Critical Comparison of Phase-Field, Peridynamics, and Crack Band Model M7 in Light of Gap Test and Classical Fracture Tests
Critical Comparison of Phase-Field, Peridynamics, and Crack Band Model M7 in Light of Gap Test and Classical Fracture Tests
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DOI：
10.1115/1.4054221
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发表时间：
2022-06-01
影响因子：
2.6
通讯作者：
Donmez, A. Abdullah
中科院分区：
文献类型：
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作者：
Bazant, Zdenek P.;Nguyen, Hoang T.;Donmez, A. Abdullah
最近设想的间隙测试及其模拟表明，混凝土、塑性硬化金属、复合材料以及可能大多数材料的断裂能G(f)（或K-c、J(cr)）可以+/- 100%变化，这取决于裂缝平行应力sigma（xx）、sigma（zz）及其历史。因此，不仅要考虑断裂过程区的有限长度，还要考虑断裂过程区的有限宽度及其张拉损伤行为。本次测试的数据，以及其他10项对断裂问题很重要的经典测试（9项针对混凝土，1项针对砂岩），被最佳地拟合用于评估最先进的相场、周动力和裂缝带模型的性能。由于裂纹带模型具有真实的边界和裂纹面条件以及张拉特性，结合最新版本M7中的微平面损伤本构律，可以很好地拟合所有数据。相反，相场模型表现不佳。动态模型（基于键和基于状态）的表现甚至更差。最近对键相关变形梯度的修正有助于改善一些实验中的预测，但不是全部。这证实了之前严格的理论批评（JAM 2016），这表明所有类型的周动力学都存在几个概念上的错误：(1)它暗示了晶格微观结构；(2)其粒子跳变相互作用是虚构的；(4)它忽略了抗剪切粒子旋转（这是使晶格离散粒子模型（LDPM）具有优越性能的原因）；(3)它对边界的表示，特别是裂缝和断裂过程带面，在物理上是不现实的；(5)它不能再现准脆性的典型特征——过渡尺寸效应。文中指出了一种误导性的做法，即只使用一个或两个与许多不同模型相匹配的简单测试来“验证”一个模型，或者展示针对一种测试类型的特别改进，而忽略了其他类型的不适合。最后，强调了裂缝平行应力在混凝土、页岩、纤维复合材料、塑性硬化金属和亚微米尺度材料等实际问题中的普遍存在。
The recently conceived gap test and its simulation revealed that the fracture energy G(f) (or K-c, J(cr)) of concrete, plastic-hardening metals, composites, and probably most materials can change by +/- 100%, depending on the crack-parallel stresses sigma(xx), sigma(zz), and their history. Therefore, one must consider not only a finite length but also a finite width of the fracture process zone, along with its tensorial damage behavior. The data from this test, along with ten other classical tests important for fracture problems (nine on concrete, one on sandstone), are optimally fitted to evaluate the performance of the state-of-art phase-field, peridynamic, and crack band models. Thanks to its realistic boundary and crack face conditions as well as its tensorial nature, the crack band model, combined with the micro-plane damage constitutive law in its latest version M7, is found to fit all data well. On the contrary, the phase-field models perform poorly. Peridynamic models (both bond based and state based) perform even worse. The recent correction in the bond-associated deformation gradient helps to improve the predictions in some experiments, but not all. This confirms the previous strictly theoretical critique (JAM 2016), which showed that peridynamics of all kinds suffers from several conceptual faults: (1) It implies a lattice microstructure; (2) its particle-skipping interactions are a fiction; (4) it ignores shear-resisted particle rotations (which are what lends the lattice discrete particle model (LDPM) its superior performance); (3) its representation of the boundaries, especially the crack and fracture process zone faces, is physically unrealistic; and (5) it cannot reproduce the transitional size effect-a quintessential characteristic of quasibrittleness. The misleading practice of "verifying" a model with only one or two simple tests matchable by many different models, or showcasing an ad hoc improvement for one type of test while ignoring misfits of others, is pointed out. In closing, the ubiquity of crack parallel stresses in practical problems of concrete, shale, fiber composites, plastic-hardening metals, and materials on submicrometer scale is emphasized.