Investigating the Influence of Boring Speed on Fatigue Life and Damage Mechanisms of Ferritic Ductile Cast Iron

This study investigates the impact of surface machining quality on the fatigue life of ductile cast iron, with particular emphasis on the inner bore wall quality, which is critical for enhancing the service life of diesel engines. A ring-shaped specimen, matching diesel engine cylinder dimensions, was machined at boring spindle speeds of 90 to 150 r/min. The results demonstrate that the average fatigue life of the specimen increased by 1.3 to 7.1 times at high spindle speeds, owing to the enhanced surface hardness, refined grain structure, and decreased surface tensile residual stress. Additionally, the analysis indicates that increased spindle speeds lead to a thicker hardened surface layer, delaying crack propagation. Fatigue life predictions using Paris' law aligned closely within a threefold error band. This research enhances our understanding of the relationship between surface machining quality and fatigue life in ductile cast iron.