Open Access

ARTICLE

Strength of Brittle Materials under High Strain Rates in DEM Simulations

by Jorge Daniel Riera¹, Letícia Fleck Fadel Miguel², Ignacio Iturrioz³

1 Department of Civil Engineering, UFRGS, Porto Alegre, Brazil. jorge.riera@ufrgs.br
2 Department of Mechanical Engineering, UFRGS, Porto Alegre, Brazil. letffm@ufrgs.br
3 Department of Mechanical Eng., UFRGS, Porto Alegre, Brazil. ignacio@mecanica.ufrgs.br

Computer Modeling in Engineering & Sciences 2011, 82(2), 113-136. https://doi.org/10.32604/cmes.2011.082.113

Abstract

In the truss-like Discrete Element Method (DEM), masses are considered lumped at nodal points and interconnected by means of uni-dimensional elements with arbitrary constitutive relations. In previous studies of the tensile fracture behavior of concrete cubic samples, it was verified that numerical predictions of fracture of non-homogeneous materials using DEM models are feasible and yield results that are consistent with the experimental evidence so far available. Applications that demand the use of large elements, in which extensive cracking within the elements of the model may be expected, require the consideration of the increase with size of the fractured area, in addition to the effective stress-strain curve for the element. This is a basic requirement in order to achieve mesh objectivity. Note that the degree of damage localization must be known a priori, which is a still unresolved difficulty of the non-linear fracture analysis of non-homogeneous large structures. In previous DEM applications, the authors have noticed that simulations conducted on samples of fragile, inhomogeneous materials subjected to various loading conditions, tend to fail under increasing loads when the loading rate increases. The issue raised questions, such as the need to explain the capacity of the method to predict, at least approximately, the increase in load-carrying capacity of structural systems subjected to impact and blast loadings, the need to assess the correlation with experimental results and to critically examine the validity of the available experimental evidence. Within this context, this paper presents the response of cubic concrete samples subjected to tension under controlled boundary displacements with increasing loading rates, obtained by simulation with the DEM. Next DEM simulations of modified Hopkinson bar tests are presented with the aim of extending the range of strain rates examined. Conclusions on model uncertainty associated to high strain or loading rates, as well as theoretical considerations on the applicability of available experimental results are finally advanced.

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Citations