Abstract
In dynamic testing of concrete-like materials, there is a need in distinguishing structural effects from genuine strain-rate effects. In this paper, this generic problem is studied by numerical simulations based on a phenomenological material model available in the commercial finite element (FE) code Abaqus. The numerical results show that the increase of the dynamic increase factor (DIF) with the increase of strain-rate in concrete-like materials in a Split Hopkinson Pressure Bar (SHPB) test is a phenomenon related not only to material strain-rate effects but also to structural effects. It was found that dilation, surface friction and lateral inertia cause lateral confinement, which enhances DIF when the strain-rate is greater than a transition strain-rate in the order of 102 s−1 . Although, genuine strain-rate effect may exist as suggested by meso-scale simulations in previous investigations, the findings in this study show that structural effects have a significant contribution to the increase of DIF, and therefore, it is necessary to correctly calibrate existing phenomenological models and interpret the results obtained from split Hopkinson pressure bar (SHPB) tests.
Highlights
It is well-known that compressive properties of concrete and similar brittle materials, e.g., mortar or rock, exhibit strain-rate dependence [1,2,3]
The dynamic increase factor (DIF) of concrete-like materials in the high strain-rate range of 101–103 s−1 is often obtained by performing dynamic test using a split Hopkinson pressure bar (SHPB); it has long been debated whether the increase of compressive strength observed in SHPB tests of unconfined specimens is an intrinsic material property or is related to structural or inertial effects [4,5,6]
The numerical study conducted in this paper shows that the increase of the dynamic increase factor (DIF) with strainrate for concrete-like materials in SHPB tests is a complex phenomenon related to material strain-rate effects and to structural effects
Summary
It is well-known that compressive properties of concrete and similar brittle materials, e.g., mortar or rock, exhibit strain-rate dependence [1,2,3]. A recent numerical study by Elmer VII et al [17] showed that the enhancement of concrete strength in SHPB tests is strongly related to shear dilation They investigated the influence of the dilation parameter of the K&C model. There is a need to improve our understanding of structural effect contributions to the observed strain-rate effects using phenomenological material models, but with meaningful parameters that can be determined for engineering numerical simulations. In this paper, this problem is addressed by presenting numerical simulations dealing with the effect of induced lateral confinement using a phenomenological material model available in the FE code Abaqus.
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