Fracture analysis of layered cast iron

Abstract

The paper analyses fractures of seminatural specimens from layered cast iron, under gigacycle loading regime, when the number of cycles exceeds N > 10(7) cycles. Cyclic loading (pure bending r = -0.62) performed according to programme started from loads below threshold stress intensity factor. Crack propagation in dross layer and main metal was investigated by optical and electronic means. Fatigue cracks sources were found not only on specimens surfaces but also in areas beneath surface at nonhomogeneous formations surroundings. It was determined by investigation that dross-type microstructure distorts crack propagation front, secondary cracks appear on the surface. Also other factors influencing crack propagation have been analysed.