ON THE FORMATION OF NEAR-TIP MICROCRACKING AND ASSOCIATED TOUGHENING EFFECTS

Based upon the concept of microcrack precursor nucleation, a micromechanics model is proposed to study the formation of near-tip microcracking and consequent toughening effects. Analytical expressions are derived for the microcrack density distribution and the size and shape of the microcracking zone. The concept of a saturated inner zone with constant microcrack density follows as a natural consequence of the model. A closed-form approximate solution for the main crack-microcrack interaction is subsequently utilized to estimate quantitatively the associated amount of microcrack toughening. Both a stationary and a steadily growing main crack are considered and the effect of the release of residual stress has also been taken into account. The relationship between the current model and other existing ones is discussed.