Fractal characterization as an indicator of rate of propagation of corrosion fatigue cracking of Chinese GC-4 ultra-high strength steel

Under the conditions of various electrochemical corrosion, the fractal characteristics of fracture surface in region of corrosion fatigue crack spread for GC-4 ultra-high strength steel were studied. The specimens with compact tension plane strain were adopted. The measured method of the fractal dimension was introduced. Experimental results have shown that in condition of weak corrosion, the good correlation of D_f and sub-stable spread rate of the crack exists, but it depends on measurement yardstick, while no explicit correlation exists in condition of strong corrosion and D_f has directivity and discrepancy in location. The micromorphologies of fracture surface were shown in experimental conditions of air, free corrosion, anode corrosion and cathode corrosion.