The effective mechanical properties of solids with distributed rough cracks

TL;DR

This paper introduces a statistical multi-step self-consistent micromechanical model to predict the elastic and plastic properties of solids with randomly distributed rough microcracks, highlighting the influence of crack roughness and size distribution.

Contribution

The study develops a novel micromechanical model incorporating crack roughness and statistical distribution effects on mechanical properties of fractured solids.

Findings

Rough crack trajectories reduce stiffness degradation compared to smooth cracks.

Statistical distribution of crack sizes significantly affects elastic and plastic properties.

Crack roughness influences the yield surface and material degradation.

Abstract

A statistical multi-step self-consistent (SMSSC) micromechanical model for predicting elastic and plastic properties of a three-dimensional Representative Volume Element (RVE) is proposed in this research. A body with randomly distributed rough penny-shaped microcracks is considered for the first time in which the distribution of cracks is included through different well-known statistical distributions. Initially, the solution for a rough cohesive penny-shaped crack is developed, and the relationship between crack nominal length and roughness is derived. Consequently, Crack Opening Displacement (COD) and the corresponding volume crack opening are calculated as a function of surface roughness. Next, the SMSSC is used to study the effects of nominal crack length distribution on a fractured medium's mechanical properties with a known statistical distribution of crack sizes. This is done by determining the energy release and evaluating its share in material degradation (elastic, plastic). The elastic properties calculated using SMSSC indicated that the fractality of crack trajectories leads to lower values of volume crack opening and, consequently, resulted in a lower level of stiffness degradation compared with previous smooth crack approximations. It is also reached that the statistical distribution of rough cracks influences the mechanical properties due to the interrelation between length and roughness. Regarding the plastic behavior, the proposed micromechanical methodology is implemented to construct a capped pressure-sensitive yielding potential function that explicitly highlights the influence of crack size statistical distribution on the yielding of cracked solids. It is evident that the statistical distribution of crack sizes which are interrelated with crack roughness, can significantly alter the corresponding yield surface of fractured media.