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The theory of the fractal structure characterizing propagation of a crack through identification of its generator is presented. It's generating fractal, the peculiarities of its construction and the way to measure its segments are defined, and a theorem on the inverse scale property of such and other of the axial symmetry property of the fractal generator are presented and demonstrated. The theory is applied on 6061-T6 aluminum samples, using SENB probes. Direction of crack propagation and its fractal dimension are calculated numerically. Results obtained from modeling the direction of crack propagation through mechanics of elastic linear fracture and the one proposed here, called geometrical fractal fracture, are compared, thus developing the mirror case.

The theoretical development of discontinuities behavior model using the complex vari able theory by means of the elliptical coordinate system in order to calculate stress in a microhole in structural steel is discussed. It is shown that discontinuities, observed at micrometric levels, grow in a fractal manner and that when discontinuity has already a hyperbolic shape, with a branch attaining an angle of 60 in relation to the horizontal line, stress value is zero. By means of comparing values of stress intensity factors ob tained in the laboratory with those obtained using the theoretical model, it may be as serted that experimental values result from the overall effect of the test on the probe.