A. Kamei

Dislocation dynamics theory for fatigue crack growth

Dislocation group dynamics theory is used to deduce a power type expression for fatigue crack growth. In general, the results reflect only a single rate process, and thus one activation energy which is small compared to those in usual rate processes. The frequency dependence for this power function type fatigue crack growth rate was also obtained, and yield reasonable agreement with experimental results from the literature.

A criterion for low-stress brittle fracture of notched specimens based on combined micro- and macro fracture mechanics—1

Abstract Based on the combined micro- and macro fracture mechanics, the two requisites necessary for the crack propagation, that is, the energy unstable requisite and the critical local stress requisite, are derived for the low-stress brittle fracture of notched specimens. Thus the fracture criterion was obtained. The criterion is compared with the experimental data, such as on the relationships between the fracture stress or the fracture toughness and the grain size diameter, the crack length, the notch tip radius or the yield stress. The good agreement is obtained.

Non-linear interaction between main crack and near-by slip band

Abstract Based on micro- and macro fracture mechanics, the basic equations for the general configuration of a crack (or a notch) and a slip band are obtained. As a special case, the coefficients of mutual interaction in stress intensity factors are calculated for the critical configuration of them corresponding to the low stress brittle fracture. The coefficients of mutual interaction are given in terms of a simple and analytical formula with a sufficiently good approximation. Furthermore, both the stress intensity factors at the tip of the crack and at the end of the slip band are obtained in simple forms applicable to fracture problems.

A concept of combined micro and macro fracture mechanics to brittle fracture

Real materials inevitably contain both stress concentrators as cracks or notches and as dislocations, that is, both macroscopic and microscopic one. From this viewpoint, a concept of combined micro and macro fracture mechanics is proposed for low-stress brittle fracture of steels.