elements. LS-DYNA implementation of this technique was adopted in this study for the solution of two problems: (1) turbofan engine blade rub against the engine’s fancase; (2) collision of an orbital debris particle with a sandwich panel of a spacecraft bus;. For the first problem, predictions of the adaptive technique are compared with those obtained using FEMonly and SPH-only models. For the second problem, a comparison of the numerical and experimental results is provided. The study highlights advantages and limitations of the adaptive modelling methodology.