This paper introduces a theoretical model for forecasting fiber orientation in 3D-printed ultra-high-performance concrete (3DP-UHPC). Initially, the dynamic evolution process of fiber alignment in 3DP-UHPC was characterized using X-ray computed tomography (X-CT) and image analysis. The results indicated that fiber alignment during extrusion process was primarily constrained by the rigid boundary of nozzle. Leveraging stereology theory, the regularity of fiber alignment affected by boundary effects was elucidated. Following layer deposition, the flattening effect resulting from the nozzle's extrusion force and gravity of upper layers influenced fiber alignment along printing direction. To quantify this impact, a flattening correction coefficient was introduced to modify fiber orientation coefficient in an ideal state. Finally, considering the overlapping effect of boundary and flattening on fiber orientation in 3DP-UHPC, a theoretical model was developed to predict fiber orientation. The model demonstrated robust adaptability, providing valuable insights into the design of 3DP-UHPC with improved fiber reinforcement efficiency.

中文翻译：

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基于立体学理论的 3D 打印超高性能混凝土中的纤维配向建模


本文介绍了一种预测 3D 打印超高性能混凝土 （3DP-UHPC） 中纤维取向的理论模型。最初，使用 X 射线计算机断层扫描 （X-CT） 和图像分析表征 3DP-UHPC 中纤维取向的动态演变过程。结果表明，挤出过程中的纤维排列主要受喷嘴刚性边界的约束。利用立体学理论，阐明了受边界效应影响的纤维排列的规律性。层沉积后，喷嘴的挤出力和上层重力产生的扁平化效应影响了沿打印方向的纤维排列。为了量化这种影响，引入了展平校正系数来修改理想状态下的纤维取向系数。最后，考虑 3DP-UHPC 中边界和展平对纤维取向的重叠影响，建立了预测纤维取向的理论模型。该模型表现出强大的适应性，为提高纤维增强效率的 3DP-UHPC 设计提供了有价值的见解。