Fracture Morphology Analysis of Frozen Red Sandstone under Impact

The deformation and failure characteristics of red sandstone under subzero temperature were studied by the split Hopkinson pressure bar (SHPB) dynamic impact test. The effects of different subzero temperatures on rock strength properties, fractal dimension, and dissipated energy were analyzed combined with microfracture morphology. The reasons for rock dynamic mechanical property deterioration under lower subzero temperatures were revealed. The research shows that low subzero temperature will cause “frostbite” of red sandstone. Under high strain rate loading, the rock will quickly lose its bearing capacity, and its dynamic mechanical strength will drop sharply. The dissipated energy W L of the frozen rock specimen is positively correlated with the fractal dimension D and closely related to the macroscopic failure characteristics. It could be concluded that greater dissipation energy leads to more serious damage of rock and accordingly results in a larger fractal dimension. Fracture morphology analysis shows that the lower subzero temperature generated remarkable cracks in the material interface of the red sandstone. The damage of the red sandstone could be explained by the fact that the crack tip had low plastic deformation ability under high strain rate loading and the composition of cement was vulnerable to the subzero temperature effect.

Determination of the high-strain rate elastic modulus of printing resins using two different split Hopkinson pressure bars

The usage of resin-based materials for 3D printing applications has been growing over the past decades. In this study, two types of resins, namely a MMA-based resin and an ABS-based tough resin, are subjected to compression tests on a split Hopkinson pressure bar to deduce their dynamic properties under high strain rate loading.Two Hopkinson bar setups are used, the first one is equipped with aluminum bars and the second one with PMMA bars. From the measured strain waves, elastic moduli at high strain rates are derived. Both setups lead to values of $E=3.4$ E = 3.4 –3.8 GPa at a strain rate of about 250 s−1. Numerical simulations support the experiments. Moreover, considering the waves gained from the two different bar setups, PMMA bars appear to be well-suited for testing resin samples and are therefore recommended for such applications.

Enhancement of Blast Resistance of R.C Beams Using Micro/Nano Silica in Presence of Steel Fibers

An analytical investigation using ABAQUS/Explicit dynamic analysis was carried out to investigate the effect of using Micro/Nano silica in the presence of steel fibers on improving the dynamic response of reinforced concrete beams. According to the results of Magnusson and Hallgren's experimental investigation, the FE model has been well verified and calibrated. The finite element test program was extended further to study the effect of tensile reinforcement ratio by (0.5%, 0.78%, and 1.13%) comparing with the enhancement of concrete’s material on the behavior of tested R.C beams under blast loading. The results where compared in terms of changes in the max deflection at mid-span and flexural toughness values. The results showed that the combination between the compressive and flexural characteristic of concrete is necessary in case of high steel reinforcement ratio to reduce the brittle behavior of the R.C structure element, especially when the R.C elements exposed to a high strain rate loading due to the addition value of (DIF) for steel reinforcement properties which make the element stiffer than usual, compared with quasi-static loading condition.

O3: EVALUATION OF A 3D PRINTED BIO-ARTIFICIAL MUSCLE-ORGANOID FOR TRAUMA RESEARCH

Introduction Organoid models serve as a robust platform for investigating injury and disease in vitro. Currently, representative models of injury are lacking to investigate the effects of traumatic damage to organs and tissues. Here we describe a three-dimensional in vitro model of high strain rate loading seen in traumatic blast injury. Method 3D printing resins were tested for Young's Modulus & Poisson Ratio using a universal testing Organoids were then loaded into a 3D Printed bioreactor for high strain rate loading using a split Hopkinson pressure bar device. machine and digital image. Euler beam theory was used to evaluate post deflection. C2C12 myoblasts were seeded in fibrin hydrogels around 3D printed posts using a custom designed jig. High strain rate loading was applied to constructs, then qPCR & Fluorescent Live/Dead staining was utilised to demonstrate cell alignment and myotube formation. Result Young's modulus of Flexible resin was 11.51Mpa. Differentiated C2C12 myoblasts were capable of alignment between posts and expression of key markers of differentiation shown by qPCR & imaging. MYH5, MYH2 & MYH1 all had a > 1.5 old increase in expression compared to undifferentiated controls. Organoids were capable of survival in bioreactor casings for over 24 hours and were intact after application of high strain rate loading. Conclusion This work demonstrates the first use of a 3D printed organoid in vitro model to investigate high strain rate loading for trauma research. This organoid is capable of high throughput analysis to facilitate genomic and protein level expression analysis. Take-home message This work demonstrates the first use of a 3D printed organoid in vitro model to investigate high strain rate loading for trauma research.