论文标题

通过建模木材建模失败机理评估的混合多相模型来描述正交材料中粘性故障

A hybrid multi-phase field model to describe cohesive failure in orthotropic materials, assessed by modeling failure mechanisms in wood

论文作者

Pech, Sebastian, Lukacevic, Markus, Füssl, Josef

论文摘要

断裂力学对于许多工程领域至关重要,因为有效设计需要精确预测结构和零件的故障。从机械和数值的角度来看,故障过程的模拟是具有挑战性的,特别是对于不均匀的材料,微观结构会影响裂纹启动和传播,并导致复杂的裂纹模式。裂缝的相位场方法是一种有前途的遇到此类材料的方法,因为它能够描述复杂的断裂现象,例如裂纹扭结,分支和聚结。此外,鉴于网格在裂缝周围是同质的,这是一种很大程度上独立的方法。但是,相位场方法的广泛使用的公式仅限于各向同性材料,并且不考虑通过材料的微结构定义的优选裂缝平面。在这项工作中,该方法被扩展为对正性本构行为和裂纹传播的优选方向进行考虑。我们表明,通过将基于应力的拆分和多个相位场变量具有可取的裂缝平面,结合了混合相位场方法,可以找到一个通用框架,用于模拟各向异性,不均匀的材料。基于应力的分裂基于虚拟的裂纹面,此处是扩展到各向异性材料。此外,还使用了一种新型的混合方法,其中根据平滑的无牵引裂纹边界条件进行声音材料的降解,这被证明是恢复观察到的裂纹模式的主要驱动因子。通过对两个示例进行详细分析来显示这:木制的单边置板和一个带有单个结和复杂纤维方向的木板。在这两种情况下,提出的新型杂种相位方法都可以实际繁殖复杂的故障模式。

Fracture mechanics is crucial for many fields of engineering, as precisely predicting failure of structures and parts is required for efficient designs. The simulation of failure processes is, from a mechanical and a numerical point of view, challenging, especially for inhomogeneous materials, where the microstructure influences crack initiation and propagation and leads to complex crack patterns. The phase field method for fracture is a promising approach to encounter such materials since it is able to describe complex fracture phenomena like crack kinking, branching and coalescence. Moreover, it is a largely mesh independent approach, given that the mesh is homogenous around the crack. However, the broadly used formulation of the phase field method is limited to isotropic materials and does not account for preferable fracture planes defined through the material's microstructure. In this work, the method is expanded to take orthotropic constitutive behavior and preferable directions of crack propagation into account. We show that by using a stress-based split and multiple phase field variables with preferable fracture planes, in combination with a hybrid phase field approach, a general framework can be found for simulating anisotropic, inhomogeneous materials. The stress-based split is based on fictitious crack faces and is, herein, expanded to anisotropic materials. Furthermore, a novel hybrid approach is used, where the degradation of the sound material is performed based on a smooth traction free crack boundary condition, which proves to be the main driving factor for recovering observed crack patterns. This is shown by means of a detailed analysis of two examples: a wooden single edge notched plate and a wood board with a single knot and complex fiber directions. In both cases, the proposed novel hybrid phase field approach can realistically reproduce complex failure modes.

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