Análise da resistência sob elevadas taxas de carregamento utilizando o método dos elementos discretos formado por barras

Abstract

The previous studies show the increase of deformation percentage creates a raise of dynamics resistance. Several authors have studied the effect of strain rate, these studies can be made experimentally based on the principle of the Hopkinson bar or by numerical simulations. This paper presents a study about the variation of influence of deformation percentage with the scale effect in quasi-fragile behavior. To study this effect, it is utilized a numerical model that combines the finite elements method (MEF) and the lattice Discreet Elements Method(LDEM). In LDEM the solid is represented by a spatial lattice bars with mass concentrated at their tips. This mixed model was implemented on commercial software Abaqus/Explicit, to simulate the behavior of polystyrene specimens and concrete with different sizes and diferente strain rates applied. The samples are prepared with the MEF on the extremity and the LDEM in the central part which has a reduction in cross-section, so the rupture occurs in the middle. In the simulations the specimens were subjected to direct tensile testing. The results showed that with the applied deformation percentage increase, the break loads also increase and the body dimension influences this behavior. The increase in tensile strength was observed without any changes in the constitutive equations or material parameter. It is also a proposal of a way to make independent the relationship between the dynamic intensification and the scale effect deformation percentage. It was also analyzed as is the spread of tensions along the test specimen for different strain rates, finding that to the largest strain rates analyzed the stresses are not uniform in the body.