Effect of Microstructures on Low-Cycle Fatigue Properties and Surface Crack Propagation Behavior in Ductile Cast Irons

Abstract

Total-strain controlled low-cycle fatigue tests were carried out at room temperature on three kinds of ductile cast iron (ferritic ductile iron ; FDI, pearlite-ferritic ductile iron ; P-FDI, and pearlitic ductile iron ; PDI) of round bar-type specimens with a small drilled notch. Fatigue deformation properties such as stress amplitude, plastic strain and cyclic stress-strain curve were measured, and the relationship between the strain amplitude and the fatigue life was investigated in the three cast irons. Propagation behavior of the surface fatigue crack initiated from the small notch was observed in detail at the surface. The fracture surface, the effects of graphite distribution and base microstructure on the crack growth behavior were investigated experimentally. The surface crack propagation rate da/dN was evaluated in the J integral range ΔJ, and the results for these cast irons were compared with the results for other metals.