A combined fracture-micromechanics model for tensile strain-softening in brittle materials, based on propagation of interacting microcracks

作者：Pichler Bernhard^*; Hellmich Christian; Mang Herbert A

来源：International Journal for Numerical and Analytical Methods in Geomechanics, 2007, 31(2): 111-132.

DOI：10.1002/nag.544

• brittle failure
• strain-softening
• tensile cracking
• micromechanics
• fracture mechanics

Strain-softening is the decline in stress at increasing strain. Although microcracking is a commonly accepted reason for strain-softening, the majority of theoretical developments involve macroscopic damage evolution laws. To improve this situation, we propose a micromechanics-based damage evolution law by combining (i) the propagation criterion for a single penny-shaped crack embedded in an infinite matrix subjected to remote stresses (taken from linear-elastic fracture mechanics) and (ii) stiffness estimates for representative material volumes comprising interacting microcracks (taken from continuum micromechanics). This combination allows for modelling tensile strain-softening as a result of propagation of interacting microcracks, i.e. as a microstructural effect. The initial degree of damage, i.e. the initial microcrack size and the number of microcracks per unit volume, implies two different types of model-predicted tensile strain-softening behaviour under strain control: (i) continuous strain-softening, which occurs in case of initial damage above a critical value, and (ii) an instantaneous stress drop at the peak load ('snap-back'), which occurs in case of initial damage below a critical value.

• 出版日期2007-2