Fractal nature of Barkhausen noise - a key to characterise the damage state of magnetic materials

To characterize materials damage the scaling behavior of the deformation structure was analyzed. As a result of that the fractal dimension of surface topog. appears to be a suitable parameter assessing different stages of fatigue and residual service time. Since magnetic domain pattern correlates well with the deformation structure, the fractal features of the subsurface materials region was tested by the magnetic Barkhausen noise signals for ferromagnetic steel samples. Different materials were investigated and a characteristic step-like dependence of the fractal dimension as a function of cyclic load no. was found. Applications of the fractal concept to industrial components will be reported.