回字形3D打印混凝土受压性能试验及数值模拟

Tests and Numerical Simulation on Compressive Properties of 3D Printing Concrete along Rectangular-Ambulatory-Plane Path

本文将回字形3D打印混凝土试样切割成中心回字型、边缘条纹型和角部拐角型三种类型试块,开展X、Y和Z三个方向的抗压强度试验,并利用基于界面黏结的有限元模型模拟其受压行为,探究回字形3D打印混凝土的强度不均匀性、各向异性和形成机理。结果表明:三种类型试块均为X向(顺打印条带方向)抗压强度最高,Z向(逐层叠加方向)强度最小,其中,中心回字型试块三个方向的平均强度最高,各向异性也最显著,但总体而言三种类型试块的平均强度差异不大;有限元模型的强度计算结果及损伤特征与试验结果基本吻合,说明黏结单元的引入能较好地模拟3D打印混凝土的界面行为;与受力方向垂直的水平界面对强度影响较大,不同加载方向上此类界面的数量和分布不同是导致3D打印混凝土强度各向异性的主要原因。上述研究为3D打印混凝土的打印路径规划提供了参考。

The concrete samples of 3D printing along rectangular-ambulatory-plane(R-a-p) path were cut into three types of test cubes:R-a-p,stripe and corner.Compressive strength tests were conducted on these specimens in X,Y and Z directions,and their compressive behaviors were simulated using the finite element models based on the interface bonding.The strength inhomogeneity,anisotropy and formation mechanism of 3D printing along R-a-p path were investigated.The test results show that the highest compressive strength of the three types specimens is in the X direction(along the printed strip direction),the lowest is in the Z direction(layer-by-layer stacking direction) and the R-a-p specimens exhibit the highest average strength of three directions and the most significant strength anisotropy.Overall,there is no great difference between the average strength of three types cubes.The strength calculation results and damage characteristics from finite element models are basically consistent with the experimental results,implying that the introduction of cohesive element can better simulate the interface behavior of 3D printing concrete.The horizontal interface perpendicular to the loading direction has a great influence on the strength,and the difference in the number and distribution of these interfaces in different loading directions is the main reason for the strength anisotropy of 3D printing concrete.The research provides a reference for the printing path planning of 3D printing concrete.