Abstract: The paper presents a novel multi-level model for quasi-brittle cracking analysis. Based on the partition of unity and information transmission technology, it provides a new non-re-meshing way to describe the cracking phenomenon in structures constructed from materials with complex microstructures. In the global model, the concept of the material particle is defined and the basic unknowns are the boundary displacements of these particles, which is different from the concept of the traditional displacement field. A series of enrichment functions with continuous steps is proposed, describing the boundary displacement affected by crack bands and allowing the intersections of crack bands with particle boundaries a priori unknown. Simultaneously, additional equations are introduced to determine element status and make the degrees of freedom of the global model remain at a stable level. Compared with previous research by our group, where the local description is equal to the global description on the boundary of a material particle, the introduced enrichment functions enable more accurate capture of the characteristics of the crack band. The model avoids the complex and dynamic model adjustments due to the activation and exit of representative volume elements (RVEs) and the accuracy of the description of the crack pattern can be ensured. The RVEs are activated at first, but then many of them exit the computation due to the unloading which reduces many of the degrees of freedom. Two examples of concrete specimens are analyzed, and the concrete fracture experiment and the digital image correlation (DIC) test are conducted. Compared with the reference solutions and the experimental data, even though the microstructure of concrete is very complex, the cracking process and crack pattern can be obtained accurately.

用于复杂微观结构准脆性开裂分析的创新多层级模型

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