Critical Comparison of Phase-Field, Peridynamics, and Crack Band Model M7 in Light of Gap Test and Classical Fracture Tests

Zdeněk P. Bažant*, Hoang T. Nguyen, A. Abdullah Dönmez

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Özet

The recently conceived gap test and its simulation revealed that the fracture energy Gf (or Kc, Jcr) of concrete, plastic-hardening metals, composites, and probably most materials can change by ±100%, depending on the crack-parallel stresses σxx, σzz, 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 microplane 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.

Orijinal dilİngilizce
Makale numarası061008
DergiJournal of Applied Mechanics, Transactions ASME
Hacim89
Basın numarası6
DOI'lar
Yayın durumuYayınlandı - Haz 2022

Bibliyografik not

Publisher Copyright:
Copyright © 2022 by ASME.

Finansman

Partial financial support under NSF grant CMMI-202964 and ARO grant W911NF-19-1-003, both to Northwestern University, is gratefully acknowledged. Thanks are due to Yuri Bazilevs, Masoud Behzadinasab, Jinhyun Choo, and Fan Fei for sharing their computer codes, and also to Florin Bobaru, Stewart Silling, Jian-Ying Wu, and Junuthula N. Reddy for their critical comments on the aforementioned ASME-IMECE lecture, which induced us to include further model variants and make the present analysis more detailed. Dat Ha is thanked for performing some preliminary checks of the phase-field models.

FinansörlerFinansör numarası
National Science FoundationCMMI-202964
Army Research OfficeW911NF-19-1-003
Northwestern University

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