About the dynamic strength enhancement of concrete-like materials in a split Hopkinson pressure bar test

Abstract. The bulk dynamic behaviour of concrete in generally known to be strain rate dependent. However, explanation of the underlying mechanisms has been a subject of debate in the research community. Among other factors, the extent of validity of existing experimental data for concrete-like materials in the high strain rate regime is believed to have further complicated the situation. This paper is concerned about the strain rate limits for dynamic testing of concrete specimens in association with the size requirement for representation of the composite material. The strain rate limits as may be established by elastic theories are discussed firstly. Representative simulation results from numerical experiments using a mesoscale model are then described, and non-uniform distributions of stress and damage under excessively high strain rates are highlighted, and this leads to discussion on the correlation between the externally measured data and the real responses within the sample material. Both dynamic compression and dynamic splitting tension are considered.

Section: Compression Simulationsupporting

confidence: 88%

“…[3][4][5][6]), without always observing a strain rate limit that is associated with guaranteeing stress uniformity. Among other factors, this is believed to have contributed, to a varying extent, to the large scatter in the observed dynamic strength increase factor (DIF) for compressive as well as tensile strengths.…”

Section: Introductionmentioning

confidence: 99%

On the strain rate limits in dynamic testing of concrete-like heterogeneous materials

Song

2012

“…[10,11]). More recent numerical studies using 2D mesoscale models provide further support to this argument (e.g.…”

Section: Dynamic Compressionmentioning

confidence: 99%

A 3-D perspective of dynamic behaviour of heterogeneous solids

Zhou

2015

Abstract. The dynamic behaviour of concrete-like materials under high strain rates has been a subject of continuous scrutiny over the years. A prevailing explanation attributes much of the dynamic increase of strength, especially under compression, to the macroscopic inertia confinement. Studies conducted by the authors' group using meso-scale computational models suggest that the heterogeneity of the material composition, in particular the involvement of the aggregates, also plays a sensible part in the process of damage evolution and the increase of the bulk strength under high strain rates, and a detailed investigation into this effect would benefit if a realistic representation of the heterogeneity in 3D can be achieved. This paper presents some recent progress in the development of a 3-D meso-scale computational model incorporating randomly-shaped 3-D aggregate particles, including the general validation of the model, and application in the simulation of the dynamic response of concrete under high strain rate compression.

“…The effect of friction on the dynamic response in SHPB tests is well-known, which leads to errors in the DIF [4,25,26], particularly in concrete-like materials due to their coarser surface when compared to metals [27] and therefore friction should not be completely neglected even though lubricants are used. Figure 3(a) shows the results of the effect of the friction coefficient µ on the dynamic response of mortar for various β and ψ.…”

Section: -P4mentioning

confidence: 99%

“…The increase of the compressive strength in dynamic testing is commonly described by using the dynamic increase factor (DIF), which is defined by the ratio of the dynamic strength to the quasi-static strength in unconfined uniaxial compression [4]. The DIF of concrete-like materials in the high strain-rate range of 10 1 -10 3 s −1 is often obtained by performing dynamic test using a split Hopkinson pressure bar (SHPB); however, 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]. It has been shown that the induced lateral confinement in SHPB test, which causes increase of DIF, may be caused by friction between the bars and the specimen [5,7], large specimen diameters [8,9], and radial inertia [10,11].…”

Section: Introductionmentioning

confidence: 99%

Effect of structurally-induced lateral confinement on split Hopkinson pressure bar test specimens of concrete-like materials

Flores‐Johnson

2015

Self Cite

Abstract. In dynamic testing of concrete-like materials, there is a need in distinguishing structural effects from genuine strainrate 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 strainrate in the order of 10 2 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.