论文标题

脆性和准脆性断裂的微态相位模型

A micromorphic phase-field model for brittle and quasi-brittle fracture

论文作者

Bharali, Ritukesh, Larsson, Fredrik, Jänicke, Ralf

论文摘要

裂缝的相位模型尽管其流行和易于实施,但其计算挑战却伴随着一套计算挑战。它们是由于骨折不可逆性而导致的非凸能功能,变异性不平等,需要极高的网格解决裂缝。在本手稿中,重点是变异不平等的数值处理。在这种情况下,流行的历史变化方法遭受了引入错误的变异不一致和不可量化的性质。一种更好的替代方法,即惩罚方法,有可能使刚度矩阵不良条件。为了规避这两个上述问题,在本手稿中提出了针对相田断裂建模的微态方法。在这种方法中,进行了能量功能的微态扩展。这将相位场转换为局部变量,同时引入了定期断裂问题的微态变量。这种相位场的规律性要求降低了,可以通过简单的“最大”操作(具有系统级别的精度)更轻松地实现断裂不可逆性的约束。在基准脆性和准脆性问题上进行的数值实验证明了该模型对于多种断裂问题的适用性和功效。

The phase-field model for fracture, despite its popularity and ease of implementation comes with its set of computational challenges. They are the non-convex energy functional, variational inequality due to fracture irreversibility, the need for extremely fine meshes to resolve the fracture. In this manuscript, the focus is on the numerical treatment of variational inequality. In this context, the popular history-variable approach suffers from variationally inconsistency and non-quantifiable nature of the error introduced. A better alternative, the penalisation approach, has the potential to render the stiffness matrix ill-conditioned. In order to circumvent both aforementioned issues, a micromorphic approach towards phase-field fracture modelling is proposed in this manuscript. Within this approach, a micromorphic extension of the energy functional is carried out. This transforms the phase-field into a local variable, while introducing a micromorphic variable that regularises the fracture problem. This reduction the regularity requirements for the phase-field enables an easier implementation of the fracture irreversibility constraint through simple 'max' operation, with system level precision. Numerical experiments carried out on benchmark brittle and quasi-brittle problems demonstrate the applicability and efficacy of the proposed model for a wide range of fracture problems.

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