The dynamic fracture of quasi-brittle materials, including rocks and concrete, is characterised by highly inhomogeneous deformation along localised cracking paths, exhibiting a significant rate-dependent effect that governs both fracture toughness and crack propagation trajectories. To capture the significant discontinuities of the localised fracturing band and its rate-dependent failure mechanisms, this study proposes a novel rate-dependent cohesive model integrated within a double-scale constitutive framework. The framework incorporates the localised failure mechanism as an intrinsic characteristic by using kinematic enrichment to account for the high deformation gradient across the localisation band. The proposed rate-dependent cohesive model distinctly incorporates the Dynamic Increase Factors (DIF) for both tensile and shear strength components to characterise mixed-mode dynamic fracture behaviour. Furthermore, by featuring a length scale intrinsically linked to the volume element size at the constitutive level, the size effects is naturally incorporated. The model's performance and promising features are demonstrated through its ability to capture dynamic fracture initiation, orientation and propagation under various impact load conditions. This opens the potential for understanding and simulating the complex dynamic fracture processes in quasi-brittle materials under high strain rate conditions, offering valuable insights for engineering applications involving impact load and dynamic structural integrity.

中文翻译：

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准脆性材料动态断裂的速率依赖性本构建模


准脆性材料（包括岩石和混凝土）的动态断裂的特点是沿局部开裂路径的高度不均匀变形，表现出显着的速率依赖效应，控制断裂韧性和裂纹扩展轨迹。为了捕捉局部压裂带的显着不连续性及其速率依赖性失效机制，本研究提出了一种新的速率依赖性内聚模型，该模型集成在双尺度本构框架中。该框架通过使用运动学富集来解释整个定位带的高变形梯度，从而将局部失效机制作为内在特征。所提出的速率相关内聚力模型明确地结合了拉伸和剪切强度分量的动态增加因子 （DIF），以表征混合模式动态断裂行为。此外，通过在本构水平上具有与体积单元尺寸内在相关的长度尺度，自然而然地纳入了尺寸效应。该模型的性能和有前途的功能通过其在各种冲击载荷条件下捕获动态裂缝起始、取向和传播的能力得到了证明。这为理解和模拟高应变速率条件下准脆性材料中复杂的动态断裂过程提供了可能性，为涉及冲击载荷和动态结构完整性的工程应用提供了有价值的见解。