Application of a Fractal Method to Quantitatively Describe Some Typical Fracture Surfaces

Abstract

By using a vertical sectioning method (VSM) or secondary electron line scanning method (SELSM), the fractal dimension D_S for surface, D_L for scanning profile were measured quantitatively on some typical fracture surfaces, namely cleavage fractures, dimple fractures and fatigue fractures of composite materials. It was shown that the measured value of D_S relates differently to the impact energy values of materials for cleavage or dimple fractures. The microstructure of materials should be considered comprehensively when relating D_S to the mechanical properties of materials. It is found that the correlation between the fractal dimension and the impact energy obtained by SELSM and VSM methods appears to be quite similar. Moreover, the quantitative measurements on the fatigue fracture surfaces of SiC/Al composite materials showed that SiC volume fraction has a strong effect on fractal dimension D_S, and that there is an obvious difference in the D_S values for fatigue fractures which are due to different fracture mechanisms. These results show that it is possible to reflect the fracture mechanism using D_S and relate it to the fracture properties of materials.