Abstract A continuum-discrete coupled modelling approach is developed in LS-DYNA to simulate complicated fragmentation phenomena of concrete under high strain-rate impact, using realistic mesoscale finite element models converted from micro X-ray computed tomography (XCT) images. In this approach, the Johnson Holmquist concrete (JHC) constitutive law based on continuum damage plasticity is used to simulate plasticity and crushing of elements, while a node-split method with contact is used to simulate discrete fracture between elements. This avoids using the popular element erosion technique, which suffers from unreal losses in mass and energy, especially under dynamic loadings with high strain rates. After the new approach is validated, extensive Monte Carlo simulations (MCS) of 93 2D FE models and one 3D model from XCT images of a 37.2mm concrete cube, consisting of aggregates, mortar, interfaces, and pores, are conducted under compressive impact with strain rates ranging from 0-1000/s and different end friction conditions. It is demonstrated that the developed modelling approach can simulate realistic failure mechanisms such as discrete fracture propagation under strain rates of 0-200/s and immediate crushing, fragmentation and prilling under higher strain rates of 500-1000/s. The predicted compressive dynamic increase factor of strength (CDIF)–strain rate curve is found well within the range of experimental data and very close to other empirical curves. Quantitative statistical calculations show that the meso-structure is the main contributor to the dynamic strength increase or reduction when the strain rate is lower than 10/s, but the inertial effect becomes dominant when the strain rate is higher than 100/s. The end friction confinement makes only 3-5% difference.

中文翻译：

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使用连续-离散耦合模型对高应变率冲击下的混凝土进行基于显微 CT 图像的模拟

摘要 在 LS-DYNA 中开发了一种连续离散耦合建模方法，使用从微 X 射线计算机断层扫描 (XCT) 图像转换而来的真实中尺度有限元模型来模拟混凝土在高应变率冲击下的复杂破碎现象。在该方法中，使用基于连续损伤塑性的 Johnson Holmquist 混凝土 (JHC) 本构定律来模拟单元的塑性和破碎，而使用接触的节点分割方法来模拟单元之间的离散断裂。这避免了使用流行的元素侵蚀技术，该技术会遭受质量和能量的不真实损失，尤其是在具有高应变率的动态载荷下。在验证新方法后，93 个 2D FE 模型和一个 3D 模型的广泛蒙特卡罗模拟 (MCS) 来自 37. 由骨料、砂浆、界面和孔隙组成的 2mm 混凝土立方体在压缩冲击下进行，应变速率范围为 0-1000/s 和不同的端部摩擦条件。结果表明，所开发的建模方法可以模拟真实的失效机制，例如在 0-200/s 应变速率下的离散裂缝扩展和在 500-1000/s 的更高应变速率下的即时破碎、破碎和造粒。预测的压缩动态强度增加因子 (CDIF) - 应变率曲线在实验数据范围内很好地发现，并且非常接近于其他经验曲线。定量统计计算表明，当应变速率低于10/s时，细观结构是动态强度增加或减少的主要贡献者，但当应变速率高于 100/s 时，惯性效应占主导地位。端部摩擦限制仅产生 3-5% 的差异。