Evaluation of Appropriate Material Models in LS-DYNA for MM-ALE Finite Element Simulations of Small-Scale Explosive Airblast Tests on Clay Soils

Abstract

This study conducted finite element simulations of a small scale, explosive airblast on clay soil in LS-DYNA using multi-material arbitrary Lagrangian–Eulerian methods. An explosive mass of 100.9 g with a 7.6 cm blast height was simulated in this study under two-dimensional conditions. The study compared four different material models to evaluate their ability to simulate explosively-induced airblast loads on cohesive soils. Material models included the Soil and Foam pressure dependent strength model, the Pseudo Tensor pressure dependent strength model, the FHWA Drucker–Prager model and the Two-Invariant Geologic Cap model. Crater dimensions were measured from the simulations and compared to the results of airblast experiments performed in another study. Three material models ran to completion with the exception of the Geologic Cap model, which terminated early in the calculation due to plasticity algorithm errors caused by the large strain increments. While the remaining three models somewhat over-predicted crater depth, the diameter dimensions and crater volumes from the Soil and Foam and particularly the Pseudo Tensor model compared very well to the experimental data. The crater shape from the FHWA model did not match particularly well with experimental results and was larger than the experimental crater. A simplified, pressure dependent strength model such as Soil and Foam model or the Pseudo Tensor model is therefore recommended for modeling small-scale airblast events on cohesive soils. The Pseudo Tensor model compared particularly well to experimental results and predicted crater dimensions very well. Additional studies with the Geologic Cap model implementing smoothed particle hydrodynamics are recommended which may resolve the errors associated with large strain increments.