STUDIES ON THE FRACTAL DIMENSION OF A FRACTURE SURFACE FORMED BY SLOW STABLE CRACK-PROPAGATION

Fractal dimensions of different parts of a fracture surface formed by slow stable crack propagation, induced by the combined effect of hydrogen and static bending moment, were determined using the method of fracture profile analysis. The results showed that the fractal dimension increases with increasing transgranular fracture which increases as the crack propagates. This means that the increase of the fractal dimension responds to the increase of the energy needed to form the fracture surface, and in our case the process of forming a fracture surface by slow stable crack propagation is one of increasing fractal dimension of the fracture surface; when the fractal dimension reaches a critical value, the crack propagation becomes unstable.