FRACTAL DIMENSION OF FRACTURED SURFACE AND FRACTURE TOUGHNESS IN METALS
金属断裂表面的分形(Fractal)与断裂韧性

The slit island method is employed to measure fractal dimensions D_F of fractured surfaces under plane strain conditions with the help of an image analysis technique for two high strength steels under different heat treatment conditions and at different test temperatures. It is shown that the fractured surfaces are of fractals. The values of D_F decrease smoothly with an increase of the logarithm values of fracture toughness K_(IC), i. e. the fractal dimensions D_F are approximately a linear function of the logarithm values of fracture toughness K_(IC). This relationship might reflect the changes in the microstructure that occured during different heat treatments and the changes in the fracture mechanism that occured at different test temperatures. The fractal dimension D_F could be regarded as a measure of fracture toughness in metels. Fi- nally, the experimental results are explained in terms of the relation between critical crack exten- sion force and the true total area of the irregular fracture surfaces.