Crack Propagation in Cast Iron.

The growth rate of fatigue cracks and the upper limit for crack propagation, the critical stress intensity K//c or fracture toughness K//I//c were determined on gray cast iron, nodular cast iron, black malleable iron, and cast steel. It was found that the type of graphite present decides crack propagation in these materials. In flake graphite cast iron, fracture toughness increases with decreasing flake length, decreasing graphite volume fraction, and increasing tensile strength. The mechanical properties of the matrix have the decisive effect on the K//c value of nodular cast iron.