Two kinds of ferritic ductile cast iron, having same chemical composition and different nodule count, i.e., high nodule count material (HNC) and low nodule count material (LNC), were low-cycle fatigued under stress-controlled cycling. The difference of nodule count induced difference in cyclic hardening behavior, LCF strength and fatigue mechanism. When LCF life was evaluated in terms of cyclic plastic strain range which includes the effect of cyclic hardening properties, both materials showed same fatigue strength. Although spheroidal graphite (SG) played an important role as a crack initiation site at an early stage of fatigue process, subsequent fatigue process was differed between HNC and LNC. In case of HNC, the fatigue process was dominated by the growth of a single crack. On the contrary, independent growth of subcracks without forming a leading crack controlled the whole fatigue process in material LNC. In addition, contradictory to number of nodule counts, the density of the initiated subcracks was higher in LNC than in HNC. Statistical analysis of three dimensional (3D) distribution of SG revealed that the difference in fatigue mechanism mentioned so far was mainly caused by the difference of distribution of SG size. Finally image processing analysis of 3D fracture surface showed that the roughness in crack growth area was larger in LNC than in HNC.
|Number of pages||6|
|Publication status||Published - 1995|
All Science Journal Classification (ASJC) codes
- Industrial and Manufacturing Engineering
- Mechanical Engineering