UHPC中钢纤维的增强机理:一种新的断裂相场模型

Strengthening mechanism of steel fiber in UHPC:A new fracture phase field model

超高性能混凝土(UHPC)是一种具有巨大潜力的复合材料。为了降低UHPC的成本并获得更好的性能,有必要研究钢纤维在UHPC中的增强机理,实践中也需要一个有效的数值模型来促进UHPC的应用。钢纤维从UHPC中拔出时会产生新的裂纹面,进而需要消耗更多的能量。基于此,推导了新裂纹及其裂纹表面能的公式,提出了一种考虑钢纤维与UHPC基体之间界面断裂能的断裂相场模型。利用该模型,对含钢纤维的三维UHPC试样进行了单轴拉伸数值模拟;开展对比实验验证了所提模型的正确性。结果表明,模拟结果与实验结果吻合较好。通过分析不同试样的新裂纹面与拉伸强度间的关系,发现UHPC的抗拉强度和残余强度随钢纤维体积含量的增加而增加,随钢纤维直径的增加而降低。进一步分析发现,UHPC的抗拉强度与钢纤维的侧表面积成正比。理论分析、数值模拟和实验表明,钢纤维在UHPC中的增强机理为:钢纤维的加入使UHPC基体与钢纤维在断裂过程中产生了一些新的裂纹,这些新裂纹消耗了更多的能量。本文研究工作可为UHPC的性能设计和开发有效的UHPC数值模型提供理论依据。

The engineering optimization of ultra-high strength concrete(UHPC) requires urgent exploration of the strengthening mechanism of steel fiber in UHPC and the establishment of an effective simulation model.In this study,we propose a new fracture phase field model that considers the fracture energy of the interface between steel fiber and UHPC matrix.The model is utilized to conduct uniaxial tensile numerical simulations of 3D UHPC incorporating steel fibers,and a comparative experiment is conducted to validate the proposed model.The results display a notable agreement between the simulation and experiment.It is found that the tensile strength and residual strength of UHPC increase with steel fiber volume content and decrease with steel fiber diameter.The inclusion of steel fibers in UHPC results in more intricate crack patterns during the fracture process.The above results can be attributed to the debonding occurring at the interface between the steel fiber and the UHPC matrix which dissipates additional energy and thus enhances the UHPC.This work establishes a theoretical foundation for UHPC performance design and the development of effective simulation methods.