Evaluation of high-cycle bending fatigue and fracture behaviors in EN-GJS700-2 ductile cast iron of crankshafts

In this article, high-cycle bending fatigue and fracture behaviors of the EN-GJS700-2 ductile cast iron, which has been widely utilized for crankshafts in engines, was experimentally evaluated. For such objective, standard specimens were extracted from the crankshaft and examined by the four-point rotary-bending high-cycle fatigue testing machine. Then, the S-N curve was evaluated for the studied material. Experiments were followed by the fracture investigation, using the scanning electron microscopy. Then, Obtained results indicated that high-cycle fatigue lifetimes were lower than the S-N curve from the FEMFAT data bank, since standard specimens were extracted from the crankshaft to consider the manufacturing effect. The failure analysis indicated different observations including striation marks (according to cyclic loading), debonding of nodular graphites from the ferritic-pearlitic matrix (as an evidence of the plastic deformation), micro-cracks and the secondary crack (near nodular graphites), cleavage marks (due to the brittle fracture), scratching marks (resulted from the friction and striking between two fracture surfaces) and inclusions.