Search

Based on the modeling method of 3D meso‐scale finite element model of plain concrete, a 3D meso‐scale finite element model of reinforced concrete is established considering the interface transition zone between reinforcement frame and mortar, and the reliability of the established meso‐scale finite element model is verified by split Hopkinson pressure bar (SHPB) test results. The failure process of reinforced concrete specimens under typical impact velocity and the influence of interface effect on specimen strength are analyzed by numerical simulation. The research results show that the 3D meso‐scale model of reinforced concrete considers the meso‐scale structure of reinforced concrete more realistically, and can better reflect the damage change process inside the material in the dynamic loading process. The weak interface effect caused by reinforcement can lead to the slight weakening of the dynamic strength of the material, but at the same time the weak interface effect of the reinforcement is also the main reason why the residual form of reinforced concrete remains well aligned with the shape of the reinforcement frame after the failure. [ABSTRACT FROM AUTHOR]

Hepatocyte nuclear factor (HNF-6) is a liver-specific protein and a key component in the differentiation process during the development of mature liver. The immunohistochemical staining and RT-PCR techniques were employed to examine the expression of HNF-6 and proliferation of Ki-67+ cells during the early regeneration of the liver on postsurgery in 3, 6, 12, and 24 h in original model of partial hepatectomy in rats. The earliest proliferating (Ki-67+) cells were observed in 3 h after surgery in liver sinusoids (liver macrophages) and then in liver parenchyma. Expression of HNF-6 in hepatocytes and epithelial cells of the bile ducts attained maximum in 6 h after surgery. At later terms, this parameter somewhat decreased, but still surpassed the control level. [ABSTRACT FROM AUTHOR]

In this study, with the meso-scale model reliably validated in our previous work (Construction and Building Materials, 2018), the waveform features of plain concrete under various loading conditions and especially with considering stress non-equilibrium are reliably reproduced and predicted. Associating with waveform features, the violation indicator of the specimen stress equilibrium in the split Hopkinson pressure bar test is identified for concrete-like damage softening materials. The concrete material behaviors for stress non-equilibrium are further analyzed, e.g. the dynamic increase factor (DIF) and damage development, etc. The conception of "damage failure volume" is introduced, and a new method of defining the development of concrete dynamic damage is given in the numerical study. What's more, the "compression wave" and "double peak" phenomena observed in the experiment are further interpreted based on the means of numerical simulation. Waveform features how to reflect the concrete material properties is also concluded. The results show that, the disappearance of the "double peak" phenomenon of reflection curve under high strain rate can be regarded as the indicator of the violation of stress equilibrium. After the violation of the stress equilibrium, the relevant DIFs of the concrete specimen will not change significantly. Especially, the concrete specimen will turn into structural response from material response. The conception of "damage failure volume" can well explain the generation of the "double peak" phenomenon of the reflection curve. The "compression wave" phenomenon of reflection curve under lower strain rates is derived from the unloading expansion recovery of the concrete specimen. Furthermore, under the same loading condition, the amplitude of the first peak of the reflection curve can be used as the evaluation standard of the bonding quality between mortar and aggregates. [ABSTRACT FROM AUTHOR]