Moving Beyond the Finite Elements, a Comparison Between the Finite Element Methods and Meshless Methods for a Ballistic Impact Simulation

For the past several decades, finite element techniques have been used extensively for the analysis of computational solid mechanics problems. However, when the distortions become very severe, especially Lagrangian finite element algorithms are not always adequate. More recently meshless methods (or particle methods) have been developed and applied to solid mechanics problems since they can efficiently be used to represent severe distortions and are more robust for dynamics problems such as high energy impacts and penetrations that involve large deformations and even erosions. Impacts at higher speeds are also challenging because of the high strain rate behavior of the materials and the significant importance of the stress wave propagation through the material. In this paper, the deformation pattern and characteristics of a thin (50 μm) foil is investigated both numerically and experimentally under impact loading of a 9 mm standard NATO bullet, at several speeds by using a 3D non-linear explicit numerical code, LS-DYNA. Different element and particle algorithms are used to obtain the best numerical representation of the problem. The differences between Lagrangian, Eulerian, ALE (Arbitrary Lagrangian- Eulerian) and SPH (Smoothed Particle Hydrodynamics) formulations are briefly compared and discussed under ballistic impact conditions. The results obtained from these different numerical models are also validated with a series of tests and are in good agreement with the experimentally measured values.