Numerical implementation of a bounding surface plasticity model for sand under high strain-rate loadings in LS-DYNA

Abstract

A rate-dependent bounding surface plasticity model for soil under high strain-rate loadings is implemented on a generic finite element platform, LS-DYNA, in order to better simulate blasting and impact problems. The model is developed based on a bounding surface hypoplasticity framework. The dilatancy, critical and bounding surfaces in the model are all rate-dependent so that the influence of strain rate on soil behaviour can be considered. The numerical implementation of the constitutive model follows an explicit modified Euler stress integration scheme. Procedures of stress updating and correction of yield surface drift are established for the rate-dependent bounding surface model. The constitutive model is finally implemented onto LS-DYNA via its user-defined material interface. As an application example, drained triaxial tests on a crushed coral sand under different strain rates are simulated. Characteristics of soil behaviour under high strain rates are reproduced. Simulation results show that the strain rate influences not only the plastic behaviour of soil, but also the uniformity of stresses and strains in the soil specimens. The numerical errors of the model are also evaluated. The numerical scheme is shown to be robust and fully compatible with the LS-DYNA finite element platform.