Study Of The Fractal Features Of Material Fatigue Fracture

The topography of fatigue fracture implicates some information of rupture dynamic. With the observation of fracture topography based on the principle of quantitative Fractography, researchers have found the self-affine phenomenon in the study of fracture roughness, which means that fracture topography has the characteristic of fractal. However, limited to the lack of means of observation, the analysis of fractal feature for fracture remains in two dimensions, that is profile analysis; the characteristic covers only the fractal dimension; the relation between fractal feature and fracture mechanism is still not clear. This article is based on the observing data of a series of fatigue experiments, to calculate the slope and intercept value of the fractal relationship function, with the use of Matlab. Then obtain the changes of these values in different directions on the fracture surface, and explain it with the help of numerical simulation in Matlab. After that this article tries to analyze the fractal feature of the artificial simulation applying the method of WTMM (Wavelet Transform Modulus Maxima). Finally explore the physical meaning of these two fractal features, in order to research the relationship between the materials, stress intensity factor, fatigue environment, and the mode of crack production and mode of crack propagation. The research shows that: the inhomogeneity of crack propagation covers up local anisotropy feature of roughness exponent; the method of WTMM can effectively analyze the status of"multi-fractal", and its result for the value of fractal dimension is also introductive; for 304 stainless steel, under atmospheric and water environments, load change will affect respectively the coupling and producing mode of fatigue crack.