Microcracks size growth prediction based on microdefects nucleation number

Abstract

The mechanical reason for rock and concrete failure is trans-scale fracture, which can be divided into three phases: (1) microcrack evolution, (2) macrocrack nucleation, (3) macrocrack growth and run-through. Using the idea that a microcrack could be regarded as a well-organized aggregation of nucleated microdefects, the size growth model of the largest microcrack based on the accumulated number of microdefect nucleation is established. In order to test the validity of the model, trans-scale fracture of a plate made of heterogeneous material is numerically simulated to display the microcrack's evolution. Statistical analysis of the number and sizes of the microcracks indicates that the predicted size of the largest microcrack according to the model is in close agreement with the measured crack size prior to peak stress, but not at all close to the measured values after the peak. At the end of the paper, some remaining problems are proposed for the further work.

Poromechanical Modeling and Numerical Simulation of Hydraulic Fracture Propagation

“…Progressive fracturing in geomaterials is a multiscale phenomenon that can be divided into three main stages: the evolution of distributed microdamage, localization and subsequent macrocrack nucleation, and macrocrack propagation. − For FEM, the entire fracture process can be represented by a damage variable D as follows: where ε t0 is the threshold strain, representing the initiation of crack nucleation; ε t u is the final strain when the fracture has transected the porous element; κ is a combined parameter, calculated as κ = ε t0 /(ε t u – ε t0 ); and ε I is the tensile strain controlling fracture opening. This tensile strain is in the same direction as the first effective principal stress σ I ′ (Figure a,b), while the effective stress follows the cohesive law (Figure c).…”

Poromechanical Modeling of Hydraulic Fracture Propagation

“…According to the coupling between the compressibility of the solid and fluid [18,19], the differential change of fluid mass, dζ can be represented as…”

“…Progressive fracturing in geo-materials transits a variety of scales and can be divided into three main stages: Evolution of distributed microdamage, localization and subsequent macrocrack nucleation and macro-crack propagation [18,19,22]. For element of FEM, the entire fracture process can be represented by a damage variable D and defined as…”