Micromechanical modeling of crack propagation in nodular cast iron with competing ductile and cleavage failure

A micromechanical model is employed to simulate the fracture of nodular cast iron in the ductile-brittle transition region. The microstructure is resolved discretely as voids in the process zone. Possible cleavage of the intervoid ligaments is modeled by a cohesive zone. This approach captures both the local fracture stress for cleavage and the energy required to drive the cleavage crack front thus allowing to simulate all stages of crack initiation and propagation in the complete ductile-brittle transition region. A comparison with experiments from literature shows that the model captures the experimental results qualitatively and quantitatively.