DFQ: Damage and Fracture of Quasibrittle Materials
Minisymposium organized by
Quasibrittle materials such as concrete, rock, some ceramics, ice, etc. when subject to mechanical action (either direct or indirectly induced by environmental effects), exhibit a transition from (visco)elastic response, to distributed microcracking , and coalescence to localized macrocracking. In the approximately three decades since the term quasi-brittle was coined, a variety of models have been developed and proposed:
- Models based on the continuum approach such as elasto-plasticity, continuum damage mechanics, and combinations of both, aside from less standard continuum formulations such as endochronic theory, etc.
- The process of localization into macrocracks has been tackled either via "discrete cracking" (fictitious crack model) or "smeared cracking" and associated regularization procedures (e.g. "crack band theory").
- Regularization procedures have been devised generally based on fracture energy, and fracture mechanics of those materials has also been in itself a source of models and theories; applicable fracture theories range from LEFM (large specimens) to NLFM (medium-size) or even strength theories (very small) and size effect laws have been proposed for the transition.
- In the last two decades a number of numerical techniques have emerged that try to reconcile all aspects of quasi-brittle material behavior, although no magic recipe seems to have been proposed as yet. Techniques such as zero-thickness interface elements or XFEM allow to integrate discrete cracks into background continuum meshes, but each has its advantages and disadvantages, requiring in some cases costly algorithms for remeshing, crack tracking, etc., and sometimes are able to handle a very limited number of cracks and are not always capable of representing merging, bridging or branching.
- Quasi-brittle materials are heterogeneous in nature, and recent years have seen mesomechanical models being proposed, which, via representation of the largest heterogeneities explicitly, are able to simplify considerably the constitutive description, and yet offer a much more powerful tool to represent the material behavior in simple and complex scenarios including not only complex mechanical scenarios but also combination of mechanical and diffusion-driven or coupled environmental actions, etc. Similar approaches have been followed at the mortar or even cement level. Multi-scale analysis offers the possibility to integrate the representations at various levels, although some conceptual aspects remain unsolved.
This MS is dedicated to the 75th anniversary of Prof. Zdeněk P. Bažant, who has devoted his entire academic life to development, among many others, of the above-mentioned topics, and has achieved the highest academic honors and recognition for his work. Contributions are welcome in those and other related topics, especially those that in one way or another take inspiration or come into contact in a broad sense with the work of Zdeněk P. Bažant.