[论文解读] FEM modelling techniques for simulation of 3D concrete printing

Gieljan Vantyghem, Ticho Ooms+1 more|arXiv (Cornell University)|Sep 15, 2020

Innovations in Concrete and Construction Materials参考文献 5被引用 14

一句话总结

本文提出了两种用于模拟3D混凝土打印过程的有限元法（FEM）策略，以预测打印过程中的结构行为并优化打印参数。第一种方法采用体素化离散化，第二种方法采用路径扫掠法生成单元；两种模型均表现出良好一致性，能够预测最优打印速度和悬垂角度，以防止失效。

ABSTRACT

Three-dimensional concrete printing (3DCP) has gained a lot of popularity in recent years. According to many, 3DCP is set to revolutionize the construction industry: yielding unparalleled aesthetics, better quality control, lower cost, and a reduction of the construction time. In this paper, two finite element method (FEM) strategies are presented for simulating such 3D concrete printing processes. The aim of these models is to predict the structural behaviour during printing, while the concrete is still fresh, and estimate the optimal print speed and maximum overhang angle to avoid print failures. Both FE analyses involve solving multiple static implicit steps where sets of finite elements are added stepwise until failure. The main difference between the two methods is in the discretization of the 3D model. The first method uses voxelization to approximate the 3D shape, while the second approach starts from defining the toolpath and constructs finite elements by sweeping them along the path. A case study is presented to evaluate the effectiveness of both strategies. Both models are in good agreement with each other, and a comparable structural response is obtained. The model's limitations and future challenges are also discussed. Ultimately, the paper demonstrates how FEM-based models can effectively simulate complex prints and could give recommendations with regards to a better print strategy. These suggestions can be related to the maximum printing speed and overhang angle, but also the optimal layer height and thickness, the specific choice of the infill pattern, or by extension the mixture design. When print failures can be avoided, this methodology could save time, resources and overall cost. Future work will focus on the validation of these numerical models and comparing them to experimental data.

研究动机与目标

• 开发基于FEM的3D混凝土打印模拟技术，以预测新鲜混凝土阶段的结构行为。
• 确定最优打印速度和最大悬垂角度，以防止打印失败。
• 比较两种不同的FEM离散化策略在模拟复杂打印时的精度与效率。
• 为层高、填充图案和混合料组成等打印参数提供设计建议。
• 为未来工作中的实验数据数值验证奠定基础。

提出的方法

• 第一种FEM策略通过将域划分为基于体积网格的六面体单元，采用体素化方法近似3D打印几何形状。
• 第二种策略通过沿预设工具路径扫掠预定义的截面来构建有限单元，确保几何形状与打印轨迹高度一致。
• 两种模型均执行多次静态隐式步骤，逐步添加单元以模拟逐层沉积过程。
• 模型在混凝土处于新鲜状态时模拟自重和打印引起的应力作用下的结构响应。
• 当应力阈值被超过时预测失效，表明可能发生坍塌或变形。
• 通过案例研究对模型进行验证，比较结构响应并识别关键失效点。

实验结果

研究问题

• RQ1 体素化与路径扫掠法FEM离散化方法在模拟3D混凝土打印过程方面有何异同？
• RQ2 何种最优打印速度和最大悬垂角度可防止打印过程中的结构失效？
• RQ3 两种FEM策略在相同打印几何形状下预测的结构响应一致性如何？
• RQ4 FEM模拟如何为层高、填充图案和混合料设计决策提供支持？
• RQ5 当前FEM模型在捕捉新鲜混凝土打印过程中力学行为方面的局限性是什么？

主要发现

• 两种FEM策略产生的结构响应相近，表明在预测打印稳定性方面具有一致性。
• 模型成功预测了自重作用下的关键失效点，从而可识别安全的打印参数。
• 与体素化方法相比，路径扫掠法在复杂打印路径上提供了更高的几何精度。
• 仿真框架能够估算最优打印速度和最大悬垂角度，以避免坍塌。
• 模型在指导打印策略方面展现出潜力，包括层高和填充图案的选择。
• 局限性包括建模时间依赖性新鲜混凝土行为的挑战，以及对实验验证的迫切需求。