Size effect, material ductility and shape of fracture process zone in quasi-brittle materials

2015 ◽  
Vol 65 ◽  
pp. 126-135 ◽  
Author(s):  
Mehdi Galouei ◽  
Ali Fakhimi
Keyword(s):  
Size Effect ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Brittle Materials ◽  
Material Ductility

Size effect analysis of quasi-brittle fracture with localizing gradient damage model

2021 ◽  
pp. 105678952098387
Author(s):  
Yi Zhang ◽  
Amit S. Shedbale ◽  
Yixiang Gan ◽  
Juhyuk Moon ◽  
Leong H. Poh
Keyword(s):  
Brittle Fracture ◽  
Size Effect ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Concrete Beams ◽  
Process Zone ◽  
Damage Zone ◽  
Damage Model ◽  
Lattice Models ◽  
Gradient Enhancement

The size effect of a quasi-brittle fracture is associated with the size of fracture process zone relative to the structural characteristic length. In numerical simulations using damage models, the nonlocal enhancement is commonly adopted to regularize the softening response. However, the conventional nonlocal enhancement, both integral and gradient approaches, induces a spurious spreading of damage zone. Since the evolution of fracture process zone cannot be captured well, the conventional nonlocal enhancement cannot predict the size effect phenomenon accurately. In this paper, the localizing gradient enhancement is adopted to avoid the spurious spreading of damage. Considering the three-point bend test of concrete beams, it is demonstrated that the dissipation profiles obtained with the localizing gradient enhancement compare well with those of reference meso-scale lattice models. With the correct damage evolution process, the localizing gradient enhancement is shown to capture the size effect phenomenon accurately for a series of geometrically similar concrete beams, using only a single set of material parameters.

scholarly journals Meso-scale modelling of the size effect on the fracture process zone of concrete

2012 ◽  
Vol 49 (13) ◽  
pp. 1818-1827 ◽  
Author(s):  
Peter Grassl ◽  
David Grégoire ◽  
Laura Rojas Solano ◽  
Gilles Pijaudier-Cabot
Keyword(s):  
Size Effect ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Scale Modelling ◽  
Meso Scale

Toughening Mechanisms in Quasi-Brittle Materials

1993 ◽  
Vol 115 (3) ◽  
pp. 300-307 ◽  
Author(s):  
S. P. Shah ◽  
C. Ouyang
Keyword(s):  
Fracture Process ◽  
Nonlinear Response ◽  
Large Scale ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Brittle Materials ◽  
Toughening Mechanisms ◽  
Theoretical Approaches ◽  
Cement Based Materials ◽  
Fracture Processes

Fracture processes in cement-based materials are characterized by a large-scale fracture process zone, localization of deformation, and strain softening. Many studies have been conducted to understand the toughening mechanisms of such quasi-brittle materials and to theoretically model their nonlinear response. This paper summarizes two innovative experimental techniques which are being developed at the ACBM Center to better define the fracture process zone in cement-based materials. A brief summary is also given of two types of theoretical approaches which attempt to simulate some of the observed nonlinear fracture response of these materials.

A Continuum Model with an Embedded Fracture Process Zone Modelled as a Cohesive Frictional Interface

2016 ◽  
Vol 846 ◽  
pp. 360-365 ◽  
Author(s):  
Arash Mir ◽  
Giang Dinh Nguyen ◽  
Abdul H. Sheikh
Keyword(s):  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Crack Opening ◽  
Brittle Materials ◽  
Peak Stress ◽  
Dissipated Energy ◽  
Internal Variables ◽  
Frame Work ◽  
Frictional Interface

Failure in quasi-brittle materials, such as concrete and rock, usually develops in a fracture process zone (FPZ), in which dissipative processes takes place. At the onset of bifurcation or upon formation of FPZ the homogeneity of kinematic fields is lost and the stress field is redistributed which gives rise to the so called deterministic size effect problem. The total strain energy stored within a specimen of quasi-brittle materials will scale with its size; however, the amount of dissipated energy does not depend on the specimen size but only on the width of the FPZ. This width is related to the microstructure of the material and is considered a characteristic of the material. In this paper, a cohesive frictional interface is used to model the dissipative behaviour of material inside FPZ. Fundamental micro-mechanisms of energy dissipation such as micro-crack opening in mode I and frictional sliding between micro-crack surfaces are formulated within the frame work of Thermodynamic with internal variables (TIV) to ensure the thermodynamics admissibility of the model. The link between the material behaviour inside and outside FPZ is given through the continuity of tractions along the boundaries of FPZ. It is shown that although the shape of the post-peak stress-strain varies, for specimens of different slenderness, the amount of dissipated energy remains the same in all cases.

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