An Eulerian approach to soil impact analysis for crashworthiness applications

Abstract

The primary motivation of this study was the development and implementation of an explicit nonlin-ear dynamic finite element based methodology for investigating the crashworthiness of small lightweight composite aircraft impacting into soft soil. The technique used to characterise and validate a numerical model for soft soil as an impact terrain is the focus of this paper. The technique used was primarily based on the use of a time explicit Eulerian-based finite element analysis code, and this technique was dem-onstrated through the finite element analysis of penetrometer drop tests into soft soil. The Eulerian-based finite element approach was considered rather than the more commonly used Lagrangian-based finite element approach in order to reduce numerical instabilities which often occur with the use of La-grangian solvers when considering problems with large deformations, which is a characteristic of crash analyses. Validation of the numerical model was based on previously published work in which pen-etrometer drop tests into soft soil/clay were performed at the Utah Test and Training Range. Experimental data were presented in this work, as well as a finite element modelling approach based on Lagrangian methods. Based on the results obtained it was concluded that an Eulerian-based approach to soft soil impact analysis, for crashworthiness applications, is valid. Greater model fidelity may possibly be gained by further investigation of the drop test methodology, viscosity effects, variation of soil mechanical prop-erties through the depth range, and strain rate effects.